Improve documentation and matching algorithm in data binders

spring-beans/src/main/java/org/springframework/beans/PropertyAccessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,8 +23,9 @@ import org.springframework.lang.Nullable;
 
 /**
  * Common interface for classes that can access named properties
- * (such as bean properties of an object or fields in an object)
- * Serves as base interface for {@link BeanWrapper}.
+ * (such as bean properties of an object or fields in an object).
+ *
+ * <p>Serves as base interface for {@link BeanWrapper}.
  *
  * @author Juergen Hoeller
  * @since 1.1

spring-context/src/main/java/org/springframework/validation/DataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -51,18 +51,20 @@ import org.springframework.util.PatternMatchUtils;
 import org.springframework.util.StringUtils;
 
 /**
- * Binder that allows for setting property values onto a target object,
- * including support for validation and binding result analysis.
- * The binding process can be customized through specifying allowed fields,
+ * Binder that allows for setting property values on a target object, including
+ * support for validation and binding result analysis.
+ *
+ * <p>The binding process can be customized by specifying allowed field patterns,
  * required fields, custom editors, etc.
  *
- * <p>Note that there are potential security implications in failing to set an array
- * of allowed fields. In the case of HTTP form POST data for example, malicious clients
- * can attempt to subvert an application by supplying values for fields or properties
- * that do not exist on the form. In some cases this could lead to illegal data being
- * set on command objects <i>or their nested objects</i>. For this reason, it is
- * <b>highly recommended to specify the {@link #setAllowedFields allowedFields} property</b>
- * on the DataBinder.
+ * <p><strong>WARNING</strong>: Data binding can lead to security issues by exposing
+ * parts of the object graph that are not meant to be accessed or modified by
+ * external clients. Therefore the design and use of data binding should be considered
+ * carefully with regard to security. For more details, please refer to the dedicated
+ * sections on data binding for
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-ann-initbinder-model-design">Spring Web MVC</a> and
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-ann-initbinder-model-design">Spring WebFlux</a>
+ * in the reference manual.
  *
  * <p>The binding results can be examined via the {@link BindingResult} interface,
  * extending the {@link Errors} interface: see the {@link #getBindingResult()} method.
@@ -96,6 +98,7 @@ import org.springframework.util.StringUtils;
  * @author Rob Harrop
  * @author Stephane Nicoll
  * @author Kazuki Shimizu
+ * @author Sam Brannen
  * @see #setAllowedFields
  * @see #setRequiredFields
  * @see #registerCustomEditor
@@ -415,13 +418,21 @@ public class DataBinder implements PropertyEditorRegistry, TypeConverter {
 	}
 
 	/**
-	 * Register fields that should be allowed for binding. Default is all
-	 * fields. Restrict this for example to avoid unwanted modifications
-	 * by malicious users when binding HTTP request parameters.
-	 * <p>Supports "xxx*", "*xxx" and "*xxx*" patterns. More sophisticated matching
-	 * can be implemented by overriding the {@code isAllowed} method.
-	 * <p>Alternatively, specify a list of <i>disallowed</i> fields.
-	 * @param allowedFields array of field names
+	 * Register field patterns that should be allowed for binding.
+	 * <p>Default is all fields.
+	 * <p>Restrict this for example to avoid unwanted modifications by malicious
+	 * users when binding HTTP request parameters.
+	 * <p>Supports {@code "xxx*"}, {@code "*xxx"}, {@code "*xxx*"}, and
+	 * {@code "xxx*yyy"} matches (with an arbitrary number of pattern parts), as
+	 * well as direct equality.
+	 * <p>The default implementation of this method stores allowed field patterns
+	 * in {@linkplain PropertyAccessorUtils#canonicalPropertyName(String) canonical}
+	 * form. Subclasses which override this method must therefore take this into
+	 * account.
+	 * <p>More sophisticated matching can be implemented by overriding the
+	 * {@link #isAllowed} method.
+	 * <p>Alternatively, specify a list of <i>disallowed</i> field patterns.
+	 * @param allowedFields array of allowed field patterns
 	 * @see #setDisallowedFields
 	 * @see #isAllowed(String)
 	 */
@@ -430,8 +441,9 @@ public class DataBinder implements PropertyEditorRegistry, TypeConverter {
 	}
 
 	/**
-	 * Return the fields that should be allowed for binding.
-	 * @return array of field names
+	 * Return the field patterns that should be allowed for binding.
+	 * @return array of allowed field patterns
+	 * @see #setAllowedFields(String...)
 	 */
 	@Nullable
 	public String[] getAllowedFields() {
@@ -439,23 +451,44 @@ public class DataBinder implements PropertyEditorRegistry, TypeConverter {
 	}
 
 	/**
-	 * Register fields that should <i>not</i> be allowed for binding. Default is none.
-	 * Mark fields as disallowed for example to avoid unwanted modifications
-	 * by malicious users when binding HTTP request parameters.
-	 * <p>Supports "xxx*", "*xxx" and "*xxx*" patterns. More sophisticated matching
-	 * can be implemented by overriding the {@code isAllowed} method.
-	 * <p>Alternatively, specify a list of <i>allowed</i> fields.
-	 * @param disallowedFields array of field names
+	 * Register field patterns that should <i>not</i> be allowed for binding.
+	 * <p>Default is none.
+	 * <p>Mark fields as disallowed, for example to avoid unwanted
+	 * modifications by malicious users when binding HTTP request parameters.
+	 * <p>Supports {@code "xxx*"}, {@code "*xxx"}, {@code "*xxx*"}, and
+	 * {@code "xxx*yyy"} matches (with an arbitrary number of pattern parts), as
+	 * well as direct equality.
+	 * <p>The default implementation of this method stores disallowed field patterns
+	 * in {@linkplain PropertyAccessorUtils#canonicalPropertyName(String) canonical}
+	 * form. As of Spring Framework 5.2.21, the default implementation also transforms
+	 * disallowed field patterns to {@linkplain String#toLowerCase() lowercase} to
+	 * support case-insensitive pattern matching in {@link #isAllowed}. Subclasses
+	 * which override this method must therefore take both of these transformations
+	 * into account.
+	 * <p>More sophisticated matching can be implemented by overriding the
+	 * {@link #isAllowed} method.
+	 * <p>Alternatively, specify a list of <i>allowed</i> field patterns.
+	 * @param disallowedFields array of disallowed field patterns
 	 * @see #setAllowedFields
 	 * @see #isAllowed(String)
 	 */
 	public void setDisallowedFields(@Nullable String... disallowedFields) {
-		this.disallowedFields = PropertyAccessorUtils.canonicalPropertyNames(disallowedFields);
+		if (disallowedFields == null) {
+			this.disallowedFields = null;
+		}
+		else {
+			String[] fieldPatterns = new String[disallowedFields.length];
+			for (int i = 0; i < fieldPatterns.length; i++) {
+				fieldPatterns[i] = PropertyAccessorUtils.canonicalPropertyName(disallowedFields[i]).toLowerCase();
+			}
+			this.disallowedFields = fieldPatterns;
+		}
 	}
 
 	/**
-	 * Return the fields that should <i>not</i> be allowed for binding.
-	 * @return array of field names
+	 * Return the field patterns that should <i>not</i> be allowed for binding.
+	 * @return array of disallowed field patterns
+	 * @see #setDisallowedFields(String...)
 	 */
 	@Nullable
 	public String[] getDisallowedFields() {
@@ -767,15 +800,20 @@ public class DataBinder implements PropertyEditorRegistry, TypeConverter {
 	}
 
 	/**
-	 * Return if the given field is allowed for binding.
-	 * Invoked for each passed-in property value.
-	 * <p>The default implementation checks for "xxx*", "*xxx" and "*xxx*" matches,
-	 * as well as direct equality, in the specified lists of allowed fields and
-	 * disallowed fields. A field matching a disallowed pattern will not be accepted
-	 * even if it also happens to match a pattern in the allowed list.
-	 * <p>Can be overridden in subclasses.
+	 * Determine if the given field is allowed for binding.
+	 * <p>Invoked for each passed-in property value.
+	 * <p>Checks for {@code "xxx*"}, {@code "*xxx"}, {@code "*xxx*"}, and
+	 * {@code "xxx*yyy"} matches (with an arbitrary number of pattern parts), as
+	 * well as direct equality, in the configured lists of allowed field patterns
+	 * and disallowed field patterns.
+	 * <p>Matching against allowed field patterns is case-sensitive; whereas,
+	 * matching against disallowed field patterns is case-insensitive.
+	 * <p>A field matching a disallowed pattern will not be accepted even if it
+	 * also happens to match a pattern in the allowed list.
+	 * <p>Can be overridden in subclasses, but care must be taken to honor the
+	 * aforementioned contract.
 	 * @param field the field to check
-	 * @return if the field is allowed
+	 * @return {@code true} if the field is allowed
 	 * @see #setAllowedFields
 	 * @see #setDisallowedFields
 	 * @see org.springframework.util.PatternMatchUtils#simpleMatch(String, String)
@@ -784,7 +822,7 @@ public class DataBinder implements PropertyEditorRegistry, TypeConverter {
 		String[] allowed = getAllowedFields();
 		String[] disallowed = getDisallowedFields();
 		return ((ObjectUtils.isEmpty(allowed) || PatternMatchUtils.simpleMatch(allowed, field)) &&
-				(ObjectUtils.isEmpty(disallowed) || !PatternMatchUtils.simpleMatch(disallowed, field)));
+				(ObjectUtils.isEmpty(disallowed) || !PatternMatchUtils.simpleMatch(disallowed, field.toLowerCase())));
 	}
 
 	/**

spring-context/src/test/java/org/springframework/validation/DataBinderTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -64,23 +64,26 @@ import org.springframework.format.support.DefaultFormattingConversionService;
 import org.springframework.format.support.FormattingConversionService;
 import org.springframework.lang.Nullable;
 import org.springframework.tests.sample.beans.BeanWithObjectProperty;
-import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+import static org.assertj.core.api.Assertions.entry;
 
 /**
+ * Unit tests for {@link DataBinder}.
+ *
  * @author Rod Johnson
  * @author Juergen Hoeller
  * @author Rob Harrop
  * @author Kazuki Shimizu
+ * @author Sam Brannen
  */
-public class DataBinderTests {
+class DataBinderTests {
 
 	@Test
-	public void testBindingNoErrors() throws BindException {
+	void bindingNoErrors() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		assertThat(binder.isIgnoreUnknownFields()).isTrue();
@@ -110,12 +113,11 @@ public class DataBinderTests {
 		assertThat(ex).isEqualTo(binder.getBindingResult());
 
 		other.reject("xxx");
-		boolean condition = !other.equals(binder.getBindingResult());
-		assertThat(condition).isTrue();
+		assertThat(other).isNotEqualTo(binder.getBindingResult());
 	}
 
 	@Test
-	public void testBindingWithDefaultConversionNoErrors() throws BindException {
+	void bindingWithDefaultConversionNoErrors() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		assertThat(binder.isIgnoreUnknownFields()).isTrue();
@@ -131,7 +133,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testNestedBindingWithDefaultConversionNoErrors() throws BindException {
+	void nestedBindingWithDefaultConversionNoErrors() throws BindException {
 		TestBean rod = new TestBean(new TestBean());
 		DataBinder binder = new DataBinder(rod, "person");
 		assertThat(binder.isIgnoreUnknownFields()).isTrue();
@@ -147,7 +149,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingNoErrorsNotIgnoreUnknown() {
+	void bindingNoErrorsNotIgnoreUnknown() {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		binder.setIgnoreUnknownFields(false);
@@ -160,7 +162,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingNoErrorsWithInvalidField() {
+	void bindingNoErrorsWithInvalidField() {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		MutablePropertyValues pvs = new MutablePropertyValues();
@@ -171,7 +173,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingNoErrorsWithIgnoreInvalid() {
+	void bindingNoErrorsWithIgnoreInvalid() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		binder.setIgnoreInvalidFields(true);
@@ -180,10 +182,14 @@ public class DataBinderTests {
 		pvs.add("spouse.age", 32);
 
 		binder.bind(pvs);
+		binder.close();
+
+		assertThat(rod.getName()).isEqualTo("Rod");
+		assertThat(rod.getSpouse()).isNull();
 	}
 
 	@Test
-	public void testBindingWithErrors() {
+	void bindingWithErrors() {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		MutablePropertyValues pvs = new MutablePropertyValues();
@@ -245,7 +251,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithSystemFieldError() {
+	void bindingWithSystemFieldError() {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		MutablePropertyValues pvs = new MutablePropertyValues();
@@ -257,7 +263,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithErrorsAndCustomEditors() {
+	void bindingWithErrorsAndCustomEditors() {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		binder.registerCustomEditor(String.class, "touchy", new PropertyEditorSupport() {
@@ -325,7 +331,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithCustomEditorOnObjectField() {
+	void bindingWithCustomEditorOnObjectField() {
 		BeanWithObjectProperty tb = new BeanWithObjectProperty();
 		DataBinder binder = new DataBinder(tb);
 		binder.registerCustomEditor(Integer.class, "object", new CustomNumberEditor(Integer.class, true));
@@ -336,7 +342,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithFormatter() {
+	void bindingWithFormatter() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 		FormattingConversionService conversionService = new FormattingConversionService();
@@ -368,7 +374,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingErrorWithFormatter() {
+	void bindingErrorWithFormatter() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 		FormattingConversionService conversionService = new FormattingConversionService();
@@ -391,7 +397,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingErrorWithParseExceptionFromFormatter() {
+	void bindingErrorWithParseExceptionFromFormatter() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 		FormattingConversionService conversionService = new FormattingConversionService();
@@ -419,7 +425,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingErrorWithRuntimeExceptionFromFormatter() {
+	void bindingErrorWithRuntimeExceptionFromFormatter() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 		FormattingConversionService conversionService = new FormattingConversionService();
@@ -447,7 +453,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithFormatterAgainstList() {
+	void bindingWithFormatterAgainstList() {
 		BeanWithIntegerList tb = new BeanWithIntegerList();
 		DataBinder binder = new DataBinder(tb);
 		FormattingConversionService conversionService = new FormattingConversionService();
@@ -469,7 +475,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingErrorWithFormatterAgainstList() {
+	void bindingErrorWithFormatterAgainstList() {
 		BeanWithIntegerList tb = new BeanWithIntegerList();
 		DataBinder binder = new DataBinder(tb);
 		FormattingConversionService conversionService = new FormattingConversionService();
@@ -492,7 +498,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithFormatterAgainstFields() {
+	void bindingWithFormatterAgainstFields() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 		FormattingConversionService conversionService = new FormattingConversionService();
@@ -525,7 +531,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingErrorWithFormatterAgainstFields() {
+	void bindingErrorWithFormatterAgainstFields() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 		binder.initDirectFieldAccess();
@@ -549,7 +555,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithCustomFormatter() {
+	void bindingWithCustomFormatter() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 		binder.addCustomFormatter(new NumberStyleFormatter(), Float.class);
@@ -578,7 +584,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingErrorWithCustomFormatter() {
+	void bindingErrorWithCustomFormatter() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 		binder.addCustomFormatter(new NumberStyleFormatter());
@@ -599,7 +605,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingErrorWithParseExceptionFromCustomFormatter() {
+	void bindingErrorWithParseExceptionFromCustomFormatter() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 
@@ -624,7 +630,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingErrorWithRuntimeExceptionFromCustomFormatter() {
+	void bindingErrorWithRuntimeExceptionFromCustomFormatter() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb);
 
@@ -649,7 +655,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testConversionWithInappropriateStringEditor() {
+	void conversionWithInappropriateStringEditor() {
 		DataBinder dataBinder = new DataBinder(null);
 		DefaultFormattingConversionService conversionService = new DefaultFormattingConversionService();
 		dataBinder.setConversionService(conversionService);
@@ -662,7 +668,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithAllowedFields() throws BindException {
+	void bindingWithAllowedFields() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod);
 		binder.setAllowedFields("name", "myparam");
@@ -672,30 +678,32 @@ public class DataBinderTests {
 
 		binder.bind(pvs);
 		binder.close();
-		assertThat(rod.getName().equals("Rod")).as("changed name correctly").isTrue();
-		assertThat(rod.getAge() == 0).as("did not change age").isTrue();
+
+		assertThat(rod.getName()).as("changed name correctly").isEqualTo("Rod");
+		assertThat(rod.getAge()).as("did not change age").isZero();
 	}
 
 	@Test
-	public void testBindingWithDisallowedFields() throws BindException {
+	void bindingWithDisallowedFields() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod);
-		binder.setDisallowedFields("age");
+		binder.setDisallowedFields(" ", "\t", "favouriteColour", null, "age");
 		MutablePropertyValues pvs = new MutablePropertyValues();
 		pvs.add("name", "Rod");
 		pvs.add("age", "32x");
+		pvs.add("favouriteColour", "BLUE");
 
 		binder.bind(pvs);
 		binder.close();
-		assertThat(rod.getName().equals("Rod")).as("changed name correctly").isTrue();
-		assertThat(rod.getAge() == 0).as("did not change age").isTrue();
-		String[] disallowedFields = binder.getBindingResult().getSuppressedFields();
-		assertThat(disallowedFields.length).isEqualTo(1);
-		assertThat(disallowedFields[0]).isEqualTo("age");
+
+		assertThat(rod.getName()).as("changed name correctly").isEqualTo("Rod");
+		assertThat(rod.getAge()).as("did not change age").isZero();
+		assertThat(rod.getFavouriteColour()).as("did not change favourite colour").isNull();
+		assertThat(binder.getBindingResult().getSuppressedFields()).containsExactlyInAnyOrder("age", "favouriteColour");
 	}
 
 	@Test
-	public void testBindingWithAllowedAndDisallowedFields() throws BindException {
+	void bindingWithAllowedAndDisallowedFields() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod);
 		binder.setAllowedFields("name", "myparam");
@@ -706,34 +714,32 @@ public class DataBinderTests {
 
 		binder.bind(pvs);
 		binder.close();
-		assertThat(rod.getName().equals("Rod")).as("changed name correctly").isTrue();
-		assertThat(rod.getAge() == 0).as("did not change age").isTrue();
-		String[] disallowedFields = binder.getBindingResult().getSuppressedFields();
-		assertThat(disallowedFields.length).isEqualTo(1);
-		assertThat(disallowedFields[0]).isEqualTo("age");
+
+		assertThat(rod.getName()).as("changed name correctly").isEqualTo("Rod");
+		assertThat(rod.getAge()).as("did not change age").isZero();
+		assertThat(binder.getBindingResult().getSuppressedFields()).containsExactly("age");
 	}
 
 	@Test
-	public void testBindingWithOverlappingAllowedAndDisallowedFields() throws BindException {
+	void bindingWithOverlappingAllowedAndDisallowedFields() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod);
 		binder.setAllowedFields("name", "age");
-		binder.setDisallowedFields("age");
+		binder.setDisallowedFields("AGE");
 		MutablePropertyValues pvs = new MutablePropertyValues();
 		pvs.add("name", "Rod");
 		pvs.add("age", "32x");
 
 		binder.bind(pvs);
 		binder.close();
-		assertThat(rod.getName().equals("Rod")).as("changed name correctly").isTrue();
-		assertThat(rod.getAge() == 0).as("did not change age").isTrue();
-		String[] disallowedFields = binder.getBindingResult().getSuppressedFields();
-		assertThat(disallowedFields.length).isEqualTo(1);
-		assertThat(disallowedFields[0]).isEqualTo("age");
+
+		assertThat(rod.getName()).as("changed name correctly").isEqualTo("Rod");
+		assertThat(rod.getAge()).as("did not change age").isZero();
+		assertThat(binder.getBindingResult().getSuppressedFields()).containsExactly("age");
 	}
 
 	@Test
-	public void testBindingWithAllowedFieldsUsingAsterisks() throws BindException {
+	void bindingWithAllowedFieldsUsingAsterisks() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		binder.setAllowedFields("nam*", "*ouchy");
@@ -760,11 +766,11 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithAllowedAndDisallowedMapFields() throws BindException {
+	void bindingWithAllowedAndDisallowedMapFields() throws BindException {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod);
 		binder.setAllowedFields("someMap[key1]", "someMap[key2]");
-		binder.setDisallowedFields("someMap['key3']", "someMap[key4]");
+		binder.setDisallowedFields("someMap['KEY3']", "SomeMap[key4]");
 
 		MutablePropertyValues pvs = new MutablePropertyValues();
 		pvs.add("someMap[key1]", "value1");
@@ -774,21 +780,18 @@ public class DataBinderTests {
 
 		binder.bind(pvs);
 		binder.close();
-		assertThat(rod.getSomeMap().get("key1")).isEqualTo("value1");
-		assertThat(rod.getSomeMap().get("key2")).isEqualTo("value2");
-		assertThat(rod.getSomeMap().get("key3")).isNull();
-		assertThat(rod.getSomeMap().get("key4")).isNull();
-		String[] disallowedFields = binder.getBindingResult().getSuppressedFields();
-		assertThat(disallowedFields.length).isEqualTo(2);
-		assertThat(ObjectUtils.containsElement(disallowedFields, "someMap[key3]")).isTrue();
-		assertThat(ObjectUtils.containsElement(disallowedFields, "someMap[key4]")).isTrue();
+
+		@SuppressWarnings("unchecked")
+		Map<String, String> someMap = (Map<String, String>) rod.getSomeMap();
+		assertThat(someMap).containsOnly(entry("key1", "value1"), entry("key2", "value2"));
+		assertThat(binder.getBindingResult().getSuppressedFields()).containsExactly("someMap[key3]", "someMap[key4]");
 	}
 
 	/**
 	 * Tests for required field, both null, non-existing and empty strings.
 	 */
 	@Test
-	public void testBindingWithRequiredFields() {
+	void bindingWithRequiredFields() {
 		TestBean tb = new TestBean();
 		tb.setSpouse(new TestBean());
 
@@ -819,7 +822,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithRequiredMapFields() {
+	void bindingWithRequiredMapFields() {
 		TestBean tb = new TestBean();
 		tb.setSpouse(new TestBean());
 
@@ -839,7 +842,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingWithNestedObjectCreation() {
+	void bindingWithNestedObjectCreation() {
 		TestBean tb = new TestBean();
 
 		DataBinder binder = new DataBinder(tb, "person");
@@ -860,7 +863,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testCustomEditorWithOldValueAccess() {
+	void customEditorWithOldValueAccess() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 
@@ -885,7 +888,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testCustomEditorForSingleProperty() {
+	void customEditorForSingleProperty() {
 		TestBean tb = new TestBean();
 		tb.setSpouse(new TestBean());
 		DataBinder binder = new DataBinder(tb, "tb");
@@ -925,7 +928,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testCustomEditorForPrimitiveProperty() {
+	void customEditorForPrimitiveProperty() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 
@@ -949,7 +952,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testCustomEditorForAllStringProperties() {
+	void customEditorForAllStringProperties() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 
@@ -981,7 +984,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testCustomFormatterForSingleProperty() {
+	void customFormatterForSingleProperty() {
 		TestBean tb = new TestBean();
 		tb.setSpouse(new TestBean());
 		DataBinder binder = new DataBinder(tb, "tb");
@@ -1021,7 +1024,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testCustomFormatterForPrimitiveProperty() {
+	void customFormatterForPrimitiveProperty() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 
@@ -1045,7 +1048,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testCustomFormatterForAllStringProperties() {
+	void customFormatterForAllStringProperties() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 
@@ -1077,7 +1080,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testJavaBeanPropertyConventions() {
+	void javaBeanPropertyConventions() {
 		Book book = new Book();
 		DataBinder binder = new DataBinder(book);
 
@@ -1101,7 +1104,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testOptionalProperty() {
+	void optionalProperty() {
 		OptionalHolder bean = new OptionalHolder();
 		DataBinder binder = new DataBinder(bean);
 		binder.setConversionService(new DefaultConversionService());
@@ -1122,7 +1125,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testValidatorNoErrors() throws Exception {
+	void validatorNoErrors() throws Exception {
 		TestBean tb = new TestBean();
 		tb.setAge(33);
 		tb.setName("Rod");
@@ -1175,15 +1178,13 @@ public class DataBinderTests {
 		assertThat(errors.getNestedPath()).isEqualTo("spouse.");
 
 		assertThat(errors.getErrorCount()).isEqualTo(1);
-		boolean condition1 = !errors.hasGlobalErrors();
-		assertThat(condition1).isTrue();
+		assertThat(errors.hasGlobalErrors()).isFalse();
 		assertThat(errors.getFieldErrorCount("age")).isEqualTo(1);
-		boolean condition = !errors.hasFieldErrors("name");
-		assertThat(condition).isTrue();
+		assertThat(errors.hasFieldErrors("name")).isFalse();
 	}
 
 	@Test
-	public void testValidatorWithErrors() {
+	void validatorWithErrors() {
 		TestBean tb = new TestBean();
 		tb.setSpouse(new TestBean());
 
@@ -1252,7 +1253,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testValidatorWithErrorsAndCodesPrefix() {
+	void validatorWithErrorsAndCodesPrefix() {
 		TestBean tb = new TestBean();
 		tb.setSpouse(new TestBean());
 
@@ -1324,7 +1325,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testValidatorWithNestedObjectNull() {
+	void validatorWithNestedObjectNull() {
 		TestBean tb = new TestBean();
 		Errors errors = new BeanPropertyBindingResult(tb, "tb");
 		Validator testValidator = new TestBeanValidator();
@@ -1343,7 +1344,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testNestedValidatorWithoutNestedPath() {
+	void nestedValidatorWithoutNestedPath() {
 		TestBean tb = new TestBean();
 		tb.setName("XXX");
 		Errors errors = new BeanPropertyBindingResult(tb, "tb");
@@ -1357,7 +1358,8 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingStringArrayToIntegerSet() {
+	@SuppressWarnings("unchecked")
+	void bindingStringArrayToIntegerSet() {
 		IndexedTestBean tb = new IndexedTestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(Set.class, new CustomCollectionEditor(TreeSet.class) {
@@ -1371,12 +1373,8 @@ public class DataBinderTests {
 		binder.bind(pvs);
 
 		assertThat(binder.getBindingResult().getFieldValue("set")).isEqualTo(tb.getSet());
-		boolean condition = tb.getSet() instanceof TreeSet;
-		assertThat(condition).isTrue();
-		assertThat(tb.getSet().size()).isEqualTo(3);
-		assertThat(tb.getSet().contains(10)).isTrue();
-		assertThat(tb.getSet().contains(20)).isTrue();
-		assertThat(tb.getSet().contains(30)).isTrue();
+		assertThat(tb.getSet()).isInstanceOf(TreeSet.class);
+		assertThat((Set<Integer>) tb.getSet()).containsExactly(10, 20, 30);
 
 		pvs = new MutablePropertyValues();
 		pvs.add("set", null);
@@ -1386,7 +1384,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingNullToEmptyCollection() {
+	void bindingNullToEmptyCollection() {
 		IndexedTestBean tb = new IndexedTestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(Set.class, new CustomCollectionEditor(TreeSet.class, true));
@@ -1394,13 +1392,12 @@ public class DataBinderTests {
 		pvs.add("set", null);
 		binder.bind(pvs);
 
-		boolean condition = tb.getSet() instanceof TreeSet;
-		assertThat(condition).isTrue();
-		assertThat(tb.getSet().isEmpty()).isTrue();
+		assertThat(tb.getSet()).isInstanceOf(TreeSet.class);
+		assertThat(tb.getSet()).isEmpty();
 	}
 
 	@Test
-	public void testBindingToIndexedField() {
+	void bindingToIndexedField() {
 		IndexedTestBean tb = new IndexedTestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(String.class, "array.name", new PropertyEditorSupport() {
@@ -1439,7 +1436,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindingToNestedIndexedField() {
+	void bindingToNestedIndexedField() {
 		IndexedTestBean tb = new IndexedTestBean();
 		tb.getArray()[0].setNestedIndexedBean(new IndexedTestBean());
 		tb.getArray()[1].setNestedIndexedBean(new IndexedTestBean());
@@ -1470,7 +1467,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testEditorForNestedIndexedField() {
+	void editorForNestedIndexedField() {
 		IndexedTestBean tb = new IndexedTestBean();
 		tb.getArray()[0].setNestedIndexedBean(new IndexedTestBean());
 		tb.getArray()[1].setNestedIndexedBean(new IndexedTestBean());
@@ -1496,7 +1493,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testSpecificEditorForNestedIndexedField() {
+	void specificEditorForNestedIndexedField() {
 		IndexedTestBean tb = new IndexedTestBean();
 		tb.getArray()[0].setNestedIndexedBean(new IndexedTestBean());
 		tb.getArray()[1].setNestedIndexedBean(new IndexedTestBean());
@@ -1522,7 +1519,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testInnerSpecificEditorForNestedIndexedField() {
+	void innerSpecificEditorForNestedIndexedField() {
 		IndexedTestBean tb = new IndexedTestBean();
 		tb.getArray()[0].setNestedIndexedBean(new IndexedTestBean());
 		tb.getArray()[1].setNestedIndexedBean(new IndexedTestBean());
@@ -1548,7 +1545,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testDirectBindingToIndexedField() {
+	void directBindingToIndexedField() {
 		IndexedTestBean tb = new IndexedTestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(TestBean.class, "array", new PropertyEditorSupport() {
@@ -1601,7 +1598,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testDirectBindingToEmptyIndexedFieldWithRegisteredSpecificEditor() {
+	void directBindingToEmptyIndexedFieldWithRegisteredSpecificEditor() {
 		IndexedTestBean tb = new IndexedTestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(TestBean.class, "map[key0]", new PropertyEditorSupport() {
@@ -1632,7 +1629,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testDirectBindingToEmptyIndexedFieldWithRegisteredGenericEditor() {
+	void directBindingToEmptyIndexedFieldWithRegisteredGenericEditor() {
 		IndexedTestBean tb = new IndexedTestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(TestBean.class, "map", new PropertyEditorSupport() {
@@ -1663,7 +1660,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testCustomEditorWithSubclass() {
+	void customEditorWithSubclass() {
 		IndexedTestBean tb = new IndexedTestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(TestBean.class, new PropertyEditorSupport() {
@@ -1697,7 +1694,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindToStringArrayWithArrayEditor() {
+	void bindToStringArrayWithArrayEditor() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(String[].class, "stringArray", new PropertyEditorSupport() {
@@ -1709,15 +1706,12 @@ public class DataBinderTests {
 		MutablePropertyValues pvs = new MutablePropertyValues();
 		pvs.add("stringArray", "a1-b2");
 		binder.bind(pvs);
-		boolean condition = !binder.getBindingResult().hasErrors();
-		assertThat(condition).isTrue();
-		assertThat(tb.getStringArray().length).isEqualTo(2);
-		assertThat(tb.getStringArray()[0]).isEqualTo("a1");
-		assertThat(tb.getStringArray()[1]).isEqualTo("b2");
+		assertThat(binder.getBindingResult().hasErrors()).isFalse();
+		assertThat(tb.getStringArray()).containsExactly("a1", "b2");
 	}
 
 	@Test
-	public void testBindToStringArrayWithComponentEditor() {
+	void bindToStringArrayWithComponentEditor() {
 		TestBean tb = new TestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		binder.registerCustomEditor(String.class, "stringArray", new PropertyEditorSupport() {
@@ -1729,15 +1723,14 @@ public class DataBinderTests {
 		MutablePropertyValues pvs = new MutablePropertyValues();
 		pvs.add("stringArray", new String[] {"a1", "b2"});
 		binder.bind(pvs);
-		boolean condition = !binder.getBindingResult().hasErrors();
-		assertThat(condition).isTrue();
+		assertThat(binder.getBindingResult().hasErrors()).isFalse();
 		assertThat(tb.getStringArray().length).isEqualTo(2);
 		assertThat(tb.getStringArray()[0]).isEqualTo("Xa1");
 		assertThat(tb.getStringArray()[1]).isEqualTo("Xb2");
 	}
 
 	@Test
-	public void testBindingErrors() {
+	void bindingErrors() {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		MutablePropertyValues pvs = new MutablePropertyValues();
@@ -1764,7 +1757,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testAddAllErrors() {
+	void addAllErrors() {
 		TestBean rod = new TestBean();
 		DataBinder binder = new DataBinder(rod, "person");
 		MutablePropertyValues pvs = new MutablePropertyValues();
@@ -1784,7 +1777,7 @@ public class DataBinderTests {
 
 	@Test
 	@SuppressWarnings("unchecked")
-	public void testBindingWithResortedList() {
+	void bindingWithResortedList() {
 		IndexedTestBean tb = new IndexedTestBean();
 		DataBinder binder = new DataBinder(tb, "tb");
 		MutablePropertyValues pvs = new MutablePropertyValues();
@@ -1802,7 +1795,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testRejectWithoutDefaultMessage() {
+	void rejectWithoutDefaultMessage() {
 		TestBean tb = new TestBean();
 		tb.setName("myName");
 		tb.setAge(99);
@@ -1820,7 +1813,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testBindExceptionSerializable() throws Exception {
+	void bindExceptionSerializable() throws Exception {
 		SerializablePerson tb = new SerializablePerson();
 		tb.setName("myName");
 		tb.setAge(99);
@@ -1849,27 +1842,27 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testTrackDisallowedFields() {
+	void trackDisallowedFields() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		binder.setAllowedFields("name", "age");
 
 		String name = "Rob Harrop";
-		String beanName = "foobar";
+		int age = 42;
 
 		MutablePropertyValues mpvs = new MutablePropertyValues();
 		mpvs.add("name", name);
-		mpvs.add("beanName", beanName);
+		mpvs.add("age", age);
+		mpvs.add("beanName", "foobar");
 		binder.bind(mpvs);
 
 		assertThat(testBean.getName()).isEqualTo(name);
-		String[] disallowedFields = binder.getBindingResult().getSuppressedFields();
-		assertThat(disallowedFields.length).isEqualTo(1);
-		assertThat(disallowedFields[0]).isEqualTo("beanName");
+		assertThat(testBean.getAge()).isEqualTo(age);
+		assertThat(binder.getBindingResult().getSuppressedFields()).containsExactly("beanName");
 	}
 
 	@Test
-	public void testAutoGrowWithinDefaultLimit() {
+	void autoGrowWithinDefaultLimit() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 
@@ -1881,7 +1874,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testAutoGrowBeyondDefaultLimit() {
+	void autoGrowBeyondDefaultLimit() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 
@@ -1893,7 +1886,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testAutoGrowWithinCustomLimit() {
+	void autoGrowWithinCustomLimit() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		binder.setAutoGrowCollectionLimit(10);
@@ -1906,7 +1899,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testAutoGrowBeyondCustomLimit() {
+	void autoGrowBeyondCustomLimit() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		binder.setAutoGrowCollectionLimit(10);
@@ -1919,7 +1912,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testNestedGrowingList() {
+	void nestedGrowingList() {
 		Form form = new Form();
 		DataBinder binder = new DataBinder(form, "form");
 		MutablePropertyValues mpv = new MutablePropertyValues();
@@ -1935,7 +1928,7 @@ public class DataBinderTests {
 	}
 
 	@Test
-	public void testFieldErrorAccessVariations() {
+	void fieldErrorAccessVariations() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		assertThat(binder.getBindingResult().getGlobalError()).isNull();
@@ -1956,7 +1949,7 @@ public class DataBinderTests {
 	}
 
 	@Test  // SPR-14888
-	public void testSetAutoGrowCollectionLimit() {
+	void setAutoGrowCollectionLimit() {
 		BeanWithIntegerList tb = new BeanWithIntegerList();
 		DataBinder binder = new DataBinder(tb);
 		binder.setAutoGrowCollectionLimit(257);
@@ -1970,7 +1963,7 @@ public class DataBinderTests {
 	}
 
 	@Test  // SPR-14888
-	public void testSetAutoGrowCollectionLimitAfterInitialization() {
+	void setAutoGrowCollectionLimitAfterInitialization() {
 		DataBinder binder = new DataBinder(new BeanWithIntegerList());
 		binder.registerCustomEditor(String.class, new StringTrimmerEditor(true));
 		assertThatIllegalStateException().isThrownBy(() ->
@@ -1979,7 +1972,7 @@ public class DataBinderTests {
 	}
 
 	@Test // SPR-15009
-	public void testSetCustomMessageCodesResolverBeforeInitializeBindingResultForBeanPropertyAccess() {
+	void setCustomMessageCodesResolverBeforeInitializeBindingResultForBeanPropertyAccess() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		DefaultMessageCodesResolver messageCodesResolver = new DefaultMessageCodesResolver();
@@ -1996,7 +1989,7 @@ public class DataBinderTests {
 	}
 
 	@Test // SPR-15009
-	public void testSetCustomMessageCodesResolverBeforeInitializeBindingResultForDirectFieldAccess() {
+	void setCustomMessageCodesResolverBeforeInitializeBindingResultForDirectFieldAccess() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		DefaultMessageCodesResolver messageCodesResolver = new DefaultMessageCodesResolver();
@@ -2011,7 +2004,7 @@ public class DataBinderTests {
 	}
 
 	@Test  // SPR-15009
-	public void testSetCustomMessageCodesResolverAfterInitializeBindingResult() {
+	void setCustomMessageCodesResolverAfterInitializeBindingResult() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		binder.initBeanPropertyAccess();
@@ -2026,7 +2019,7 @@ public class DataBinderTests {
 	}
 
 	@Test  // SPR-15009
-	public void testSetMessageCodesResolverIsNullAfterInitializeBindingResult() {
+	void setMessageCodesResolverIsNullAfterInitializeBindingResult() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		binder.initBeanPropertyAccess();
@@ -2040,8 +2033,7 @@ public class DataBinderTests {
 	}
 
 	@Test  // SPR-15009
-	public void testCallSetMessageCodesResolverTwice() {
-
+	void callSetMessageCodesResolverTwice() {
 		TestBean testBean = new TestBean();
 		DataBinder binder = new DataBinder(testBean, "testBean");
 		binder.setMessageCodesResolver(new DefaultMessageCodesResolver());

spring-web/src/main/java/org/springframework/web/bind/ServletRequestDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -28,6 +28,15 @@ import org.springframework.web.util.WebUtils;
  * Special {@link org.springframework.validation.DataBinder} to perform data binding
  * from servlet request parameters to JavaBeans, including support for multipart files.
  *
+ * <p><strong>WARNING</strong>: Data binding can lead to security issues by exposing
+ * parts of the object graph that are not meant to be accessed or modified by
+ * external clients. Therefore the design and use of data binding should be considered
+ * carefully with regard to security. For more details, please refer to the dedicated
+ * sections on data binding for
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-ann-initbinder-model-design">Spring Web MVC</a> and
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-ann-initbinder-model-design">Spring WebFlux</a>
+ * in the reference manual.
+ *
  * <p>See the DataBinder/WebDataBinder superclasses for customization options,
  * which include specifying allowed/required fields, and registering custom
  * property editors.

spring-web/src/main/java/org/springframework/web/bind/WebDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,6 +34,15 @@ import org.springframework.web.multipart.MultipartFile;
  * the Servlet API; serves as base class for more specific DataBinder variants,
  * such as {@link org.springframework.web.bind.ServletRequestDataBinder}.
  *
+ * <p><strong>WARNING</strong>: Data binding can lead to security issues by exposing
+ * parts of the object graph that are not meant to be accessed or modified by
+ * external clients. Therefore the design and use of data binding should be considered
+ * carefully with regard to security. For more details, please refer to the dedicated
+ * sections on data binding for
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-ann-initbinder-model-design">Spring Web MVC</a> and
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-ann-initbinder-model-design">Spring WebFlux</a>
+ * in the reference manual.
+ *
  * <p>Includes support for field markers which address a common problem with
  * HTML checkboxes and select options: detecting that a field was part of
  * the form, but did not generate a request parameter because it was empty.

spring-web/src/main/java/org/springframework/web/bind/annotation/ExceptionHandler.java

@@ -97,6 +97,7 @@ import java.lang.annotation.Target;
  * @author Arjen Poutsma
  * @author Juergen Hoeller
  * @since 3.0
+ * @see ControllerAdvice
  * @see org.springframework.web.context.request.WebRequest
  */
 @Target(ElementType.METHOD)

spring-web/src/main/java/org/springframework/web/bind/annotation/InitBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,15 +23,24 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- * Annotation that identifies methods which initialize the
+ * Annotation that identifies methods that initialize the
  * {@link org.springframework.web.bind.WebDataBinder} which
  * will be used for populating command and form object arguments
  * of annotated handler methods.
  *
- * <p>Such init-binder methods support all arguments that {@link RequestMapping}
- * supports, except for command/form objects and corresponding validation result
- * objects. Init-binder methods must not have a return value; they are usually
- * declared as {@code void}.
+ * <p><strong>WARNING</strong>: Data binding can lead to security issues by exposing
+ * parts of the object graph that are not meant to be accessed or modified by
+ * external clients. Therefore the design and use of data binding should be considered
+ * carefully with regard to security. For more details, please refer to the dedicated
+ * sections on data binding for
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-ann-initbinder-model-design">Spring Web MVC</a> and
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-ann-initbinder-model-design">Spring WebFlux</a>
+ * in the reference manual.
+ *
+ * <p>{@code @InitBinder} methods support all arguments that
+ * {@link RequestMapping @RequestMapping} methods support, except for command/form
+ * objects and corresponding validation result objects. {@code @InitBinder} methods
+ * must not have a return value; they are usually declared as {@code void}.
  *
  * <p>Typical arguments are {@link org.springframework.web.bind.WebDataBinder}
  * in combination with {@link org.springframework.web.context.request.WebRequest}
@@ -39,6 +48,7 @@ import java.lang.annotation.Target;
  *
  * @author Juergen Hoeller
  * @since 2.5
+ * @see ControllerAdvice
  * @see org.springframework.web.bind.WebDataBinder
  * @see org.springframework.web.context.request.WebRequest
  */

spring-web/src/main/java/org/springframework/web/bind/annotation/ModelAttribute.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -31,18 +31,27 @@ import org.springframework.ui.Model;
  * for controller classes with {@link RequestMapping @RequestMapping}
  * methods.
  *
- * <p>Can be used to expose command objects to a web view, using
- * specific attribute names, through annotating corresponding
- * parameters of an {@link RequestMapping @RequestMapping} method.
+ * <p><strong>WARNING</strong>: Data binding can lead to security issues by exposing
+ * parts of the object graph that are not meant to be accessed or modified by
+ * external clients. Therefore the design and use of data binding should be considered
+ * carefully with regard to security. For more details, please refer to the dedicated
+ * sections on data binding for
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-ann-initbinder-model-design">Spring Web MVC</a> and
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-ann-initbinder-model-design">Spring WebFlux</a>
+ * in the reference manual.
  *
- * <p>Can also be used to expose reference data to a web view
- * through annotating accessor methods in a controller class with
+ * <p>{@code @ModelAttribute} can be used to expose command objects to a web view,
+ * using specific attribute names, by annotating corresponding parameters of an
+ * {@link RequestMapping @RequestMapping} method.
+ *
+ * <p>{@code @ModelAttribute} can also be used to expose reference data to a web
+ * view by annotating accessor methods in a controller class with
  * {@link RequestMapping @RequestMapping} methods. Such accessor
  * methods are allowed to have any arguments that
  * {@link RequestMapping @RequestMapping} methods support, returning
  * the model attribute value to expose.
  *
- * <p>Note however that reference data and all other model content is
+ * <p>Note however that reference data and all other model content are
  * not available to web views when request processing results in an
  * {@code Exception} since the exception could be raised at any time
  * making the content of the model unreliable. For this reason
@@ -52,6 +61,7 @@ import org.springframework.ui.Model;
  * @author Juergen Hoeller
  * @author Rossen Stoyanchev
  * @since 2.5
+ * @see ControllerAdvice
  */
 @Target({ElementType.PARAMETER, ElementType.METHOD})
 @Retention(RetentionPolicy.RUNTIME)
@@ -77,7 +87,7 @@ public @interface ModelAttribute {
 	String name() default "";
 
 	/**
-	 * Allows declaring data binding disabled directly on an {@code @ModelAttribute}
+	 * Allows data binding to be disabled directly on an {@code @ModelAttribute}
 	 * method parameter or on the attribute returned from an {@code @ModelAttribute}
 	 * method, both of which would prevent data binding for that attribute.
 	 * <p>By default this is set to {@code true} in which case data binding applies.

spring-web/src/main/java/org/springframework/web/bind/support/WebExchangeDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,6 +36,15 @@ import org.springframework.web.server.ServerWebExchange;
  * Specialized {@link org.springframework.validation.DataBinder} to perform data
  * binding from URL query parameters or form data in the request data to Java objects.
  *
+ * <p><strong>WARNING</strong>: Data binding can lead to security issues by exposing
+ * parts of the object graph that are not meant to be accessed or modified by
+ * external clients. Therefore the design and use of data binding should be considered
+ * carefully with regard to security. For more details, please refer to the dedicated
+ * sections on data binding for
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-ann-initbinder-model-design">Spring Web MVC</a> and
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-ann-initbinder-model-design">Spring WebFlux</a>
+ * in the reference manual.
+ *
  * @author Rossen Stoyanchev
  * @since 5.0
  */

spring-web/src/main/java/org/springframework/web/bind/support/WebRequestDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,6 +35,15 @@ import org.springframework.web.multipart.MultipartRequest;
  * Special {@link org.springframework.validation.DataBinder} to perform data binding
  * from web request parameters to JavaBeans, including support for multipart files.
  *
+ * <p><strong>WARNING</strong>: Data binding can lead to security issues by exposing
+ * parts of the object graph that are not meant to be accessed or modified by
+ * external clients. Therefore the design and use of data binding should be considered
+ * carefully with regard to security. For more details, please refer to the dedicated
+ * sections on data binding for
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-ann-initbinder-model-design">Spring Web MVC</a> and
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-ann-initbinder-model-design">Spring WebFlux</a>
+ * in the reference manual.
+ *
  * <p>See the DataBinder/WebDataBinder superclasses for customization options,
  * which include specifying allowed/required fields, and registering custom
  * property editors.

spring-web/src/test/java/org/springframework/web/method/annotation/InitBinderDataBinderFactoryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -116,7 +116,7 @@ public class InitBinderDataBinderFactoryTests {
 		WebDataBinder dataBinder = factory.createBinder(this.webRequest, null, "foo");
 
 		assertThat(dataBinder.getDisallowedFields()).isNotNull();
-		assertThat(dataBinder.getDisallowedFields()[0]).isEqualTo("requestParam-22");
+		assertThat(dataBinder.getDisallowedFields()[0]).isEqualToIgnoringCase("requestParam-22");
 	}
 
 	private WebDataBinderFactory createFactory(String methodName, Class<?>... parameterTypes)

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/InitBinderBindingContextTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -121,7 +121,7 @@ public class InitBinderBindingContextTests {
 		WebDataBinder dataBinder = context.createDataBinder(exchange, null, "foo");
 
 		assertThat(dataBinder.getDisallowedFields()).isNotNull();
-		assertThat(dataBinder.getDisallowedFields()[0]).isEqualTo("requestParam-22");
+		assertThat(dataBinder.getDisallowedFields()[0]).isEqualToIgnoringCase("requestParam-22");
 	}
 
 

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ExtendedServletRequestDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -29,6 +29,15 @@ import org.springframework.web.servlet.HandlerMapping;
  * Subclass of {@link ServletRequestDataBinder} that adds URI template variables
  * to the values used for data binding.
  *
+ * <p><strong>WARNING</strong>: Data binding can lead to security issues by exposing
+ * parts of the object graph that are not meant to be accessed or modified by
+ * external clients. Therefore the design and use of data binding should be considered
+ * carefully with regard to security. For more details, please refer to the dedicated
+ * sections on data binding for
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web.html#mvc-ann-initbinder-model-design">Spring Web MVC</a> and
+ * <a href="https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-ann-initbinder-model-design">Spring WebFlux</a>
+ * in the reference manual.
+ *
  * @author Rossen Stoyanchev
  * @since 3.1
  */

src/docs/asciidoc/web/web-data-binding-model-design.adoc

@@ -0,0 +1,95 @@
+In the context of web applications, _data binding_ involves the binding of HTTP request
+parameters (that is, form data or query parameters) to properties in a model object and
+its nested objects.
+
+Only `public` properties following the
+https://www.oracle.com/java/technologies/javase/javabeans-spec.html[JavaBeans naming conventions]
+are exposed for data binding — for example, `public String getFirstName()` and
+`public void setFirstName(String)` methods for a `firstName` property.
+
+TIP: The model object, and its nested object graph, is also sometimes referred to as a
+_command object_, _form-backing object_, or _POJO_ (Plain Old Java Object).
+
+By default, Spring permits binding to all public properties in the model object graph.
+This means you need to carefully consider what public properties the model has, since a
+client could target any public property path, even some that are not expected to be
+targeted for a given use case.
+
+For example, given an HTTP form data endpoint, a malicious client could supply values for
+properties that exist in the model object graph but are not part of the HTML form
+presented in the browser. This could lead to data being set on the model object and any
+of its nested objects, that is not expected to be updated.
+
+The recommended approach is to use a _dedicated model object_ that exposes only
+properties that are relevant for the form submission. For example, on a form for changing
+a user's email address, the model object should declare a minimum set of properties such
+as in the following `ChangeEmailForm`.
+
+[source,java,indent=0,subs="verbatim,quotes"]
+----
+	public class ChangeEmailForm {
+
+		private String oldEmailAddress;
+		private String newEmailAddress;
+
+		public void setOldEmailAddress(String oldEmailAddress) {
+			this.oldEmailAddress = oldEmailAddress;
+		}
+
+		public String getOldEmailAddress() {
+			return this.oldEmailAddress;
+		}
+
+		public void setNewEmailAddress(String newEmailAddress) {
+			this.newEmailAddress = newEmailAddress;
+		}
+
+		public String getNewEmailAddress() {
+			return this.newEmailAddress;
+		}
+
+	}
+----
+
+If you cannot or do not want to use a _dedicated model object_ for each data
+binding use case, you **must** limit the properties that are allowed for data binding.
+Ideally, you can achieve this by registering _allowed field patterns_ via the
+`setAllowedFields()` method on `WebDataBinder`.
+
+For example, to register allowed field patterns in your application, you can implement an
+`@InitBinder` method in a `@Controller` or `@ControllerAdvice` component as shown below:
+
+[source,java,indent=0,subs="verbatim,quotes"]
+----
+	@Controller
+	public class ChangeEmailController {
+
+		@InitBinder
+		void initBinder(WebDataBinder binder) {
+			binder.setAllowedFields("oldEmailAddress", "newEmailAddress");
+		}
+
+		// @RequestMapping methods, etc.
+
+	}
+----
+
+In addition to registering allowed patterns, it is also possible to register _disallowed
+field patterns_ via the `setDisallowedFields()` method in `DataBinder` and its subclasses.
+Please note, however, that an "allow list" is safer than a "deny list". Consequently,
+`setAllowedFields()` should be favored over `setDisallowedFields()`.
+
+Note that matching against allowed field patterns is case-sensitive; whereas, matching
+against disallowed field patterns is case-insensitive. In addition, a field matching a
+disallowed pattern will not be accepted even if it also happens to match a pattern in the
+allowed list.
+
+[WARNING]
+====
+It is extremely important to properly configure allowed and disallowed field patterns
+when exposing your domain model directly for data binding purposes. Otherwise, it is a
+big security risk.
+
+Furthermore, it is strongly recommended that you do **not** use types from your domain
+model such as JPA or Hibernate entities as the model object in data binding scenarios.
+====

src/docs/asciidoc/web/webflux.adoc

@@ -3288,6 +3288,11 @@ controller-specific `Formatter` instances, as the following example shows:
 ----
 <1> Adding a custom formatter (a `DateFormatter`, in this case).
 
+[[webflux-ann-initbinder-model-design]]
+==== Model Design
+[.small]#<<web.adoc#mvc-ann-initbinder-model-design, Web MVC>>#
+
+include::web-data-binding-model-design.adoc[]
 
 
 [[webflux-ann-controller-exceptions]]

src/docs/asciidoc/web/webmvc.adoc

@@ -3662,6 +3662,13 @@ controller-specific `Formatter` implementations, as the following example shows:
 ----
 <1> Defining an `@InitBinder` method on a custom formatter.
 
+[[mvc-ann-initbinder-model-design]]
+==== Model Design
+[.small]#<<web-reactive.adoc#webflux-ann-initbinder-model-design, WebFlux>>#
+
+include::web-data-binding-model-design.adoc[]
+
+
 [[mvc-ann-exceptionhandler]]
 === Exceptions
 [.small]#<<web-reactive.adoc#webflux-ann-controller-exceptions, WebFlux>>#