Improve null-safety to fix some Spring Boot warnings

Issue: SPR-15540

spring-beans/src/main/java/org/springframework/beans/factory/NoSuchBeanDefinitionException.java

@@ -18,6 +18,7 @@ package org.springframework.beans.factory;
 
 import org.springframework.beans.BeansException;
 import org.springframework.core.ResolvableType;
+import org.springframework.lang.Nullable;
 
 /**
  * Exception thrown when a {@code BeanFactory} is asked for a bean instance for which it
@@ -100,6 +101,7 @@ public class NoSuchBeanDefinitionException extends BeansException {
 	/**
 	 * Return the name of the missing bean, if it was a lookup <em>by name</em> that failed.
 	 */
+	@Nullable
 	public String getBeanName() {
 		return this.beanName;
 	}
@@ -108,6 +110,7 @@ public class NoSuchBeanDefinitionException extends BeansException {
 	 * Return the required type of the missing bean, if it was a lookup <em>by type</em>
 	 * that failed.
 	 */
+	@Nullable
 	public Class<?> getBeanType() {
 		return (this.resolvableType != null ? this.resolvableType.resolve() : null);
 	}
@@ -117,6 +120,7 @@ public class NoSuchBeanDefinitionException extends BeansException {
 	 * <em>by type</em> that failed.
 	 * @since 4.3.4
 	 */
+	@Nullable
 	public ResolvableType getResolvableType() {
 		return this.resolvableType;
 	}

spring-beans/src/main/java/org/springframework/beans/factory/UnsatisfiedDependencyException.java

@@ -17,6 +17,7 @@
 package org.springframework.beans.factory;
 
 import org.springframework.beans.BeansException;
+import org.springframework.lang.Nullable;
 import org.springframework.util.StringUtils;
 
 /**
@@ -42,7 +43,7 @@ public class UnsatisfiedDependencyException extends BeanCreationException {
 	 * @param msg the detail message
 	 */
 	public UnsatisfiedDependencyException(
-			String resourceDescription, String beanName, String propertyName, String msg) {
+			@Nullable String resourceDescription, @Nullable String beanName, String propertyName, String msg) {
 
 		super(resourceDescription, beanName,
 				"Unsatisfied dependency expressed through bean property '" + propertyName + "'" +
@@ -57,7 +58,7 @@ public class UnsatisfiedDependencyException extends BeanCreationException {
 	 * @param ex the bean creation exception that indicated the unsatisfied dependency
 	 */
 	public UnsatisfiedDependencyException(
-			String resourceDescription, String beanName, String propertyName, BeansException ex) {
+			@Nullable String resourceDescription, @Nullable String beanName, String propertyName, BeansException ex) {
 
 		this(resourceDescription, beanName, propertyName, "");
 		initCause(ex);
@@ -72,7 +73,7 @@ public class UnsatisfiedDependencyException extends BeanCreationException {
 	 * @since 4.3
 	 */
 	public UnsatisfiedDependencyException(
-			String resourceDescription, String beanName, InjectionPoint injectionPoint, String msg) {
+			@Nullable String resourceDescription, @Nullable String beanName, @Nullable InjectionPoint injectionPoint, String msg) {
 
 		super(resourceDescription, beanName,
 				"Unsatisfied dependency expressed through " + injectionPoint +
@@ -89,7 +90,7 @@ public class UnsatisfiedDependencyException extends BeanCreationException {
 	 * @since 4.3
 	 */
 	public UnsatisfiedDependencyException(
-			String resourceDescription, String beanName, InjectionPoint injectionPoint, BeansException ex) {
+			@Nullable String resourceDescription, @Nullable String beanName, @Nullable InjectionPoint injectionPoint, BeansException ex) {
 
 		this(resourceDescription, beanName, injectionPoint, "");
 		initCause(ex);
@@ -100,6 +101,7 @@ public class UnsatisfiedDependencyException extends BeanCreationException {
 	 * Return the injection point (field or method/constructor parameter), if known.
 	 * @since 4.3
 	 */
+	@Nullable
 	public InjectionPoint getInjectionPoint() {
 		return this.injectionPoint;
 	}

spring-beans/src/main/java/org/springframework/beans/factory/config/ConfigurableListableBeanFactory.java

@@ -21,6 +21,7 @@ import java.util.Iterator;
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
+import org.springframework.lang.Nullable;
 
 /**
  * Configuration interface to be implemented by most listable bean factories.
@@ -105,7 +106,7 @@ public interface ConfigurableListableBeanFactory
 	 * @throws NoSuchBeanDefinitionException if there is no bean with the given name
 	 * defined in this factory
 	 */
-	BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;
+	BeanDefinition getBeanDefinition(@Nullable String beanName) throws NoSuchBeanDefinitionException;
 
 	/**
 	 * Return a unified view over all bean names managed by this factory.

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.java

@@ -1738,7 +1738,7 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 	 * @see ChildBeanDefinition
 	 * @see org.springframework.beans.factory.config.ConfigurableListableBeanFactory#getBeanDefinition
 	 */
-	protected abstract BeanDefinition getBeanDefinition(String beanName) throws BeansException;
+	protected abstract BeanDefinition getBeanDefinition(@Nullable String beanName) throws BeansException;
 
 	/**
 	 * Create a bean instance for the given merged bean definition (and arguments).

spring-beans/src/main/java/org/springframework/beans/factory/support/BeanDefinitionRegistry.java

@@ -20,6 +20,7 @@ import org.springframework.beans.factory.BeanDefinitionStoreException;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.core.AliasRegistry;
+import org.springframework.lang.Nullable;
 
 /**
  * Interface for registries that hold bean definitions, for example RootBeanDefinition
@@ -74,7 +75,7 @@ public interface BeanDefinitionRegistry extends AliasRegistry {
 	 * @return the BeanDefinition for the given name (never {@code null})
 	 * @throws NoSuchBeanDefinitionException if there is no such bean definition
 	 */
-	BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;
+	BeanDefinition getBeanDefinition(@Nullable String beanName) throws NoSuchBeanDefinitionException;
 
 	/**
 	 * Check if this registry contains a bean definition with the given name.

spring-beans/src/main/java/org/springframework/beans/factory/support/DefaultListableBeanFactory.java

@@ -195,7 +195,7 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 	 * Specify an id for serialization purposes, allowing this BeanFactory to be
 	 * deserialized from this id back into the BeanFactory object, if needed.
 	 */
-	public void setSerializationId(String serializationId) {
+	public void setSerializationId(@Nullable String serializationId) {
 		if (serializationId != null) {
 			serializableFactories.put(serializationId, new WeakReference<>(this));
 		}
@@ -671,7 +671,7 @@ public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFacto
 	}
 
 	@Override
-	public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
+	public BeanDefinition getBeanDefinition(@Nullable String beanName) throws NoSuchBeanDefinitionException {
 		BeanDefinition bd = this.beanDefinitionMap.get(beanName);
 		if (bd == null) {
 			if (this.logger.isTraceEnabled()) {

spring-beans/src/main/java/org/springframework/beans/factory/support/RootBeanDefinition.java

@@ -117,7 +117,7 @@ public class RootBeanDefinition extends AbstractBeanDefinition {
 	 * @param beanClass the class of the bean to instantiate
 	 * @see #setBeanClass
 	 */
-	public RootBeanDefinition(Class<?> beanClass) {
+	public RootBeanDefinition(@Nullable Class<?> beanClass) {
 		super();
 		setBeanClass(beanClass);
 	}
@@ -131,7 +131,7 @@ public class RootBeanDefinition extends AbstractBeanDefinition {
 	 * @since 5.0
 	 * @see #setInstanceSupplier
 	 */
-	public <T> RootBeanDefinition(Class<T> beanClass, Supplier<T> instanceSupplier) {
+	public <T> RootBeanDefinition(@Nullable Class<T> beanClass, @Nullable Supplier<T> instanceSupplier) {
 		super();
 		setBeanClass(beanClass);
 		setInstanceSupplier(instanceSupplier);
@@ -147,7 +147,7 @@ public class RootBeanDefinition extends AbstractBeanDefinition {
 	 * @since 5.0
 	 * @see #setInstanceSupplier
 	 */
-	public <T> RootBeanDefinition(Class<T> beanClass, String scope, Supplier<T> instanceSupplier) {
+	public <T> RootBeanDefinition(@Nullable Class<T> beanClass, String scope, @Nullable Supplier<T> instanceSupplier) {
 		super();
 		setBeanClass(beanClass);
 		setScope(scope);
@@ -162,7 +162,7 @@ public class RootBeanDefinition extends AbstractBeanDefinition {
 	 * @param dependencyCheck whether to perform a dependency check for objects
 	 * (not applicable to autowiring a constructor, thus ignored there)
 	 */
-	public RootBeanDefinition(Class<?> beanClass, int autowireMode, boolean dependencyCheck) {
+	public RootBeanDefinition(@Nullable Class<?> beanClass, int autowireMode, boolean dependencyCheck) {
 		super();
 		setBeanClass(beanClass);
 		setAutowireMode(autowireMode);
@@ -178,7 +178,7 @@ public class RootBeanDefinition extends AbstractBeanDefinition {
 	 * @param cargs the constructor argument values to apply
 	 * @param pvs the property values to apply
 	 */
-	public RootBeanDefinition(Class<?> beanClass, ConstructorArgumentValues cargs, MutablePropertyValues pvs) {
+	public RootBeanDefinition(@Nullable Class<?> beanClass, ConstructorArgumentValues cargs, MutablePropertyValues pvs) {
 		super(cargs, pvs);
 		setBeanClass(beanClass);
 	}

spring-beans/src/main/java/org/springframework/beans/factory/support/SimpleBeanDefinitionRegistry.java

@@ -23,6 +23,7 @@ import org.springframework.beans.factory.BeanDefinitionStoreException;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.core.SimpleAliasRegistry;
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.StringUtils;
 
@@ -57,7 +58,7 @@ public class SimpleBeanDefinitionRegistry extends SimpleAliasRegistry implements
 	}
 
 	@Override
-	public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
+	public BeanDefinition getBeanDefinition(@Nullable String beanName) throws NoSuchBeanDefinitionException {
 		BeanDefinition bd = this.beanDefinitionMap.get(beanName);
 		if (bd == null) {
 			throw new NoSuchBeanDefinitionException(beanName);

spring-context/src/main/java/org/springframework/context/support/GenericApplicationContext.java

@@ -330,7 +330,7 @@ public class GenericApplicationContext extends AbstractApplicationContext implem
 	}
 
 	@Override
-	public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
+	public BeanDefinition getBeanDefinition(@Nullable String beanName) throws NoSuchBeanDefinitionException {
 		return this.beanFactory.getBeanDefinition(beanName);
 	}
 

spring-core/src/main/java/org/springframework/core/annotation/AnnotationUtils.java

@@ -231,7 +231,7 @@ public abstract class AnnotationUtils {
 	 * @see AnnotatedElement#getAnnotations()
 	 */
 	@Nullable
-	public static Annotation[] getAnnotations(AnnotatedElement annotatedElement) {
+	public static Annotation[] getAnnotations(@Nullable AnnotatedElement annotatedElement) {
 		try {
 			return synthesizeAnnotationArray(annotatedElement.getAnnotations(), annotatedElement);
 		}
@@ -1441,7 +1441,7 @@ public abstract class AnnotationUtils {
 	}
 
 	@SuppressWarnings("unchecked")
-	static <A extends Annotation> A synthesizeAnnotation(A annotation, Object annotatedElement) {
+	static <A extends Annotation> A synthesizeAnnotation(A annotation, @Nullable Object annotatedElement) {
 		if (annotation == null) {
 			return null;
 		}
@@ -1548,8 +1548,7 @@ public abstract class AnnotationUtils {
 	 * @see #synthesizeAnnotation(Annotation, AnnotatedElement)
 	 * @see #synthesizeAnnotation(Map, Class, AnnotatedElement)
 	 */
-	@Nullable
-	static Annotation[] synthesizeAnnotationArray(@Nullable Annotation[] annotations, @Nullable Object annotatedElement) {
+	static Annotation[] synthesizeAnnotationArray(Annotation[] annotations, @Nullable Object annotatedElement) {
 		if (annotations == null) {
 			return null;
 		}

spring-core/src/main/java/org/springframework/core/env/PropertySourcesPropertyResolver.java

@@ -38,7 +38,7 @@ public class PropertySourcesPropertyResolver extends AbstractPropertyResolver {
 	 * Create a new resolver against the given property sources.
 	 * @param propertySources the set of {@link PropertySource} objects to use
 	 */
-	public PropertySourcesPropertyResolver(PropertySources propertySources) {
+	public PropertySourcesPropertyResolver(@Nullable PropertySources propertySources) {
 		this.propertySources = propertySources;
 	}
 

spring-core/src/main/java/org/springframework/lang/NonNullApi.java

@@ -18,6 +18,7 @@ import javax.annotation.meta.TypeQualifierDefault;
  *
  * @author Sebastien Deleuze
  * @since 5.0
+ * @see NonNull
  * @see javax.annotation.Nonnull
  */
 @Documented

spring-core/src/main/java/org/springframework/util/ReflectionUtils.java

@@ -140,7 +140,8 @@ public abstract class ReflectionUtils {
 	 * @param target the target object from which to get the field
 	 * @return the field's current value
 	 */
-	public static Object getField(Field field, Object target) {
+	@Nullable
+	public static Object getField(Field field, @Nullable Object target) {
 		try {
 			return field.get(target);
 		}

spring-core/src/main/java/org/springframework/util/StringUtils.java

@@ -978,7 +978,7 @@ public abstract class StringUtils {
 	 * @param array the original {@code String} array
 	 * @return the resulting array (of the same size) with trimmed elements
 	 */
-	public static String[] trimArrayElements(String[] array) {
+	public static String[] trimArrayElements(@Nullable String[] array) {
 		if (ObjectUtils.isEmpty(array)) {
 			return new String[0];
 		}

spring-web/src/main/java/org/springframework/web/context/WebApplicationContext.java

@@ -19,6 +19,7 @@ package org.springframework.web.context;
 import javax.servlet.ServletContext;
 
 import org.springframework.context.ApplicationContext;
+import org.springframework.lang.Nullable;
 
 /**
  * Interface to provide configuration for a web application. This is read-only while
@@ -100,6 +101,7 @@ public interface WebApplicationContext extends ApplicationContext {
 	 * Return the standard Servlet API ServletContext for this application.
 	 * <p>Also available for a Portlet application, in addition to the PortletContext.
 	 */
+	@Nullable
 	ServletContext getServletContext();
 
 }

spring-web/src/main/java/org/springframework/web/util/HtmlUtils.java

@@ -16,6 +16,7 @@
 
 package org.springframework.web.util;
 
+import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -58,7 +59,7 @@ public abstract class HtmlUtils {
 	 * @param input the (unescaped) input string
 	 * @return the escaped string
 	 */
-	public static String htmlEscape(String input) {
+	public static String htmlEscape(@Nullable String input) {
 		return htmlEscape(input, WebUtils.DEFAULT_CHARACTER_ENCODING);
 	}
 
@@ -78,7 +79,7 @@ public abstract class HtmlUtils {
 	 * @return the escaped string
 	 * @since 4.1.2
 	 */
-	public static String htmlEscape(String input, String encoding) {
+	public static String htmlEscape(@Nullable String input, String encoding) {
 		Assert.notNull(encoding, "Encoding is required");
 		if (input == null) {
 			return null;
@@ -109,7 +110,7 @@ public abstract class HtmlUtils {
 	 * @param input the (unescaped) input string
 	 * @return the escaped string
 	 */
-	public static String htmlEscapeDecimal(String input) {
+	public static String htmlEscapeDecimal(@Nullable String input) {
 		return htmlEscapeDecimal(input, WebUtils.DEFAULT_CHARACTER_ENCODING);
 	}
 
@@ -129,7 +130,7 @@ public abstract class HtmlUtils {
 	 * @return the escaped string
 	 * @since 4.1.2
 	 */
-	public static String htmlEscapeDecimal(String input, String encoding) {
+	public static String htmlEscapeDecimal(@Nullable String input, String encoding) {
 		Assert.notNull(encoding, "Encoding is required");
 		if (input == null) {
 			return null;
@@ -161,7 +162,7 @@ public abstract class HtmlUtils {
 	 * @param input the (unescaped) input string
 	 * @return the escaped string
 	 */
-	public static String htmlEscapeHex(String input) {
+	public static String htmlEscapeHex(@Nullable String input) {
 		return htmlEscapeHex(input, WebUtils.DEFAULT_CHARACTER_ENCODING);
 	}
 
@@ -181,7 +182,7 @@ public abstract class HtmlUtils {
 	 * @return the escaped string
 	 * @since 4.1.2
 	 */
-	public static String htmlEscapeHex(String input, String encoding) {
+	public static String htmlEscapeHex(@Nullable String input, String encoding) {
 		Assert.notNull(encoding, "Encoding is required");
 		if (input == null) {
 			return null;
@@ -220,7 +221,7 @@ public abstract class HtmlUtils {
 	 * @param input the (escaped) input string
 	 * @return the unescaped string
 	 */
-	public static String htmlUnescape(String input) {
+	public static String htmlUnescape(@Nullable String input) {
 		if (input == null) {
 			return null;
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/RequestMappingInfo.java

@@ -69,9 +69,9 @@ public final class RequestMappingInfo implements RequestCondition<RequestMapping
 	private final RequestConditionHolder customConditionHolder;
 
 
-	public RequestMappingInfo(String name, PatternsRequestCondition patterns, RequestMethodsRequestCondition methods,
-			ParamsRequestCondition params, HeadersRequestCondition headers, ConsumesRequestCondition consumes,
-			ProducesRequestCondition produces, RequestCondition<?> custom) {
+	public RequestMappingInfo(@Nullable String name, @Nullable PatternsRequestCondition patterns, @Nullable RequestMethodsRequestCondition methods,
+			@Nullable ParamsRequestCondition params, @Nullable HeadersRequestCondition headers, @Nullable ConsumesRequestCondition consumes,
+			@Nullable ProducesRequestCondition produces, @Nullable RequestCondition<?> custom) {
 
 		this.name = (StringUtils.hasText(name) ? name : null);
 		this.patternsCondition = (patterns != null ? patterns : new PatternsRequestCondition());
@@ -86,9 +86,9 @@ public final class RequestMappingInfo implements RequestCondition<RequestMapping
 	/**
 	 * Creates a new instance with the given request conditions.
 	 */
-	public RequestMappingInfo(PatternsRequestCondition patterns, RequestMethodsRequestCondition methods,
-			ParamsRequestCondition params, HeadersRequestCondition headers, ConsumesRequestCondition consumes,
-			ProducesRequestCondition produces, RequestCondition<?> custom) {
+	public RequestMappingInfo(@Nullable PatternsRequestCondition patterns, @Nullable RequestMethodsRequestCondition methods,
+			@Nullable ParamsRequestCondition params, @Nullable HeadersRequestCondition headers, @Nullable ConsumesRequestCondition consumes,
+			@Nullable ProducesRequestCondition produces, @Nullable RequestCondition<?> custom) {
 
 		this(null, patterns, methods, params, headers, consumes, produces, custom);
 	}
@@ -96,7 +96,7 @@ public final class RequestMappingInfo implements RequestCondition<RequestMapping
 	/**
 	 * Re-create a RequestMappingInfo with the given custom request condition.
 	 */
-	public RequestMappingInfo(RequestMappingInfo info, RequestCondition<?> customRequestCondition) {
+	public RequestMappingInfo(RequestMappingInfo info, @Nullable RequestCondition<?> customRequestCondition) {
 		this(info.name, info.patternsCondition, info.methodsCondition, info.paramsCondition, info.headersCondition,
 				info.consumesCondition, info.producesCondition, customRequestCondition);
 	}

spring-webmvc/src/main/java/org/springframework/web/servlet/HandlerExecutionChain.java

@@ -54,7 +54,7 @@ public class HandlerExecutionChain {
 	 * Create a new HandlerExecutionChain.
 	 * @param handler the handler object to execute
 	 */
-	public HandlerExecutionChain(Object handler) {
+	public HandlerExecutionChain(@Nullable Object handler) {
 		this(handler, (HandlerInterceptor[]) null);
 	}
 
@@ -64,7 +64,7 @@ public class HandlerExecutionChain {
 	 * @param interceptors the array of interceptors to apply
 	 * (in the given order) before the handler itself executes
 	 */
-	public HandlerExecutionChain(Object handler, HandlerInterceptor... interceptors) {
+	public HandlerExecutionChain(@Nullable Object handler, HandlerInterceptor... interceptors) {
 		if (handler instanceof HandlerExecutionChain) {
 			HandlerExecutionChain originalChain = (HandlerExecutionChain) handler;
 			this.handler = originalChain.getHandler();

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

@@ -71,9 +71,9 @@ public final class RequestMappingInfo implements RequestCondition<RequestMapping
 	private final RequestConditionHolder customConditionHolder;
 
 
-	public RequestMappingInfo(String name, PatternsRequestCondition patterns, RequestMethodsRequestCondition methods,
-			ParamsRequestCondition params, HeadersRequestCondition headers, ConsumesRequestCondition consumes,
-			ProducesRequestCondition produces, RequestCondition<?> custom) {
+	public RequestMappingInfo(@Nullable String name, @Nullable PatternsRequestCondition patterns, @Nullable RequestMethodsRequestCondition methods,
+			@Nullable ParamsRequestCondition params, @Nullable HeadersRequestCondition headers, @Nullable ConsumesRequestCondition consumes,
+			@Nullable ProducesRequestCondition produces, @Nullable RequestCondition<?> custom) {
 
 		this.name = (StringUtils.hasText(name) ? name : null);
 		this.patternsCondition = (patterns != null ? patterns : new PatternsRequestCondition());
@@ -88,9 +88,9 @@ public final class RequestMappingInfo implements RequestCondition<RequestMapping
 	/**
 	 * Creates a new instance with the given request conditions.
 	 */
-	public RequestMappingInfo(PatternsRequestCondition patterns, RequestMethodsRequestCondition methods,
-			ParamsRequestCondition params, HeadersRequestCondition headers, ConsumesRequestCondition consumes,
-			ProducesRequestCondition produces, RequestCondition<?> custom) {
+	public RequestMappingInfo(@Nullable PatternsRequestCondition patterns, @Nullable RequestMethodsRequestCondition methods,
+			@Nullable ParamsRequestCondition params, @Nullable HeadersRequestCondition headers, @Nullable ConsumesRequestCondition consumes,
+			@Nullable ProducesRequestCondition produces, @Nullable RequestCondition<?> custom) {
 
 		this(null, patterns, methods, params, headers, consumes, produces, custom);
 	}
@@ -98,7 +98,7 @@ public final class RequestMappingInfo implements RequestCondition<RequestMapping
 	/**
 	 * Re-create a RequestMappingInfo with the given custom request condition.
 	 */
-	public RequestMappingInfo(RequestMappingInfo info, RequestCondition<?> customRequestCondition) {
+	public RequestMappingInfo(RequestMappingInfo info, @Nullable RequestCondition<?> customRequestCondition) {
 		this(info.name, info.patternsCondition, info.methodsCondition, info.paramsCondition, info.headersCondition,
 				info.consumesCondition, info.producesCondition, customRequestCondition);
 	}