Add converters between Enum and Integer

spring-core/src/main/java/org/springframework/core/convert/support/DefaultConversionService.java

@@ -142,6 +142,9 @@ public class DefaultConversionService extends GenericConversionService {
 
 		converterRegistry.addConverterFactory(new StringToEnumConverterFactory());
 		converterRegistry.addConverter(new EnumToStringConverter((ConversionService) converterRegistry));
+		
+		converterRegistry.addConverterFactory(new IntegerToEnumConverterFactory());
+		converterRegistry.addConverter(new EnumToIntegerConverter((ConversionService) converterRegistry));
 
 		converterRegistry.addConverter(new StringToLocaleConverter());
 		converterRegistry.addConverter(Locale.class, String.class, new ObjectToStringConverter());

spring-core/src/main/java/org/springframework/core/convert/support/EnumToIntegerConverter.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.convert.support;
+
+import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.TypeDescriptor;
+import org.springframework.core.convert.converter.ConditionalConverter;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.util.ClassUtils;
+
+/**
+ * Calls {@link Enum#ordinal()} to convert a source Enum to a Integer.
+ * This converter will not match enums with interfaces that can be converted.
+ *
+ * @author Yanming Zhou (zhouyanming@gmail.com)
+ * @since 4.3
+ */
+final class EnumToIntegerConverter implements Converter<Enum<?>, Integer>, ConditionalConverter {
+
+	private final ConversionService conversionService;
+
+
+	public EnumToIntegerConverter(ConversionService conversionService) {
+		this.conversionService = conversionService;
+	}
+
+
+	@Override
+	public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
+		for (Class<?> interfaceType : ClassUtils.getAllInterfacesForClass(sourceType.getType())) {
+			if (this.conversionService.canConvert(TypeDescriptor.valueOf(interfaceType), targetType)) {
+				return false;
+			}
+		}
+		return true;
+	}
+
+	@Override
+	public Integer convert(Enum<?> source) {
+		return source.ordinal();
+	}
+
+}

spring-core/src/main/java/org/springframework/core/convert/support/IntegerToEnumConverterFactory.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.core.convert.support;
+
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.core.convert.converter.ConverterFactory;
+
+/**
+ * Converts from a Integer to a {@link java.lang.Enum} by calling {@link Class#getEnumConstants()}.
+ *
+ * @author Yanming Zhou (zhouyanming@gmail.com)
+ * @since 4.3
+ */
+@SuppressWarnings({"unchecked", "rawtypes"})
+final class IntegerToEnumConverterFactory implements ConverterFactory<Integer, Enum> {
+
+	@Override
+	public <T extends Enum> Converter<Integer, T> getConverter(Class<T> targetType) {
+		Class<?> enumType = targetType;
+		while (enumType != null && !enumType.isEnum()) {
+			enumType = enumType.getSuperclass();
+		}
+		if (enumType == null) {
+			throw new IllegalArgumentException(
+					"The target type " + targetType.getName() + " does not refer to an enum");
+		}
+		return new IntegerToEnum(enumType);
+	}
+
+
+	private class IntegerToEnum<T extends Enum> implements Converter<Integer, T> {
+
+		private final Class<T> enumType;
+
+		public IntegerToEnum(Class<T> enumType) {
+			this.enumType = enumType;
+		}
+
+		@Override
+		public T convert(Integer source) {
+			if (source == null) {
+				return null;
+			}
+			return enumType.getEnumConstants()[source];
+		}
+	}
+
+}

spring-core/src/test/java/org/springframework/core/convert/support/DefaultConversionServiceTests.java

@@ -243,6 +243,26 @@ public class DefaultConversionServiceTests {
 	public void testEnumToString() {
 		assertEquals("BAR", conversionService.convert(Foo.BAR, String.class));
 	}
+	
+	@Test
+	public void testIntegerToEnum() throws Exception {
+		assertEquals(Foo.BAR, conversionService.convert(0, Foo.class));
+	}
+	
+	@Test
+	public void testIntegerToEnumWithSubclass() throws Exception {
+		assertEquals(SubFoo.BAZ, conversionService.convert(1, SubFoo.BAR.getClass()));
+	}
+	
+	@Test
+	public void testIntegerToEnumNull() {
+		assertEquals(null, conversionService.convert(null, Foo.class));
+	}
+	
+	@Test
+	public void testEnumToInteger() {
+		assertEquals(0, conversionService.convert(Foo.BAR, Integer.class));
+	}
 
 	@Test
 	public void testStringToEnumSet() throws Exception {