org.springframework.core.convert.support.ObjectToObjectConverter Maven / Gradle / Ivy
/*
* Copyright 2002-2013 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 java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.Set;
import org.springframework.core.convert.ConversionFailedException;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;
/**
* Generic converter that attempts to convert a source Object to a target type
* by delegating to methods on the target type.
*
* Calls a static {@code valueOf(sourceType)} or Java 8 style {@code of|from(sourceType)}
* method on the target type to perform the conversion, if such a method exists. Otherwise,
* it checks for a {@code to[targetType.simpleName]} method on the source type calls
* the target type's constructor that accepts a single {@code sourceType} argument, if such
* a constructor exists. If neither strategy works, it throws a ConversionFailedException.
*
* @author Keith Donald
* @author Juergen Hoeller
* @since 3.0
*/
final class ObjectToObjectConverter implements ConditionalGenericConverter {
@Override
public Set getConvertibleTypes() {
return Collections.singleton(new ConvertiblePair(Object.class, Object.class));
}
@Override
public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
if (sourceType.getType().equals(targetType.getType())) {
// no conversion required
return false;
}
return (String.class.equals(targetType.getType()) ?
(ClassUtils.getConstructorIfAvailable(String.class, sourceType.getType()) != null) :
hasToMethodOrOfMethodOrConstructor(targetType.getType(), sourceType.getType()));
}
@Override
public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (source == null) {
return null;
}
Class sourceClass = sourceType.getType();
Class targetClass = targetType.getType();
try {
if (!String.class.equals(targetClass)) {
Method method = getToMethod(targetClass, sourceClass);
if (method != null) {
ReflectionUtils.makeAccessible(method);
return method.invoke(source);
}
method = getOfMethod(targetClass, sourceClass);
if (method != null) {
ReflectionUtils.makeAccessible(method);
return method.invoke(null, source);
}
}
Constructor constructor = ClassUtils.getConstructorIfAvailable(targetClass, sourceClass);
if (constructor != null) {
return constructor.newInstance(source);
}
}
catch (InvocationTargetException ex) {
throw new ConversionFailedException(sourceType, targetType, source, ex.getTargetException());
}
catch (Throwable ex) {
throw new ConversionFailedException(sourceType, targetType, source, ex);
}
throw new IllegalStateException("No static valueOf/of/from(" + sourceClass.getName() +
") method or Constructor(" + sourceClass.getName() + ") exists on " + targetClass.getName());
}
private static boolean hasToMethodOrOfMethodOrConstructor(Class targetClass, Class sourceClass) {
return (getToMethod(targetClass, sourceClass) != null ||
getOfMethod(targetClass, sourceClass) != null ||
ClassUtils.getConstructorIfAvailable(targetClass, sourceClass) != null);
}
private static Method getToMethod(Class targetClass, Class sourceClass) {
Method method = ClassUtils.getMethodIfAvailable(sourceClass, "to" + targetClass.getSimpleName());
return (method != null && targetClass.equals(method.getReturnType()) ? method : null);
}
static Method getOfMethod(Class targetClass, Class sourceClass) {
Method method = ClassUtils.getStaticMethod(targetClass, "valueOf", sourceClass);
if (method == null) {
method = ClassUtils.getStaticMethod(targetClass, "of", sourceClass);
if (method == null) {
method = ClassUtils.getStaticMethod(targetClass, "from", sourceClass);
}
}
return method;
}
}