org.springframework.core.convert.support.GenericConversionService Maven / Gradle / Ivy
/*
* Copyright 2002-2015 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.Array;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.springframework.core.ResolvableType;
import org.springframework.core.convert.ConversionException;
import org.springframework.core.convert.ConversionFailedException;
import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.ConverterNotFoundException;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalConverter;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.core.convert.converter.Converter;
import org.springframework.core.convert.converter.ConverterFactory;
import org.springframework.core.convert.converter.ConverterRegistry;
import org.springframework.core.convert.converter.GenericConverter;
import org.springframework.core.convert.converter.GenericConverter.ConvertiblePair;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ConcurrentReferenceHashMap;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
/**
* Base {@link ConversionService} implementation suitable for use in most environments.
* Indirectly implements {@link ConverterRegistry} as registration API through the
* {@link ConfigurableConversionService} interface.
*
* @author Keith Donald
* @author Juergen Hoeller
* @author Chris Beams
* @author Phillip Webb
* @author David Haraburda
* @since 3.0
*/
public class GenericConversionService implements ConfigurableConversionService {
/**
* General NO-OP converter used when conversion is not required.
*/
private static final GenericConverter NO_OP_CONVERTER = new NoOpConverter("NO_OP");
/**
* Used as a cache entry when no converter is available. This converter is never
* returned.
*/
private static final GenericConverter NO_MATCH = new NoOpConverter("NO_MATCH");
/** Java 8's java.util.Optional.empty() */
private static Object javaUtilOptionalEmpty = null;
static {
try {
Class clazz = ClassUtils.forName("java.util.Optional", GenericConversionService.class.getClassLoader());
javaUtilOptionalEmpty = ClassUtils.getMethod(clazz, "empty").invoke(null);
}
catch (Exception ex) {
// Java 8 not available - conversion to Optional not supported then.
}
}
private final Converters converters = new Converters();
private final Map converterCache =
new ConcurrentReferenceHashMap(64);
// ConverterRegistry implementation
@Override
public void addConverter(Converter converter) {
ResolvableType[] typeInfo = getRequiredTypeInfo(converter, Converter.class);
Assert.notNull(typeInfo, "Unable to the determine sourceType and targetType " +
" which your Converter converts between; declare these generic types.");
addConverter(new ConverterAdapter(converter, typeInfo[0], typeInfo[1]));
}
@Override
public void addConverter(Class sourceType, Class targetType, Converter converter) {
addConverter(new ConverterAdapter(
converter, ResolvableType.forClass(sourceType), ResolvableType.forClass(targetType)));
}
@Override
public void addConverter(GenericConverter converter) {
this.converters.add(converter);
invalidateCache();
}
@Override
public void addConverterFactory(ConverterFactory converterFactory) {
ResolvableType[] typeInfo = getRequiredTypeInfo(converterFactory, ConverterFactory.class);
Assert.notNull(typeInfo, "Unable to the determine source type and target range type R which your " +
"ConverterFactory converts between; declare these generic types.");
addConverter(new ConverterFactoryAdapter(converterFactory,
new ConvertiblePair(typeInfo[0].resolve(), typeInfo[1].resolve())));
}
@Override
public void removeConvertible(Class sourceType, Class targetType) {
this.converters.remove(sourceType, targetType);
invalidateCache();
}
// ConversionService implementation
@Override
public boolean canConvert(Class sourceType, Class targetType) {
Assert.notNull(targetType, "targetType to convert to cannot be null");
return canConvert((sourceType != null ? TypeDescriptor.valueOf(sourceType) : null),
TypeDescriptor.valueOf(targetType));
}
@Override
public boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType) {
Assert.notNull(targetType, "targetType to convert to cannot be null");
if (sourceType == null) {
return true;
}
GenericConverter converter = getConverter(sourceType, targetType);
return (converter != null);
}
/**
* Return whether conversion between the sourceType and targetType can be bypassed.
* More precisely, this method will return true if objects of sourceType can be
* converted to the targetType by returning the source object unchanged.
* @param sourceType context about the source type to convert from
* (may be {@code null} if source is {@code null})
* @param targetType context about the target type to convert to (required)
* @return {@code true} if conversion can be bypassed; {@code false} otherwise
* @throws IllegalArgumentException if targetType is {@code null}
* @since 3.2
*/
public boolean canBypassConvert(TypeDescriptor sourceType, TypeDescriptor targetType) {
Assert.notNull(targetType, "targetType to convert to cannot be null");
if (sourceType == null) {
return true;
}
GenericConverter converter = getConverter(sourceType, targetType);
return (converter == NO_OP_CONVERTER);
}
@Override
@SuppressWarnings("unchecked")
public T convert(Object source, Class targetType) {
Assert.notNull(targetType, "targetType to convert to cannot be null");
return (T) convert(source, TypeDescriptor.forObject(source), TypeDescriptor.valueOf(targetType));
}
@Override
public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
Assert.notNull(targetType, "targetType to convert to cannot be null");
if (sourceType == null) {
Assert.isTrue(source == null, "source must be [null] if sourceType == [null]");
return handleResult(null, targetType, convertNullSource(null, targetType));
}
if (source != null && !sourceType.getObjectType().isInstance(source)) {
throw new IllegalArgumentException("source to convert from must be an instance of " +
sourceType + "; instead it was a " + source.getClass().getName());
}
GenericConverter converter = getConverter(sourceType, targetType);
if (converter != null) {
Object result = ConversionUtils.invokeConverter(converter, source, sourceType, targetType);
return handleResult(sourceType, targetType, result);
}
return handleConverterNotFound(source, sourceType, targetType);
}
/**
* Convenience operation for converting a source object to the specified targetType,
* where the targetType is a descriptor that provides additional conversion context.
* Simply delegates to {@link #convert(Object, TypeDescriptor, TypeDescriptor)} and
* encapsulates the construction of the sourceType descriptor using
* {@link TypeDescriptor#forObject(Object)}.
* @param source the source object
* @param targetType the target type
* @return the converted value
* @throws ConversionException if a conversion exception occurred
* @throws IllegalArgumentException if targetType is {@code null},
* or sourceType is {@code null} but source is not {@code null}
*/
public Object convert(Object source, TypeDescriptor targetType) {
return convert(source, TypeDescriptor.forObject(source), targetType);
}
@Override
public String toString() {
return this.converters.toString();
}
// Protected template methods
/**
* Template method to convert a {@code null} source.
* The default implementation returns {@code null} or the Java 8
* {@link java.util.Optional#empty()} instance if the target type is
* {@code java.util.Optional}. Subclasses may override this to return
* custom {@code null} objects for specific target types.
* @param sourceType the sourceType to convert from
* @param targetType the targetType to convert to
* @return the converted null object
*/
protected Object convertNullSource(TypeDescriptor sourceType, TypeDescriptor targetType) {
if (javaUtilOptionalEmpty != null && targetType.getObjectType().equals(javaUtilOptionalEmpty.getClass())) {
return javaUtilOptionalEmpty;
}
return null;
}
/**
* Hook method to lookup the converter for a given sourceType/targetType pair.
* First queries this ConversionService's converter cache.
* On a cache miss, then performs an exhaustive search for a matching converter.
* If no converter matches, returns the default converter.
* @param sourceType the source type to convert from
* @param targetType the target type to convert to
* @return the generic converter that will perform the conversion,
* or {@code null} if no suitable converter was found
* @see #getDefaultConverter(TypeDescriptor, TypeDescriptor)
*/
protected GenericConverter getConverter(TypeDescriptor sourceType, TypeDescriptor targetType) {
ConverterCacheKey key = new ConverterCacheKey(sourceType, targetType);
GenericConverter converter = this.converterCache.get(key);
if (converter != null) {
return (converter != NO_MATCH ? converter : null);
}
converter = this.converters.find(sourceType, targetType);
if (converter == null) {
converter = getDefaultConverter(sourceType, targetType);
}
if (converter != null) {
this.converterCache.put(key, converter);
return converter;
}
this.converterCache.put(key, NO_MATCH);
return null;
}
/**
* Return the default converter if no converter is found for the given sourceType/targetType pair.
*
Returns a NO_OP Converter if the sourceType is assignable to the targetType.
* Returns {@code null} otherwise, indicating no suitable converter could be found.
* @param sourceType the source type to convert from
* @param targetType the target type to convert to
* @return the default generic converter that will perform the conversion
*/
protected GenericConverter getDefaultConverter(TypeDescriptor sourceType, TypeDescriptor targetType) {
return (sourceType.isAssignableTo(targetType) ? NO_OP_CONVERTER : null);
}
// Internal helpers
private ResolvableType[] getRequiredTypeInfo(Object converter, Class genericIfc) {
ResolvableType resolvableType = ResolvableType.forClass(converter.getClass()).as(genericIfc);
ResolvableType[] generics = resolvableType.getGenerics();
if (generics.length < 2) {
return null;
}
Class sourceType = generics[0].resolve();
Class targetType = generics[1].resolve();
if (sourceType == null || targetType == null) {
return null;
}
return generics;
}
private void invalidateCache() {
this.converterCache.clear();
}
private Object handleConverterNotFound(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (source == null) {
assertNotPrimitiveTargetType(sourceType, targetType);
return null;
}
if (sourceType.isAssignableTo(targetType) && targetType.getObjectType().isInstance(source)) {
return source;
}
throw new ConverterNotFoundException(sourceType, targetType);
}
private Object handleResult(TypeDescriptor sourceType, TypeDescriptor targetType, Object result) {
if (result == null) {
assertNotPrimitiveTargetType(sourceType, targetType);
}
return result;
}
private void assertNotPrimitiveTargetType(TypeDescriptor sourceType, TypeDescriptor targetType) {
if (targetType.isPrimitive()) {
throw new ConversionFailedException(sourceType, targetType, null,
new IllegalArgumentException("A null value cannot be assigned to a primitive type"));
}
}
/**
* Adapts a {@link Converter} to a {@link GenericConverter}.
*/
@SuppressWarnings("unchecked")
private final class ConverterAdapter implements ConditionalGenericConverter {
private final Converter converter;
private final ConvertiblePair typeInfo;
private final ResolvableType targetType;
public ConverterAdapter(Converter converter, ResolvableType sourceType, ResolvableType targetType) {
this.converter = (Converter) converter;
this.typeInfo = new ConvertiblePair(sourceType.resolve(Object.class), targetType.resolve(Object.class));
this.targetType = targetType;
}
@Override
public Set getConvertibleTypes() {
return Collections.singleton(this.typeInfo);
}
@Override
public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
// Check raw type first...
if (!this.typeInfo.getTargetType().equals(targetType.getObjectType())) {
return false;
}
// Full check for complex generic type match required?
ResolvableType rt = targetType.getResolvableType();
if (!(rt.getType() instanceof Class) && !rt.isAssignableFrom(this.targetType) &&
!this.targetType.hasUnresolvableGenerics()) {
return false;
}
return !(this.converter instanceof ConditionalConverter) ||
((ConditionalConverter) this.converter).matches(sourceType, targetType);
}
@Override
public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (source == null) {
return convertNullSource(sourceType, targetType);
}
return this.converter.convert(source);
}
@Override
public String toString() {
return (this.typeInfo + " : " + this.converter);
}
}
/**
* Adapts a {@link ConverterFactory} to a {@link GenericConverter}.
*/
@SuppressWarnings("unchecked")
private final class ConverterFactoryAdapter implements ConditionalGenericConverter {
private final ConverterFactory converterFactory;
private final ConvertiblePair typeInfo;
public ConverterFactoryAdapter(ConverterFactory converterFactory, ConvertiblePair typeInfo) {
this.converterFactory = (ConverterFactory) converterFactory;
this.typeInfo = typeInfo;
}
@Override
public Set getConvertibleTypes() {
return Collections.singleton(this.typeInfo);
}
@Override
public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
boolean matches = true;
if (this.converterFactory instanceof ConditionalConverter) {
matches = ((ConditionalConverter) this.converterFactory).matches(sourceType, targetType);
}
if (matches) {
Converter converter = this.converterFactory.getConverter(targetType.getType());
if (converter instanceof ConditionalConverter) {
matches = ((ConditionalConverter) converter).matches(sourceType, targetType);
}
}
return matches;
}
@Override
public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
if (source == null) {
return convertNullSource(sourceType, targetType);
}
return this.converterFactory.getConverter(targetType.getObjectType()).convert(source);
}
@Override
public String toString() {
return (this.typeInfo + " : " + this.converterFactory);
}
}
/**
* Key for use with the converter cache.
*/
private static final class ConverterCacheKey {
private final TypeDescriptor sourceType;
private final TypeDescriptor targetType;
public ConverterCacheKey(TypeDescriptor sourceType, TypeDescriptor targetType) {
this.sourceType = sourceType;
this.targetType = targetType;
}
@Override
public boolean equals(Object other) {
if (this == other) {
return true;
}
if (!(other instanceof ConverterCacheKey)) {
return false;
}
ConverterCacheKey otherKey = (ConverterCacheKey) other;
return (ObjectUtils.nullSafeEquals(this.sourceType, otherKey.sourceType) &&
ObjectUtils.nullSafeEquals(this.targetType, otherKey.targetType));
}
@Override
public int hashCode() {
return (ObjectUtils.nullSafeHashCode(this.sourceType) * 29 +
ObjectUtils.nullSafeHashCode(this.targetType));
}
@Override
public String toString() {
return ("ConverterCacheKey [sourceType = " + this.sourceType +
", targetType = " + this.targetType + "]");
}
}
/**
* Manages all converters registered with the service.
*/
private static class Converters {
private final Set globalConverters = new LinkedHashSet();
private final Map converters =
new LinkedHashMap(36);
public void add(GenericConverter converter) {
Set convertibleTypes = converter.getConvertibleTypes();
if (convertibleTypes == null) {
Assert.state(converter instanceof ConditionalConverter,
"Only conditional converters may return null convertible types");
this.globalConverters.add(converter);
}
else {
for (ConvertiblePair convertiblePair : convertibleTypes) {
ConvertersForPair convertersForPair = getMatchableConverters(convertiblePair);
convertersForPair.add(converter);
}
}
}
private ConvertersForPair getMatchableConverters(ConvertiblePair convertiblePair) {
ConvertersForPair convertersForPair = this.converters.get(convertiblePair);
if (convertersForPair == null) {
convertersForPair = new ConvertersForPair();
this.converters.put(convertiblePair, convertersForPair);
}
return convertersForPair;
}
public void remove(Class sourceType, Class targetType) {
this.converters.remove(new ConvertiblePair(sourceType, targetType));
}
/**
* Find a {@link GenericConverter} given a source and target type.
* This method will attempt to match all possible converters by working
* through the class and interface hierarchy of the types.
* @param sourceType the source type
* @param targetType the target type
* @return a matching {@link GenericConverter}, or {@code null} if none found
*/
public GenericConverter find(TypeDescriptor sourceType, TypeDescriptor targetType) {
// Search the full type hierarchy
List> sourceCandidates = getClassHierarchy(sourceType.getType());
List> targetCandidates = getClassHierarchy(targetType.getType());
for (Class sourceCandidate : sourceCandidates) {
for (Class targetCandidate : targetCandidates) {
ConvertiblePair convertiblePair = new ConvertiblePair(sourceCandidate, targetCandidate);
GenericConverter converter = getRegisteredConverter(sourceType, targetType, convertiblePair);
if (converter != null) {
return converter;
}
}
}
return null;
}
private GenericConverter getRegisteredConverter(TypeDescriptor sourceType,
TypeDescriptor targetType, ConvertiblePair convertiblePair) {
// Check specifically registered converters
ConvertersForPair convertersForPair = this.converters.get(convertiblePair);
if (convertersForPair != null) {
GenericConverter converter = convertersForPair.getConverter(sourceType, targetType);
if (converter != null) {
return converter;
}
}
// Check ConditionalConverters for a dynamic match
for (GenericConverter globalConverter : this.globalConverters) {
if (((ConditionalConverter) globalConverter).matches(sourceType, targetType)) {
return globalConverter;
}
}
return null;
}
/**
* Returns an ordered class hierarchy for the given type.
* @param type the type
* @return an ordered list of all classes that the given type extends or implements
*/
private List> getClassHierarchy(Class type) {
List> hierarchy = new ArrayList>(20);
Set> visited = new HashSet>(20);
addToClassHierarchy(0, ClassUtils.resolvePrimitiveIfNecessary(type), false, hierarchy, visited);
boolean array = type.isArray();
int i = 0;
while (i < hierarchy.size()) {
Class candidate = hierarchy.get(i);
candidate = (array ? candidate.getComponentType() : ClassUtils.resolvePrimitiveIfNecessary(candidate));
Class superclass = candidate.getSuperclass();
if (superclass != null && superclass != Object.class && superclass != Enum.class) {
addToClassHierarchy(i + 1, candidate.getSuperclass(), array, hierarchy, visited);
}
addInterfacesToClassHierarchy(candidate, array, hierarchy, visited);
i++;
}
if (Enum.class.isAssignableFrom(type)) {
addToClassHierarchy(hierarchy.size(), Enum.class, array, hierarchy, visited);
addToClassHierarchy(hierarchy.size(), Enum.class, false, hierarchy, visited);
addInterfacesToClassHierarchy(Enum.class, array, hierarchy, visited);
}
addToClassHierarchy(hierarchy.size(), Object.class, array, hierarchy, visited);
addToClassHierarchy(hierarchy.size(), Object.class, false, hierarchy, visited);
return hierarchy;
}
private void addInterfacesToClassHierarchy(Class type, boolean asArray,
List> hierarchy, Set> visited) {
for (Class implementedInterface : type.getInterfaces()) {
addToClassHierarchy(hierarchy.size(), implementedInterface, asArray, hierarchy, visited);
}
}
private void addToClassHierarchy(int index, Class type, boolean asArray,
List> hierarchy, Set> visited) {
if (asArray) {
type = Array.newInstance(type, 0).getClass();
}
if (visited.add(type)) {
hierarchy.add(index, type);
}
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append("ConversionService converters =\n");
for (String converterString : getConverterStrings()) {
builder.append('\t').append(converterString).append('\n');
}
return builder.toString();
}
private List getConverterStrings() {
List converterStrings = new ArrayList();
for (ConvertersForPair convertersForPair : converters.values()) {
converterStrings.add(convertersForPair.toString());
}
Collections.sort(converterStrings);
return converterStrings;
}
}
/**
* Manages converters registered with a specific {@link ConvertiblePair}.
*/
private static class ConvertersForPair {
private final LinkedList converters = new LinkedList();
public void add(GenericConverter converter) {
this.converters.addFirst(converter);
}
public GenericConverter getConverter(TypeDescriptor sourceType, TypeDescriptor targetType) {
for (GenericConverter converter : this.converters) {
if (!(converter instanceof ConditionalGenericConverter) ||
((ConditionalGenericConverter) converter).matches(sourceType, targetType)) {
return converter;
}
}
return null;
}
@Override
public String toString() {
return StringUtils.collectionToCommaDelimitedString(this.converters);
}
}
/**
* Internal converter that performs no operation.
*/
private static class NoOpConverter implements GenericConverter {
private final String name;
public NoOpConverter(String name) {
this.name = name;
}
@Override
public Set getConvertibleTypes() {
return null;
}
@Override
public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
return source;
}
@Override
public String toString() {
return this.name;
}
}
}