org.springframework.core.convert.converter.GenericConverter Maven / Gradle / Ivy
/*
* Copyright 2002-2017 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
*
* https://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.converter;
import java.util.Set;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* Generic converter interface for converting between two or more types.
*
* This is the most flexible of the Converter SPI interfaces, but also the most complex.
* It is flexible in that a GenericConverter may support converting between multiple source/target
* type pairs (see {@link #getConvertibleTypes()}. In addition, GenericConverter implementations
* have access to source/target {@link TypeDescriptor field context} during the type conversion
* process. This allows for resolving source and target field metadata such as annotations and
* generics information, which can be used to influence the conversion logic.
*
*
This interface should generally not be used when the simpler {@link Converter} or
* {@link ConverterFactory} interface is sufficient.
*
*
Implementations may additionally implement {@link ConditionalConverter}.
*
* @author Keith Donald
* @author Juergen Hoeller
* @since 3.0
* @see TypeDescriptor
* @see Converter
* @see ConverterFactory
* @see ConditionalConverter
*/
public interface GenericConverter {
/**
* Return the source and target types that this converter can convert between.
*
Each entry is a convertible source-to-target type pair.
*
For {@link ConditionalConverter conditional converters} this method may return
* {@code null} to indicate all source-to-target pairs should be considered.
*/
@Nullable
Set getConvertibleTypes();
/**
* Convert the source object to the targetType described by the {@code TypeDescriptor}.
* @param source the source object to convert (may be {@code null})
* @param sourceType the type descriptor of the field we are converting from
* @param targetType the type descriptor of the field we are converting to
* @return the converted object
*/
@Nullable
Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType);
/**
* Holder for a source-to-target class pair.
*/
final class ConvertiblePair {
private final Class sourceType;
private final Class targetType;
/**
* Create a new source-to-target pair.
* @param sourceType the source type
* @param targetType the target type
*/
public ConvertiblePair(Class sourceType, Class targetType) {
Assert.notNull(sourceType, "Source type must not be null");
Assert.notNull(targetType, "Target type must not be null");
this.sourceType = sourceType;
this.targetType = targetType;
}
public Class getSourceType() {
return this.sourceType;
}
public Class getTargetType() {
return this.targetType;
}
@Override
public boolean equals(@Nullable Object other) {
if (this == other) {
return true;
}
if (other == null || other.getClass() != ConvertiblePair.class) {
return false;
}
ConvertiblePair otherPair = (ConvertiblePair) other;
return (this.sourceType == otherPair.sourceType && this.targetType == otherPair.targetType);
}
@Override
public int hashCode() {
return (this.sourceType.hashCode() * 31 + this.targetType.hashCode());
}
@Override
public String toString() {
return (this.sourceType.getName() + " -> " + this.targetType.getName());
}
}
}