001/* 002 * Copyright 2002-2015 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.core.convert.converter; 018 019import java.util.Set; 020 021import org.springframework.core.convert.TypeDescriptor; 022import org.springframework.util.Assert; 023 024/** 025 * Generic converter interface for converting between two or more types. 026 * 027 * <p>This is the most flexible of the Converter SPI interfaces, but also the most complex. 028 * It is flexible in that a GenericConverter may support converting between multiple source/target 029 * type pairs (see {@link #getConvertibleTypes()}. In addition, GenericConverter implementations 030 * have access to source/target {@link TypeDescriptor field context} during the type conversion 031 * process. This allows for resolving source and target field metadata such as annotations and 032 * generics information, which can be used to influence the conversion logic. 033 * 034 * <p>This interface should generally not be used when the simpler {@link Converter} or 035 * {@link ConverterFactory} interface is sufficient. 036 * 037 * <p>Implementations may additionally implement {@link ConditionalConverter}. 038 * 039 * @author Keith Donald 040 * @author Juergen Hoeller 041 * @since 3.0 042 * @see TypeDescriptor 043 * @see Converter 044 * @see ConverterFactory 045 * @see ConditionalConverter 046 */ 047public interface GenericConverter { 048 049 /** 050 * Return the source and target types that this converter can convert between. 051 * <p>Each entry is a convertible source-to-target type pair. 052 * <p>For {@link ConditionalConverter conditional converters} this method may return 053 * {@code null} to indicate all source-to-target pairs should be considered. 054 */ 055 Set<ConvertiblePair> getConvertibleTypes(); 056 057 /** 058 * Convert the source object to the targetType described by the {@code TypeDescriptor}. 059 * @param source the source object to convert (may be {@code null}) 060 * @param sourceType the type descriptor of the field we are converting from 061 * @param targetType the type descriptor of the field we are converting to 062 * @return the converted object 063 */ 064 Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType); 065 066 067 /** 068 * Holder for a source-to-target class pair. 069 */ 070 final class ConvertiblePair { 071 072 private final Class<?> sourceType; 073 074 private final Class<?> targetType; 075 076 /** 077 * Create a new source-to-target pair. 078 * @param sourceType the source type 079 * @param targetType the target type 080 */ 081 public ConvertiblePair(Class<?> sourceType, Class<?> targetType) { 082 Assert.notNull(sourceType, "Source type must not be null"); 083 Assert.notNull(targetType, "Target type must not be null"); 084 this.sourceType = sourceType; 085 this.targetType = targetType; 086 } 087 088 public Class<?> getSourceType() { 089 return this.sourceType; 090 } 091 092 public Class<?> getTargetType() { 093 return this.targetType; 094 } 095 096 @Override 097 public boolean equals(Object other) { 098 if (this == other) { 099 return true; 100 } 101 if (other == null || other.getClass() != ConvertiblePair.class) { 102 return false; 103 } 104 ConvertiblePair otherPair = (ConvertiblePair) other; 105 return (this.sourceType == otherPair.sourceType && this.targetType == otherPair.targetType); 106 } 107 108 @Override 109 public int hashCode() { 110 return (this.sourceType.hashCode() * 31 + this.targetType.hashCode()); 111 } 112 113 @Override 114 public String toString() { 115 return (this.sourceType.getName() + " -> " + this.targetType.getName()); 116 } 117 } 118 119}