001/* 002 * Copyright 2002-2018 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.http.converter; 018 019import java.io.IOException; 020import java.io.OutputStream; 021import java.lang.reflect.Type; 022 023import org.springframework.http.HttpHeaders; 024import org.springframework.http.HttpOutputMessage; 025import org.springframework.http.MediaType; 026import org.springframework.http.StreamingHttpOutputMessage; 027import org.springframework.lang.Nullable; 028 029/** 030 * Abstract base class for most {@link GenericHttpMessageConverter} implementations. 031 * 032 * @author Sebastien Deleuze 033 * @author Juergen Hoeller 034 * @since 4.2 035 * @param <T> the converted object type 036 */ 037public abstract class AbstractGenericHttpMessageConverter<T> extends AbstractHttpMessageConverter<T> 038 implements GenericHttpMessageConverter<T> { 039 040 /** 041 * Construct an {@code AbstractGenericHttpMessageConverter} with no supported media types. 042 * @see #setSupportedMediaTypes 043 */ 044 protected AbstractGenericHttpMessageConverter() { 045 } 046 047 /** 048 * Construct an {@code AbstractGenericHttpMessageConverter} with one supported media type. 049 * @param supportedMediaType the supported media type 050 */ 051 protected AbstractGenericHttpMessageConverter(MediaType supportedMediaType) { 052 super(supportedMediaType); 053 } 054 055 /** 056 * Construct an {@code AbstractGenericHttpMessageConverter} with multiple supported media type. 057 * @param supportedMediaTypes the supported media types 058 */ 059 protected AbstractGenericHttpMessageConverter(MediaType... supportedMediaTypes) { 060 super(supportedMediaTypes); 061 } 062 063 064 @Override 065 protected boolean supports(Class<?> clazz) { 066 return true; 067 } 068 069 @Override 070 public boolean canRead(Type type, @Nullable Class<?> contextClass, @Nullable MediaType mediaType) { 071 return (type instanceof Class ? canRead((Class<?>) type, mediaType) : canRead(mediaType)); 072 } 073 074 @Override 075 public boolean canWrite(@Nullable Type type, Class<?> clazz, @Nullable MediaType mediaType) { 076 return canWrite(clazz, mediaType); 077 } 078 079 /** 080 * This implementation sets the default headers by calling {@link #addDefaultHeaders}, 081 * and then calls {@link #writeInternal}. 082 */ 083 @Override 084 public final void write(final T t, @Nullable final Type type, @Nullable MediaType contentType, 085 HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException { 086 087 final HttpHeaders headers = outputMessage.getHeaders(); 088 addDefaultHeaders(headers, t, contentType); 089 090 if (outputMessage instanceof StreamingHttpOutputMessage) { 091 StreamingHttpOutputMessage streamingOutputMessage = (StreamingHttpOutputMessage) outputMessage; 092 streamingOutputMessage.setBody(outputStream -> writeInternal(t, type, new HttpOutputMessage() { 093 @Override 094 public OutputStream getBody() { 095 return outputStream; 096 } 097 @Override 098 public HttpHeaders getHeaders() { 099 return headers; 100 } 101 })); 102 } 103 else { 104 writeInternal(t, type, outputMessage); 105 outputMessage.getBody().flush(); 106 } 107 } 108 109 @Override 110 protected void writeInternal(T t, HttpOutputMessage outputMessage) 111 throws IOException, HttpMessageNotWritableException { 112 113 writeInternal(t, null, outputMessage); 114 } 115 116 /** 117 * Abstract template method that writes the actual body. Invoked from {@link #write}. 118 * @param t the object to write to the output message 119 * @param type the type of object to write (may be {@code null}) 120 * @param outputMessage the HTTP output message to write to 121 * @throws IOException in case of I/O errors 122 * @throws HttpMessageNotWritableException in case of conversion errors 123 */ 124 protected abstract void writeInternal(T t, @Nullable Type type, HttpOutputMessage outputMessage) 125 throws IOException, HttpMessageNotWritableException; 126 127}