一、@ResponseBody

@ResponseBody作用於方法上，將返回結果直接以Json等格式返回，直接封裝到response物件的Body中，不經過SpringMVC的檢視解析器。一般用於前後端分離的專案，或者Ajax等非同步請求。

@ResponseBody
public Student getStudent(Integer id){
      Student student = sstudentService.getStudent(id);
　　　　return student;
}
//前端得到的Json資料：
'{"id":"201541030102","name":"劉聰"，"sex":"男"}'
 

二、@RequestBody

@RequestBody作用方法的形參，將前端傳來的Json等格式的資料封裝到javabean中。它會直接讀取讀取Request請求的body部分資料，再使用HttpMessageConverter進行解析。

//前端傳來的的Json資料：
'{"id":"201541030102","name":"劉聰"，"sex":"男"}'

@ResponseBody
public Integer setStudent(@ResponseBody Student student){
      Integer total = sstudentService.setStudent(stedent);
　　　　return total;
}
 

三、HttpMessageConverter

HTTP的請求報文就是一種字串，在java中會被封裝在ServletInputStream流裡，我們在從流中獲得資料，HTTP的響應報文則是通過ServletOutputStream流進行向外輸出的。

獲得請求報文的資訊實際就是HttpMessageConverter介面通過相應的實現類來解析流中的資訊，並轉化為Spring中可以使用的Javabean的過程，響應過程相反。

HttpMessageConverter介面原始碼；

/*
 * Copyright 2002-2010 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.http.converter;

import java.io.IOException;
import java.util.List;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;

/**
 * Strategy interface that specifies a converter that can convert from and to HTTP requests and responses.
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 3.0
 */
public interface HttpMessageConverter<T> {

	/**
	 * Indicates whether the given class can be read by this converter.
	 * @param clazz the class to test for readability
	 * @param mediaType the media type to read, can be {@code null} if not specified.
	 * Typically the value of a {@code Content-Type} header.
	 * @return {@code true} if readable; {@code false} otherwise
	 */
	boolean canRead(Class<?> clazz, MediaType mediaType);

	/**
	 * Indicates whether the given class can be written by this converter.
	 * @param clazz the class to test for writability
	 * @param mediaType the media type to write, can be {@code null} if not specified.
	 * Typically the value of an {@code Accept} header.
	 * @return {@code true} if writable; {@code false} otherwise
	 */
	boolean canWrite(Class<?> clazz, MediaType mediaType);

	/**
	 * Return the list of {@link MediaType} objects supported by this converter.
	 * @return the list of supported media types
	 */
	List<MediaType> getSupportedMediaTypes();

	/**
	 * Read an object of the given type form the given input message, and returns it.
	 * @param clazz the type of object to return. This type must have previously been passed to the
	 * {@link #canRead canRead} method of this interface, which must have returned {@code true}.
	 * @param inputMessage the HTTP input message to read from
	 * @return the converted object
	 * @throws IOException in case of I/O errors
	 * @throws HttpMessageNotReadableException in case of conversion errors
	 */
	T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
			throws IOException, HttpMessageNotReadableException;

	/**
	 * Write an given object to the given output message.
	 * @param t the object to write to the output message. The type of this object must have previously been
	 * passed to the {@link #canWrite canWrite} method of this interface, which must have returned {@code true}.
	 * @param contentType the content type to use when writing. May be {@code null} to indicate that the
	 * default content type of the converter must be used. If not {@code null}, this media type must have
	 * previously been passed to the {@link #canWrite canWrite} method of this interface, which must have
	 * returned {@code true}.
	 * @param outputMessage the message to write to
	 * @throws IOException in case of I/O errors
	 * @throws HttpMessageNotWritableException in case of conversion errors
	 */
	void write(T t, MediaType contentType, HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException;

}
 

一些相關的實現類