@RequestMapping(value = "test")    @ResponseBody    public Object test() {        Map<String,String> param = new HashMap<>();        param.put("name","userwyh");        return param;    }

@ControllerAdvicepublic class MyResponseBodyAdvice implements ResponseBodyAdvice<Object> {    @Override    public boolean supports(MethodParameter methodParameter, Class<? extends HttpMessageConverter<?>> aClass) {        return true;    }    @Override    public Object beforeBodyWrite(Object o, MethodParameter methodParameter, MediaType mediaType, Class<? extends HttpMessageConverter<?>> aClass, ServerHttpRequest serverHttpRequest, ServerHttpResponse serverHttpResponse) {        return "hello,world";    }}

protected final List<HttpMessageConverter<?>> messageConverters;

package com.userwyh.spring.controller;import org.slf4j.Logger;import org.springframework.http.HttpOutputMessage;import org.springframework.http.MediaType;import org.springframework.http.converter.HttpMessageNotWritableException;import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;import org.springframework.util.StreamUtils;import java.io.IOException;import java.lang.reflect.Type;import java.nio.charset.Charset;import static org.slf4j.LoggerFactory.getLogger;/** * Created by userwyh on 2017/3/4. */public class MappingJackson2HttpMessageConverterFactory {    private static final Logger logger = getLogger(MappingJackson2HttpMessageConverterFactory.class);    public MappingJackson2HttpMessageConverter init() {        return new MappingJackson2HttpMessageConverter(){            /**             * 重写Jackson消息转换器的writeInternal方法             * SpringMVC选定了具体的消息转换类型后,会调用具体类型的write方法,将Java对象转换后写入返回内容             */            @Override            protected void writeInternal(Object object, Type type, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {                if (object instanceof String){                    logger.info("在MyResponseBodyAdvice进行转换时返回值变成String了,不能用原来选定消息转换器进行转换,直接使用StringHttpMessageConverter转换");                    //StringHttpMessageConverter中就是用以下代码写的                    Charset charset = this.getContentTypeCharset(outputMessage.getHeaders().getContentType());                    StreamUtils.copy((String)object, charset, outputMessage.getBody());                }else{                    logger.info("返回值不是String类型,还是使用之前选择的转换器进行消息转换");                    super.writeInternal(object, type, outputMessage);                }            }            private Charset getContentTypeCharset(MediaType contentType) {                return contentType != null && contentType.getCharset() != null?contentType.getCharset():this.getDefaultCharset();            }        };    }}

<mvc:annotation-driven>        <mvc:message-converters>            <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter">                <property name="supportedMediaTypes">                    <list>                        <value>image/jpeg</value>                        <value>image/png</value>                        <value>image/gif</value>                    </list>                </property>            </bean>            <bean  factory-bean="mappingJackson2HttpMessageConverterFactory" factory-method="init"                   class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" >            </bean>        </mvc:message-converters>    </mvc:annotation-driven>    <bean id="mappingJackson2HttpMessageConverterFactory" class = "com.userwyh.spring.controller.MappingJackson2HttpMessageConverterFactory" />

    @RequestMapping(value = "test")    @ResponseBody    public Object test() {        Map<String,String> param = new HashMap<>();        param.put("name","userwyh");        if(condition){            return "hello,world";        }        return param;    }