SpringMVC返回不带引号的字符串方案汇总

问题

项目使用springboot开发的，大部分出参为json，使用的fastJson。

现在有的接口需要返回一个success字符串，发现返回结果为“success”，多带了双引号。这是因为fastJson对出参做了处理。

方案一：fastJson添加string类型的解析器（推荐）

创建一个配置类

@Configuration
@EnableWebMvc
public class WebConfiguration extends WebMvcConfigurerAdapter {@Beanpublic StringHttpMessageConverter stringHttpMessageConverter(){return new StringHttpMessageConverter(StandardCharsets.UTF_8);}@Beanpublic FastJsonHttpMessageConverter fastJsonHttpMessageConverter(){FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();converter.setFeatures(SerializerFeature.DisableCircularReferenceDetect);converter.setCharset(StandardCharsets.UTF_8);return converter;}@Overridepublic void configureMessageConverters(List<HttpMessageConverter<?>> converters) {//添加字符转解析器converters.add(stringHttpMessageConverter());//添加json解析器converters.add(fastJsonHttpMessageConverter());}@Overridepublic void extendMessageConverters(List<HttpMessageConverter<?>> converters) {converters.clear();converters.add(stringHttpMessageConverter());converters.add(fastJsonHttpMessageConverter());}
}

方案二：修改springMVC配置文件（springMVC）

网上通用的办法是在springMVC配置文件spring-servlet.xml中加入如下配置项：

<mvc:annotation-driven><mvc:message-converters>  <!-- 去除返回字符串时的引号，处理字符串引号配置要放在上面！ --><bean class="org.springframework.http.converter.StringHttpMessageConverter"><constructor-arg value="UTF-8" /><!-- 避免出现乱码 -->  <property name="supportedMediaTypes">  <list>  <value>text/plain;charset=UTF-8</value>  </list>  </property></bean><!-- 其他处理 -->  <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" /></mvc:message-converters> 
</mvc:annotation-driven>

也可以在applicationContext-velocity.xml，配置JSON返回模板时直接配置进去

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:aop="http://www.springframework.org/schema/aop"xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"xmlns:mvc="http://www.springframework.org/schema/mvc" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<!-- 返回JSON模版 --><bean id="mappingJackson2HttpMessageConverter"class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"><property name="supportedMediaTypes"><list><value>text/json;charset=UTF-8</value><!-- <value>text/html;charset=UTF-8</value> <value>application/json;charset=UTF-8</value> --></list></property></bean><bean id="stringHttpMessageConverter" class="org.springframework.http.converter.StringHttpMessageConverter" /><beanclass="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"><property name="messageConverters"><list><ref bean="mappingJackson2HttpMessageConverter" /><ref bean="stringHttpMessageConverter" /></list></property></bean><!-- 配置视图的显示 --><bean id="viewResolver" class="org.springframework.web.servlet.view.velocity.VelocityViewResolver">  <property name="prefix" value="/" /><property name="suffix" value=".html" /><property name="contentType" value="text/html;charset=UTF-8" /><property name="requestContextAttribute" value="request"/><!-- <property name="toolboxConfigLocation" value="/velocity-toolbox.xml" />--><property name="dateToolAttribute" value="dateTool" /><property name="numberToolAttribute" value="numberTool" /><property name="exposeRequestAttributes" value="true" /><property name="exposeSessionAttributes" value="true" /></bean>
</beans>

方案三：重写Jackson消息转换器的writeInternal方法（springMVC）

创建一个MappingJackson2HttpMessageConverter的工厂类

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*/@Overrideprotected 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();}};}
}

在spring mvc的配置文件中添加如下配置

<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.common.MappingJackson2HttpMessageConverterFactory" />

方案四：response.getWriter().write()写到界面

 @PostMapping("/test")public void test(@RequestBody Req req, HttpServletResponse response) throw Exception{res = service.test(req);response.getWriter().write(res);response.getWriter().flush();response.getWriter().close();}

方案五：重写json的MessageCoverter

@Configuration
@EnableWebMvc
public class WebConfig implements WebMvcConfigurer {@Beanpublic StringHttpMessageConverter stringHttpMessageConverter() {return new StringHttpMessageConverter();}@Overridepublic void configureMessageConverters(List<HttpMessageConverter<?>> converters) {converters.add(stringHttpMessageConverter());}
}

@Configuration
@Slf4j
public class WebMvcConfig extends WebMvcConfigurationSupport {/*** 使用fastjson转换器* * @param converters*/@Overridepublic void configureMessageConverters(List<HttpMessageConverter<?>> converters) {super.configureMessageConverters(converters);FastJsonHttpMessageConverter fastConverter = new FastJsonHttpMessageConverter();FastJsonConfig fastJsonConfig = new FastJsonConfig();fastJsonConfig.setSerializerFeatures(SerializerFeature.PrettyFormat,SerializerFeature.WriteNullListAsEmpty, SerializerFeature.WriteNullStringAsEmpty,SerializerFeature.DisableCircularReferenceDetect);List<MediaType> supportedMediaTypes = new ArrayList<>();supportedMediaTypes.add(MediaType.APPLICATION_JSON);supportedMediaTypes.add(MediaType.APPLICATION_ATOM_XML);supportedMediaTypes.add(MediaType.APPLICATION_FORM_URLENCODED);supportedMediaTypes.add(MediaType.APPLICATION_OCTET_STREAM);supportedMediaTypes.add(MediaType.APPLICATION_PDF);supportedMediaTypes.add(MediaType.APPLICATION_RSS_XML);supportedMediaTypes.add(MediaType.APPLICATION_XHTML_XML);supportedMediaTypes.add(MediaType.APPLICATION_XML);supportedMediaTypes.add(MediaType.IMAGE_GIF);supportedMediaTypes.add(MediaType.IMAGE_JPEG);supportedMediaTypes.add(MediaType.IMAGE_PNG);supportedMediaTypes.add(MediaType.TEXT_EVENT_STREAM);supportedMediaTypes.add(MediaType.TEXT_HTML);supportedMediaTypes.add(MediaType.TEXT_MARKDOWN);supportedMediaTypes.add(MediaType.TEXT_PLAIN);supportedMediaTypes.add(MediaType.TEXT_XML);fastConverter.setSupportedMediaTypes(supportedMediaTypes);fastConverter.setFastJsonConfig(fastJsonConfig);converters.add(fastConverter);}}