SpringMVC返回不带引号的字符串方案汇总

落日映苍穹つ 2023-10-16 10:34 50阅读 0赞

## 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 {
        
    
        @Bean
        public StringHttpMessageConverter stringHttpMessageConverter(){
        
            return new StringHttpMessageConverter(StandardCharsets.UTF_8);
        }
    
        @Bean
        public FastJsonHttpMessageConverter fastJsonHttpMessageConverter(){
        
            FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
            converter.setFeatures(SerializerFeature.DisableCircularReferenceDetect);
            converter.setCharset(StandardCharsets.UTF_8);
            return converter;
        }
    
        @Override
        public 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());
        }
    
        @Override
        public 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>  
            	
                <bean class="org.springframework.http.converter.StringHttpMessageConverter">
    				<constructor-arg value="UTF-8" />
    				  
    		        <property name="supportedMediaTypes">  
    		            <list>  
    		                <value>text/plain;charset=UTF-8</value>  
    		            </list>  
    		        </property>
    			</bean>
    		      
    		    <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.xsd
           http://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">
    
    	<bean id="mappingJackson2HttpMessageConverter"
    		class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
    		<property name="supportedMediaTypes">
    			<list>
    				<value>text/json;charset=UTF-8</value>
    				
    			</list>
    		</property>
    	</bean>
    	<bean id="stringHttpMessageConverter" class="org.springframework.http.converter.StringHttpMessageConverter" />
    	<bean
    		class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    		<property name="messageConverters">
    			<list>
    				<ref bean="mappingJackson2HttpMessageConverter" />
    				<ref bean="stringHttpMessageConverter" />
    			</list>
    		</property>
    	</bean>
        
        <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="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
                 */
                @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();
                }
            };
        }
    }

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 {
        
        @Bean
        public StringHttpMessageConverter stringHttpMessageConverter() {
        
            return new StringHttpMessageConverter();
        }
        @Override
        public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        
            converters.add(stringHttpMessageConverter());
        }
    }

@Configuration
    @Slf4j
    public class WebMvcConfig extends WebMvcConfigurationSupport {
        
    
        /**
         * 使用fastjson转换器
         * 
         * @param converters
         */
        @Override
        public 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);
        }
    
    }

### 参考： ###

SpringMVC返回字符串去掉引号：https://blog.csdn.net/u013268066/article/details/51603604

Spring MVC中对response数据去除字符串的双引号：https://blog.csdn.net/qq\_26472621/article/details/102678232

解决springMvc返回字符串有双引号：https://blog.csdn.net/weixin\_45359027/article/details/97131384

springmvc返回不带引号的字符串：https://blog.csdn.net/weixin\_34390996/article/details/92531295

SpringBoot返回字符串,多双引号：https://blog.csdn.net/baidu\_27055141/article/details/91544019