1、需求
通过POST接口传List<Object> 类型的参数，由于项目比较老，使用的ssh框架，spring的版本是4.0.9，这种需求在springboot里面很好实现，可是在老版本的ssh里面就遇到了问题。
2、问题排查
1、首先接口信息如下：
@RequestMapping(value = "/receiveHiddens", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON_VALUE)
@ResponseBody
public ApiResultJson receiveHiddens(@RequestBody List<TSBaseUser> users){
ApiResultJson resultJson = new ApiResultJson();
System.out.println(users);
return resultJson;
}
2、postman测试
image.png
测试报错结果如下
org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/json;charset=UTF-8' not supported
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.readWithMessageConverters(HandlerMethodInvoker.java:645)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveRequestBody(HandlerMethodInvoker.java:604)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:353)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:170)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandlerMethod(AnnotationMethodHandlerAdapter.java:446)
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle(AnnotationMethodHandlerAdapter.java:434)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:863)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.jeecgframework.core.interceptors.CrosFilter.doFilter(CrosFilter.java:31)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.jeecgframework.core.aop.GZipFilter.doFilter(GZipFilter.java:88)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:140)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.orm.hibernate4.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:150)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:651)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:409)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:754)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1376)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
3、debug问题查找
由于是ssh项目，接口肯定会走DispatchServlet里面的doDispatch()方法，在这个方法里面一直走下去。
image.png
在HandlerMethodInvoker.readWithMessageConverters 方法里面报错了。具体代码如下。
在messageConverter.canRead(paramType, contentType)方法里面，继续往下找
List<MediaType> allSupportedMediaTypes = new ArrayList();
if (this.messageConverters != null) {
HttpMessageConverter[] var6 = this.messageConverters;
int var7 = var6.length;
for(int var8 = 0; var8 < var7; ++var8) {
HttpMessageConverter<?> messageConverter = var6[var8];
allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes());
if (messageConverter.canRead(paramType, contentType)) {
if (logger.isDebugEnabled()) {
logger.debug("Reading [" + paramType.getName() + "] as \"" + contentType + "\" using [" + messageConverter + "]");
}
return messageConverter.read(paramType, inputMessage);
}
}
}
public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
JavaType javaType = this.getJavaType(type, contextClass);
return this.objectMapper.canDeserialize(javaType) && this.canRead(mediaType);
}
//上面的 this.canRead(mediaType)是在AbstractHttpMessageConverter里面canRead()方法
protected boolean canRead(MediaType mediaType) {
if (mediaType == null) {
return true;
} else {
Iterator var2 = this.getSupportedMediaTypes().iterator();
MediaType supportedMediaType;
do {
//就是在这里，getSupportedMediaTypes()方法里没有找到Content type为 'application/json;charset=UTF-8'的，所以报错
if (!var2.hasNext()) {
return false;
}
supportedMediaType = (MediaType)var2.next();
} while(!supportedMediaType.includes(mediaType));
return true;
}
}
3、分析过程
Content type为 'application/json;charset=UTF-8'是最常见的类型，其它接口都正常，为什么就这个接口不行，后来查很多 blog发现是因为没有配置解析List<Object>类型参数的解析器，所以HandlerMethodInvoker无法解析方法参数，最后找到了解决方法，在xml配置文件里面添加如下配置，里面重要的就是Jaxb2RootElementHttpMessageConverter和MappingJackson2HttpMessageConverter两个messageConverter，这样才能正常解析List类型参数。
<!-- 定义注解驱动Controller方法处理适配器 ,注：该适配器必须声明在<mvc:annotation-driven />之前，否则不能正常处理参数类型的转换 -->
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
<property name="messageConverters">
<list>
<bean class="org.springframework.http.converter.xml.Jaxb2RootElementHttpMessageConverter" />
<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter" />
</list>
</property>
</bean>
<!-- 会自动注册RequestMappingHandlerMapping与RequestMappingHandlerAdapter
两个bean,是spring MVC为@Controllers分发请求所必须的。 并提供了：数据绑定支持，@NumberFormatannotation支持，@DateTimeFormat支持，@Valid支持，读写XML的支持（JAXB），读写JSON的支持（Jackson） -->
<mvc:annotation-driven />
4、postman测试结果
image.png
