MessageTemplate导致在MVC控制器中没有发现异常的转换器？

Question

控制器代码

@Autowired
    MessageChannel invokeChannel;
    @RequestMapping(value="/invoke/{payload}")
    public ResponseEntity<String> sayHello(@PathVariable String payload)
    {
        //trigger gateway to send a message     
        MessagingTemplate template = new MessagingTemplate();       
        template.send(invokeChannel, new GenericMessage<String>(payload));      
        return new ResponseEntity<String>(payload, HttpStatus.OK);
    }

例外

java.lang.IllegalArgumentException：没有为以下类型的返回值找到转换器：class java.lang.string org.springframework.web.servlet.mvc.method.annotation.abstractMessageConterMethodProcessor.writeWithWithMessageConverters（80)org.springframework.web.servlet.mvc.method.annotation.servletInvocableHandlerMethod.InvokeandHandland(servletInvocableHandlerMethod.java:126)org.springframework.web.servlet.mvc.method.annotation.requestMappingHandlerAdapter.InvokeHandlormethod(requestMappingHandlerAdapter.java:814)org.springframework.web.servlet.mvc.method.mmvc.method.abstractHandlerMethodAdapter.handle（abstractHandlerMethodAdapter.java:85)org.springframework.web.servlet.dispatcherservlet.doDispatch（dispatcherservlet.java:959)org.springframework.web.servlet.dispatcherservlet.doService（dispatcherservlet.java:893)org.springframework.web.servlet.dispatcherservlet.doService（frameworkServlet.Service(frameworkServlet.java:845)javax.servlet.http.httpservlet.Service(httpservlet.java:729)org.apache.tomcat.websocket.server.wsfilter.doFilter(wsfilter.java:52)

我找不到是什么原因造成的。未到达return new ResponseEntity(...)处的断点。

我的webmvcconfig

@EnableWebMvc
@Configuration
@ComponentScan({ "helloworldmvc" })
public class WebappConfig extends WebMvcConfigurerAdapter {

    @Bean
    public static PropertySourcesPlaceholderConfigurer propertyConfigIn() {
        return new PropertySourcesPlaceholderConfigurer();
    }

    @Override
    public void configureMessageConverters(
            List<HttpMessageConverter<?>> converters) {
        converters.add(new MongoMessageConverter());
    }
}

Answer 1

//触发网关发送消息

您应该确保template.send（invokeChannel)的流确实是单向的。没有一个网关可以在那里等待依靠。这是你的评论，比如：

未到达return new ResponseEntity(...)处的断点。

    List<MediaType> producibleMediaTypes = getProducibleMediaTypes(servletRequest, clazz, type);

    if (value != null && producibleMediaTypes.isEmpty()) {
        throw new IllegalArgumentException("No converter found for return value of type: " + clazz);
    }