调用Spring（4.x）Rest服务

Question

即使我看到很多关于这个问题的问题，但没有人对我有用。 我正在尝试发布一个简单的REST服务，但并不重要，我做的，它不工作。

我的第一个方法是创建一个REST控制器是这样的：

@RestController 
public class ProductsRestController { 

    @Autowired 
    private ProductService productService; 

    @Transactional 
    @RequestMapping(value = "/listproducts") 
    public List<Product> products() { 
     return this.productService.findAll(); 
    } 
} 

当调用它（通过浏览器）一个HttpMediaTypeNotAcceptableException被抛出

谷歌搜索我达到了这个Question。 提出的解决方案是配置一个MappingJacksonHttpMessageConverter并将其添加到AnnotationMethodHandlerAdapter。由于这些豆类在春天4.x的过时，我用RequestMappingHandlerAdapter与MappingJackson2HttpMessageConverter这样（我WebMvcConfigurerAdapter内）：

这conduced我以下错误：

java.lang.ClassNotFoundException: com.fasterxml.jackson.core.JsonProcessingException 

我增加了所需的依赖

<artifactId>jackson-core</artifactId> 
<artifactId>jackson-databind</artifactId> 

和结果上：

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.IllegalStateException: getOutputStream() has already been called for this response 
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:978) 
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857) 
    javax.servlet.http.HttpServlet.service(HttpServlet.java:621) 
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842) 
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728) 
    org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88) 
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118) 
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:85) 
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:57) 
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50) 
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342) 
    org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192) 
    org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160) 
    org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344) 
    org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261) 

再次使用谷歌搜索我到达了这个其他Question但这一个都没有用。

有没有人知道底层的问题是什么？

在此先感谢！ 此致敬礼。

Answer 1

无论问题是什么，总会有更多的事情要做。 这个其他Question帮助解决了我的问题。

事情是产品类有引用到其他bean的引用再次，所以循环引用正在发生。使用DTO解决了这个问题。

感谢大家的支持。