Question

尽管我已经看到很多关于这个问题的问题，但没有人对我有用。我试图发布一个简单的REST服务，但不重要的是我做了什么，它没有用。

我的第一个方法是创建一个这样的REST控制器：

@RestController
public class ProductsRestController {

    @Autowired
    private ProductService  productService;

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

调用它时（通过浏览器）抛出了HttpMediaTypeNotAcceptableException

谷歌搜索到达Question。建议的解决方案是配置MappingJacksonHttpMessageConverter并将其添加到AnnotationMethodHandlerAdapter。由于这些bean在Spring 4.x中已弃用，因此我使用RequestMappingHandlerAdapter和MappingJackson2HttpMessageConverter这种方式（在我的WebMvcConfigurerAdapter中）：

@Override
public void configureMessageConverters (final List<HttpMessageConverter<?>> converters) {
    converters.add(new MappingJackson2HttpMessageConverter());
}

这导致我出现以下错误：

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

我添加了所需的依赖项

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

结果：

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)

再次谷歌搜索我到达了另一个Question但是这个都没有用。

有谁知道底层问题是什么？

提前致谢！问候。

Answer 1

无论问题是什么，总会有进一步的谷歌搜索。另一个Question有助于解决我的问题。

问题是 Product 类引用了再次引用Product的其他bean，因此会发生循环引用。使用DTO解决了这个问题。

感谢大家的支持。

调用Spring（4.x）Rest服务

1 个答案: