如何使用Spring MVC設計通用響應構建器/ RESTful Web服務？

Question

嘗試使用Spring MVC構建RESTful Web服務。

控制器應返回特定的Java類型，但響應正文必須是通用信封。如何才能做到這一點？

下面的代碼段是我到目前爲止有：

控制器的方法：

@Controller 
    @RequestMapping(value = "/mycontroller") 
    public class MyController { 

     public ServiceDetails getServiceDetails() { 
      return new ServiceDetails("MyService"); 
     } 
    } 

響應信封：

public class Response<T> { 

     private String message; 
     private T responseBody; 

    } 

ServiceDetails代碼：

public class ServiceDetails { 

     private String serviceName; 

     public ServiceDetails(String serviceName) { 
      this.serviceName = serviceName; 
     } 
    } 

給客戶的預期最終響應應顯示爲：

@Controller 
@RequestMapping(value = "/mycontroller") 
public class MyRestController { 

    @Autowired 
    private MyController myController; 

    @RequestMapping(value = "/details") 
    public @ResponseBody Response<ServiceDetails> getServiceDetails() { 
     return new Response(myController.getServiceDetails(),"Operation OK"); 
    } 
} 

該解決方案保留原始MyController獨立的來源：

{ 

    "message" : "Operation OK" 
    "responseBody" : { 
         "serviceName" : "MyService" 
         } 

    } 

Answer 1

你可以做的有MyRestController只是包裹導致Response這個樣子你的REST代碼。看來你需要包括傑克遜在你的類路徑，以便Spring會自動神奇地序列化到JSON（見this瞭解詳細信息）

編輯

看來你需要的東西更通用的......所以這裏一條建議。

@Controller 
@RequestMapping(value = "/mycontroller") 
public class MyGenericRestController { 

    @Autowired 
    private MyController myController; 

    //this will match all "/myController/*" 
    @RequestMapping(value = "/{operation}") 
    public @ResponseBody Response getGenericOperation(String @PathVariable operation) { 
      Method operationToInvoke = findMethodWithRequestMapping(operation); 
      Object responseBody = null; 
      try{ 
       responseBody = operationToInvoke.invoke(myController); 
      }catch(Exception e){ 
       e.printStackTrace(); 
       return new Response(null,"operation failed"); 
      } 
     return new Response(responseBody ,"Operation OK"); 
    } 

    private Method findMethodWithRequestMapping(String operation){ 
     //TODO 
     //This method will use reflection to find a method annotated 
     //@RequestMapping(value=<operation>) 
     //in myController 
     return ... 
    } 
} 

並保留原始「myController的」差不多，因爲它是：

@Controller 
public class MyController { 

    //this method is not expected to be called directly by spring MVC 
    @RequestMapping(value = "/details") 
    public ServiceDetails getServiceDetails() { 
     return new ServiceDetails("MyService"); 
    } 
} 

主要問題有這樣的：MyController的@RequestMapping無需可能被一些自定義的註釋被替換（和適應findMethodWithRequestMapping到對此自定義註釋執行自省）。

Answer 2

默認情況下，Spring MVC使用org.springframework.http.converter.json.MappingJacksonHttpMessageConverter通過Jackson序列化/反序列化JSON。

我不知道這是否是一個好主意，但您解決問題的方法之一是擴展此類，並重寫writeInternal方法：

public class CustomMappingJacksonHttpMessageConverter extends MappingJacksonHttpMessageConverter { 

    @Override 
    protected void writeInternal(Object object, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException { 
     super.writeInternal(new Response(object, "Operation OK"), outputMessage); 
    } 
} 

如果您使用XML配置，可以啓用自定義轉換器，如下所示：

<mvc:annotation-driven> 
    <mvc:message-converters> 
     <bean class="path.to.CustomMappingJacksonHttpMessageConverter"> 
    </mvc:message-converters> 
</mvc:annotation-driven>