如何使用Jersey缓存响应？

Question

我正在尝试使用Jersey开发restful API.我有一个特定的get操作的GET API,我的GET从同一个客户端同时进行.是否可以缓存响应？任何指针都表示赞赏.

谢谢

Answer 1

您可以使用CacheControl,eTag - 按照下面的示例代码

// In your jersey method
    final EntityTag eTag = new EntityTag(resource.getId() + "_" +
     resource.getLastModified().getTime());
    final CacheControl cacheControl = new CacheControl();
    cacheControl.setMaxAge(-1);

    ResponseBuilder builder = request.evaluatePreconditions(
         resource.getLastModified(), eTag);

    // the resoruce's information was modified, return it
    if (builder == null) {
         builder = Response.ok(resource);
    }

    // the resource's information was not modified, return a 304

    return builder.cacheControl(cacheControl).lastModified(
         resource.getLastModified()).tag(eTag).build();

替换resource为您的Resource实例.

Answer 2

解决方案摘要:

1. 请求作为方法参数

   接口:

   @Path("myentity")
   public interface MyEntityResource
   
       @GET
       @Produces(MediaType.APPLICATION_JSON)
       public Response getMyEntity(@Context final Request request);
   }
   

   执行:

   public class MyEntityResourceImpl implements MyEntityResource
   
       @Override
       public Response getMyEntity(final Request request) {
   
           final MyEntity myEntity = ... // load entity
           final String eTagValue = ... // calclutate value of ETag
   
           final EntityTag eTag = new EntityTag(eTagValue);
   
           ResponseBuilder responseBuilder = request.evaluatePreconditions(eTag);
   
           if (responseBuilder == null) {
               return Response.ok(user).tag(eTag).build();
           }
   
           return responseBuilder.build();
       }
   }
   

   缺点:

   • 实现细节Request暴露

   • 返回类型Reponse是通用的

   • 在WADL中缺少返回类型的语法

   • 客户代理与不必要的参数Request

2. 请求作为实例变量

   接口:

   @Path("myentity")
   public interface MyEntityResource
   
       @GET
       @Produces(MediaType.APPLICATION_JSON)
       public Response getMyEntity();
   }
   

   执行:

   public class MyEntityResourceImpl implements MyEntityResource
   
       @Context
       private Request request
   
       @Override
       public Response getMyEntity() {
   
           final MyEntity myEntity = ... // load entity
           final String eTagValue = ... // calclutate value of ETag
   
           final EntityTag eTag = new EntityTag(eTagValue);
   
           ResponseBuilder responseBuilder = request.evaluatePreconditions(eTag);
   
           if (responseBuilder == null) {
               return Response.ok(user).tag(eTag).build();
           }
   
           return responseBuilder.build();
       }
   }
   

   缺点:

   • 返回类型Reponse是通用的

   • 在WADL中缺少返回类型的语法

   • 依赖注入@Context很复杂,请参阅/sf/ask/2326831041/

3. ShallowEtagHeaderFilter作为Web过滤器

   web.xml中:

   <filter>
       <filter-name>etagFilter</filter-name>
       <filter-class>org.springframework.web.filter.ShallowEtagHeaderFilter</filter-class>
   </filter>
   <filter-mapping>
       <filter-name>etagFilter</filter-name>
       <url-pattern>/api/*</url-pattern>
   </filter-mapping>
   

   接口:

   @Path("myentity")
   public interface MyEntityResource
   
       @GET
       @Produces(MediaType.APPLICATION_JSON)
       public MyEntity getMyEntity();
   }
   

   执行:

   public class MyEntityResourceImpl implements MyEntityResource
   
       @Override
       public MyEntity getMyEntity() {
   
           final MyEntity myEntity = ... // load entity
           return myEntity;
       }
   }
   

   缺点:

   • 糟糕的服务器性能,请参阅JavaDoc

   • 仅适用于未提交的响应

   • 没有弱ETag的支持

4. 自定义WriterInterceptor作为JAX-RS拦截器

   拦截器:

   public class CustomInterceptor implements WriterInterceptor {
   
       @Context
       private Request request;
   
       @Override
       public void aroundWriteTo(WriterInterceptorContext context) throws IOException, WebApplicationException {
   
           OutputStream old = context.getOutputStream();
   
           ByteArrayOutputStream buffer = new ByteArrayOutputStream();
   
           try {
   
               context.setOutputStream(buffer);
               context.proceed();
   
               byte[] entity = buffer.toByteArray();
   
               String etag = ... // calclutate value of ETag
               context.getHeaders().putSingle(HttpHeaders.ETAG, etag);
   
               ResponseBuilder responseBuilder = request.evaluatePreconditions(eTag);
   
               if (responseBuilder == null) {
                    throw new WebApplicationException(responseBuilder.status(Response.Status.NOT_MODIFIED).header(HttpHeaders.ETAG, etag).build());
               }
   
               old.write(entity);
   
           } finally {
               context.setOutputStream(old);
           }
       }
   }
   

   另请参见:ServerCacheInterceptor(Resteasy)

   接口:

   @Path("myentity")
   public interface MyEntityResource
   
       @GET
       @Produces(MediaType.APPLICATION_JSON)
       public MyEntity getMyEntity();
   }
   

   执行:

   public class MyEntityResourceImpl implements MyEntityResource
   
       @Override
       public MyEntity getMyEntity() {
   
           final MyEntity myEntity = ... // load entity
           return myEntity;
       }
   }
   

   缺点:

   • 没有针对Jersey的预定义拦截器

   • 服务器性能不佳

   • 没有弱ETag的支持

   • 丑陋的解决方法 WebApplicationException