我使用jersey在Java中实现RESTful Web Service并在上运行它Tomcat7。
Tomcat7
我有此查询以获取任务列表:
@GET @Path("/users/{username}/") @Consumes(MediaType.APPLICATION_JSON) @Produces(MediaType.APPLICATION_JSON) public Response taskList(@PathParam("username") String username) { Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); List<Task> tasks = null; try { tasks = (List<Task>)session.createQuery("from Task as t where t.user.username = :name order by t.project.key ASC, t.deliverable.key ASC, t.activity.key ASC, t.start ASC").setString("name", username).list(); } catch (HibernateException e) { e.printStackTrace(); session.getTransaction().rollback(); } session.getTransaction().commit(); return Response.ok().entity(tasks).build(); }
我用jersey客户端测试它,例如:
try { response = service.path("task/users/are/").type("application/json").get(ClientResponse.class); s = response.getEntity(String.class); System.out.println(s); } catch (Exception e) { e.printStackTrace(); }
结果示例:
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Timelog","date":1328396400000,"category":{"id":100,"key":"scrum","name":"Scrum","description":"","cost":0.0,"orderIndex":1,"parent":null},"valueType":0,"fixValue":0.0,"done":0,"task_id":0},"parent":{"id":1266,"description":"","key":"other","name":"Other","project":{"id":115,"key":"are","name":"Master Thesis","description":"Android client for Timelog","date":1328396400000,"category":{"id":100,"key":"scrum","name":"Scrum","description":"","cost":0.0,"orderIndex":1,"parent":null},"valueType":0,"fixValue":0.0,"done":0,"task_id":0},"parent":null,"user":null,"orderIndex":0,"done":false,"minEstimate":null,"maxEstimate":null,"task_id":0},"user":{"id":28,"username":"are","hash":"$2a$10$G0e7cjXtn60XmAhUx8JpNOYk.EwpIEwDvc2mBaNsTGqQe1tgIZAxy"},"orderIndex":3,"done":false,"minEstimate":10.0,"maxEstimate":30.0,"task_id":0},"link":""},{"id":5324,"start":1331254080000,"end":1331254800000,"description":"","started":false,"user":{"id":28,"username":"are","hash":"$2a$10$G0e7cjXtn60XmAhUx8JpNOYk.EwpIEwDvc2mBaNsTGqQe1tgIZAxy"},"project":{"id":115,"key":"are","name":"Master Thesis","description":"Android client for 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days)","cost":300.0,"orderIndex":5,"parent":{"id":100,"key":"scrum","name":"Scrum","description":"","cost":0.0,"orderIndex":1,"parent":null}},"deliverable":{"id":1237,"description":"","key":"o","name":"Other","project":{"id":109,"key":"mre","name":"Master Thesis Ali Rezaei","description":"Timelog Android","date":1328223600000,"category":{"id":100,"key":"scrum","name":"Scrum","description":"","cost":0.0,"orderIndex":1,"parent":null},"valueType":0,"fixValue":0.0,"done":0,"task_id":0},"parent":{"id":1236,"description":"","key":"other","name":"Other","project":{"id":109,"key":"mre","name":"Master Thesis Ali Rezaei","description":"Timelog Android","date":1328223600000,"category":{"id":100,"key":"scrum","name":"Scrum","description":"","cost":0.0,"orderIndex":1,"parent":null},"valueType":0,"fixValue":0.0,"done":0,"task_id":0},"parent":null,"user":null,"orderIndex":0,"done":false,"minEstimate":null,"maxEstimate":null,"task_id":0},"user":null,"orderIndex":2,"done":true,"minEstimate":null,"maxEstimate":null,"task_id":0},"link":""}]
它非常适合此用户( 和 )和除其中一个用户之外的所有其他用户。
该用户在数据库中具有 大量 任务,因此出现了此错误:
Caused by: java.io.IOException: Premature EOF at sun.net.www.http.ChunkedInputStream.readAheadBlocking(Unknown Source) at sun.net.www.http.ChunkedInputStream.readAhead(Unknown Source) at sun.net.www.http.ChunkedInputStream.read(Unknown Source) at java.io.FilterInputStream.read(Unknown Source) at sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.read(Unknown Source) at sun.nio.cs.StreamDecoder.readBytes(Unknown Source) at sun.nio.cs.StreamDecoder.implRead(Unknown Source) at sun.nio.cs.StreamDecoder.read(Unknown Source) at java.io.InputStreamReader.read(Unknown Source) at java.io.Reader.read(Unknown Source) at com.sun.jersey.core.util.ReaderWriter.readFromAsString(ReaderWriter.java:171) at com.sun.jersey.core.util.ReaderWriter.readFromAsString(ReaderWriter.java:157) at com.sun.jersey.core.provider.AbstractMessageReaderWriterProvider.readFromAsString(AbstractMessageReaderWriterProvider.java:114) at com.sun.jersey.core.impl.provider.entity.StringProvider.readFrom(StringProvider.java:73) at com.sun.jersey.core.impl.provider.entity.StringProvider.readFrom(StringProvider.java:58) at com.sun.jersey.api.client.ClientResponse.getEntity(ClientResponse.java:554) ... 2 more
感谢您的帮助。
附加物
我发现问题不在服务器端。它在客户端。我有一个面临内存不足问题的Android客户端。
问题是我该如何在客户端解决此问题。你有什么主意吗?
如果返回的项目数量确实 很大, 则另一个选择是将数据分页回客户端。如果列表足够多,那么它可能甚至对用户和界面都没有用(不确定您的使用经验)。例如,查看StackOverflow- 每天都有大量帖子,但是界面(可能还有后端查询模式)可以分页数据。
简单的分页方法是“更多”模式
/users/{username}/tasks?top=n
如果以25开始,那么可能还有更多链接可以拉到前50位等等。有点像ios邮件和其他类似的应用程序。
另一种方法是“页面”
/users/{username}/tasks?page=1
有趣的问题是您是否希望该集合稳定。换句话说,该用户的任务正在更改,因此转到第2页可能会跳过项目或显示第1页中的项目-除非您为该用户保留“查询”状态- 可能存储结果集(可以是ID )在数据库,中间层(有问题的多个AT)或在客户端(返回所有ID并具有客户端页面列/数据)中的一种-类似于虚拟列表视图。
当您使用庞大的数据集时,仅返回所有数据通常不是正确的答案,然后开始使分页等方法变得复杂。
希望能引起人们对不同选择的思考。可能不是您问题的确切答案。