java - 在 Rest API 中使用路由器 - java

Question

package firstREST;

import org.restlet.Application;
import org.restlet.Component;
import org.restlet.Restlet;
import org.restlet.data.Protocol;
import org.restlet.routing.Router;

public class Faculty extends Application {
    public static void main(String[] args) {
        Component comp = new Component();
        comp.getServers().add(Protocol.HTTP, 8080);
        Application app = new Faculty();
        comp.getDefaultHost().attach(app);
        try {
            comp.start();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    @Override
    public Restlet createInboundRoot() {
        Router router = new Router(getContext());
        router.attach("/attendance/faculty/select", Faculty_Get.class);
        router.attach("/attendance/faculty/insert", Faculty_Insert.class);
        return router;

    }
}

以上代码无效。当我打开一个 url http://localhost:8080/attendance/faculty/select 运行服务器后，它不会工作。我怎样才能使这项工作？谁能帮忙？

Faculty_Get Class:

package firstREST;

import org.restlet.resource.Get;
import org.restlet.resource.ServerResource;
import org.json.JSONArray;
import org.json.JSONObject;
import java.sql.*;

public class Faculty_Get extends ServerResource {
    @Get ("json")
    public String present( String name ) throws Exception {
          // Values.
          String getName = null;
          String getPost = null;
          String getCourse = null;
          String getDepartment = null;
          String getPresents = null;
          String getAbsents = null;

          // Get values.
          String jSonString = getQuery().getValues( "data" );

          // Decode jSon.
          JSONArray mJsonArray = new JSONArray( jSonString );
          JSONObject mJsonObject = new JSONObject();
          for ( int i = 0; i < mJsonArray.length(); i++ ) {
              mJsonObject = mJsonArray.getJSONObject(i);
              getName = mJsonObject.getString( "name" );
          }

          // Database.
          try
          {
             Class.forName("com.mysql.jdbc.Driver").newInstance();
             Connection myconn = DriverManager.getConnection("jdbc:mysql://localhost:3306/attendance", "root", "");
             PreparedStatement ps = myconn.prepareStatement("SELECT * FROM faculty where name = '" + getName + "'");
             ResultSet rs = ps.executeQuery();
             while( rs.next() )
             {
                 getName = rs.getString( "name" );
                 getPost = rs.getString( "post" );
                 getCourse = rs.getString( "course" );
                 getDepartment = rs.getString( "department" );
                 getPresents = rs.getString( "presents" );
                 getAbsents = rs.getString( "absents" );
             }
             return "name="+getName+"&post="+getPost+"&course="+getCourse+"&department="+getDepartment+"&presents="+getPresents+"&absents="+getAbsents;
          }
          catch(Exception e)
          {
              throw e;
          }
    }
}

错误:

May 18, 2015 6:17:10 PM org.restlet.resource.UniformResource doCatch
WARNING: Exception or error caught in resource
java.lang.NullPointerException
    at java.io.StringReader.<init>(Unknown Source)
    at org.json.JSONTokener.<init>(JSONTokener.java:83)
    at org.json.JSONArray.<init>(JSONArray.java:145)
    at firstREST.Faculty_Get.present(Faculty_Get.java:24)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.restlet.resource.ServerResource.doHandle(ServerResource.java:449)
    at org.restlet.resource.ServerResource.get(ServerResource.java:648)
    at org.restlet.resource.ServerResource.doHandle(ServerResource.java:530)
    at org.restlet.resource.ServerResource.doNegotiatedHandle(ServerResource.java:590)
    at org.restlet.resource.ServerResource.doConditionalHandle(ServerResource.java:302)
    at org.restlet.resource.ServerResource.handle(ServerResource.java:849)
    at org.restlet.resource.Finder.handle(Finder.java:513)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.routing.Router.doHandle(Router.java:500)
    at org.restlet.routing.Router.handle(Router.java:740)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.engine.application.StatusFilter.doHandle(StatusFilter.java:154)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.engine.ChainHelper.handle(ChainHelper.java:114)
    at org.restlet.engine.application.ApplicationHelper.handle(ApplicationHelper.java:75)
    at org.restlet.Application.handle(Application.java:391)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.routing.Router.doHandle(Router.java:500)
    at org.restlet.routing.Router.handle(Router.java:740)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.routing.Router.doHandle(Router.java:500)
    at org.restlet.routing.Router.handle(Router.java:740)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.engine.application.StatusFilter.doHandle(StatusFilter.java:154)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.routing.Filter.doHandle(Filter.java:159)
    at org.restlet.routing.Filter.handle(Filter.java:206)
    at org.restlet.engine.ChainHelper.handle(ChainHelper.java:114)
    at org.restlet.Component.handle(Component.java:391)
    at org.restlet.Server.handle(Server.java:491)
    at org.restlet.engine.http.connector.BaseServerHelper.handle(BaseServerHelper.java:161)
    at org.restlet.engine.http.connector.BaseServerHelper.handleInbound(BaseServerHelper.java:170)
    at org.restlet.engine.http.connector.BaseHelper.handleNextInbound(BaseHelper.java:421)
    at org.restlet.engine.http.connector.Connection.readMessages(Connection.java:698)
    at org.restlet.engine.http.connector.Controller$2.run(Controller.java:98)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at java.lang.Thread.run(Unknown Source)

May 18, 2015 6:17:10 PM org.restlet.engine.log.LogFilter afterHandle
INFO: 2015-05-18    18:17:10    127.0.0.1   -   -   8080    GET /attendance/faculty/select  -   500 486 0   30  http://localhost:8080   Mozilla/5.0 (Windows NT 6.1; rv:40.0) Gecko/20100101 Firefox/40.0   -

这是我在刷新浏览器时遇到的错误。我不知道是什么导致了这个问题。

Answer 1

我认为您可以使事情变得更简单，而且您的应用程序并不是真正的 RESTful ;-) 我强烈认为以正确的方式使用 ReSTLet 将有助于解决您的问题。似乎您使用方法 getQuery 而您没有查询字符串。此外，此类查询参数似乎不适用于这种情况。

在继续之前，我建议您查看此链接以设计 Web API/RESTful 服务:https://templth.wordpress.com/2014/12/15/designing-a-web-api/ .

以下是我对您在问题中提供的代码的评论:

• 您应该将一种资源用于列表资源，另一种用于单个资源。所以我想要这样的东西:

  @Override
  public Restlet createInboundRoot() {
      Router router = new Router(getContext());
      router.attach("/attendance/faculty/{name}", FacultyServerResource.class);
      router.attach("/attendance/faculty/", FacultyListServerResource.class);
      return router;
  }
  

  在资源路径中使用操作名称(如 select 或 insert)不是 RESTful。您应该利用现有的 HTTP 方法来满足您的需求。

  token {name} 对应于一个路径变量。这意味着附加的服务器资源将被称为任何值。例如，/attendance/faculty/facultyName1 或 /attendance/faculty/facultyName2 这样的 URL 将匹配。此外，ReSTLet 会自动设置属性 name 中的值。对于 URL #1，名称是 facultyName1，对于 URL #2，名称是 facultyName2。

  您作为方法 attach 的第一个参数提供的字符串可以看作是一种正则表达式。

• 您应该使用路径变量来指定加载教员的标准(教员姓名)。查看资源路径 /attendance/faculty/{name} 中的元素 {name}。 ReSTLet 将允许您通过其 API 简单地获得此提示。所以我会按如下所述调整您的服务器资源的代码:

  public class FacultyServerResource extends ServerResource {
      @Get ("json")
      public String present() throws Exception {
          String facultyName = (String)getAttribute("name");
          (...)
      }
  

  作为提醒，在注释Get 中指定值json 允许配置内容协商，并说明此方法仅在客户端想要接收JSON 内容。

• 您应该在服务器资源中处理有关返回内容的 bean。您可以简单地从您的方法 present 返回它。根据您的代码，我将创建一个这样的 bean:

  public class Faculty {
      private String name;
      private String post;
      private String course;
      private String department;
      private List<String> presents;
      private List<String> absents;
      // Getters and setters
      (...)
  }
  

  并更新方法present:

  @Get ("json")
  public Faculty present() throws Exception {
      (...)
      Faculty faculty = new Faculty();
      faculty.setName("...");
      faculty.setPost("...");
      (...)
      return faculty;
  }
  

  要使用这种方法，您只需在类路径中添加扩展 org.reSTLet.ext.jackson(及其依赖项)。

• 在服务器资源类中我不明白的是为什么要使用 getQuery 方法。后者用于从查询参数中获取提示，并且通常必须与这样的 URL 一起使用:/attendance/faculty/facultyName?param1=something&param2=somethingelse。您将获得如下参数值:

  String param1Value = getQuery().getValues("param1");
  // or
  String param2Value = getQueryValue("param2");
  

  在您的情况下，这将为空，因为您没有查询字符串/查询参数。我不明白你的查询参数 data 的用途。

• 您应该考虑的另一件事是使用连接池，因为在 Web 环境中创建到数据库的 JDBC 连接效率不高。此外，您不能限制打开的连接数。有 DBCP 或 C3P0 等工具提供此类功能。

希望对您有所帮助，有什么不明白的可以随时问我!蒂埃里