RESTLET开发实例

1 前提

　　由于近期工作的需要，要把RESTLET应用到项目中，于是在网上参考了一些资料的基础上，实践了一个关于RESTLET接口的小例子。

　　Restlet的思想是：HTTP客户端与HTTP服务器之间的差别，对架构来说无所谓。一个软件应可以既充当Web客户端又充当Web服务器，而无须采用两套完全不同的APIs。

　　Restlet提供了多个版本:Java SE、Java EE、android、Google AppEngine、Google Web Toolkit、Android。这里我们使用的是jee版本。

　　RESTLET的实现可以采用JAX-RS方式，也可以采用其他方式，见：

http://www.iteye.com/topic/85928

本例子是采用JAX-RS的API开发的，这种方式提供了一种基于注解的模型来描述分布式资源，可以利用注解的功能提供资源的位置、传递等。可以在一个Resource类中同时对外提供多个rest接口服务。具体的实现步骤见如下章节。

2 实例开发

2.1 工程说明

此处可以建立一个web工程，也可以建立一个JAVASE工程，如何应用就UP TO YOU了，此处的例子只是为了梳理下RESTLET的开发流程，不涉及到web界面的应用，所以就建立了一个普通的JAVASE的工程。工程的结构图如下：

我们的工程分为如下几个部分：Server启动模块、Application模块、modle模块、REST接口实现的resource模块和客户端模块。

工程所依赖的jar包，是最基本的这个6个包，因为数据的传输使用的JSON，所以json包是必须的，如果想扩展功能，请自行添加其余的包。

2.2 Server端启动部分

RestJaxRsServer类的代码如下：

 package com.scott.restlet;

 import org.restlet.Component;
 import org.restlet.data.Protocol;

 import com.scott.restlet.application.RestJaxRsApplication;

 public class RestJaxRsServer {

     public static void main(String[] args) throws Exception {
         Component component = new Component();
         component.getServers().add(Protocol.HTTP, 8082);
         component.getDefaultHost().attach(new RestJaxRsApplication(null));
         component.start();

         System.out.println("The restlet server started ...");
     }
 }

此代码中指定了我们的HTTP的绑定端口，地址就是本地默认的ip。另外，代码中有一个RestJaxRsApplication，这是每个Application能够管理一组restlet接口。

2.3 Application部分

在application包中有两个类，一个是RestJaxRsApplication类，继承了org.restlet.ext.jaxrs.JaxRsApplication，作为运行类，用于初始化REST的运行环境，其代码如下：

 package com.scott.restlet.application;

 import org.restlet.Context;
 import org.restlet.ext.jaxrs.JaxRsApplication;

 public class RestJaxRsApplication extends JaxRsApplication {

     public RestJaxRsApplication(Context context) {
         super(context);
         this.add(new MyApplication());
     }

 }

另外一个是MyApplication，作为应用类，继承了javax.ws.rs.core.Application，这里面绑定了我们的RESTLET的接口RESOURCE类，可以将多个资源绑定在HashSet中，代码如下：

 package com.scott.restlet.application;

 import java.util.HashSet;
 import java.util.Set;

 import javax.ws.rs.core.Application;

 import com.scott.restlet.resource.StudentResource;
 import com.scott.restlet.resource.TeacherResource;

 public class MyApplication extends Application {

     @Override
     public Set<Class<?>> getClasses() {
         Set<Class<?>> resources = new HashSet<Class<?>>();

         resources.add(StudentResource.class);
         resources.add(TeacherResource.class);

         return resources;
     }

 }

2.4 模型部分

此实例的操作模型比较简单，就是一个Student类和一个Teacher类，代码如下：

Student：

 package com.scott.restlet.modle;

 public class Student {

     private int id;
     private String name;
     private int sex;
     private int age;
     private int grade;

     public int getGrade() {
         return grade;
     }

     public void setGrade(int grade) {
         this.grade = grade;
     }

     public int getId() {
         return id;
     }

     public void setId(int id) {
         this.id = id;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public int getSex() {
         return sex;
     }

     public void setSex(int sex) {
         this.sex = sex;
     }

     public int getAge() {
         return age;
     }

     public void setAge(int age) {
         this.age = age;
     }
 }

Teacher：

 package com.scott.restlet.modle;

 public class Teacher {

     private int id;
     private String name;
     private int sex;
     private int age;
     private String subject;

     public int getId() {
         return id;
     }
     public void setId(int id) {
         this.id = id;
     }
     public String getName() {
         return name;
     }
     public void setName(String name) {
         this.name = name;
     }
     public int getSex() {
         return sex;
     }
     public void setSex(int sex) {
         this.sex = sex;
     }
     public int getAge() {
         return age;
     }
     public void setAge(int age) {
         this.age = age;
     }
     public String getSubject() {
         return subject;
     }
     public void setSubject(String subject) {
         this.subject = subject;
     }
 }

2.5 RESOURCE部分

这部分是我们的RESTLET接口实现部分，此处我们有两个接口实现类，一个是StudentResource，一个是TeacherResource，分别对外提供不同的REST接口服务。至于StorageOperator类，把它当做一个内存数据库好了，其实就是一个HashMap，StudentResource和TeacherResource的操作会在StorageOperator类中具体实现。代码如下：

StudentResource：

 package com.scott.restlet.resource;

 import javax.ws.rs.DELETE;
 import javax.ws.rs.GET;
 import javax.ws.rs.POST;
 import javax.ws.rs.PUT;
 import javax.ws.rs.Path;
 import javax.ws.rs.PathParam;
 import javax.ws.rs.Produces;

 import org.restlet.data.Form;
 import org.restlet.representation.Representation;

 import com.scott.restlet.modle.Student;

 @Path("/TestRestlet/student/")
 public class StudentResource {

     @GET
     @Path("{id}/json")
     @Produces("application/json")
     public Student getStudentJson(@PathParam("id") int id) {
         return StorageOperator.findStudent(id);
     }

     @POST
     @Path("add")
     public String addStudent(Representation entity) {

         //get parameters from client
         Form form = new Form(entity);
         String name = form.getFirstValue("name");
         int grade = Integer.parseInt(form.getFirstValue("grade"));
         int sex = Integer.parseInt(form.getFirstValue("sex"));
         int age = Integer.parseInt(form.getFirstValue("age"));

         Student student = new Student();
         student.setGrade(grade);
         student.setName(name);
         student.setSex(sex);
         student.setAge(age);

         int id = StorageOperator.studentID + 1;
         student.setId(id);
         return String.valueOf(StorageOperator.addStudent(student));
     }

     @PUT
     @Path("update")
     public String updateStudent(Representation entity) {
         Form form = new Form(entity);

         int id = Integer.parseInt(form.getFirstValue("id"));
         Student student = StorageOperator.findStudent(id);

         if (student == null) {
             return "null";
         }else{
             String name = form.getFirstValue("name");
             int grade = Integer.parseInt(form.getFirstValue("grade"));
             int sex = Integer.parseInt(form.getFirstValue("sex"));
             int age = Integer.parseInt(form.getFirstValue("age"));

             student.setGrade(grade);
             student.setName(name);
             student.setSex(sex);
             student.setAge(age);

             return String.valueOf(StorageOperator.updateStudent(student));
         }
     }

     @DELETE
     @Path("delete/{id}")
     public String deleteStudent(@PathParam("id") int id) {
         int status = StorageOperator.deleteStudent(id);
         return String.valueOf(status);
     }

 }

TeacherResource：

 package com.scott.restlet.resource;

 import javax.ws.rs.DELETE;
 import javax.ws.rs.GET;
 import javax.ws.rs.POST;
 import javax.ws.rs.PUT;
 import javax.ws.rs.Path;
 import javax.ws.rs.PathParam;
 import javax.ws.rs.Produces;

 import org.restlet.data.Form;
 import org.restlet.representation.Representation;

 import com.scott.restlet.modle.Teacher;

 @Path("/TestRestlet/teacher/")
 public class TeacherResource {
     @GET
     @Path("{id}/json")
     @Produces("application/json")
     public Teacher getTeacherJson(@PathParam("id") int id) {
         return StorageOperator.findTeacher(id);
     }

     @POST
     @Path("add")
     public String addTeacher(Representation entity) {

         //get parameters from client
         Form form = new Form(entity);
         String name = form.getFirstValue("name");
         String subject = form.getFirstValue("subject");
         int sex = Integer.parseInt(form.getFirstValue("sex"));
         int age = Integer.parseInt(form.getFirstValue("age"));

         Teacher teacher = new Teacher();
         teacher.setSubject(subject);
         teacher.setName(name);
         teacher.setSex(sex);
         teacher.setAge(age);

         int id = StorageOperator.teacherID + 1;
         teacher.setId(id);
         return String.valueOf(StorageOperator.addTeacher(teacher));
     }

     @PUT
     @Path("update")
     public String updateTeacher(Representation entity) {
         Form form = new Form(entity);

         int id = Integer.parseInt(form.getFirstValue("id"));
         Teacher teacher = StorageOperator.findTeacher(id);

         if (teacher == null) {
             return "null";
         }else{
             String name = form.getFirstValue("name");
             String subject = form.getFirstValue("subject");
             int sex = Integer.parseInt(form.getFirstValue("sex"));
             int age = Integer.parseInt(form.getFirstValue("age"));

             teacher.setSubject(subject);
             teacher.setName(name);
             teacher.setSex(sex);
             teacher.setAge(age);

             return String.valueOf(StorageOperator.updateTeacher(teacher));
         }
     }

     @DELETE
     @Path("delete/{id}")
     public String deleteTeacher(@PathParam("id") int id) {
         int status = StorageOperator.deleteTeacher(id);
         return String.valueOf(status);
     }
 }

StorageOperator：

 package com.scott.restlet.resource;

 import java.util.HashMap;

 import com.scott.restlet.modle.Student;
 import com.scott.restlet.modle.Teacher;

 public class StorageOperator {
     public static int studentID = 1;
     public static int teacherID = 1;

     public static HashMap<Integer, Student> students = new HashMap<Integer, Student>();
     public static HashMap<Integer, Teacher> teachers = new HashMap<Integer, Teacher>();

     static {
         Student student = new Student();
         student.setId(1);
         student.setGrade(3);
         student.setName("Scott");
         student.setSex(0);
         student.setAge(18);
         students.put(student.getId(), student);

         Teacher teacher = new Teacher();
         teacher.setId(1);
         teacher.setSubject("MATH");
         teacher.setName("Toney");
         teacher.setSex(1);
         teacher.setAge(27);
         teachers.put(teacher.getId(), teacher);
     }

     public static Student findStudent(int id) {
         return students.get(id);
     }

     public static int addStudent(Student student) {
         students.put(student.getId(), student);
         return student.getId();
     }

     public static int updateStudent(Student student) {
         return addStudent(student);
     }

     public static int deleteStudent(int id) {
         if (students.get(id) != null) {
             students.remove(id);
             return 1;
         }
         return 0;
     }

     public static Teacher findTeacher(int id) {
         return teachers.get(id);
     }

     public static int addTeacher(Teacher teacher) {
         teachers.put(teacher.getId(), teacher);
         return teacher.getId();
     }

     public static int updateTeacher(Teacher teacher) {
         return addTeacher(teacher);
     }

     public static int deleteTeacher(int id) {
         if (teachers.get(id) != null) {
             teachers.remove(id);
             return 1;
         }
         return 0;
     }

 }

在类的上面标注的PATH注解，作为全局的一个路径变量，方法上部的PATH注解都以类注解作为相对路径。并且，Produce表示返回的数据格式，此处是JSON类型。至于GET和POST，可以简单的理解为：

POST   /uri     创建

DELETE /uri/xxx 删除

PUT    /uri/xxx 更新或创建

GET    /uri/xxx 查看

2.6 客户端部分

客户端的访问REST接口，可以通过浏览器来输入url访问，也可以通过代码来访问，通过代码来访问的代码此处封装在了Client类中，代码如下：

StudentOperateClient：

 package com.scott.restlet.client;

 import java.io.IOException;

 import org.restlet.data.Form;
 import org.restlet.resource.ClientResource;
 import org.restlet.resource.ResourceException;

 public class StudentOperateClient {
     public static void testGetStudent(String url) {
         ClientResource client = new ClientResource(url + "student/1/json");
         try {
             System.out.println("Student get " + client.get().getText());
         } catch (ResourceException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     public static void testAddStudent(String url) {
         ClientResource client = new ClientResource(url + "student/add");
         try {
             Form form = new Form();
             form.add("name", "Scott007");
             form.add("grade", "3");
             form.add("sex", "0");
             form.add("age", "15");

             String id = client.post(form.getWebRepresentation()).getText();

             System.out.println("Student add " + id);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     public static void testUpdateStudent(String url) {
         ClientResource client = new ClientResource(url + "student/update");
         try {
             Form form = new Form();
             form.add("name", "Scott007");
             form.add("grade", "4");
             form.add("sex", "0");
             form.add("id", "1");
             form.add("age", "16");

             String id = client.put(form.getWebRepresentation()).getText();

             System.out.println("Student update " + id);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     public static void testDeleteStudent(String url) {
         ClientResource client = new ClientResource(url + "student/delete/1");
         try {
             System.out.println("Student delete " + client.delete().getText());
         } catch (ResourceException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

TeacherOperateClient：

 package com.scott.restlet.client;

 import java.io.IOException;

 import org.restlet.data.Form;
 import org.restlet.resource.ClientResource;
 import org.restlet.resource.ResourceException;

 public class TeacherOperateClient {
     public static void testGetTeacher(String url) {
         ClientResource client = new ClientResource(url + "teacher/1/json");
         try {
             System.out.println("Teacher get " + client.get().getText());
         } catch (ResourceException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     public static void testAddTeacher(String url) {
         ClientResource client = new ClientResource(url + "teacher/add");
         try {
             Form form = new Form();

             form.add("name", "Scott008");
             form.add("subject", "MATH");
             form.add("sex", "0");
             form.add("age", "27");

             String id = client.post(form.getWebRepresentation()).getText();

             System.out.println("Teacher add " + id);
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     public static void testUpdateTeacher(String url) {
         ClientResource client = new ClientResource(url + "teacher/update");
         try {
             Form form = new Form();

             form.add("age", "28");
             form.add("name", "Scott008");
             form.add("subject", "English");
             form.add("sex", "0");
             form.add("id", "1");

             String id = client.put(form.getWebRepresentation()).getText();
             System.out.println("Teacher update " + id);

         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     public static void testDeleteTeacher(String url) {
         ClientResource client = new ClientResource(url + "teacher/delete/1");
         try {
             System.out.println("Teacher delete " + client.delete().getText());
         } catch (ResourceException e) {
             e.printStackTrace();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }
 }

Client：

 package com.scott.restlet.client;

 public class Client {

     public static final String url = "http://localhost:8082/TestRestlet/";

     public static void main(String args[]){

         StudentOperateClient.testGetStudent(url);
         StudentOperateClient.testUpdateStudent(url);

         TeacherOperateClient.testGetTeacher(url);
         TeacherOperateClient.testUpdateTeacher(url);
     }
 }

2.7 运行

运行，得到如下结果：

服务端启动后：

2013-9-3 23:22:51 org.restlet.engine.http.connector.HttpServerHelper start
信息: Starting the internal HTTP server on port 8082
The restlet server started ...

客户端启动后的客户端信息：

2013-9-3 23:24:12 org.restlet.engine.http.connector.HttpClientHelper start
信息: Starting the default HTTP client
Student get {"id":1,"sex":0,"age":18,"name":"Scott","grade":3}
2013-9-3 23:24:12 org.restlet.engine.http.connector.HttpClientHelper start
信息: Starting the default HTTP client
Student update 1
2013-9-3 23:24:12 org.restlet.engine.http.connector.HttpClientHelper start
信息: Starting the default HTTP client
Teacher get {"id":1,"sex":1,"subject":"MATH","age":27,"name":"Toney"}
2013-9-3 23:24:12 org.restlet.engine.http.connector.HttpClientHelper start
信息: Starting the default HTTP client
Teacher update 1

客户端启动的服务端信息：

2013-9-3 23:22:51 org.restlet.engine.http.connector.HttpServerHelper start
信息: Starting the internal HTTP server on port 8082
The restlet server started ...
2013-9-3 23:24:12 org.restlet.engine.log.LogFilter afterHandle
信息: 2013-09-03    23:24:12    127.0.0.1    -    -    8082    GET    /TestRestlet/student/1/json    -    200    -    0    70    http://localhost:8082    Restlet-Framework/2.0.6    -
2013-9-3 23:24:12 org.restlet.engine.log.LogFilter afterHandle
信息: 2013-09-03    23:24:12    127.0.0.1    -    -    8082    PUT    /TestRestlet/student/update    -    200    1    39    4    http://localhost:8082    Restlet-Framework/2.0.6    -
2013-9-3 23:24:12 org.restlet.engine.log.LogFilter afterHandle
信息: 2013-09-03    23:24:12    127.0.0.1    -    -    8082    GET    /TestRestlet/teacher/1/json    -    200    -    0    1    http://localhost:8082    Restlet-Framework/2.0.6    -
2013-9-3 23:24:13 org.restlet.engine.log.LogFilter afterHandle
信息: 2013-09-03    23:24:13    127.0.0.1    -    -    8082    PUT    /TestRestlet/teacher/update    -    200    1    47    2    http://localhost:8082    Restlet-Framework/2.0.6    -

当然，此处的例子规模和功能都很小，是在参考了[2]的基础上稍加改造，算是可以作为学习RESTLET的第一步吧。

3 一些可参考的网址

[1]http://whui0110.iteye.com/blog/1682388

[2]http://www.infoq.com/cn/articles/rest-introduction

[3]http://www.lifeba.org/arch/restlet_develop_jax-rs_service_1.html