REST（三）Restlet实现REST

Restlet项目为“建立REST概念与Java类之间的映射”提供了一个轻量级而全面的框架。它可用于实现任何种类的REST式系统，而不仅仅是REST式Web服务。
Restlet参考REST标准的术语，如：资源（resource）、表示（representation）、连接器（connector）、组件（component）、媒体类型（media type）、语言（language），等等。Restlet增加了一些专门的类（如Application、Filter、Finder、Router和Route），用以简化restlets的彼此结合，以及简化把收到的请求（incoming requests）映射为处理它们的资源。

其他Restlet介绍见：Restlet 入门。本节简单介绍restlet2+spring4的集成及客户端访问。

1.spring web基础环境
见上一节Jersey创建的web工程testRest。

2.REST地址
与上一节类似，设计restlet模块rest接口地址：
/restlet/teachers GET 获取所有资源
/restlet/teachers POST 创建新资源，content中包含资源内容
/restlet/teacher/{id} GET 获取编号为id的资源
/restlet/teacher/{id} PUT 更新编号为id的资源，content中包含资源内容
/restlet/teacher/{id} DELETE 删除编号为id的资源

3.restlet库
在项目pom.xml中加入Restlet依赖：

<repositories>
	<repository>
		<id>maven-restlet</id>
		<name>Restlet repository</name>
		<url>https://maven.restlet.com</url>
	</repository>
</repositories>
<properties>
	<restlet.version>2.3.5</restlet.version>
	<fastjson.version>1.2.7</fastjson.version>
</properties>
<dependencies>	
	...
	<!-- restlet begin -->
	<dependency>
		<groupId>org.restlet.jee</groupId>
		<artifactId>org.restlet</artifactId>
		<version>${restlet.version}</version>
	</dependency>
	<dependency>
		<groupId>org.restlet.jee</groupId>
		<artifactId>org.restlet.ext.json</artifactId>
		<version>${restlet.version}</version>
	</dependency>
	<dependency>
		<groupId>org.restlet.jee</groupId>
		<artifactId>org.restlet.ext.spring</artifactId>
		<version>${restlet.version}</version>
	</dependency>
	<dependency>
		<groupId>org.restlet.jee</groupId>
		<artifactId>org.restlet.ext.servlet</artifactId>
		<version>${restlet.version}</version>
	</dependency>
	<dependency>
		<groupId>org.restlet.jee</groupId>
		<artifactId>org.restlet.ext.xml</artifactId>
		<version>${restlet.version}</version>
	</dependency>
	<dependency>
		<groupId>org.restlet.jee</groupId>
		<artifactId>org.restlet.ext.oauth</artifactId>
		<version>${restlet.version}</version>
	</dependency>
	<!-- json 相关jar包 -->
	<dependency>
		<groupId>com.alibaba</groupId>
		<artifactId>fastjson</artifactId>
		<version>${fastjson.version}</version>
	</dependency>
	<dependency>
		<groupId>com.google.guava</groupId>
		<artifactId>guava</artifactId>
		<version>${guava.version}</version>
	</dependency>
	<!-- restlet end -->
	...

Restlet使用版本2.3.5，并加入servlet、spring、json、xml等包。因Restlet库不在中央仓库中，所以要加入https://maven.restlet.com仓库。

4.Servlet
配置Restlet访问入口。

<!-- restlet -->
<servlet>
	<servlet-name>restlet</servlet-name>
	<servlet-class>org.restlet.ext.spring.SpringServerServlet</servlet-class>
	<init-param>
		<param-name>org.restlet.component</param-name>
		<param-value>component</param-value>
	</init-param>
</servlet>
<servlet-mapping>
	<servlet-name>restlet</servlet-name>
	<url-pattern>/restlet/*</url-pattern>
</servlet-mapping>

Restlet Servlet将拦截/restlet/*下的所有访问。
Restlet与web、spring集成后，不需要再自己实现Router、Application、Component。但需要在spring中进行配置。
在配置文件目录src\main\resources\下创建restlet配置目录config\restlet，并创建配置文件restlet.xml：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
	xmlns:p="http://www.springframework.org/schema/p" xmlns:mvc="http://www.springframework.org/schema/mvc"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
	http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
						http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"
	default-autowire="byName" default-lazy-init="true">

	<bean id="component" class="org.restlet.ext.spring.SpringComponent">
		<property name="defaultTarget" ref="router" />
	</bean>
	<bean id="router" class="org.restlet.ext.spring.SpringBeanRouter"></bean>

</beans>

此处定义的component bean将被web.xml配置的Restlet servlet引用。

5.实现api
在com.sunbin.test.restlet新增TeachersResource类，以实现/teachers路径的接口：

package com.sunbin.test.restlet;

import java.util.HashMap;
import java.util.Map;

import org.restlet.data.Form;
import org.restlet.ext.json.JsonRepresentation;
import org.restlet.representation.Representation;
import org.restlet.resource.Get;
import org.restlet.resource.Post;
import org.restlet.resource.ServerResource;
import org.springframework.beans.factory.annotation.Autowired;

import com.alibaba.fastjson.JSON;
import com.sunbin.test.teacher.pojo.Teacher;
import com.sunbin.test.teacher.service.TeacherService;

public class TeachersResource extends ServerResource {

	@Autowired
	private TeacherService teacherService;

	@Get
	public Representation get() {
		System.out.println("Restlet TeachersResource.get");
		Map map = new HashMap();
		map.put("teachers", teacherService.list());
		return new JsonRepresentation(JSON.toJSONString(map));
	}
	
	@Post("*:json")
	public Representation post(Representation entity){
		Map map = new HashMap();
		try {
			Form form = new Form(entity);
			System.out.println("Restlet TeachersResource.post:"+form);
			Teacher teacher = new Teacher();
			teacher.setName(form.getFirstValue("name"));
			teacher.setAge(Integer.parseInt(form.getFirstValue("age")));
			teacherService.save(teacher);
			map.put("status", "y");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return new JsonRepresentation(JSON.toJSONString(map));
	}
}

用到了以下Restlet自带注解：
@Get：GET请求的响应方法。
@Post("*:json")：POST请求的响应方法，指定*可接受各种Content-Type的请求数据，json可返回Content-Type:application/json数据。

需要注意的是，Restlet自带的json返回new JsonRepresentation(map)会对Map中的键值简单调用toString，再返回json串例如：{"teachers":["Teacher [id=1, age=1, name=a]","Teacher [id=2, age=2, name=b]"]}，这就不是标准json了。所以干脆使用阿里的fastjson库先将结果转成JSONString，再返回：{"teachers":[{"age":1,"id":1,"name":"a"},{"age":2,"id":2,"name":"b"}]}。

新增TeacherResource类，以实现/teacher/{id}路径的接口：

package com.sunbin.test.restlet;


import java.util.HashMap;
import java.util.Map;


import org.restlet.data.Form;
import org.restlet.ext.json.JsonRepresentation;
import org.restlet.representation.Representation;
import org.restlet.resource.Delete;
import org.restlet.resource.Get;
import org.restlet.resource.Put;
import org.restlet.resource.ServerResource;
import org.springframework.beans.factory.annotation.Autowired;

import com.alibaba.fastjson.JSON;
import com.sunbin.test.teacher.pojo.Teacher;
import com.sunbin.test.teacher.service.TeacherService;

public class TeacherResource extends ServerResource{

	@Autowired
	private TeacherService teacherService;

	@Get
	public Representation get(){
		String id = (String)getRequest().getAttributes().get("id");
		System.out.println("Restlet TeacherResource.get:"+id);
		Teacher teacher = new Teacher();
		teacher.setId(Integer.parseInt(id));
		Map map = new HashMap();
		map.put("teacher", teacherService.get(teacher));
		return new JsonRepresentation(JSON.toJSONString(map));
	}

	@Put	
	public Representation put(Representation entity){
		Map map = new HashMap();
		try {
			String id = (String)getRequest().getAttributes().get("id");
			Form form = new Form(entity);
			System.out.println("Restlet TeacherResource.put:"+id+":"+form);
			Teacher teacher = new Teacher();
			teacher.setId(Integer.parseInt(id));
			teacher.setName(form.getFirstValue("name"));
			teacher.setAge(Integer.parseInt(form.getFirstValue("age")));
			teacherService.update(teacher);
			map.put("status", "y");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return new JsonRepresentation(JSON.toJSONString(map));
	}

	@Delete
	public Representation delete(){
		Map map = new HashMap();
		try {
			String id = (String)getRequest().getAttributes().get("id");
			System.out.println("Restlet TeacherResource.delete:"+id);
			Teacher teacher = new Teacher();
			teacher.setId(Integer.parseInt(id));
			teacherService.remove(teacher);
			map.put("status", "y");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return new JsonRepresentation(JSON.toJSONString(map));
	}
}

同样使用的不是JAX-RS注解，而是Restlet自带注解（大小写不同）。

restlet的路径绑定需要配置在spring文件中。在restlet.xml中增加配置：

	<bean name="/teacher/{id}" id="teacherResource"
		class="com.sunbin.test.restlet.TeacherResource" scope="prototype">
	</bean>
	<bean name="/teachers" id="teachersResource"
		class="com.sunbin.test.restlet.TeachersResource" scope="prototype">
	</bean>

6.js测试
使用上一节的测试页面src\main\webapp\rest\index.jsp进行测试：

...
	<script type="text/javascript">
		// 测试框架
		//var restType = "jersey";
		var restType = "restlet";
		//var restType = "resteasy";
		//var restType = "restCxf";
		//var restType = "restMvc";
...

重新部署后，使用浏览器访问http://localhost:8080/testRest/rest，测试内容和jersey测试相同。

7.RestletClient测试
Restlet提供Client库用于测试REST接口。
新建TestRestlet类，代码如下：

package com.sunbin.test.restlet;

import java.io.IOException;

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

public class TestRestlet {

	public static final String URL_BASE = "http://localhost:8080/testRest/restlet/";

	/**
	 * @param args
	 * @throws IOException
	 * @throws ResourceException
	 */
	public static void main(String[] args) throws Exception {
		// TODO Auto-generated method stub
		String module = "teacher";
		String url = "";
		ClientResource client = null;
		String entity = "";
		String result = "";

		url = URL_BASE + module + "s";
		System.out.println("get\t " + url);
		client = new ClientResource(url);
		result = client.get().getText();
		System.out.println(result);

		url = URL_BASE + module + "s";
		System.out.println("post\t " + url);
		client = new ClientResource(url);
		entity = "name=a&age=1";
		result = client.post(entity).getText();
		System.out.println(result);

		url = URL_BASE + module + "s";
		System.out.println("get\t " + url);
		client = new ClientResource(url);
		result = client.get().getText();
		System.out.println(result);

		url = URL_BASE + module + "/1";
		System.out.println("get\t " + url);
		client = new ClientResource(url);
		result = client.get().getText();
		System.out.println(result);

		url = URL_BASE + module + "/1";
		System.out.println("put\t " + url);
		client = new ClientResource(url);
		entity = "name=aa&age=11";
		result = client.put(entity).getText();
		System.out.println(result);

		url = URL_BASE + module + "s";
		System.out.println("get\t " + url);
		client = new ClientResource(url);
		result = client.get().getText();
		System.out.println(result);

		url = URL_BASE + module + "/1";
		System.out.println("delete\t " + url);
		client = new ClientResource(url);
		result = client.delete().getText();
		System.out.println(result);

		url = URL_BASE + module + "s";
		System.out.println("get\t " + url);
		client = new ClientResource(url);
		result = client.get().getText();
		System.out.println(result);
	}

}

测试结果与Jersey类似。

8.部署至jboss
将Restlet Web工程部署至jboss，会因为jboss类加载配置导致无法启动。
需要修改jboss目录/modules/system/layers/base/sun/jdk/main下的module.xml文件：

<dependencies>
	<system export="true">
		<paths>
			...
			<path name="com/sun/net/httpserver"/>
			...

加入httpserver配置行。

9.Restlet访问session
Restlet不推荐在Resource中访问会话信息，因为这是违背REST的无状态设计的。
但如果需要在Resource中访问Session，可以按以下代码获取：

import org.restlet.Request;
import org.restlet.engine.adapter.HttpRequest;
import org.restlet.engine.adapter.ServerCall;
import org.restlet.ext.servlet.internal.ServletCall;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

...
Request request = getRequest();
if (request instanceof HttpRequest) {
	final ServerCall httpCall = ((HttpRequest) request)
			.getHttpCall();
	if (httpCall instanceof ServletCall) {
		HttpServletRequest httpServletRequest = ((ServletCall) httpCall)
				.getRequest();
		HttpSession session = httpServletRequest.getSession();
...