REST（四）RESTEasy实现REST

RESTEasy是JBoss的一个开源项目，提供各种框架帮助你构建RESTful Web Services和RESTful Java应用程序。它是JAX-RS规范的一个完整实现并通过JCP认证。作为一个JBOSS的项目，它当然能和JBOSS应用服务器很好地集成在一起。但是，它也能在任何运行JDK5或以上版本的Servlet容器中运行。RESTEasy还提供一个RESTEasy JAX-RS客户端调用框架。能够很方便与EJB、Seam、Guice、Spring和Spring MVC集成使用。支持在客户端与服务器端自动实现GZIP解压缩。

其他RESTEasy介绍见官网：http://resteasy.jboss.org/。本节简单介绍RESTEasy2+spring4的集成及客户端访问。

1.spring web基础环境
见之前章节创建的web工程testRest。

2.REST地址
与上一节类似，设计RESTEasy模块/resteasy/*。

3.RESTEasy库
在项目pom.xml中加入RESTEasy依赖：

<properties>
	<!-- resteasy高版本要求jdk1.8，使用低版本 -->
	<resteasy.version>3.0.0.Final</resteasy.version>
</properties>
<dependencies>	
	...
	<!-- resteasy begin -->
	<dependency>
		<groupId>org.jboss.resteasy</groupId>
		<artifactId>resteasy-jaxrs</artifactId>
		<version>${resteasy.version}</version>
	</dependency>
	<dependency>
		<groupId>org.jboss.resteasy</groupId>
		<artifactId>resteasy-client</artifactId>
		<version>${resteasy.version}</version>
	</dependency>
	<dependency>
		<groupId>org.jboss.resteasy</groupId>
		<artifactId>resteasy-spring</artifactId>
		<version>${resteasy.version}</version>
	</dependency>
	<dependency>
		<groupId>org.jboss.resteasy</groupId>
		<artifactId>resteasy-jackson-provider</artifactId>
		<version>${resteasy.version}</version>
	</dependency>
	<!-- resteasy end -->
	...

版本使用3.0.0.Final，因为更新的版本要求jdk1.8才能运行。

4.Servlet
配置RESTEasy访问入口。

<!-- resteasy -->
<context-param>
	<param-name>resteasy.resources</param-name>
	<param-value>
		com.sunbin.test.resteasy.TeachersResource,com.sunbin.test.resteasy.TeacherResource
	</param-value>
</context-param>
<context-param>
	<param-name>resteasy.servlet.mapping.prefix</param-name>
	<param-value>/resteasy</param-value>
</context-param>
<listener>
	<listener-class>org.jboss.resteasy.plugins.server.servlet.ResteasyBootstrap</listener-class>
</listener>
<servlet>
	<servlet-name>resteasy</servlet-name>
	<servlet-class>org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher</servlet-class>
</servlet>
<servlet-mapping>
	<servlet-name>resteasy</servlet-name>
	<url-pattern>/resteasy/*</url-pattern>
</servlet-mapping>

resteasy Servlet将拦截/resteasy/*下的所有访问。
RESTEasy与web、spring集成后，不需要再自己实现Application、Component等组件，也不需要配置文件进行路径配置，仅需要使用@Path注解。

5.实现api
新建com.sunbin.test.resteasy包，新增TeachersResource类，以实现/teachers路径的接口：

package com.sunbin.test.resteasy;

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

import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import org.springframework.beans.factory.annotation.Autowired;

import com.sunbin.test.teacher.pojo.Teacher;
import com.sunbin.test.teacher.service.TeacherService;

@Path("/teachers")
@Produces(MediaType.APPLICATION_JSON)
public class TeachersResource {

	@Autowired
	private TeacherService teacherService;

	@GET
	public Map get() {
		System.out.println("Resteasy TeachersResource.get");
		Map map = new HashMap();
		map.put("teachers", teacherService.list());
		return map;
	}

	@POST
	public Map post(@FormParam("age") int age, @FormParam("name") String name) {
		Map map = new HashMap();
		try {
			Teacher teacher = new Teacher();
			teacher.setName(name);
			teacher.setAge(age);
			System.out.println("Resteasy TeachersResource.post:" + teacher);
			teacherService.save(teacher);
			map.put("status", "y");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return map;
	}

}

路径注解@Path、返回类型注解@Produces、访问方法@GET、参数读取@FormParam，都和Jersey的JAX-RS相同。

重新部署项目后，访问http://localhost:8080/testRest/resteasy/teachers，发现报错：
java.lang.NullPointerException
com.sunbin.test.resteasy.TeachersResource.get(TeachersResource.java:29)
检查后发现是teacherService.list()语句中teacherService为null，@Autowired注解没有生效。
尝试使用xml配置方式实现teacherService注入，或使用jsr规范自有的@Inject、@Resource注解也不生效。

为什么会这样？分析是因为RESTEasy和spring的beanfactory之间依赖注入的问题。
RESTEasy官网手册推荐以下两种解决方法：
1.通过WebApplicationContextUtils工具类获取ApplicationContext对象
2.自定义工具类
具体使用方法见我之前的文章：spring4学习（三）在非Spring类中获取Bean

为了方便注入，这里采用第二种方法：定义Context工具类SpringContextHolder并配置至spring。之后需要对Resource类进行改造：

package com.sunbin.test.resteasy;

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

import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import com.sunbin.common.spring.SpringContextHolder;
import com.sunbin.test.teacher.pojo.Teacher;
import com.sunbin.test.teacher.service.TeacherService;

@Path("/teachers")
@Produces(MediaType.APPLICATION_JSON)
public class TeachersResource {

	private TeacherService teacherService;

	public TeachersResource() {
		super();
		// 不能自动注入，需要手动getBean赋值
		teacherService = (TeacherService) SpringContextHolder
				.getBean("teacherService");
		// TODO Auto-generated constructor stub
	}

	@GET
	public Map get() {
		System.out.println("Resteasy TeachersResource.get");
		Map map = new HashMap();
		map.put("teachers", teacherService.list());
		return map;
	}

	@POST
	public Map post(@FormParam("age") int age, @FormParam("name") String name) {
		Map map = new HashMap();
		try {
			Teacher teacher = new Teacher();
			teacher.setName(name);
			teacher.setAge(age);
			System.out.println("Resteasy TeachersResource.post:" + teacher);
			teacherService.save(teacher);
			map.put("status", "y");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return map;
	}

}

在TeachersResource类的构造方法中手动通过SpringContextHolder获取Bean，再赋值给resource。

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

package com.sunbin.test.resteasy;

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

import javax.ws.rs.DELETE;
import javax.ws.rs.FormParam;
import javax.ws.rs.GET;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import com.sunbin.common.spring.SpringContextHolder;
import com.sunbin.test.teacher.pojo.Teacher;
import com.sunbin.test.teacher.service.TeacherService;

@Path("teacher/{id}")
@Produces(MediaType.APPLICATION_JSON)
public class TeacherResource {

	private TeacherService teacherService;

	public TeacherResource() {
		super();
		teacherService = (TeacherService) SpringContextHolder
				.getBean("teacherService");
		// TODO Auto-generated constructor stub
	}

	@GET
	public Map get(@PathParam("id") int id) {
		System.out.println("Resteasy TeacherResource.get:" + id);
		Teacher teacher = new Teacher();
		teacher.setId(id);
		Map map = new HashMap();
		map.put("teacher", teacherService.get(teacher));
		return map;
	}

	@PUT
	public Map put(@PathParam("id") int id, @FormParam("age") int age,
			@FormParam("name") String name) {
		Map map = new HashMap();
		try {
			Teacher teacher = new Teacher();
			teacher.setId(id);
			teacher.setName(name);
			teacher.setAge(age);
			System.out.println("Resteasy TeacherResource.put:" + id + ":"
					+ teacher);
			teacherService.update(teacher);
			map.put("status", "y");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return map;
	}

	@DELETE
	public Map delete(@PathParam("id") int id) {
		Map map = new HashMap();
		try {
			System.out.println("Resteasy TeacherResource.delete:" + id);
			Teacher teacher = new Teacher();
			teacher.setId(id);
			teacherService.remove(teacher);
			map.put("status", "y");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return map;
	}

}

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Restlet测试相同。

7.RESTEasy Client测试
RESTEasy提供Client库用于测试REST接口。
新建TestResteasy类，代码如下：

package com.sunbin.test.resteasy;

import javax.ws.rs.client.Entity;
import javax.ws.rs.core.Form;

import org.jboss.resteasy.client.jaxrs.ResteasyClient;
import org.jboss.resteasy.client.jaxrs.ResteasyClientBuilder;
import org.jboss.resteasy.client.jaxrs.ResteasyWebTarget;

public class TestResteasy {

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

	public static void main(String[] args) {
		ResteasyClient client = new ResteasyClientBuilder().build();
		String module = "teacher";
		String url = "";
		String result = "";
		Entity<Form> entity = null;
		Form form = null;
		ResteasyWebTarget baseTarget = client.target(URL_BASE);
		ResteasyWebTarget target = null;

		url = URL_BASE + module + "s";
		System.out.println("get\t" + url);
		target = baseTarget.path(module + "s");
		result = target.request().get(String.class);
		System.out.println(result);

		url = URL_BASE + module + "s";
		System.out.println("post\t " + url);
		target = baseTarget.path(module + "s");
		form = new Form().param("age", "1").param("name", "a");
		entity = Entity.form(form);
		result = target.request().post(entity, String.class);
		System.out.println(result);

		url = URL_BASE + module + "s";
		System.out.println("get\t" + url);
		target = baseTarget.path(module + "s");
		result = target.request().get(String.class);
		System.out.println(result);

		url = URL_BASE + module + "/1";
		System.out.println("get\t " + url);
		target = baseTarget.path(module + "/1");
		result = target.request().get(String.class);
		System.out.println(result);

		url = URL_BASE + module + "/1";
		System.out.println("put\t " + url);
		target = baseTarget.path(module + "/1");
		form = new Form().param("age", "11").param("name", "aa");
		entity = Entity.form(form);
		result = target.request().put(entity, String.class);
		System.out.println(result);

		url = URL_BASE + module + "s";
		System.out.println("get\t" + url);
		target = baseTarget.path(module + "s");
		result = target.request().get(String.class);
		System.out.println(result);

		url = URL_BASE + module + "/1";
		System.out.println("delete\t " + url);
		target = baseTarget.path(module + "/1");
		result = target.request().delete(String.class);
		System.out.println(result);

		url = URL_BASE + module + "s";
		System.out.println("get\t" + url);
		target = baseTarget.path(module + "s");
		result = target.request().get(String.class);
		System.out.println(result);
	}
}

测试结果与Restlet类似。