REST（二）Jersey实现REST

Jersey是JAX-RS（JSR311）开源参考实现，用于构建RESTful Web service。它包含三个部分：
核心服务器（Core Server）通过提供JSR 311中标准化的注释和API标准化，可以用直观的方式开发RESTful Web服务。
核心客户端（Core Client） Jersey客户端API能够帮助开发者与RESTful服务轻松通信；
集成（Integration） Jersey还提供可以轻松继承Spring、Guice、Apache Abdera的库。

本节使用Jersey集成Spring搭建。

1.spring web基础环境
eclipse的Maven Web工程，工程名为testRest。集成spring并创建简单的Teacher模块，包含POJO、SERVICE、DAO层简单代码，使用spring注解注入bean。
见 spring mvc系列，第六篇使用springmvc实现了REST。
后续各框架陆续并入该工程。

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

3.jersey库
在项目pom.xml中加入Jersey依赖：

<properties>
	<jersey.version>2.25.1</jersey.version>
</properties>
<dependencies>	
	...
	<!-- jersey begin -->
	<dependency>
		<groupId>org.glassfish.jersey.containers</groupId>
		<!-- if your container implements Servlet API older than 3.0, use "jersey-container-servlet-core" -->
		<artifactId>jersey-container-servlet</artifactId>
		<version>${jersey.version}</version>
	</dependency>
	<!-- Required only when you are using JAX-RS Client -->
	<dependency>
		<groupId>org.glassfish.jersey.core</groupId>
		<artifactId>jersey-client</artifactId>
		<version>${jersey.version}</version>
	</dependency>
	<dependency>
		<groupId>org.glassfish.jersey.ext</groupId>
		<artifactId>jersey-spring3</artifactId>
		<version>${jersey.version}</version>
		<exclusions>
			<exclusion>
				<groupId>org.springframework</groupId>
				<artifactId>spring</artifactId>
			</exclusion>
			<exclusion>
				<groupId>org.springframework</groupId>
				<artifactId>spring-core</artifactId>
			</exclusion>
			<exclusion>
				<groupId>org.springframework</groupId>
				<artifactId>spring-web</artifactId>
			</exclusion>
			<exclusion>
				<groupId>org.springframework</groupId>
				<artifactId>spring-beans</artifactId>
			</exclusion>
			<exclusion>
				<groupId>org.springframework</groupId>
				<artifactId>spring-context</artifactId>
			</exclusion>
		</exclusions>
	</dependency>
	<dependency>
		<groupId>org.codehaus.jackson</groupId>
		<artifactId>jackson-jaxrs</artifactId>
		<version>1.8.11</version>
	</dependency>
	<!-- jersey end -->	
	...

使用Jersey老版本2.25.1，与spring4集成也可使用jersey-spring3包。不使用jersey-client调用api可不载入该依赖。

4.Servlet
配置Jersey访问入口。

<!-- jersey -->
<servlet>
	<servlet-name>Jersey REST Service</servlet-name>
	<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
	<init-param>
		<param-name>javax.ws.rs.Application</param-name>
		<param-value>com.sunbin.test.jersey.JerseyConfig</param-value>
	</init-param>
	<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
	<servlet-name>Jersey REST Service</servlet-name>
	<url-pattern>/jersey/*</url-pattern>
</servlet-mapping>

Jersey Servlet将拦截/jersey/*下的所有访问。
因为Jersey服务必须通过容器来访问，实践过程中发现直接在web.xml中配置：
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>com.sunbin.test.jersey</param-value>
</init-param>
不生效，还是需要实现Application来设置扫描的包路径。
新增JerseyConfig类：

package com.sunbin.test.jersey;

import org.glassfish.jersey.server.ResourceConfig;

import org.codehaus.jackson.jaxrs.JacksonJsonProvider;

// TODO: Auto-generated Javadoc
/**
 * The Class JerseyConfig.
 */
public class JerseyConfig extends ResourceConfig {

	/**
	 * Instantiates a new jersey config.
	 */
	public JerseyConfig() {
		// 配置扫描包
		packages("com.sunbin.test.jersey");
		// 配置json转换。配置后如果api定义返回类型为json、且pojo注解XmlRootElement，将自动转为json返回；否则需要自己转换
		register(JacksonJsonProvider.class);
	}
}

Jersey将com.sunbin.test.jersey包下的类中的注解，转换为REST服务。

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

package com.sunbin.test.jersey;

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("Jersey 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("Jersey TeachersResource.post:" + teacher);
			teacherService.save(teacher);
			map.put("status", "y");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return map;
	}
}

用到了以下JAX-RS注解：
@Path("teachers")绑定路径：/servlet路径/teachers。可在类和方法上加注解。
@Produces(MediaType.APPLICATION_JSON)支持返回类型：application/json。可支持多种类型，按请求header：AcceptType返回。
@GET：GET请求的响应方法。
@POST：POST请求的响应方法。
@FormParam("age") int age, @FormParam("name") String name：获取通过application/x-www-form-urlencoded方式提交的参数。

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

package com.sunbin.test.jersey;

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

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

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

	@Autowired
	private TeacherService teacherService;

	@GET
	public Map get(@PathParam("id") int id) {
		System.out.println("Jersey 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("Jersey 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("Jersey 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;
	}
}

用到了以下JAX-RS注解：
@PathParam("id")：获取路径参数{id}
@PUT：PUT请求的响应方法。
@DELETE：DELETE请求的响应方法。

6.js测试
Jersey不像springmvc一样，可以通过在POST form中增加_method=PUT/DELETE隐藏参数的方法来支持表单直接提交PUT/DELETE，所以要通过javascript或者程序来访问。
先使用jquery库来进行ajax访问测试。
在src\main\webapp\rest目录下新建index.jsp：

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
	<title>teacher</title>
	<script type="text/javascript" src="<%=path %>/resources/js/jquery-3.2.0.js"></script>
	<script type="text/javascript">
		// 测试框架
		var restType = "jersey";
		//var restType = "restlet";
		//var restType = "resteasy";
		//var restType = "restCxf";
		//var restType = "restMvc";
		
		// 初始化加载
		$(document).ready(function(){
			list();
			var ajaxOption = null;
			$("#saveButton").click(function(){
				save();
			});
		});
		// GET /teachers
		function list(){
			$.ajax({
				url:"../"+ restType +"/teachers",
				dataType:"json",
				success:function(data){
					$("#listBody").empty();
					$.each(data.teachers, function(i, item){
						var teacherTr = "<tr><form name='updateForm_"+item.id+"' action='teacher/update' method='POST'>"
							+"<td><input type='hidden' name='id' id='id_"+item.id+"' value='"+item.id+"'/>"+item.id+"</td>"
							+"<td><input type='text' name='name' id='name_"+item.id+"' value='"+item.name+"' /></td>"
							+"<td><input type='text' name='age' id='age_"+item.id+"' value='"+item.age+"' /></td>"
							+"<td><a href='javascript:void(0);' onclick='get("+item.id+");'>get</a> "
							+"<a href='javascript:void(0);' onclick='remove("+item.id+");'>remove</a> "
							+"<input type='submit' value='update' id='updateButton_"+item.id+"' onclick='update("+item.id+");' /></td></tr>";
						$("#listBody").append(teacherTr);
					});
				}
			});
		}
		// POST /teachers
		function save(){
			$("#saveButton").attr("disabled", true);
			$.ajax({
				url:"../"+ restType +"/teachers",
				type:"POST",
				data:"name="+$("#name").val()+"&"+"age="+$("#age").val(),
				dataType:"json",
				complete:function(){
					$("#saveButton").attr("disabled", false);
				},
				success:function(data){
					alert(data.status);
					$("#name").val('');
					$("#age").val('');
					list();
				}
			});
		}
		// GET /teachers/{id}
		function get(id){
			$.ajax({
				url:"../"+ restType +"/teacher/"+id,
				dataType:"json",
				success:function(data){
					var teacherInfo = "id:"+data.teacher.id+"\nname:"+data.teacher.name+"\nage:"+data.teacher.age;
					alert(teacherInfo);
				}
			});
		}
		// DELETE /teachers/{id}
		function remove(id){
			$.ajax({
				url:"../"+ restType +"/teacher/"+id,
				type:"DELETE",
				dataType:"json",
				success:function(data){
					alert(data.status);
					list();
				}
			});
		}
		// PUT /teachers/{id}
		function update(id){
			$("#updateButton_"+id).attr("disabled", true);
			$.ajax({
				url:"../"+ restType +"/teacher/"+id,
				type:"PUT",
				data:"&name="+$("#name_"+id).val()+"&"+"age="+$("#age_"+id).val(),
				dataType:"json",
				complete:function(data){
					$("#updateButton_"+id).attr("disabled", false);
				},
				success:function(data){
					alert(data.status);
					list();
				}
			});
		}
	</script>
</head>
<body>
	save
	<form name="saveForm" action="teacher/save" method="POST">
		name:<input type="text" name="name" id="name" /> 
		
 
		age:<input type="text" name="age" id="age" /> 
		
 
		<input type="button" value="save" id="saveButton" />
	</form>
	<br/>
	list
	<table border="1">
		<thead>
			<tr>
				<td>id</td>
				<td>name</td>
				<td>age</td>
				<td>操作</td>
			</tr>
		</thead>
		<tbody id="listBody">
			<!-- 无用，通过js增加行 -->
			<c:forEach items="${list }" var="teacher">
				<tr>
					<form name="updateForm_${teacher.id}" action="teacher/update" method="POST">
					<td><input type="hidden" name="id" id="id" value="${teacher.id}" />${teacher.id}</td>
					<td><input type="text" name="name" id="name" value="${teacher.name}" /></td>
					<td><input type="text" name="age" id="age" value="${teacher.age}" /></td>
					<td>[url=javascript:void(0);]get[/url] [url=javascript:void(0);]remove[/url] <input type="submit" value="update" id="updateButton_${teacher.id}" /></td>
					</form>
				</tr>
			</c:forEach>
		</tbody>
	</table>
</body>
</html>

重新部署后，使用浏览器访问 http://localhost:8080/testRest/rest，可以看到页面：

通过js访问REST api，就类似网站使用第三方登录（QQ、微博等）后访问用户头像昵称的过程，当然登录时一般使用OAUTH2.0 做认证方案。

7.JerseyClient测试
Jersey提供Client库用于测试JAX-RS接口。Client不仅可用来测Jersey REST，也可以用来测试其他框架实现的接口和http服务。
新建TestJersey类，代码如下：

package com.sunbin.test.jersey;

import javax.ws.rs.client.Client;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.Entity;
import javax.ws.rs.client.WebTarget;
import javax.ws.rs.core.Form;

public class TestJersey {

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

	public static void main(String[] args) {
		Client client = ClientBuilder.newClient();
		String module = "teacher";
		String url = "";
		String result = "";
		Entity<Form> entity = null;
		Form form = null;
		WebTarget baseTarget = client.target(URL_BASE);
		WebTarget 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);
	}
}

测试结果如下：

get	http://localhost:8080/testRest/jersey/teachers
{"teachers":[]}
post	 http://localhost:8080/testRest/jersey/teachers
{"status":"y"}
get	http://localhost:8080/testRest/jersey/teachers
{"teachers":[{"id":1,"age":1,"name":"a"}]}
get	 http://localhost:8080/testRest/jersey/teacher/1
{"teacher":{"id":1,"age":1,"name":"a"}}
put	 http://localhost:8080/testRest/jersey/teacher/1
{"status":"y"}
get	http://localhost:8080/testRest/jersey/teachers
{"teachers":[{"id":1,"age":11,"name":"aa"}]}
delete	 http://localhost:8080/testRest/jersey/teacher/1
{"status":"y"}
get	http://localhost:8080/testRest/jersey/teachers
{"teachers":[]}

通过js访问REST api，类似于服务端、桌面应用、移动端APP使用第三方登录（QQ、微信等）后访问用户数据并保存的过程。

REST（二）Jersey实现REST

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