dubbo的简单应用

一. dubbo简介

　　dubbo是一个分布式服务框架，致力于提供高性能和透明化的RPC远程服务调用方案，是阿里巴巴SOA服务化治理方案的核心框架。

二. 架构

　　引用dubbo的架构图：

1 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
2     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> 3     <modelVersion>4.0.0</modelVersion>
4     <groupId>com.bigbang</groupId>
5     <artifactId>consumer</artifactId>
6     <packaging>war</packaging>
7     <version>0.0.1-SNAPSHOT</version>
8     <name>consumer</name>
9     <properties>
10         <spring.version>3.2.4.RELEASE</spring.version>
11     </properties>
12     <dependencies>
13         <dependency>
14             <groupId>junit</groupId>
15             <artifactId>junit</artifactId>
16             <version>3.8.1</version>
17             <scope>test</scope>
18         </dependency>
19         <dependency>
20             <groupId>javax.servlet</groupId>
21             <artifactId>servlet-api</artifactId>
22             <version>2.3</version>
23         </dependency>
24         <dependency>
25             <groupId>org.springframework</groupId>
26             <artifactId>spring-context</artifactId>
27             <version>${spring.version}</version>
28         </dependency>
29
30         <dependency>
31             <groupId>org.springframework</groupId>
32             <artifactId>spring-core</artifactId>
33             <version>${spring.version}</version>
34         </dependency>
35
36         <dependency>
37             <groupId>org.springframework</groupId>
38             <artifactId>spring-beans</artifactId>
39             <version>${spring.version}</version>
40         </dependency>
41
42         <dependency>
43             <groupId>org.springframework</groupId>
44             <artifactId>spring-webmvc</artifactId>
45             <version>${spring.version}</version>
46         </dependency>
47         <dependency>
48             <groupId>org.springframework</groupId>
49             <artifactId>spring-orm</artifactId>
50             <version>${spring.version}</version>
51         </dependency>
52
53         <dependency>
54             <groupId>com.alibaba</groupId>
55             <artifactId>dubbo</artifactId>
56             <version>2.5.3</version>
57         </dependency>
58
59         <dependency>
60             <groupId>com.bigbang</groupId>
61             <artifactId>service</artifactId>
62             <version>0.0.1-SNAPSHOT</version>
63         </dependency>
64     </dependencies>
65     <build>
66         <plugins>
67             <plugin>
68                 <groupId>org.apache.maven.plugins</groupId>
69                 <artifactId>maven-compiler-plugin</artifactId>
70                 <configuration>
71                     <source>1.8</source>
72                     <target>1.8</target>
73                 </configuration>
74             </plugin>
75         </plugins>
76         <finalName>consumer</finalName>
77     </build>
78 </project>

pom.xml

　　application.xml配置文件如下：

　　

1 <?xml version="1.0" encoding="UTF-8"?>
2 <beans xmlns="http://www.springframework.org/schema/beans"
3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
4     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"> 5
6     <import resource="dubbo.xml" />
7 </beans>

　　dubbo.xml配置文件如下：

　　

1 <?xml version="1.0" encoding="UTF-8"?>
2 <beans xmlns="http://www.springframework.org/schema/beans"
3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
4     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://code.alibabatech.com/schema/dubbo
5     http://code.alibabatech.com/schema/dubbo/dubbo.xsd"> 6
7     <!-- 消费方应用名，用于计算依赖关系，不是匹配条件，不要与提供方一样 -->
8     <dubbo:application name="consumer" />
9
10     <!-- 使用multicast广播注册中心暴露发现服务地址 -->
11     <dubbo:registry address="multicast://224.5.6.7:1234" />
12
13     <!-- 用dubbo协议在20880端口暴露服务 -->
14     <dubbo:protocol name="dubbo" port="20880" />
15
16     <!-- 生成远程服务代理，可以和本地bean一样使用 -->
17     <dubbo:reference id="userService" interface="com.bigbang.service.UserService" />
18 </beans>

　　项目启动配置文件web.xml:

　　

1 <?xml version="1.0" encoding="UTF-8"?>
2 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
3     xmlns="http://java.sun.com/xml/ns/javaee"
4     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 5     id="WebApp_ID" version="2.5">
6     <display-name>consumer</display-name>
7     <context-param>
8         <param-name>contextConfigLocation</param-name>
9         <param-value>classpath*:applicationContext.xml</param-value>
10     </context-param>
11     <listener>
12         <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
13     </listener>
14     <welcome-file-list>
15         <welcome-file>index.jsp</welcome-file>
16     </welcome-file-list>
17     <servlet>
18         <description>用户查询servlet</description>
19         <display-name>UserQueryServlet</display-name>
20         <servlet-name>UserQueryServlet</servlet-name>
21         <servlet-class>com.bigbang.servlet.UserQueryServlet</servlet-class>
22         <load-on-startup>1</load-on-startup>
23     </servlet>
24     <servlet-mapping>
25         <servlet-name>UserQueryServlet</servlet-name>
26         <url-pattern>/userQueryServlet</url-pattern>
27     </servlet-mapping>
28 </web-app>

　　 index.jsp页面很简单，就是做一个提交form的请求：

　　

1 <form action="/userQueryServlet" method="post">
2         ID:<input name="id" type="text" placeholder="请输入要查询的id" /><br/>
3     <input type="submit" value="sumbit"/>
4 </form>

　　UserServlet.java代码也很简单，仅仅用于接收请求并且调用暴露的服务：

　　

1 package com.bigbang.servlet;
2
3 import java.io.IOException;
4 import javax.servlet.ServletException;
5 import javax.servlet.http.HttpServlet;
6 import javax.servlet.http.HttpServletRequest;
7 import javax.servlet.http.HttpServletResponse;
8
9 import org.springframework.web.context.ContextLoader;
10 import org.springframework.web.context.WebApplicationContext;
11
12 import com.bigbang.common.domain.User;
13 import com.bigbang.service.UserService;
14
15 public class UserQueryServlet extends HttpServlet {
16     private static final long serialVersionUID = 1L;
17
18     private UserService userService;
19
20     /**
21      * @see HttpServlet#HttpServlet()
22      */
23     public UserQueryServlet() {
24         super();
25     }
26
27     /**
28      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
29      *      response)
30      */
31     protected void doGet(HttpServletRequest request, HttpServletResponse response)
32             throws ServletException, IOException {
33         doPost(request, response);
34     }
35
36     /**
37      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
38      *      response)
39      */
40     protected void doPost(HttpServletRequest request, HttpServletResponse response)
41             throws ServletException, IOException {
42         String idStr = request.getParameter("id");
43         Long id = Long.parseLong(idStr);
44         User user = userService.getUserById(id);
45         response.getWriter().write(user.toString());
46     }
47
48     @Override
49     public void init() throws ServletException {
50         super.init();
51         WebApplicationContext applicationContext = ContextLoader.getCurrentWebApplicationContext();
52         UserService userService = (UserService) applicationContext.getBean("userService");
53         this.userService = userService;
54         System.out.println("获取userService对象完成：" + userService);
55     }
56
57 }

　　在servlet的init()方法中，我使用了spring类获取暴露的服务接口，实际上获取到的是dubbo创建的代理对象。

　　

四. 运行

　　因为dubbo是基于长连接发送数据的，所以消息订阅者在启动时就会去查找这个认为已经注册的服务，如果不存在这个服务，则会报错。所以应该先注册服务，在开启订阅者订阅。故应该先启动Provider项目再启动Consumer项目。

　　一切运行成功之后，打开Consumer的index.jsp页面：

　　


　　输入id点击提交之后：

　　


　　说明服务调用成功，分布式作用起效了。

五. 总结

　　此代码仅作为抛砖引玉的作用，用来说明dubbo的基本应用。dubbo官方的文档写的很详细，从配置到说明示例。目前很多地方还没有探索到，比如启动是顺序其实可以设置服务启动时候是否检查，暴露服务的协议使用hessian还是dubbo，服务超时连接设置、服务暴露方式使用zookeeper等等。