SpringMVC实现Restful风格的WebService

1.环境

JDK7
MyEclipse2014
tomcat8
maven 3.3.3
spring4.1.4

2.创建maven工程

　　使用MyEclipse创建maven工程的方式可以参考这篇博文(链接1), 该博文中的第四小结是关于如何创建SpringMVC+maven教程。下面只给出创建好的目录结构，其中的部分文件如java程序是后面要完成的。

3.指定依赖文件

　　maven具有特定的文件结构，并通过pom.xml来管理工程。下面是在实现Restful时需要的依赖。

 1 <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
 2   <modelVersion>4.0.0</modelVersion>
 3   <groupId>com.dy.xidian</groupId>
 4   <artifactId>transport</artifactId>
 5   <version>0.0.1-SNAPSHOT</version>
 6   <packaging>war</packaging>
 7   <name>transport Maven Webapp</name>
 8   <url>http://maven.apache.org</url>
 9   
10   <properties>
11     <spring.version>4.1.4.RELEASE</spring.version>
12   </properties>
13   
14   <dependencies>
15       <dependency>
16          <groupId>junit</groupId>
17       <artifactId>junit</artifactId>
18       <version>3.8.1</version>
19       <scope>test</scope>
20     </dependency>
21     <dependency>
22         <groupId>org.springframework</groupId>
23         <artifactId>spring-core</artifactId>
24         <version>${spring.version}</version>
25     </dependency>
26     <dependency>
27       <groupId>org.springframework</groupId>
28       <artifactId>spring-context</artifactId>
29       <version>${spring.version}</version>
30     </dependency>
31     <dependency>
32       <groupId>org.springframework</groupId>
33       <artifactId>spring-webmvc</artifactId>
34       <version>${spring.version}</version>
35     </dependency>
36     <!-- web项目编译时需要，部署到tomcat中就不需要了 -->
37     <dependency>
38       <groupId>javax.servlet</groupId>
39       <artifactId>servlet-api</artifactId>
40       <version>2.5</version>
41       <scope>provided</scope>
42     </dependency>
43     <dependency>
44     <groupId>javax.servlet.jsp</groupId>
45       <artifactId>jsp-api</artifactId>
46       <version>2.2</version>
47     <scope>provided</scope>
48     </dependency>
49  
50     <dependency>
51          <groupId>com.fasterxml.jackson.core</groupId>
52       <artifactId>jackson-databind</artifactId>
53       <version>2.3.4</version>
54     </dependency>
55     <dependency>
56       <groupId>com.fasterxml.jackson.core</groupId>
57        <artifactId>jackson-annotations</artifactId>
58       <version>2.4.0</version>
59     </dependency>
60     <dependency>
61       <groupId>com.fasterxml.jackson.core</groupId>
62       <artifactId>jackson-core</artifactId>
63       <version>2.4.3</version>
64     </dependency>
65   </dependencies>
66  
67   <build>
68     <finalName>transport</finalName>
69   </build>
70 </project>

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4.配置web.xml

　　web.xml的配置过程十分简单，只需指定dispatchServlet即可。

 1 <!DOCTYPE web-app PUBLIC
 2  "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 3  "http://java.sun.com/dtd/web-app_2_3.dtd" >
 4 
 5 <web-app>
 6   <display-name>Archetype Created Web Application</display-name>
 7   
 8   <context-param>
 9        <param-name>contextConfigLocation</param-name>
10      <param-value>/WEB-INF/transport-servlet.xml</param-value>
11   </context-param>
12   <servlet>    
13         <servlet-name>transport</servlet-name>    
14         <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>    
15         <load-on-startup>1</load-on-startup>
16     </servlet>    
17    <servlet-mapping>    
18        <servlet-name>transport</servlet-name>  
19        <url-pattern>/</url-pattern>    
20     </servlet-mapping>  
21   <listener>
22       <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
23   </listener>
24 </web-app>

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5.配置spring的配置文件(spring-servlet.xml)

　　配置该文件时，约束文档要指定成spring4的约束，因为spring4实现了对restful的支持。

 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     xmlns:context="http://www.springframework.org/schema/context"
 5     xmlns:mvc="http://www.springframework.org/schema/mvc"
 6     xsi:schemaLocation="http://www.springframework.org/schema/beans 
 7         http://www.springframework.org/schema/beans/spring-beans.xsd
 8         http://www.springframework.org/schema/context 
 9         http://www.springframework.org/schema/context/spring-context-4.1.xsd
10         http://www.springframework.org/schema/mvc
11          http://www.springframework.org/schema/mvc/spring-mvc-4.1.xsd">
12 
13     <mvc:annotation-driven />
14     <context:component-scan base-package="com.dy.xidian" />
15 </beans>

6.controller的实现

　　前面是已经把准备工作做完了，下面进入编程阶段。关于Restful风格的webService相信大家已经做过功课了，这里不在累述。因为应答是json格式，所以我们需要进行下面的工作。

6.1建立bean类

　　在开始的图片中，我们可以看到有个Greeting.java类，它其实就是一个bean类，具体代码如下。

 1 package com.dy.xidian;
 2 
 3 public class Greeting {
 4     private final long id;
 5     private final String content;
 6 
 7     public Greeting(long id, String content) {
 8         this.id = id;
 9         this.content = content;
10     }
11 
12     public long getId() {
13         return id;
14     }
15 
16     public String getContent() {
17         return content;
18     }
19 }

6.2 在控制器中处理请求

　　SpringMVC会将请求交给一个控制器来处理，所以我们必须实现这样一个控制器，不过这个控制器在编写时要遵循restful风格。

　　GreetingController.java

 1 package com.dy.xidian;
 2 
 3 import java.util.concurrent.atomic.AtomicLong;
 4 
 5 import org.springframework.web.bind.annotation.RequestMapping;
 6 import org.springframework.web.bind.annotation.RequestParam;
 7 import org.springframework.web.bind.annotation.RestController;
 8 
 9 @RestController
10 public class GreetingController {
11     private static final String template = "Hello, %s!";
12     private final AtomicLong counter = new AtomicLong();
13 
14     @RequestMapping("/getuser")
15     public Greeting greeting(
16             @RequestParam(value = "name", defaultValue = "World") String name) {
17         return new Greeting(counter.incrementAndGet(), String.format(template,
18                 name));
19     }
20 }