Spring RESTful服务接收和返回JSON最佳实践

返回JSON

1) 用Maven构建web项目：

构建过程参考limingnihao的blog（写得相当的详细！！！）：使用Eclipse构建Maven的SpringMVC项目

注解@ResponseBody可以将结果（一个包含字符串和JavaBean的Map），转换成JSON。由于Spring是采用对JSON进行了封装的jackson来生成JSON和返回给客户端,所以这里需要添加jackson的相关包。项目的pom.xml配置如下：

<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/maven-v4_0_0.xsd">  
    <modelVersion>4.0.0</modelVersion>  
    <groupId>com.watson</groupId>  
    <artifactId>rest-spring</artifactId>  
    <packaging>war</packaging>  
    <version>0.0.1-SNAPSHOT</version>  
    <name>rest-spring Maven Webapp</name>  
    <url>http://maven.apache.org</url>  
      
    <dependencies>  
        <!-- 省略其他配置,具体可以参考附件-->  
        ......  
        <dependency>  
            <groupId>org.codehaus.jackson</groupId>  
            <artifactId>jackson-mapper-asl</artifactId>  
            <version>1.4.2</version>  
        </dependency>  
        <dependency>  
            <groupId>org.codehaus.jackson</groupId>  
            <artifactId>jackson-core-asl</artifactId>  
            <version>1.4.2</version>  
        </dependency>  
    </dependencies>  
</project> 

2) 在web.xml配置Spring的请求处理的Servlet，具体设置：

<?xml version="1.0" encoding="UTF-8"?>  
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"  
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"  
    version="2.5">  
  
    <display-name>Spring-Rest</display-name>  
    <servlet>  
        <servlet-name>rest</servlet-name>  
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
        <init-param>  
            <param-name>contextConfigLocation</param-name>  
            <param-value>/WEB-INF/rest-servlet.xml</param-value>  
        </init-param>  
        <load-on-startup>1</load-on-startup>  
    </servlet>  
  
    <servlet-mapping>  
        <servlet-name>rest</servlet-name>  
        <url-pattern>/</url-pattern>  
    </servlet-mapping>  
</web-app>

3) 在rest-servlet.xml中配置如下：

<beans xmlns="http://www.springframework.org/schema/beans"  
    xmlns:context="http://www.springframework.org/schema/context"  
    xmlns:mvc="http://www.springframework.org/schema/mvc"   
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xsi:schemaLocation="  
        http://www.springframework.org/schema/beans       
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd  
        http://www.springframework.org/schema/context   
        http://www.springframework.org/schema/context/spring-context-3.0.xsd  
        http://www.springframework.org/schema/mvc  
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">  
   
    <context:component-scan base-package="com.mkyong.common.controller" />  
    <mvc:annotation-driven />  
  
</beans>

为了解决乱码问题，需要添加如下配置，并且这里可以显示的添加 MappingJacksonHttpMessageConverter这个转换器。

<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">  
    <property name="messageConverters">  
        <list>  
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">  
                <property name="supportedMediaTypes">  
                    <list>  
                        <value>text/plain;charset=UTF-8</value>  
                    </list>  
                </property>  
            </bean>  
            <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter" />  
        </list>  
    </property>  
</bean>

4) 编写自己的服务组件类，使用MVC的annotation风格，使用 @ResponseBody处理返回值。具体代码如下：

@RequestMapping("/jsonfeed")  
public @ResponseBody Object getJSON(Model model) {  
    List<TournamentContent> tournamentList = new ArrayList<TournamentContent>();  
    tournamentList.add(TournamentContent.generateContent("FIFA", new Date(), "World Cup", "www.fifa.com/worldcup/"));  
    tournamentList.add(TournamentContent.generateContent("FIFA", new Date(), "U-20 World Cup", "www.fifa.com/u20worldcup/"));  
    tournamentList.add(TournamentContent.generateContent("FIFA", new Date(), "U-17 World Cup", "www.fifa.com/u17worldcup/"));  
    tournamentList.add(TournamentContent.generateContent("中超", new Date(), "中超", "www.fifa.com/confederationscup/"));  
    model.addAttribute("items", tournamentList);  
    model.addAttribute("status", 0);  
      
    return model;  
}

5)将运行项目，在浏览器中输入http://[host]:[port]/[appname]/jsonfeed.json，例如楼主的实例中输入如下：http://localhost:7070/rest-spring/jsonfeed/，得到结果为：

{"status":0,"items":[{"name":"World Cup","id":8,"link":"www.fifa.com/worldcup/","author":"FIFA","publicationDate":1334559460940},{"name":"U-20 World Cup","id":9,"link":"www.fifa.com/u20worldcup/","author":"FIFA","publicationDate":1334559460940},{"name":"U-17 World Cup","id":10,"link":"www.fifa.com/u17worldcup/","author":"FIFA","publicationDate":1334559460940},{"name":"Confederations Cup","id":11,"link":"www.fifa.com/confederationscup/","author":"FIFA","publicationDate":1334559460940}]}  

这里我们也可以利用Spring3MVC中对试图和内容协商的方法来处理返回JSON的情况，下面步骤接上面第2步：

3) 在rest-servlet.xml中对相关进行具体的设置：

<?xml version="1.0" encoding="UTF-8"?>  
<beans xmlns="http://www.springframework.org/schema/beans"  
    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context"  
    xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:tx="http://www.springframework.org/schema/tx"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xsi:schemaLocation="http://www.springframework.org/schema/aop   
        http://www.springframework.org/schema/aop/spring-aop-3.0.xsd   
        http://www.springframework.org/schema/beans   
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd   
        http://www.springframework.org/schema/context   
        http://www.springframework.org/schema/context/spring-context-3.0.xsd   
        http://www.springframework.org/schema/mvc   
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd   
        http://www.springframework.org/schema/tx   
        http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">  
  
    <!-- 自动搜索@Controller标注的类，包括其下面的子包 -->  
    <context:component-scan base-package="com.watson.rest" />  
  
    <!-- 根据客户端的不同的请求决定不同的view进行响应, 如 /blog/1.json /blog/1.xml -->  
    <bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">  
        <!-- 设置为true以忽略对Accept Header的支持 -->  
        <property name="ignoreAcceptHeader" value="true" />  
          
        <!-- 在没有扩展名时即: "/blog/1" 时的默认展现形式 -->  
        <property name="defaultContentType" value="text/html" />  
  
        <!-- 扩展名至mimeType的映射,即 /blog.json => application/json -->  
        <property name="mediaTypes">  
            <map>  
                <entry key="html" value="text/html" />  
                <entry key="pdf" value="application/pdf" />  
                <entry key="xsl" value="application/vnd.ms-excel" />  
                <entry key="xml" value="application/xml" />  
                <entry key="json" value="application/json" />  
            </map>  
        </property>  
      
        <!-- 用于开启 /blog/123?format=json 的支持 -->  
        <property name="favorParameter" value="false" />  
        <property name="viewResolvers">  
            <list>  
                <bean class="org.springframework.web.servlet.view.BeanNameViewResolver" />  
                <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">  
                    <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />  
                    <property name="prefix" value="/pages" />  
                    <property name="suffix" value=".jsp"></property>  
                </bean>  
            </list>  
        </property>  
        <property name="defaultViews">  
            <list>  
                <!-- for application/json -->  
                <bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView" />  
                <!-- for application/xml -->  
                <!--   
                <bean class="org.springframework.web.servlet.view.xml.MarshallingView">   
                    <property name="marshaller">   
                        <bean class="org.springframework.oxm.xstream.XStreamMarshaller"/>   
                    </property>   
                </bean>   
                -->  
            </list>  
        </property>  
    </bean>  
</beans>

4)编写自己的服务组件类，使用MVC的annotation风格，这里可以不再使用@ResponseBody断言。具体代码如下：

//FINAL   
package com.watson.rest.json;  
  
import org.springframework.stereotype.Controller;  
import org.springframework.ui.Model;  
import org.springframework.web.bind.annotation.RequestMapping;  
  
import com.watson.rest.feeds.TournamentContent;  
  
import java.util.ArrayList;  
import java.util.Date;  
import java.util.List;  
  
  
@Controller  
public class FeedController {  
    @RequestMapping("/jsonfeed")  
    public String getJSON(Model model) {  
        List<TournamentContent> tournamentList = new ArrayList<TournamentContent>();  
        tournamentList.add(TournamentContent.generateContent("FIFA", new Date(), "World Cup", "www.fifa.com/worldcup/"));  
        tournamentList.add(TournamentContent.generateContent("FIFA", new Date(), "U-20 World Cup", "www.fifa.com/u20worldcup/"));  
        tournamentList.add(TournamentContent.generateContent("FIFA", new Date(), "U-17 World Cup", "www.fifa.com/u17worldcup/"));  
        tournamentList.add(TournamentContent.generateContent("FIFA", new Date(), "Confederations Cup", "www.fifa.com/confederationscup/"));  
        model.addAttribute("items", tournamentList);  
        model.addAttribute("status", 0);  
        return "jsontournamenttemplate";  
    }  
}

这里的TournamentContent是自定义的POJO类：

public class TournamentContent {  
    private static int idCounter = 0;  
    private String author;  
    private Date publicationDate;  
    private String name;  
    private String link;  
    private int id;  
  
    public static TournamentContent generateContent(String author, Date date, String name, String link) {  
        TournamentContent content = new TournamentContent();  
        content.author = author;  
        content.publicationDate = date;  
        content.name = name;  
        content.link = link;  
        content.id = idCounter++;  
  
        return content;  
    }  
      
    //省略getter、setter  
}

5)将运行项目，在浏览器中输入http://[host]:[port]/[appname]/jsonfeed.json，例如楼主的实例中输入如下：http://localhost:7070/rest-spring/jsonfeed.json，得到结果为：

{"status":0,"items":[{"name":"World Cup","id":8,"link":"www.fifa.com/worldcup/","author":"FIFA","publicationDate":1334559460940},{"name":"U-20 World Cup","id":9,"link":"www.fifa.com/u20worldcup/","author":"FIFA","publicationDate":1334559460940},{"name":"U-17 World Cup","id":10,"link":"www.fifa.com/u17worldcup/","author":"FIFA","publicationDate":1334559460940},{"name":"Confederations Cup","id":11,"link":"www.fifa.com/confederationscup/","author":"FIFA","publicationDate":1334559460940}]}

至此，Spring RESTful服务返回JSON的实践基本完成（因为这里对EXCEPTION的处理还够）。个人认为第一种方式更加适合一般的使用，特别是显示的添加MappingJacksonHttpMessageConverter这个转换器和对乱码的处理。

接收JSON
使用 @RequestBody 注解前台只需要向 Controller 提交一段符合格式的 JSON，Spring 会自动将其拼装成 bean。
1)在上面的项目中使用第一种方式处理返回JSON的基础上，增加如下方法：

@RequestMapping(value="/add",method=RequestMethod.POST)  
@ResponseBody  
public Object addUser(@RequestBody User user)  
{  
    System.out.println(user.getName() + " " + user.getAge());  
    return new HashMap<String, String>().put("success", "true");  
}

 

这里的POJO如下：

public class User {  
    private String name;  
    private String age;  
  
    //getter setter  
}

2）而在前台，我们可以用 jQuery 来处理 JSON。从这里，我得到了一个 jQuery 的插件，可以将一个表单的数据返回成JSON对象：

$.fn.serializeObject = function(){  
    var o = {};  
    var a = this.serializeArray();  
    $.each(a, function(){  
        if (o[this.name]) {  
            if (!o[this.name].push) {  
                o[this.name] = [o[this.name]];  
            }  
            o[this.name].push(this.value || '');  
        }  
        else {  
            o[this.name] = this.value || '';  
        }  
    });  
    return o;  
};  

以下是使用 jQuery 接收、发送 JSON 的代码：

$(document).ready(function(){  
    jQuery.ajax({  
        type: 'GET',  
        contentType: 'application/json',  
        url: 'jsonfeed.do',  
        dataType: 'json',  
        success: function(data){  
            if (data && data.status == "0") {  
                $.each(data.data, function(i, item){  
                    $('#info').append("姓名：" + item.name +"，年龄：" +item.age);  
                });  
            }  
        },  
        error: function(){  
            alert("error")  
        }  
    });  
    $("#submit").click(function(){  
        var jsonuserinfo = $.toJSON($('#form').serializeObject());  
        jQuery.ajax({  
            type: 'POST',  
            contentType: 'application/json',  
            url: 'add.do',  
            data: jsonuserinfo,  
            dataType: 'json',  
            success: function(data){  
                alert("新增成功！");  
            },  
            error: function(){  
                alert("error")  
            }  
        });  
    });  
});  

但是似乎用Spring这套东西真是个麻烦的事情，相对Jersey对RESTful的实现来看，确实有很多不简洁的地方。