本文详细介绍了Spring3如何通过Jackson实现JSON数据的转换与响应，包括异常处理、Map、List、对象的JSON表现形式，并提供了实际代码示例与页面配置。重点解决了集成JSON时遇到的406错误问题，推荐使用Spring3版本3.1.1release来避免此bug。
spring3 已经集成了jackson，本身支持页面的ajax获取数据。在版本中我们无需任何配置，只需下载jackson-all的包，放置在lib目录中，在controller中采用@ResponseBody 标记，就可以直接把Map，list 及各种对象直接转换为json对象的形式展现在前端。
1、spring3支持的各种类型转换为json对象的实例如下
在controller层中我们设置如下4种类型，分别是异常信息（结合上篇文章），Map，List及object对象，controller层代码如下：
package com.jason.web;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;
import com.jason.domain.User;
import com.jason.exception.BusinessException;
import com.jason.service.UserService;
import com.jason.util.Constants;
import com.jason.web.dto.LoginCommand;
@Controller
public class LoginController {
@Autowired
private UserService userService;
/**
* jump into the login page
*
* @return
* @throws BusinessException
* @throws
* @throws BusinessException
*/
@RequestMapping(value = "/index.html")
public String loginPage() throws BusinessException {
return Constants.LOGIN_PAGE;
}
/**
* get the json object
*
* @return
* @throws Exception
*/
@RequestMapping(value = "/josonException.html")
public @ResponseBody
Map<String, Object> getjson() throws BusinessException {
Map<String, Object> map = new HashMap<String, Object>();
try {
map.put("content", "123");
map.put("result", true);
map.put("account", 1);
throw new Exception();
} catch (Exception e) {
throw new BusinessException("detail of ajax exception information");
}
}
/**
* get the json object
*
* @return
* @throws Exception
*/
@RequestMapping(value = "/josonMap.html")
public @ResponseBody Map<String, Object> getjsonMap() throws BusinessException {
Map<String, Object> map = new HashMap<String, Object>();
map.put("content", "123");
map.put("result", true);
map.put("account", 1);
return map;
}
/**
* get the json object
*
* @return
* @throws Exception
*/
@RequestMapping(value = "/josonList.html")
public @ResponseBody List getjsonList() throws BusinessException {
LoginCommand loginCommand = new LoginCommand();
loginCommand.setUserName("admin");
loginCommand.setPassword("123456");
loginCommand.setKaptchaCode("9943");
List list = new ArrayList();
list.add(0,loginCommand);
list.add(1,loginCommand);
list.add(2,loginCommand);
list.add(3,loginCommand);
list.add(4,loginCommand);
list.add(5,loginCommand);
return list;
}
/**
* get the json object
*
* @return
* @throws Exception
*/
@RequestMapping(value = "/josonObject.html")
public @ResponseBody LoginCommand getjsonObject() throws BusinessException {
LoginCommand loginCommand = new LoginCommand();
loginCommand.setUserName("admin");
loginCommand.setPassword("123456");
loginCommand.setKaptchaCode("9943");
return loginCommand;
}
/**
* login in operation
*
* @param request
* @param loginCommand
* @return
* @throws IOException
*/
@RequestMapping(value = "/login.html")
public ModelAndView loginIn(HttpServletRequest request,
HttpServletResponse respone, LoginCommand loginCommand)
throws IOException {
boolean isValidUser = userService.hasMatchUser(
loginCommand.getUserName(), loginCommand.getPassword());
boolean isValidateCaptcha = validateCaptcha(request, loginCommand);
ModelAndView modeview = new ModelAndView(Constants.LOGIN_PAGE);
if (!isValidUser) {
// if have more information,you can put a map to modelView,this use
// internalization
modeview.addObject("loginError", "login.user.error");
return modeview;
} else if (!isValidateCaptcha) {
// if have more information,you can put a map to modelView,this use
// internalization
modeview.addObject("loginError", "login.user.kaptchaError");
return modeview;
} else {
User user = userService.findUserByUserName(loginCommand
.getUserName());
user.setLastIp(request.getLocalAddr());
user.setLastVisit(new Date());
userService.loginSuccess(user);
// we can also use
request.getSession().setAttribute(Constants.LOGINED, user);
String uri = (String) request.getSession().getAttribute(
Constants.CURRENTPAGE);
if (uri != null
&& !StringUtils.equalsIgnoreCase(uri,
Constants.CAPTCHA_IMAGE)) {
respone.sendRedirect(request.getContextPath() + uri);
}
return new ModelAndView(Constants.FRONT_MAIN_PAGE);
}
}
/**
* logout operation
*
* @param request
* @param response
* @return
*/
@RequestMapping(value = "/logout.html")
public ModelAndView logout(HttpServletRequest request,
HttpServletResponse response) {
/*
* HttpServletRequest.getSession(ture) equals to
* HttpServletRequest.getSession() means a new session created if no
* session exists request.getSession(false) means if session exists get
* the session,or value null
*/
HttpSession session = request.getSession(false);
if (session != null) {
session.invalidate();
}
return new ModelAndView("redirect:/index.jsp");
}
/**
* check the Captcha code
*
* @param request
* @param command
* @return
*/
protected Boolean validateCaptcha(HttpServletRequest request, Object command) {
String captchaId = (String) request.getSession().getAttribute(
com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
String response = ((LoginCommand) command).getKaptchaCode();
if (!StringUtils.equalsIgnoreCase(captchaId, response)) {
return false;
}
return true;
}
}
页面配置如下：分别测试异常，map，list及对象
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ include file="/common/taglibs.jsp"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>spring login information</title>
<script type="text/javascript">
function ajaxTestException()
{
$.ajax( {
type : 'GET',
//contentType : 'application/json',
url : '${basePath}/josonException.html',
async: false,//禁止ajax的异步操作，使之顺序执行。
dataType : 'json',
success : function(data,textStatus){
alert(JSON.stringify(data));
},
error : function(data,textstatus){
alert(data.responseText);
}
});
}
function ajaxTestMap()
{
$.ajax( {
type : 'GET',
//contentType : 'application/json',
url : '${basePath}/josonMap.html',
async: false,//禁止ajax的异步操作，使之顺序执行。
dataType : 'json',
success : function(data,textStatus){
alert(JSON.stringify(data));
},
error : function(data,textstatus){
alert(data.responseText);
}
});
}
function ajaxTestList()
{
$.ajax( {
type : 'GET',
//contentType : 'application/json',
url : '${basePath}/josonList.html',
async: false,//禁止ajax的异步操作，使之顺序执行。
dataType : 'json',
success : function(data,textStatus){
alert(JSON.stringify(data));
},
error : function(data,textstatus){
alert(data.responseText);
}
});
}
function ajaxTestObject()
{
$.ajax( {
type : 'GET',
//contentType : 'application/json',
url : '${basePath}/josonObject.html',
async: false,//禁止ajax的异步操作，使之顺序执行。
dataType : 'json',
success : function(data,textStatus){
alert(JSON.stringify(data));
},
error : function(data,textstatus){
alert(data.responseText);
}
});
}
</script>
</head>
<body>
<table cellpadding="0" cellspacing="0" style="width:100%;">
<tr>
<td rowspan="2" style="width:30px;">
</td>
<td style="height:72px;">
<div>
spring login front information
</div>
<div>
${loginedUser.userName},欢迎您进入Spring login information，您当前积分为${loginedUser.credits};
</div>
<div>
<a href="${basePath}/backendmain.html">后台管理</a>
</div>
</td>
<td>
<div>
<a href="${basePath}/logout.html">退出</a>
</div>
</td>
</tr>
<tr>
<td style="height:72px;">
<div>
<input type=button value="Ajax Exception Test" onclick="ajaxTestException();"></input>
</div>
</td>
<td style="height:72px;">
<div>
<input type=button value="Ajax Map Test" onclick="ajaxTestMap();"></input>
</div>
</td>
<td style="height:72px;">
<div>
<input type=button value="Ajax List Test" onclick="ajaxTestList();"></input>
</div>
</td>
<td style="height:72px;">
<div>
<input type=button value="Ajax Object Test" onclick="ajaxTestObject();"></input>
</div>
</td>
</tr>
</table>
</body>
</html>运行代码，到达登录成功界面及获取的结果如下：
2、集成Json对象时，常常会抛如下的406错误：The resource identified by this request is only capable of generating responses with characteristics not acceptable according to the request "accept" headers ()。
针对这个问题，网络上有好多的答案，五花八门，其实这个本身是spring的bug导致，在spring的rc版本中都会出现这个问题，而不能支持ajax方式，而不是jackson.jar的问题。目前，解决这个问题的spring版本是3.1.1 release版本。而目前最新的spring rc版本仍然存在这个问题。
至此，spring3支持json方式介绍到这里。
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