Spring Mvc——基本使用

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注：以下例子都是建立在第一个例子的基础上修改

1、@ResponseBody

该注解放置在一个方法上，表示会将方法的返回值写入到Http response body内（实际处理：Spring mvc 通过HttpMessageConverter消息转换器接口类将返回值转换成对应消息，然后将消息写入到Http response body内）。

 

首先在第一个例子的UserController类中添加以下代码，去构建初始化数据

	private static Map<String,User> map = new HashMap<String,User>();
	static{
		for(int i=0;i<10;i++){
			User user = new User("zhangsan"+i, (int) (Math.random()*50));
			map.put("zhangsan"+i,user);
		}
	}

  

在UserController类中添加如下方法。

1.返回字符串

	//返回字符串处理例子 http://localhost:8080/springmvctest/helloworld.shtml
	@RequestMapping("helloworld")
	@ResponseBody
	public Object helloworld(){
		return "helloworld";
	}

  

测试结果：输入http://localhost:8080/springmvctest/helloworld.shtml，浏览器显示

helloworld

2.实体bean转json

	//实体bean转json http://localhost:8080/springmvctest/getUser.shtml
	@RequestMapping("getUser")
	@ResponseBody
	public Object getUser(){
		User user = new User("zhangsan", (int) (Math.random()*50));
		return user;
	}

 

测试结果：输入http://localhost:8080/springmvctest/getUser.shtml，浏览器显示

{"name":"zhangsan","age":26}

3.数组转json

	//数组转json http://localhost:8080/springmvctest/getUsers.shtml
	@RequestMapping("getUsers")
	@ResponseBody
	public Object getUsers(){
		return map.values().toArray();
	}

测试结果：输入http://localhost:8080/springmvctest/getUsers.shtml，浏览器显示

[{"name":"zhangsan1","age":0},{"name":"zhangsan2","age":1}]

4.Collection集合转json

	//Collection集合转json http://localhost:8080/springmvctest/getUserCollection.shtml
	@RequestMapping("getUserCollection")
	@ResponseBody
	public Object getUserCollection(){
		return map.values();
	}

测试结果：输入http://localhost:8080/springmvctest/getUserCollection.shtml，浏览器显示

[{"name":"zhangsan1","age":0},{"name":"zhangsan2","age":1}]

5.Map集合转json

	//Map集合转json http://localhost:8080/springmvctest/getUserMap.shtml
	@RequestMapping("getUserMap")
	@ResponseBody
	public Object getUserMap(){
		return map;
	}

测试结果：输入http://localhost:8080/springmvctest/getUserMap.shtml，浏览器显示

{"zhangsan1":{"name":"zhangsan1","age":0},"zhangsan2":{"name":"zhangsan2","age":1}} 

2、@PathVariable

该注解用在方法参数上，被注解的参数的值将在对应的Url路径上。

	//PathVariable注解例子 http://localhost:8080/springmvctest/get/zhangsan1.shtml
	@RequestMapping("get/{username}")
	@ResponseBody
	public Object get(@PathVariable String username){
		User user = map.get(username);
		return user;
	}

	//PathVariable注解使用正则表达式 http://localhost:8080/springmvctest/get1/zhangsan1.shtml
	@RequestMapping("get1/{username:[a-z]+[1]}")
	@ResponseBody
	public Object get1(@PathVariable String username){
		User user = map.get(username);
		return user;
	}

测试结果如下

输入http://localhost:8080/springmvctest/get/zhangsan1.shtml，浏览器展示

{"name":"zhangsan1","age":0}

输入 http://localhost:8080/springmvctest/get/zhangsan1.shtml，浏览器展示

{"name":"zhangsan1","age":0}

 

3、@RequestParam

 @RequestParam注解使用在方法参数上，使用它可以接收请求的参数。

	//RequestParam注解 http://localhost:8080/springmvctest/getByusername.shtml?username=zhangsan1
	@RequestMapping("getByusername")
	@ResponseBody
	public Object getByusername(@RequestParam String username){
		User user = map.get(username);
		return user;
	}

测试结果：输入http://localhost:8080/springmvctest/getByusername.shtml?username=zhangsan1，浏览器展示

{"name":"zhangsan1","age":12}

4、@RequestBody

 @RequestBody注解使用在方法参数上，用来接收请求Body内容

	//RequestBody注解 http://localhost:8080/springmvctest/getRequestBody.shtml
	@RequestMapping("getRequestBody")
	@ResponseBody
	public Object getRequestBody(@RequestBody String requestBody){
		
		return "testRequestBody:"+requestBody;
	}

 

测试结果如下

url ——》 http://localhost:8080/springmvctest/getRequestBody.shtml

请求体——》test

浏览器显示结果 testRequestBody:test

测试设置如下

测试响应结果如下

5、@ModelAttribute

@ModelAttribute可用于方法体和方法参数上，使用在方法参数上可将请求参数转换为对应model对象，使用在方法体上暂不考虑。

	//ModelAttribute注解 http://localhost:8080/springmvctest/getUserByUser.shtml?name=lisi&age=32
	@RequestMapping(value="getUserByUser")
	@ResponseBody
	public Object getUserByUser(@ModelAttribute("user") User user){
		
		return user;
	}

运行结果：输入 http://localhost:8080/springmvctest/getUserByUser.shtml?name=lisi&age=32，浏览器展示如下

{"name":"lisi","age":32}

6、请求和响应对象作为方法接收参数

spring mvc可让HttpServletRequest和HttpServletResponse对象作为方法的接收参数 

	//请求、响应作为方法参数 http://localhost:8080/springmvctest/getUserByRequest.shtml?name=wangwu&age=32
	@RequestMapping(value="getUserByRequest")
	@ResponseBody
	public Object getUserByRequest(HttpServletRequest request , HttpServletResponse response){
		String name = request.getParameter("name");
		int age = Integer.parseInt(request.getParameter("age"));
		return new User(name , age);
	}

运行结果：输入http://localhost:8080/springmvctest/getUserByRequest.shtml?name=wangwu&age=32，在浏览器展示如下

{"name":"wangwu","age":32}

7、文件上传 

spring mvc支持文件上传，并且支持多文件。spring mvc文件上传解析器是CommonsMultipartResolver（如果使用Servlet3.0，则使用StandardServletMultipartResolver解析器 ）。

1.在spring-mvc.xml配置文件下添加解析器。

<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"></bean>	

2.在pom.xml文件下添加fileupload上传jar包。

		<!-- 文件上传包 -->
		<dependency>
			<groupId>commons-fileupload</groupId>
			<artifactId>commons-fileupload</artifactId>
			<version>1.3.1</version>
		</dependency>

3.添加方法

	//上传文件 http://localhost:8080/springmvctest/upload.shtml
	@RequestMapping(value="upload")
	@ResponseBody
	public Object upload(@RequestParam("files") MultipartFile[] files){
		StringBuffer sb = new StringBuffer();
		for(MultipartFile file : files){
			int size = (int) (file.getSize()/1024);
			sb.append("upload success,this file size is "+size+"KB.<br/>");
		}
		return sb.toString();
	}

4.测试结果如下图

 

 

8、@ExceptionHandler

@ExceptionHandler注解使用在方法体上，使用它将可以拦截处理该Controller类的所有的异常，其值为一个数组，即可拦截多种异常。使用注解只能拦截当前Controller类，代码不好复用，可自己实现HandlerExceptionResolver，然后在Xml配置文件中配置，达到异常统一处理

1、使用注解方法

	//ExceptionHandler注解例子 http://localhost:8080/springmvctest/exceptiontest.shtml
	@RequestMapping("exceptiontest")
	public void exceptiontest(){
		String str = null;
//		Integer.parseInt(str);//报NumberFormatException异常
		str.trim();//报NullPointerException异常
	}
	
	@ResponseBody
	@ExceptionHandler(value={NullPointerException.class,NumberFormatException.class})
	public Object exception(Exception e){
		return "it is error page:" + e.getMessage();
	}

运行结果输入http://localhost:8080/springmvctest/exceptiontest.shtml，浏览器展示如下

it is error page:null

2、使用HandlerExceptionResolver接口类，自定义处理异常。

(1).创建异常处理类HandlerException，该类实现HandlerExceptionResolver接口

package com.springmvctest.handler;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerExceptionResolver;
import org.springframework.web.servlet.ModelAndView;

public class HandlerException implements HandlerExceptionResolver {

	public ModelAndView resolveException(HttpServletRequest request,
			HttpServletResponse response, Object handler, Exception ex) {
		
		ModelAndView mav = new ModelAndView("error");
		mav.addObject("msg", ex.getMessage());
		
		return mav;
	}

}

(2).在spring-mvc.xml配置文件中配置HandlerException类

<bean class="com.springmvctest.handler.HandlerException"></bean>

(3).在jsp文件夹下构建error.jsp。

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
  </head>
  
  <body>
    erro页面<br/>
    异常为：${msg} <br/>

  </body>
</html>

(4).在UserController类中添加如下方法

	//异常统一处理例子 http://localhost:8080/springmvctest/exceptiontest1.shtml
	@RequestMapping("exceptiontest1")
	public void exceptiontest1(){
		int i = 1/0;
	}

(5).运行结果如下

输入http://localhost:8080/springmvctest/exceptiontest1.shtml，浏览器展示如下 

erro页面
异常为：/ by zero 

源码见附件