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开始接触springmvc，有点期待，有点兴奋。单今天的一点小事差点让我崩溃了。在这记录下，不是记录什么技术点，纯粹是警告下自己，再小心不为过啊！
做了个小例子：
搭好springmvc的架子，导好相关的包（当让做文件上传commons-fileupload.jar这个肯定是必须要的）。
①配置好web.xml 文件：
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1"> <!-- 配置 SpringMVC 的 DispatcherServlet --> <!-- The front controller of this Spring Web application, responsible for handling all application requests --> <servlet> <servlet-name>springDispatcherServlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:springmvc.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <!-- Map all requests to the DispatcherServlet for handling --> <servlet-mapping> <servlet-name>springDispatcherServlet</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> <!-- 配置 HiddenHttpMethodFilter :把POST 請求转化为DELETE、PUT 请求--> <filter> <filter-name>HiddenHttpMethodFilter</filter-name> <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class> </filter> <filter-mapping> <filter-name>HiddenHttpMethodFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> </web-app>
②配置好springmvc.xml文件：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:mvc="http://www.springframework.org/schema/mvc" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.2.xsd"> <!-- 配置自动扫描包 --> <context:component-scan base-package="com.springmvc"></context:component-scan> <!-- 配置是图解析器 --> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="prefix" value="/WEB-INF/views/"></property> <property name="suffix" value=".jsp"></property> </bean> <!-- 配置MultipartResover :用于文件上传 --> <bean id="multipartResover" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"> <property name="defaultEncoding" value="UTF-8"></property> <property name="maxUploadSize" value="1024000"></property> </bean> </beans>
③然后开始写jsp文件index.jsp:
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html> <head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title> </head>
<body> <form id="form" action="testFileUpload" method="Post" enctype="multipart/form-data">
File: <input type="file" name="file" />
Desc: <input type="text" name="desc" />
<input type="submit" value="Submit" />
</form>
</body>
</html>
④开始写Java代码：
package com.springmvc.test;
import java.io.IOException;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
@Controller
public class SpringMVCTest {
@RequestMapping("/testFileUpload")
public String testFileUpload(@RequestParam(value="desc",required=false) String desc,
@RequestParam(value="file",required=false) MultipartFile file) throws IOException{
System.out.println("desc: "+ desc);
System.out.println("originalFilename: " + file.getOriginalFilename());
System.out.println("InputStream: " +file.getInputStream());
return "success";
}
}
相关的文件配好了，有个success.jsp就写了，随便写个页面就行。
开始跑吧，一跑就出错了nullpoint，查原因“System.out.println("originalFilename: " + file.getOriginalFilename());”空指针，就是说file为null,怎么会呢？
相关的配置和包都有啊，一步步看下来发现配置springmvc.xml文件时Id写错了，少了个“l”,id应该是“配置multipartResolver”,悲剧啊……所以写东西一定要小心啊，能copy的就尽量copy吧，不然稍微一不注意就悲催了……
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原文地址：http://www.cnblogs.com/big-xuzhou/p/4883575.html
