解决SpringMVC接收前台上传文件为null

朴灿烈づ我的快乐病毒、 2021-09-26 06:10 627阅读 0赞

这个问题的需求来源于，我前端传递图片后，需要在Controller中通过name映射进行获取，在获取的过程中出现了获取他的值为null的状况，发生这种状况的情形会有很多种，这边不一一列举，主要告诉大家如何正确获取。

## 1.前端界面 ##

需要注意的是，因为这边会引用jquery.form.js,所以在form中一定要加入enctype="multipart/form-data"属性

<form id="jvForm" action="add.do" method="post" enctype="multipart/form-data">
    		<table cellspacing="1" cellpadding="2" width="100%" border="0" class="pn-ftable">
    			<tbody>
    				<tr>
    					<td width="20%" class="pn-flabel pn-flabel-h">
    						<span class="pn-frequired">*</span>
    						品牌名称:</td><td width="80%" class="pn-fcontent">
    						<input type="text" class="required" name="name" maxlength="100"/>
    					</td>
    				</tr>
    				<tr>
    					<td width="20%" class="pn-flabel pn-flabel-h">
    						<span class="pn-frequired">*</span>
    						上传商品图片(90x150尺寸):</td>
    						<td width="80%" class="pn-fcontent">
    						注:该尺寸图片必须为90x150。
    					</td>
    				</tr>
    				<tr>
    					<td width="20%" class="pn-flabel pn-flabel-h"></td>
    						<td width="80%" class="pn-fcontent">
    						<img width="100" height="100" id="allUrl"/>
    						<input type="file" οnchange="uploadPic()" name="pic"/>
    					</td>
    				</tr>
    				<tr>
    					<td width="20%" class="pn-flabel pn-flabel-h">
    						品牌描述:</td><td width="80%" class="pn-fcontent">
    						<input type="text" class="required" name="description" maxlength="80"  size="60"/>
    					</td>
    				</tr>
    				<tr>
    					<td width="20%" class="pn-flabel pn-flabel-h">
    						排序:</td><td width="80%" class="pn-fcontent">
    						<input type="text" class="required" name="sort" maxlength="80"/>
    					</td>
    				</tr>
    				<tr>
    					<td width="20%" class="pn-flabel pn-flabel-h">
    						是否可用:</td><td width="80%" class="pn-fcontent">
    						<input type="radio" name="isDisplay" value="1" checked="checked"/>可用
    						<input type="radio" name="isDisplay" value="0"/>不可用
    					</td>
    				</tr>
    			</tbody>
    			<tbody>
    				<tr>
    					<td class="pn-fbutton" colspan="2">
    						<input type="submit" class="submit" value="提交"/>   <input type="reset" class="reset" value="重置"/>
    					</td>
    				</tr>
    			</tbody>
    		</table>
    	</form>

## 2.jquery部分 ##

需要引入jquery，以及jquery.form

## 3.开启SpringMVC文件上传功能 ##

SpringMVC的文件上传功能默认是关闭的，所以需要开启

### (1)首先需要引入相关的jar包 ###

<dependency>  
        <groupId>commons-fileupload</groupId>  
        <artifactId>commons-fileupload</artifactId>  
        <version>1.3.1</version>  
    </dependency>

### (2)其次需要在spring-mvc.xml中进行配置 ###

<?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:aop="http://www.springframework.org/schema/aop"
    	xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jdbc="http://www.springframework.org/schema/jdbc"
    	xmlns:context="http://www.springframework.org/schema/context"
    	xsi:schemaLocation="
         http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-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/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc-3.0.xsd
         http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
         http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd">
    	<context:component-scan base-package="com.gwd.shopping" use-default-filters="false">
    		<context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
    	</context:component-scan>
        
        
        <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        	
        	 <property name="maxUploadSize" value="1048576"/>
        </bean>
    	
    	<bean id="jspViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    		<property name="prefix" value="/WEB-INF/console/"/>
    		<property name="suffix" value=".jsp"/>
    	</bean>
    </beans>

## 4.Controller的编写 ##

这里pic名称需要与前端中file的名称要一致，且要配置@RequestParam(value="pic",required=false，楼主就是因为一开始没有配置value=“pic”,导致获取初始名称一直为null

@Controller
    @RequestMapping(value="/upload")
    public class UploadController {
    	@RequestMapping(value="/uploadPic.do")
    	//false表示不是必须传递该值
    	public void uploadPic(@RequestParam(value="pic",required=false)MultipartFile pic){
    		
    		System.out.println(pic.getOriginalFilename());
    	} 
    }