对于上传功能,我们在项目中是经常会用到的,比如用户注册的时候,上传用户头像,这个时候就会使用到上传的功能。而对于下载,使用场景也很常见,比如我们项目中有个使用说明是是pdf版的,会提供给用户进行下载的功能。相对于来说,这两个功能都是很常见。
完整的项目目录:https://codechina.csdn.net/dreaming_coder/springmvc-upload-download
1. 新建搭建SpringMVC开发环境
1.1 pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.ice</groupId>
<artifactId>demo</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>14</maven.compiler.source>
<maven.compiler.target>14</maven.compiler.target>
</properties>
<dependencies>
<!--文件上传-->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.4</version>
</dependency>
<!--servlet-api导入高版本的-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.2</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<!-- spring -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.3.2</version>
</dependency>
</dependencies>
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
</build>
</project>
1.2 web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
version="4.0">
<!--1.注册servlet-->
<servlet>
<servlet-name>SpringMVC</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!--通过初始化参数指定SpringMVC配置文件的位置,进行关联-->
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</init-param>
<!-- 启动顺序,数字越小,启动越早 -->
<load-on-startup>1</load-on-startup>
</servlet>
<!--所有请求都会被springmvc拦截 -->
<servlet-mapping>
<servlet-name>SpringMVC</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<filter>
<filter-name>encoding</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encoding</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!-- 超时时间 -->
<session-config>
<session-timeout>15</session-timeout>
</session-config>
</web-app>
1.3 applicationContext.xml
<?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.xsd
http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
<!-- mvc注解驱动 -->
<mvc:annotation-driven/>
<!-- 让Spring MVC不处理静态资源 -->
<mvc:default-servlet-handler/>
<!-- 自动扫描包,让指定包下的注解生效,由IOC容器统一管理 -->
<context:component-scan base-package="com.ice.controller"/>
<!--文件上传配置-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<!-- 请求的编码格式,必须和jSP的pageEncoding属性一致,以便正确读取表单的内容,默认为ISO-8859-1 -->
<property name="defaultEncoding" value="utf-8"/>
<!-- 上传文件大小上限,单位为字节(10485760=10M) -->
<property name="maxUploadSize" value="10485760"/>
<property name="maxInMemorySize" value="40960"/>
</bean>
<!-- 视图解析器 -->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
id="internalResourceViewResolver">
<!-- 前缀 -->
<property name="prefix" value="/WEB-INF/jsp/"/>
<!-- 后缀 -->
<property name="suffix" value=".jsp"/>
</bean>
</beans>
注意!!!这个 bean 的 id 必须为:multipartResolver , 否则上传文件会报 400 400 400 的错误!在这里栽过坑,教训!
2. 编写前端界面
2.1 index.jsp
前端表单要求:为了能上传文件,必须将表单的 method
设置为 POST
,并将 enctype
设置为 multipart/form-data
。只有在这样的情况下,浏览器才会把用户选择的文件以二进制数据发送给服务器。
对表单中的
enctype
属性做个详细的说明:
application/x-www=form-urlencoded
:默认方式,只处理表单域中的value
属性值,采用这种编码方式的表单会将表单域中的值处理成 URL 编码方式。multipart/form-data
:这种编码方式会以二进制流的方式来处理表单数据,这种编码方式会把文件域指定文件的内容也封装到请求参数中,不会对字符编码。text/plain
:除了把空格转换为 “+” 号外,其他字符都不做编码处理,这种方式适用直接通过表单发送邮件。
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Upload</title>
</head>
<body>
<form action="/upload" enctype="multipart/form-data" method="post">
<input type="file" name="file" multiple="multiple"/> <br/><br/>
<input type="submit" value="upload">
</form>
</body>
</html>
2.2 success.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Success</title>
</head>
<body>
<h2>上传成功</h2><br>
<hr/>
<a href="/download">点击下载</a>
</body>
</html>
3. 编写 Controller
CommonsMultipartFile 的 常用方法:
- String getOriginalFilename():获取上传文件的原名
- InputStream getInputStream():获取文件流
- void transferTo(File dest):将上传文件保存到一个目录文件中
package com.ice.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;
import java.util.Arrays;
@Controller
public class FileController {
@RequestMapping("/upload")
public String fileUpload2(@RequestParam("file") CommonsMultipartFile[] files, HttpServletRequest request) {
//上传路径保存设置
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()) {
realPath.mkdir();
}
//上传文件地址
System.out.println("上传文件保存地址:" + realPath);
Arrays.stream(files).forEach(file -> {
try {
file.transferTo(new File(realPath + "/" + file.getOriginalFilename()));
} catch (IOException e) {
e.printStackTrace();
}
});
return "success";
}
@RequestMapping(value = "/download")
public String downloads(HttpServletResponse response, HttpServletRequest request) throws Exception {
//要下载的图片地址
String path = request.getServletContext().getRealPath("/upload");
String fileName = "小黄人.jpg";
//1、设置response 响应头
response.reset(); //设置页面不缓存,清空buffer
response.setCharacterEncoding("UTF-8"); //字符编码
response.setContentType("multipart/form-data"); //二进制传输数据
//设置响应头
response.setHeader("Content-Disposition",
"attachment;fileName=" + URLEncoder.encode(fileName, "UTF-8"));
File file = new File(path, fileName);
//2、 读取文件--输入流
InputStream input = new FileInputStream(file);
//3、 写出文件--输出流
OutputStream out = response.getOutputStream();
byte[] buff = new byte[1024];
int index = 0;
//4、执行 写出操作
while ((index = input.read(buff)) != -1) {
out.write(buff, 0, index);
out.flush();
}
out.close();
input.close();
return null;
}
}
4. 测试启动 Tomcat
选择文件点击upload上传后:
打的war包结构如下: