一、文件的上传
1、方式一
（1）基础配置：
pom.xml：导入依赖等：
<?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>pers.zhb</groupId>
<artifactId>spring_file</artifactId>
<version>1.0-SNAPSHOT</version>
<!--依赖-->
<dependencies>
<!--spring-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.2.5.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>4.2.4.RELEASE</version>
</dependency>
<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.3</version>
</dependency>
<!--servlet-->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>servlet-api</artifactId>
<version>2.5</version>
</dependency>
</dependencies>
<!--在bulid中配置resources，防止资源导出失败的问题-->
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>true</filtering>
</resource>
</resources>
</build>
</project>
applicationContext.xml：对文件上传进行配置
<?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: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
https://www.springframework.org/schema/context/spring-context.xsd
http://www.springframework.org/schema/mvc
https://www.springframework.org/schema/mvc/spring-mvc.xsd">
<!--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="pers.zhb.controller"></context:component-scan>
<!--静态资源过滤，让Springmvc不处理静态资源，如css、js等-->
<mvc:default-servlet-handler></mvc:default-servlet-handler>
<!--使得注解生效-->
<mvc:annotation-driven></mvc:annotation-driven>
<!--视图解析器，前缀和后缀-->
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver" id="internalResourceViewResolver">
<property name="prefix" value="/"></property>
<property name="suffix" value=".jsp"></property>
</bean>
<!--文件上传-->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
<!--请求的编码格式，必须和jsp的pageEncoding属性的值保持一致，以便正确读取表单的内容，默认为ISO-8859-1-->
<!--multipartResolver：以二进制形式传输数据-->
<property name="defaultEncoding" value="utf-8"></property>
<!--上传文件大小的上限-->
<property name="maxUploadSize" value="10485760"></property>
<property name="maxInMemorySize" value="40960"></property>
</bean>
</beans>
web.xml：配置前端控制器、处理乱码的过滤器：
<?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">
<!-- 前端控制器 -->
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<!--绑定springmvc的配置文件-->
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup><!--启动服务器即创建-->
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<filter>
<filter-name>EncodingFilter</filter-name>
<filter-class>pers.zhb.filter.EncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>EncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
过滤器：
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
servletRequest.setCharacterEncoding("utf-8");
servletResponse.setCharacterEncoding("utf-8");
filterChain.doFilter(servletRequest,servletResponse);
}
(2)文件上传的核心代码：
页面：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<form method="post" action="${pageContext.request.contextPath}/upload" enctype="multipart/form-data">
<input type="file" name="file">
<input type="submit" value="upload">
</form>
</body>
</html>
控制器：
@RequestMapping("upload")
//批量上传CommonsMultipartFile为数组即可
public String fileUpload(@RequestParam("file")CommonsMultipartFile file, HttpServletRequest request)throws IOException{
//获取文件名
String uploadFileName=file.getOriginalFilename();
//如果文件名为空直接回到首页
if("".equals(uploadFileName)){
return "redirect:/index.jsp";
}
System.out.println("上传的文件的文件名为："+uploadFileName);
//上传路径保存设置
String path=request.getSession().getServletContext().getRealPath("/upload");
//如果路径不存在，创建一个
File realPath =new File(path);
if(!realPath.exists()){
realPath.mkdir();
}
System.out.println("文件保存地址为："+realPath);
InputStream inputStream=file.getInputStream();//文件输入流
OutputStream outputStream=new FileOutputStream(new File(realPath,uploadFileName));//文件输出流，文件的保存地址和文件的文件名
//读取写入
int len=0;
byte[] buffer=new byte[1024];
while ((len= inputStream.read(buffer))!=-1){
outputStream.write(buffer,0,len);
outputStream.flush();
}
outputStream.close();
inputStream.close();
return "redirect:/index.jsp";
}
采用缓冲数组的方式读取文件可以加快文件处理的速度
（3）测试：
2、方式二
（1）控制器：
@RequestMapping("upload")
public String fileUpload(@RequestParam("file")CommonsMultipartFile file, HttpServletRequest request)throws IOException{
//上传路径保存设置
String path = request.getSession().getServletContext().getRealPath("upload");
File realPath=new File(path);
if(!realPath.exists()){
realPath.mkdir();
}
//上传文件地址
System.out.println("上传文件的保存地址为："+realPath);
//通过commosMultipartFile的方法直接写入文件
file.transferTo(new File(realPath+"/"+file.getOriginalFilename()));
return "redirect:/index.jsp";
}
二、文件的下载
（1）页面：
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>$Title$</title>
</head>
<body>
<center>
<h3>
<a href="${pageContext.request.contextPath}/download">下载图片</a>
</h3>
</center>
</form>
</body>
</html>
（2）控制器：
@RequestMapping("download")
public String download(HttpServletResponse response,HttpServletRequest request)throws Exception{
//要下载的文件的路径
String path=request.getSession().getServletContext().getRealPath("/upload");
String fileName="1.jpg";
//设置response响应头
response.reset();//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
response.setHeader("Content-Disposition","attachment;fileName="+ URLEncoder.encode(fileName,"utf-8"));
File file=new File(path,fileName);
InputStream inputStream=new FileInputStream(file);
OutputStream outputStream=response.getOutputStream();
byte[] buff=new byte[1024];
int index=0;
//执行写出操作
while((index=inputStream.read(buff))!=-1){
outputStream.write(buff,0,index);
outputStream.flush();
}
outputStream.close();
inputStream.close();
return null;
}
（3）测试：
下载后图片可以正常打开