借鉴博客:https://www.cnblogs.com/hellokuangshen/p/11289940.html
文件上传和下载
springMVC 可以很好的支持文件上传,但是SpringMVC上下文中默认没有装配MultipartResolver,因此默认情况下其不能处理文件上传工作。如果想使用Spring的文件上传功能,则需要在上下文中配置MultipartResolver。
准备工作
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。
<form action="" enctype="multipart/form-data" method="post">
<input type="file" name="file"/>
<input type="submit">
</form>
一旦设置了enctype为multipart/form-data,浏览器即会采用二进制流的方式来处理表单数据,而对于文件上传的处理则涉及在服务器端解析原始的HTTP响应。
Spring MVC为文件上传提供了直接的支持,这种支持是用即插即用的MultipartResolver实现的。Spring MVC使用Apache Commons FileUpload技术实现了一个MultipartResolver实现类:CommonsMultipartResolver。因此,SpringMVC的文件上传还需要依赖Apache Commons FileUpload的组件。
在springmvc-servlet.xml进行配置文件如下:
注意!!!这个bena的id必须为:multipartResolver , 否则上传文件会报400的错误!在这里栽过坑,教训!
<!--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>
除此之外,我们还需要导入文件上传的jar包,commons-fileupload , Maven会自动帮我们导入他的依赖包 commons-io包;
<!--文件上传-->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.3</version>
</dependency>
我们会使用它的实现类 CommonsMultipartFile , 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
我们去实际测试一下
springMVC实现文件上传
方式一:采用流的方式上传文件
controller文件:
//文件上传:流
@RequestMapping("/upload")
@ResponseBody
public String upload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//1.获得文件名
String filename = file.getOriginalFilename();
if ("".equals(filename)){
return "文件不存在";
}
//2.上传文件保存路径
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()){
realPath.mkdir();
}
//3.上传文件
InputStream is = file.getInputStream();
FileOutputStream os = new FileOutputStream(new File(realPath, filename));
int len = 0;
byte[] buffer = new byte[1024];
while ((len=is.read(buffer))!=-1){
os.write(buffer,0,len);
os.flush();
}
//4.关闭流
os.close();
is.close();
return "上传完毕";
}
前端页面:
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>
<form enctype="multipart/form-data" method="post" action="${pageContext.request.contextPath}/upload2">
<input type="file" name="file">
<<input type="submit">
</form>
</body>
</html>
结果输出:
采用file.Transto 来上传
controller:
文件上传:CommonsMultipartFile
@RequestMapping(value = "/upload2")
@ResponseBody
public String upload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//上传文件保存路径
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()){
realPath.mkdir();
}
//transferTo:将文件写入到磁盘,参数就是一个文件
file.transferTo(new File(realPath+"/"+file.getOriginalFilename()));
return "上传完毕";
}
其他文件配置不变
完整项目实现
项目结构:
pom.xml文件配置:
<?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">
<parent>
<artifactId>SpringMVC</artifactId>
<groupId>com.kuang</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>demo07_springmvc_file_intercepter</artifactId>
<packaging>war</packaging>
<name>demo07_springmvc_file_intercepter Maven Webapp</name>
<!-- FIXME change it to the project's website -->
<url>http://www.example.com</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.11</version>
<scope>test</scope>
</dependency>
<!--文件上传和下载的包commons-fileupload,依赖于commons-io-->
<!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.3</version>
</dependency>
</dependencies>
<build>
<finalName>demo07_springmvc_file_intercepter</finalName>
<pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
<plugins>
<plugin>
<artifactId>maven-clean-plugin</artifactId>
<version>3.1.0</version>
</plugin>
<!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
<plugin>
<artifactId>maven-resources-plugin</artifactId>
<version>3.0.2</version>
</plugin>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
</plugin>
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.22.1</version>
</plugin>
<plugin>
<artifactId>maven-war-plugin</artifactId>
<version>3.2.2</version>
</plugin>
<plugin>
<artifactId>maven-install-plugin</artifactId>
<version>2.5.2</version>
</plugin>
<plugin>
<artifactId>maven-deploy-plugin</artifactId>
<version>2.8.2</version>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
web.xml文件配置:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<!--配置过滤器-->
<filter>
<filter-name>myFilter</filter-name>
<!--<filter-class>com.kuang.filter.GenericEncodingFilter</filter-class>-->
<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>
<!--/* 包括.jsp-->
<filter-mapping>
<filter-name>myFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
springmvc-servlet.xml文件配置:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<servlet>
<servlet-name>springmvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:springmvc-servlet.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springmvc</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<!--配置过滤器-->
<filter>
<filter-name>myFilter</filter-name>
<!--<filter-class>com.kuang.filter.GenericEncodingFilter</filter-class>-->
<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>
<!--/* 包括.jsp-->
<filter-mapping>
<filter-name>myFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>
fileUploadController文件:
package com.kuang.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.commons.CommonsMultipartFile;
import sun.security.util.Length;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URL;
import java.net.URLEncoder;
@Controller
public class FileUploadController {
//文件上传:流
@RequestMapping("/upload")
@ResponseBody
public String upload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//1.获得文件名
String filename = file.getOriginalFilename();
if ("".equals(filename)){
return "文件不存在";
}
//2.上传文件保存路径
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()){
realPath.mkdir();
}
//3.上传文件
InputStream is = file.getInputStream();
FileOutputStream os = new FileOutputStream(new File(realPath, filename));
int len = 0;
byte[] buffer = new byte[1024];
while ((len=is.read(buffer))!=-1){
os.write(buffer,0,len);
os.flush();
}
//4.关闭流
os.close();
is.close();
return "上传完毕";
}
//文件上传:CommonsMultipartFile
@RequestMapping(value = "/upload2")
@ResponseBody
public String upload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {
//上传文件保存路径
String path = request.getServletContext().getRealPath("/upload");
File realPath = new File(path);
if (!realPath.exists()){
realPath.mkdir();
}
//transferTo:将文件写入到磁盘,参数就是一个文件
file.transferTo(new File(realPath+"/"+file.getOriginalFilename()));
return "上传完毕";
}
}
文件下载实现
文件下载步骤:
设置 response 响应头
读取文件 – InputStream
写出文件 – OutputStream
执行操作
关闭流 (先开后关)
代码实现:
@RequestMapping(value="/download")
public String downloads(HttpServletResponse response) throws Exception{
//要下载的图片地址
String path = "C:/Users/Administrator/Desktop/";
String fileName = "1.png";
//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;
}