Java实现上传和下载功能（支持多个文件同时上传）
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2022-03-15 08:13:26
文件上传一直是web项目中必不可少的一项功能。项目结构如下：（这是我之前创建的ssm整合的框架项目，在这上面添加文件上传与下载）主要的是fileuploadcontroller，doupload.js...
文件上传一直是web项目中必不可少的一项功能。
项目结构如下：（这是我之前创建的ssm整合的框架项目，在这上面添加文件上传与下载）
主要的是fileuploadcontroller，doupload.jsp,up.jsp,springmvc.xml
1.先编写up.jsp
<form action="doupload.jsp" enctype="multipart/form-data" method="post"> <p>上传者：<input type="text" name="user"></p> <p>选择文件：<input type="file" name="nfile"></p> <p>选择文件：<input type="file" name="nfile1"></p> <p><input type="submit" value="提交"></p> </form>
以上便是up.jsp的核心代码；
2.编写doupload.jsp
<%
request.setcharacterencoding("utf-8");
string uploadfilename = ""; //上传的文件名
string fieldname = ""; //表单字段元素的name属性值
//请求信息中的内容是否是multipart类型
boolean ismultipart = servletfileupload.ismultipartcontent(request);
//上传文件的存储路径（服务器文件系统上的绝对文件路径）
string uploadfilepath = request.getsession().getservletcontext().getrealpath("upload/" );
if (ismultipart) {
fileitemfactory factory = new diskfileitemfactory();
servletfileupload upload = new servletfileupload(factory);
try {
//解析form表单中所有文件
list<fileitem> items = upload.parserequest(request);
iterator<fileitem> iter = items.iterator();
while (iter.hasnext()) { //依次处理每个文件
fileitem item = (fileitem) iter.next();
if (item.isformfield()){ //普通表单字段
fieldname = item.getfieldname(); //表单字段的name属性值
if (fieldname.equals("user")){
//输出表单字段的值
out.print(item.getstring("utf-8")+"上传了文件。<br/>");
}
}else{ //文件表单字段
string filename = item.getname();
if (filename != null && !filename.equals("")) {
file fullfile = new file(item.getname());
file savefile = new file(uploadfilepath, fullfile.getname());
item.write(savefile);
uploadfilename = fullfile.getname();
out.print("上传成功后的文件名是："+uploadfilename);
out.print("\t\t下载链接:"+"<a href='download.action?name="+uploadfilename+"'>"+uploadfilename+"</a>");
out.print("<br/>");
}
}
}
} catch (exception e) {
e.printstacktrace();
}
}
%>
该页面主要是内容是，通过解析request，并设置上传路径，创建一个迭代器，先进行判空，再通过循环来实现多个文件的上传，再输出文件信息的同时打印文件下载路径。
效果图：
3.编写filtercontroller实现文件下载的功能（相对上传比较简单）：
@controller
public class fileuploadcontroller {
@requestmapping(value="/download")
public responseentity<byte[]> download(httpservletrequest request,httpservletresponse response,@requestparam("name") string filename)throws exception {
//下载显示的文件名，解决中文名称乱码问题
filename=new string(filename.getbytes("iso-8859-1"),"utf-8");
//下载文件路径
string path = request.getservletcontext().getrealpath("/upload/");
file file = new file(path + file.separator + filename);
httpheaders headers = new httpheaders();
//下载显示的文件名，解决中文名称乱码问题
string downloadfielname = new string(filename.getbytes("iso-8859-1"),"utf-8");
//通知浏览器以attachment（下载方式）打开图片
headers.setcontentdispositionformdata("content-disposition", downloadfielname);
//application/octet-stream ： 二进制流数据（最常见的文件下载）。
headers.setcontenttype(mediatype.application_octet_stream);
return new responseentity<byte[]>(fileutils.readfiletobytearray(file),
headers, httpstatus.created);
}
}
4.实现上传文件的功能还需要在springmvc中配置bean：
<bean id="multipartresolver" class="org.springframework.web.multipart.commons.commonsmultipartresolver"> <!-- 上传文件大小上限，单位为字节（10mb） --> <property name="maxuploadsize"> <value>10485760</value> </property> <!-- 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</value> </property> </bean>
完整代码如下：
up.jsp
<%@ page language="java" import="java.util.*" pageencoding="utf-8"%> <!doctype html public "-//w3c//dtd html 4.01 transitional//en"> <html> <head> <title>file控件</title> </head> <body> <form action="doupload.jsp" enctype="multipart/form-data" method="post"> <p>上传者：<input type="text" name="user"></p> <p>选择文件：<input type="file" name="nfile"></p> <p>选择文件：<input type="file" name="nfile1"></p> <p><input type="submit" value="提交"></p> </form> </body> </html>
doupload.jsp
<%@ page language="java" pageencoding="utf-8"%>
<%@page import="java.io.*,java.util.*"%>
<%@page import="org.apache.commons.fileupload.*"%>
<%@page import="org.apache.commons.fileupload.disk.diskfileitemfactory" %>
<%@page import="org.apache.commons.fileupload.servlet.servletfileupload"%>
<!doctype html public "-//w3c//dtd html 4.01 transitional//en">
<html>
<head>
<title>上传处理页面</title>
</head>
<body>
<%
request.setcharacterencoding("utf-8");
string uploadfilename = ""; //上传的文件名
string fieldname = ""; //表单字段元素的name属性值
//请求信息中的内容是否是multipart类型
boolean ismultipart = servletfileupload.ismultipartcontent(request);
//上传文件的存储路径（服务器文件系统上的绝对文件路径）
string uploadfilepath = request.getsession().getservletcontext().getrealpath("upload/" );
if (ismultipart) {
fileitemfactory factory = new diskfileitemfactory();
servletfileupload upload = new servletfileupload(factory);
try {
//解析form表单中所有文件
list<fileitem> items = upload.parserequest(request);
iterator<fileitem> iter = items.iterator();
while (iter.hasnext()) { //依次处理每个文件
fileitem item = (fileitem) iter.next();
if (item.isformfield()){ //普通表单字段
fieldname = item.getfieldname(); //表单字段的name属性值
if (fieldname.equals("user")){
//输出表单字段的值
out.print(item.getstring("utf-8")+"上传了文件。<br/>");
}
}else{ //文件表单字段
string filename = item.getname();
if (filename != null && !filename.equals("")) {
file fullfile = new file(item.getname());
file savefile = new file(uploadfilepath, fullfile.getname());
item.write(savefile);
uploadfilename = fullfile.getname();
out.print("上传成功后的文件名是："+uploadfilename);
out.print("\t\t下载链接:"+"<a href='download.action?name="+uploadfilename+"'>"+uploadfilename+"</a>");
out.print("<br/>");
}
}
}
} catch (exception e) {
e.printstacktrace();
}
}
%>
</body>
</html>
fileuploadcontroller.java
package ssm.me.controller;
import java.io.file;
import java.net.urldecoder;
import java.util.iterator;
import java.util.list;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import org.apache.commons.fileupload.fileitem;
import org.apache.commons.fileupload.fileitemfactory;
import org.apache.commons.fileupload.disk.diskfileitemfactory;
import org.apache.commons.fileupload.servlet.servletfileupload;
import org.apache.commons.io.fileutils;
import org.junit.runners.parameterized.parameter;
import org.springframework.http.httpheaders;
import org.springframework.http.httpstatus;
import org.springframework.http.mediatype;
import org.springframework.http.responseentity;
import org.springframework.stereotype.controller;
import org.springframework.ui.model;
import org.springframework.web.bind.annotation.modelattribute;
import org.springframework.web.bind.annotation.requestmapping;
import org.springframework.web.bind.annotation.requestmethod;
import org.springframework.web.bind.annotation.requestparam;
import org.springframework.web.multipart.multipartfile;
@controller
public class fileuploadcontroller {
@requestmapping(value="/download")
public responseentity<byte[]> download(httpservletrequest request,httpservletresponse response,@requestparam("name") string filename)throws exception {
//下载显示的文件名，解决中文名称乱码问题
filename=new string(filename.getbytes("iso-8859-1"),"utf-8");
//下载文件路径
string path = request.getservletcontext().getrealpath("/upload/");
file file = new file(path + file.separator + filename);
httpheaders headers = new httpheaders();
//下载显示的文件名，解决中文名称乱码问题
string downloadfielname = new string(filename.getbytes("iso-8859-1"),"utf-8");
//通知浏览器以attachment（下载方式）打开图片
headers.setcontentdispositionformdata("content-disposition", downloadfielname);
//application/octet-stream ： 二进制流数据（最常见的文件下载）。
headers.setcontenttype(mediatype.application_octet_stream);
return new responseentity<byte[]>(fileutils.readfiletobytearray(file),
headers, httpstatus.created);
}
}
springmvc.xml（仅供参考，有的地方不可以照搬）
<?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:mvc="http://www.springframework.org/schema/mvc" xmlns:context="http://www.springframework.org/schema/context" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemalocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.2.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd"> <!-- 一个用于自动配置注解的注解配置 --> <mvc:annotation-driven></mvc:annotation-driven> <!-- 扫描该包下面所有的controller --> <context:component-scan base-package="ssm.me.controller"></context:component-scan> <!-- 视图解析器 --> <bean class="org.springframework.web.servlet.view.internalresourceviewresolver"></bean> <bean id="multipartresolver" class="org.springframework.web.multipart.commons.commonsmultipartresolver"> <!-- 上传文件大小上限，单位为字节（10mb） --> <property name="maxuploadsize"> <value>10485760</value> </property> <!-- 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</value> </property> </bean> </beans>
web.xml（仅供参考，有的地方不可以照搬）
<?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"> <display-name>student</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list> <servlet> <servlet-name>springmvc</servlet-name> <servlet-class>org.springframework.web.servlet.dispatcherservlet</servlet-class> <!-- 初始化参数 --> <init-param> <param-name>contextconfiglocation</param-name> <param-value>classpath:springmvc.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>springmvc</servlet-name> <url-pattern>*.action</url-pattern> </servlet-mapping> <context-param> <param-name>contextconfiglocation</param-name> <param-value>classpath:spring/applicationcontext-*.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.contextloaderlistener</listener-class> </listener> </web-app>
以上便为文件上传和下载的全部代码，博主亲测过，没有问题。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。