java实现文件上传下载 - 快网idc优惠网

本文实例为大家分享了java实现文件上传下载的具体代码，供大家参考，具体内容如下

一.上传

1.前端：

<form method="post" action="fileupload" enctype="multipart/form-data">

　　<input type="file" name="uploadfile" />

　　<br/>

　　<input type="submit" value="上传" />

</form>

2.后台：

100

import java.io.file;

import java.io.ioexception;

import java.io.printwriter;

import java.util.list;

import javax.servlet.servletexception;

import javax.servlet.annotation.webservlet;

import javax.servlet.http.httpservlet;

import javax.servlet.http.httpservletrequest;

import javax.servlet.http.httpservletresponse;

import org.apache.commons.fileupload.fileitem;

import org.apache.commons.fileupload.disk.diskfileitemfactory;

import org.apache.commons.fileupload.servlet.servletfileupload;

import dao.filedao;

@webservlet("/fileupload")

public class fileupload extends httpservlet {

private static final long serialversionuid = 1l;

// 上传配置

private static final int memory_threshold = 1024 * 1024 * 3; // 3mb

private static final int max_file_size = 1024 * 1024 * 40; // 40mb

private static final int max_request_size = 1024 * 1024 * 50; // 50mb

public fileupload() {

super();

}

protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {

request.setcharacterencoding("utf-8");

response.setcharacterencoding("utf-8");

response.setcontenttype("text/html;charset=utf-8");

printwriter out = response.getwriter();

if (!servletfileupload.ismultipartcontent(request)) {

// 如果不是则停止

out.println("error: 表单必须包含 enctype=multipart/form-data");

out.flush();

return;

}

// 配置上传参数

diskfileitemfactory factory = new diskfileitemfactory();

// 设置内存临界值 - 超过后将产生临时文件并存储于临时目录中

factory.setsizethreshold(memory_threshold);

// 设置临时存储目录

factory.setrepository(new file(system.getproperty("java.io.tmpdir")));

servletfileupload upload = new servletfileupload(factory);

// 设置最大文件上传值

upload.setfilesizemax(max_file_size);

// 设置最大请求值 (包含文件和表单数据)

upload.setsizemax(max_request_size);

// 中文处理

upload.setheaderencoding("utf-8");

string uploadpath = request.getservletcontext().getrealpath("/files");

file uploaddir = new file(uploadpath);

if (!uploaddir.exists()) {

uploaddir.mkdir();

}

try {

// 解析请求的内容提取文件数据

list<fileitem> formitems = upload.parserequest(request);

if (formitems != null && formitems.size() > 0) {

// 迭代表单数据

for (fileitem item : formitems) {

// 处理不在表单中的字段

if (!item.isformfield()) {

string filename = new file(item.getname()).getname();

string filepath = uploadpath + file.separator + filename;

file storefile = new file(filepath);

// 在控制台输出文件的上传路径

// system.out.println(filepath);

// 保存文件到硬盘

if(storefile.exists()) {

out.println("上传失败，文件已存在！");

}else {

item.write(storefile);

out.println("文件上传成功!");

}

} catch (exception ex) {

response.getwriter().println("文件上传成功!");

}

protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {

doget(request, response);

}

二.下载

1.下载链接：

filedownload?filename="+urlencoder.encode(filename,"utf-8")　——— 需要对url中的中文参数进行编码，否则会出现乱码

2.后台：

import java.io.file;

import java.io.fileinputstream;

import java.io.ioexception;

import java.io.printwriter;

import java.net.urlencoder;

import javax.servlet.servletexception;

import javax.servlet.annotation.webservlet;

import javax.servlet.http.httpservlet;

import javax.servlet.http.httpservletrequest;

import javax.servlet.http.httpservletresponse;

@webservlet("/filedownload")

public class filedownload extends httpservlet {

private static final long serialversionuid = 1l;

public filedownload() {

super();

}

protected void doget(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {

request.setcharacterencoding("utf-8");

response.setcharacterencoding("utf-8");

printwriter out = response.getwriter();

string dirpath = request.getservletcontext().getrealpath("/files");

string filename = urlencoder.encode(request.getparameter("filename"),"utf-8"); //需要对url中的中文参数进行编码，否则出现乱码

response.getwriter().println(filename);

string filepath = dirpath + file.separator + filename;

response.setcontenttype("application/octet-stream");

response.setheader("content-disposition", "attachment; filename=\\"" + filename + "\\"");

fileinputstream fileinputstream = new fileinputstream(filepath);

int i = 0;

while ((i = fileinputstream.read()) != -1) {

out.write(i);

}

fileinputstream.close();

out.close();

}

protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {

doget(request, response);

}

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快网idc。

原文链接：https://www.cnblogs.com/DOLFAMINGO/p/9559185.html

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