java实现文件上传下载

java实现文件上传下载

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：

2.后台：

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 =http:// 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.sethttp://FileSizeMax(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 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.printlnhttp://(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);

}

}

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