对于文件上传，浏览器在上传的过程中是将文件以流的形式上传到服务端的。如果直接使用Servlet获取上传文件的输入流然后再解析里面的请求参数是比较麻烦，所以一般选择采用apache的开源工具common-fileupload这个文件上传组件。这个common-fileupload上传组件的jar包可以去apache官网上面下载点击下载。common-fileupload是依赖于common-io这个包的，所以还需要下载这个包。
一、文件上传
1.文件上传页面upload.jsp代码如下：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>上传文件</title>
</head>
<body>
<form action="/upload" method="post" enctype="multipart/form-data">
desc : <input type="text" name="desc"><br>
上传 : <input type="file" name="file"><br>
<button>上传文件</button>
</form>
</body>
</html>
2.处理文件上传的UploadServlet页面代码如下:
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.UUID;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.IOUtils;
@WebServlet("/upload")
public class UploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.getRequestDispatcher("/WEB-INF/views/upload.jsp").forward(req, resp);
}
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 1.设置文件上传路径
File saveDir = new File("d:/upload");
if (!saveDir.exists()) {
saveDir.mkdir();
}
// 2.设置文件上传的临时路径
File tempDir = new File("d:/temp");
if (!tempDir.exists()) {
tempDir.mkdir();
}
// 3.判断form中是否设置enctype属性为mutilpart/form-data
if (ServletFileUpload.isMultipartContent(req)) {
DiskFileItemFactory factory = new DiskFileItemFactory();
// 4.1设置临时文件夹
factory.setRepository(tempDir);
// 4.2设置缓冲区大小
factory.setSizeThreshold(10 * 1024);// 10KB
// 5.设置上传文件的最大空间
ServletFileUpload servletFileUpload = new ServletFileUpload(factory);
servletFileUpload.setSizeMax(10 * 1024 * 1024);// 10M
try {
// 6.获取所有表单元素(普通表单元素、上传文件元素)，并包装成FileItem的对象集合
List<FileItem> items = servletFileUpload.parseRequest(req);
for (FileItem item : items) {
// 7.判断表单元素是普通元素还是文件元素
if (item.isFormField()) { // 普通元素
System.out.println(item.getFieldName());// 获取name属性
System.out.println(item.getString("UTF-8"));// 获取表单元素值
} else { // 文件元素
System.out.println(item.getName());// 获取上传文件的名称
System.out.println(item.getFieldName());// 获取name属性
// 8.获取上传文件并存储
String fileName = item.getName();// 获取上传文件的名称
String newName = UUID.randomUUID().toString() + fileName.substring(fileName.lastIndexOf("."));
InputStream inputStream = item.getInputStream();
FileOutputStream outputStream = new FileOutputStream(new File(saveDir, newName));
IOUtils.copy(inputStream, outputStream);
outputStream.flush();
outputStream.close();
inputStream.close();
System.out.println("上传成功!");
}
}
} catch (FileUploadException e) {
e.printStackTrace();
}
}
}
}
二、文件下载
1.文件下载页面jsp代码如下：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>文件下载</title>
</head>
<body>
<a href="/download?file=6300b057-a809-4cfc-9c6a-8a123de08790.jpg&name=my.jpg">下载照片</a>
<a href="/download?file=mysql.pdf">下载PDF</a>
<a href="/download?file=admin.zip">下载ZIP</a>
</body>
</html>
2.处理文件下载的DownloadServlet页面代码如下:
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
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.io.IOUtils;
import org.apache.commons.lang3.StringUtils;
@WebServlet("/download")
public class DownloadServlet extends HttpServlet{
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String fileName = req.getParameter("file");
String name = req.getParameter("name");
//fileName = new String(fileName.getBytes("ISO8859-1"),"UTF-8");
// 在高版本servlet3.0+ 是不用考虑中文乱码问题
System.out.println(fileName);
File saveDir = new File("d:/upload");
File file = new File(saveDir, fileName);
// 判断下载文件是否存在
if(file.exists()) {
if(StringUtils.isNotEmpty(name)) {
// 设置MIME类型，进行下载
resp.setContentType("application/octet-stream");
// 设置文件大小
resp.setContentLengthLong(file.length());
fileName = new String(fileName.getBytes("UTF-8"),"ISO8859-1");
// 设置下载文件文件名
resp.addHeader("Content-Disposition", "attachment; filename=\"" + name + "\"");
}
// 响应输出流
OutputStream output = resp.getOutputStream();
// 文件输入流
InputStream input = new FileInputStream(file);
IOUtils.copy(input, output);
output.flush();
output.close();
input.close();
} else {
resp.sendError(404, "文件找不到");
}
}
}
