1、文件上传
- JSP
1. 设置input的type设置为file
2. form表单的method设置为post get请求回将文件名字传给后台而不是文件本身
3.form的表单的enctype设置multipart/form-data,以二进制形式传递数据
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<form action="/upload" method="post" enctype="multipart/form-data">
<input type="file" name="img"><br/>
<input type="submit" value="上传">
</form>
</body>
</html>
- Servlet
@WebServlet("/upload")
public class uploadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
//通过输入流获取客户端传来的数据 读到内存
InputStream inputStream = req.getInputStream();
Reader reader = new InputStreamReader(inputStream);
BufferedReader bufferedReader = new BufferedReader(reader);
//通过输出流将数据流输出到本地硬盘
//获取文件夹的绝对路径
String path = req.getServletContext().getRealPath("/file/copy.txt");
OutputStream outputStream = new FileOutputStream(path);
Writer writer = new OutputStreamWriter(outputStream);
BufferedWriter bufferedWriter = new BufferedWriter(writer);
String str = "";
while ((str = bufferedReader.readLine())!=null){
bufferedWriter.write(str);
}
bufferedReader.close();
bufferedWriter.close();
outputStream.close();;
writer.close();
reader.close();
inputStream.close();
}
}
输入文件copy.txt
- 组件: fileupload 阿帕奇
导入jar包
1. common-io.jar
2. commons.fileupload.jar
1.fileupload:组件可以将所有的请求信息都解析成FileItem对象 可以通过对fileItem对象的操作完成上传 面向对象操作
2.读取文本文件使用字节流 会把文本中的段落 空格都可以读取 同时也可以读取图片，而字符流只能读取文字 不能识别段落 空格和图片
@WebServlet("/upload")
public class uploadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
DiskFileItemFactory fileItemFactory = new DiskFileItemFactory();
ServletFileUpload servletFileUpload = new ServletFileUpload(fileItemFactory);
try {
List<FileItem> list = servletFileUpload.parseRequest(req);
for (FileItem fileItem:list){
System.out.println(fileItem.getName());//test.txt
System.out.println(fileItem.getFieldName());//img 对应jsp标签的name <input type="file" name="img"><br/>
//如果是文本
if (fileItem.isFormField()){
String name = fileItem.getFieldName();
String value = fileItem.getString("UTF-8");
System.out.println(value);
}else {
//文件
InputStream inputStream = fileItem.getInputStream();
String path = req.getServletContext().getRealPath("/file/"+fileItem.getName());
OutputStream outputStream = new FileOutputStream(path);
int temp = 0;
while ((temp = inputStream.read())!=-1){
outputStream.write(temp);
}
outputStream.close();
inputStream.close();
System.out.println("输出成功");
}
}
} catch (FileUploadException e) {
e.printStackTrace();
}
}
}
image.png
2、文件下载
@WebServlet("/downloadServlet")
public class downloadServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//设置响应的方式 下载
resp.setContentType("application/x-msdownload");
String fileName = "1.png";
//设置下载后的文件名
resp.setHeader("Content-Disposition","attachment:filename="+fileName);
//获取输出流
OutputStream outputStream = resp.getOutputStream();
String path = req.getServletContext().getRealPath("file/download.png");
InputStream inputStream = new FileInputStream(path);
int temp = 0;
while ((temp = inputStream.read()) != -1){
outputStream.write(temp);
}
inputStream.close();
outputStream.close();
}
}
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