JavaWeb--上传文件到web

上传文件

文件上传过程

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文件上传注意事项

• 1.为保证服务器安全，上传文件应该放在外界无法直接访问你得目录下，比如放在WEB-INF目录下
• 2.为防止文件覆盖现象的发生，要为文件产生一个唯一的文件名 （添加时间戳 或者 uuid 或者MD5 或者位运算）
• 3.要限制上传文件的大小
• 4.可以限制上传文件的类型，在收到上传文件名时，要判断后缀名是否合格。

需要用到的类详解

• ServletFileUpload 负责处理上传的文件数据，并将表单中每个输入项封装成一个FileItem对象，在使用ServletFileUpload对象解析请求时，需要DiskFileItemFactory对象。所以，我们需要在进行解析工作前构造号DiskFileItemFactory对象，通过ServletFileUpload对象的构造方法，或setFileItemFactory()方法设置ServletFileUpload对象的fileItemFactory属性。
  
  

工程文件结构

具体实现

package edu.cqupt.servlet;

import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.ProgressListener;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.List;
import java.util.UUID;

public class FileServlet  extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String msg = null;
        if(!ServletFileUpload.isMultipartContent(req)){ //判断文件是带文件表单还是普通表单
            return;    //终止运行，说明这一定是一个不带文件的
        }
        String uploadPath = this.getServletContext().getRealPath("/WEB-INF/upload");//为保证服务器安全，上传文件应该放在外界无法直接访问你得目录下，比如放在WEB-INF目录下
        String tempPath = this.getServletContext().getRealPath("/WEB-INF/temp"); // 缓存
        File uploadFile = new File(uploadPath);
        if(!uploadFile.exists()){
            uploadFile.mkdir();
        }
        File file = new File(tempPath);
        if(!file.exists()){
            file.mkdir();
        }
        try {
            //1.创建 DiskFileItemFactory
            DiskFileItemFactory factory = getDiskFileItemFactory(file);
            //2.获取ServletFileUpload
            ServletFileUpload upload = getServletFileUpload(factory);
            // 3.处理上传文件
             msg = uploadParseRequest(upload,req,uploadPath);
        } catch (FileUploadException e) {
            e.printStackTrace();
        }
        req.setAttribute("msg",msg); // 请求转发消息
        req.getRequestDispatcher("info.jsp").forward(req,resp);
    }

    public static DiskFileItemFactory getDiskFileItemFactory(File file){
        DiskFileItemFactory factory = new DiskFileItemFactory();
        factory.setSizeThreshold(1024*1024);    // 缓存区大小为1M
        factory.setRepository(file);            // 临时目录的保存目录，需要一个file
        return  factory;
    }
    public static ServletFileUpload getServletFileUpload(DiskFileItemFactory factory){
        ServletFileUpload upload = new ServletFileUpload(factory);
        upload.setProgressListener(new ProgressListener() {
            @Override
            public void update(long pBytesRead, long pContentLength, int pItems) {
                System.out.println("总大小：" + pContentLength + "已上传：" + pBytesRead + "已上传：" + (int)(((double)pBytesRead/(double)pContentLength)*100)+ "%" );
            }
        });
        upload.setHeaderEncoding("UTF-8");
        upload.setFileSizeMax(1024*1024*10);
        upload.setSizeMax(1024*1024*10);
        return upload;
    }

    public static String  uploadParseRequest(ServletFileUpload upload,HttpServletRequest req,String uploadPath) throws FileUploadException, IOException {
        String message = null;
        List<FileItem> fileItems = upload.parseRequest(req);
        for (FileItem fileItem : fileItems) {
            if (fileItem.isFormField()) {
                String name = fileItem.getFieldName();
                String value = fileItem.getString("utf-8");
                System.out.println(name + ":" + value);
            } else {
                String uploadFileName = fileItem.getName();
                System.out.println("上传的文件名:" + uploadFileName);
                if (uploadFileName.trim().equals("") || uploadFileName == null) {
                    continue;
                }
                String fileName = uploadFileName.substring(uploadFileName.lastIndexOf("/") + 1);
                String fileExtName = uploadFileName.substring(uploadFileName.lastIndexOf(".") + 1);
                System.out.println("文件信息：[文件名："+fileName + "	文件类型：" +fileExtName + "]");
                String uuidPath = UUID.randomUUID().toString();
                String realPath = uploadPath + "/" + uuidPath;
                File realPathFile = new File(realPath);
                if (!realPathFile.exists()) {
                    realPathFile.mkdir();
                }
                InputStream is = fileItem.getInputStream();
                FileOutputStream fos = new FileOutputStream(realPath + "/" + fileName);
                byte[] buffer = new byte[1024];
                int len = 0;
                while ((len = is.read(buffer)) != -1) {
                    fos.write(buffer, 0, len);
                }
                fos.close();
                is.close();
                message = "文件上传成功";
                fileItem.delete();
            }
        }
        return message;
    }
}

index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
        <%--通过表单上传文件
            get:上传文件有大小限制：5kb
            post没有大小限制
        --%>
        <form action="${pageContext.request.contextPath}/upload.do" method="post" enctype="multipart/form-data">
            上传用户:<input type="text" name = "username" ><br/>
              <p><input type="file" name = "file1"></p>
              <p><input type="file" name = "file2"></p>
              <p><input type="submit" value="上传">|<input type="reset" value="重置"></p>
        </form>
  </body>
</html>

info.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
   ${msg}
</body>
</html>

web.xml

 <servlet>
        <servlet-name>FileServlet</servlet-name>
        <servlet-class>edu.cqupt.servlet.FileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>FileServlet</servlet-name>
        <url-pattern>/upload.do</url-pattern>
    </servlet-mapping>

实验效果

找到这个目录，然后通过文件目录进入