%--
 Created by IntelliJ IDEA.
 User: Lenovo
 Date: 2020/6/19
 Time: 22:53
 Learn from https://www.bilibili.com/video/BV18z411i7gh?t=23p=192
 To change this template use File | Settings | File Templates.
--%>
%@ page contentType="text/html;charset=UTF-8" language="java" %>
html>
head>
  title>文件上傳/title>
/head>
body>
  !--文件上傳對表單的要求-->
  !--
    1、表單中的請求提交方式必須是POST
    2、表單中應指定所提交的請求位multipart請求，通過在form/>標簽中添加enctype屬性
      其值為multipart/form-data
    3、 表單
  -->
  form method="POST" action="http://localhost:8888/hello/UploadImageServlet" enctype="multipart/form-data">
    編號input type="text" name="BNO">/br>
    名字input type="text" name="BNAME">/br>
    照片input type="file" name="picutreUrl">/br>
    input type="submit" value="注冊">
  /form>
/body>
/html>

package Servlet.bookServlet;

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 javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.List;


@WebServlet(name = "UploadImageServlet")
public class UploadImageServlet extends HttpServlet {
  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doPost(request,response);
  }
  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //1、判斷請求是不是multipart請求
    if(!ServletFileUpload.isMultipartContent(request)){
      throw new RuntimeException("當前請求不支持文件上傳");
    }
    System.out.println("開始上傳文件");
    //2、創建FileItem工廠==>文件寫入硬盤的作用
    try {
      DiskFileItemFactory factory = new DiskFileItemFactory();
      //3、創建temp臨時文件夾
      String tempPath ="D:\\tomcat\\apache-tomcat-9.0.35-windows-x64\\apache-tomcat-9.0.35\\webapps\\librarySystem\\web\\net\\temp";
      File tempFile = new File(tempPath);
      factory.setRepository(tempFile);
      //4、設置使用臨時文件的邊界值,大于該值，上傳文件先保存在臨時文件中，小于該值，則直接寫入內存
      //單位是字節
      factory.setSizeThreshold(1024*1024*1);

      //5、創建文件上傳核心組件
      // 調用ServletFileUpload.parseRequest方法解析request對象，得到一個保存了所有上傳內容的List對象。
      ServletFileUpload upload = new ServletFileUpload(factory);
      upload.setHeaderEncoding("utf-8");//可以解決文件名中文亂碼
      upload.setFileSizeMax(1024*1024*2);

      String bNo="defaultBNo",bName="defaultBName";
      //6、解析請求
      ListFileItem> items =upload.parseRequest(request);
      //7、遍歷請求
      for(FileItem item:items){
        //普通表單項，上傳名字，編號等普通信息的上i傳
        if(item.isFormField()){
          String fileName = item.getFieldName();// name屬性值
          String fileValue = item.getString("utf-8");// name對應的value值
          System.out.println(fileName + " -- " + fileValue);
          if(fileName.equalsIgnoreCase("BNO")){
            bNo = fileValue;
          }
          if(fileName.equalsIgnoreCase("BNAME")){
            bName = fileValue;
          }
         }
        else{//上傳圖片等
          String fileName = item.getName();
          System.out.println("上傳文件名字:"+fileName);
          String suffix = fileName.substring(fileName.lastIndexOf('.'));//獲取文件類型
          String newFileName = bNo+"_"+bName+suffix;
          System.out.println(newFileName);
          //獲取輸入流，其中有上傳文件的內容
          InputStream is = item.getInputStream();
          //String path = this.getServletContext().getRealPath("/net/bookImage");//獲得當前項目保存服務器地址，也就是web文件夾下
          String path ="D:\\tomcat\\apache-tomcat-9.0.35-windows-x64\\apache-tomcat-9.0.35\\webapps\\librarySystem\\web\\net\\bookImage";
          //文件夾內文件數目有上限，但是可以創建子目錄
            //獲取當前系統時間
            Calendar now = Calendar.getInstance();
            int year = now.get(Calendar.YEAR);
            int month = now.get(Calendar.MONTH)+1;
            int day = now.get(Calendar.DAY_OF_MONTH);
            path = path+"/"+year+"/"+month+"/"+day;
            //若該目錄不存在，直接創建新目錄
            File dirFile = new File(path);
            if(!dirFile.exists()){
              dirFile.mkdirs();
            }
          //創建目標文件，用來保存上傳文件
          File desFile = new File(path,newFileName);
          //創建文件輸出流
          OutputStream os = new FileOutputStream(desFile);
          //將輸入流數據寫入到輸出流中
          int len=-1;
          byte[]buf = new byte[1024];
          while((len=is.read(buf))!=-1){
            os.write(buf,0,len);
          }
          //desFile.delete();//刪除臨時文件
          os.close();//輸出流
          is.close();//輸入流
          //刪除臨時文件
          item.delete();
        }
      }
    } catch (FileUploadException e) {
      e.printStackTrace();
    }
  }
}