ajax upload file to servlet

1. js

$(function() {
    
    

	// js判断文件大小
	function findSize(field_id) {
    
    
         let fileInput = $("#"+field_id)[0];
         let byteSize  = fileInput.files[0].size;
         return ( Math.ceil(byteSize / 1024 / 1024) ); // Size returned in MB.
    }
    
    // 上传图片按钮 <button type="button"> upload </button>
	$("#upload-img").click(function () {
    
    

         if (!$("#show-img").prop("src")) {
    
    
             return;
         }

         //let imgSize = $("#upload-input")[0].files[0].size;
         let imgSize = findSize("upload-input");
         // console.log(imgSize);

         if (imgSize >= 2) {
    
    
             //$("#myModal1").modal('show');
             alert('请选择2MB以下的图片');
             return;
         }

         let formData = new FormData($("#img-form")[0]);
         $.ajax({
    
    
             url: "/WebMusicPlayer/uploadFile",
             data: formData,
             type: "post",
             cache: false,
             processData: false,/*无需数据处理*/
             contentType: false,
             success: function (img_name) {
    
    
                 // img_name in server
                 $("#music-list-img").val(img_name);
                 // change current page image
                 $("#list-img").css('display', 'inline');
                 $("#list-img").prop('src', $("#show-img").prop('src'));
                 // close modal
                 $("#upd-img").modal('hide');
             },
             error: function (e) {
    
    
                 console.log(e);
             }
         });

     });

});

2. servlet (jsp smart upload)

package com.lovely.action;


import com.jspsmart.upload.Files;
import com.jspsmart.upload.SmartUpload;
import com.jspsmart.upload.SmartUploadException;

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.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.UUID;

/**
 * use smart_upload upload (song_list and song) files..
 */
@WebServlet(name = "UploadFile", urlPatterns = "/uploadFile")
public class UploadFile extends HttpServlet {
    
    

    public static String path;

    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    
    

        //1.创建文件上传对象
        SmartUpload su = new SmartUpload();
        //2.初始化文件上传对象
        su.initialize(getServletConfig(), req, resp);
        //3.设置相关属性（限制条件）

        su.setCharset("utf-8");
        //设置允许上传的文件类型
        su.setAllowedFilesList("jpg,png,bmp");
        //su.setAllowedFilesList("txt");
        //设置允许上传的文件的最大值（单位字节）
        //设置 2MB
        su.setMaxFileSize(1024*1024*2);
        //设置不允许上传的文件类型
//		try {
    
    
//			su.setDeniedFilesList("zip,7z");
//		} catch (SQLException e) {
    
    
//			e.printStackTrace();
//		}
        try {
    
    
            //4.文件上传
            su.upload();

            //取其他数据
            //必须在upload()方法之后
            //使用su.getRequest()
            System.out.println("用户名:"+su.getRequest().getParameter("userName"));

            //5.获得上传文件
            Files files = su.getFiles();
            com.jspsmart.upload.File f = files.getFile(0);

            //6.保存文件到服务器指定目录
            //使用Servlet上下文对象获得项目的根路径（真实路径）
            String filePath = getServletContext().getRealPath("/music-manage/img");
            System.out.println("项目根路径："+filePath);

            File file = new File(filePath);
            //判断文件夹是否存在
            if(!file.exists()){
    
    
                file.mkdirs();
            }

            //保存文件
            //生成全球唯一字符串UUID.randomUUID())
            //获得文件后缀 f.getFileExt()
            String fileName = UUID.randomUUID()+"."+f.getFileExt();
            filePath = filePath+"/"+ fileName;

            f.saveAs(filePath);

            System.out.println("上传成功");

            resp.setContentType("text/plain;charset=utf-8");
            PrintWriter out = resp.getWriter();
            out.print(fileName);
            out.close();
        } catch (SmartUploadException e) {
    
    
            e.printStackTrace();
            System.out.println("文件上传失败");
        }

    }
}