java webApp异步上传图片实现代码

<div id="div1" class="photo"> 
 <input type="file" id="choose" accept="image/*" multiple >
 <a id="upload">上传图片</a> 
 <a class="myinputimg" onclick="selectphoto();">从图库中选择</a>
 <a class="myinputimg" id="back">取消</a>
</div>

<script type="text/javascript">
 //获取上传图片的input表单元素
 var filechooser = document.getElementById("choose");
 //创建用于压缩图片的canvas
 var canvas = document.createElement("canvas");
 //获取canvas的视觉属性
 var ctx = canvas.getContext('2d');
 //瓦片canva
 var tCanvas = document.createElement("canvas");
 var tctx = tCanvas.getContext("2d");
 //画布的大小
 var maxsize = 100 * 1024;
 //上传图片点击事件
 $("#upload").on("click", function() {
  filechooser.click();
  })
  .on("touchstart", function() {
  //添加元素属性
  $(this).addClass("touch");
  })
  .on("touchend", function() {
  //移除元素属性
  $(this).removeClass("touch");
  });
 //元素改变 
 filechooser.onchange = function() {
 //如果选择为空，返回操作
 if (!this.files.length) return;
 //创建上传图片的数组
 var files = Array.prototype.slice.call(this.files);
 //选择为数量大于1张时，反回操作，这里根据需求设定；pc端测试一次可以上传若干张图片，移动端选择一张，页面只能预览一张。由于是移动端，所以作此判断。
 if (files.length >1) {
  alert("一次只能上传1张图片");
  return;
 }
 //遍历上传图片的文件数组，可不用遍历，直接取即可。
 files.forEach(function(file, i) {
 //判断图片格式
  if (!/\/(?:jpeg|png|gif)/i.test(file.type)) return;
  var reader = new FileReader();
  var li = document.createElement("li");
//   获取图片大小
  var size = file.size / 1024 > 1024 ? (~~(10 * file.size / 1024 / 1024)) / 10 + "MB" : ~~(file.size / 1024) + "KB";
  //图片预览
  li.innerHTML = '<div class="progress"><span></span></div><div class="size">' + size + '</div>';
  //追加图片预览代码；
  $(".img-list").append($(li));
  reader.onload = function() {
  var result = this.result;
  var img = new Image();
  img.src = result;
  //图片显示
  $(li).css("background-image", "url(" + result + ")");
  //如果图片大小小于100kb，则直接上传
  if (result.length <= maxsize) {
   img = null;
   upload(result, file.type, $(li));
   return;
  }
//  图片加载完毕之后进行压缩，然后上传
  if (img.complete) {
   callback();
  } else {
   img.onload = callback;
  }
  function callback() {
   var data = compress(img);
   upload(data, file.type, $(li));
   img = null;
  }
  };
  reader.readAsDataURL(file);
 });
 };
 //以下是图片压缩相关；
 //使用canvas对大图片进行压缩
 function compress(img) {
 var initSize = img.src.length;
 var width = img.width;
 var height = img.height;
 //如果图片大于四百万像素，计算压缩比并将大小压至400万以下
 var ratio;
 if ((ratio = width * height / 4000000) > 1) {
  ratio = Math.sqrt(ratio);
  width /= ratio;
  height /= ratio;
 } else {
  ratio = 1;
 }
 canvas.width = width;
 canvas.height = height;
 //铺底色
 ctx.fillStyle = "#fff";
 ctx.fillRect(0, 0, canvas.width, canvas.height);
 //如果图片像素大于100万则使用瓦片绘制
 var count;
 if ((count = width * height / 1000000) > 1) {
  count = ~~(Math.sqrt(count) + 1); //计算要分成多少块瓦片
 // 计算每块瓦片的宽和高
  var nw = ~~(width / count);
  var nh = ~~(height / count);
  tCanvas.width = nw;
  tCanvas.height = nh;
  for (var i = 0; i < count; i++) {
  for (var j = 0; j < count; j++) {
   tctx.drawImage(img, i * nw * ratio, j * nh * ratio, nw * ratio, nh * ratio, 0, 0, nw, nh);
   ctx.drawImage(tCanvas, i * nw, j * nh, nw, nh);
  }
  }
 } else {
  ctx.drawImage(img, 0, 0, width, height);
 }
 //进行最小压缩
 var ndata = canvas.toDataURL('image/jpeg', 0.1);
 console.log('压缩前：' + initSize);
 console.log('压缩后：' + ndata.length);
 console.log('压缩率：' + ~~(100 * (initSize - ndata.length) / initSize) + "%");
 tCanvas.width = tCanvas.height = canvas.width = canvas.height = 0;
 return ndata;
 }
 //图片上传，将base64的图片转成二进制对象，塞进formdata上传
 function upload(basestr, type, $li) {
 var text = window.atob(basestr.split(",")[1]);
 var buffer = new Uint8Array(text.length);
 var pecent = 0, loop = null;
 for (var i = 0; i < text.length; i++) {
  buffer[i] = text.charCodeAt(i);
 }
 var blob = getBlob([buffer], type);
 var xhr = new XMLHttpRequest();
 var formdata = getFormData();
 formdata.append('upload', blob);
 //异步请求kindeditor插件的上传图片jsp页面
 xhr.open('post', '<%=request.getContextPath()%>/kindeditor/jsp/upload_json.jsp');
 xhr.onreadystatechange = function() {
  if (xhr.readyState == 4 && xhr.status == 200) { 
  //返回服务器端的图片地址 
  var face_img=xhr.responseText;
  var id=$("#arId").text();
  //异步像数据库中添加图片
  $.ajax({
   type:"POST",
   //异步请求Struts的action类将图片地址插入数据库
   url:"add_article_faceurl.action",
   dataType:"json",
   data:"faceurl="+face_img+"&id="+id,
   async:true,
   success: function(msg){ 
   //取添加数据库中的图片相关的id值，存入页面隐藏区域
    $("#arId").text(msg);
   },
   error: function(a){}
  });   
  }
 };
 //模拟上传进度显示
 //数据发送进度，前50%展示该进度
 xhr.upload.addEventListener('progress', function(e) {
  if (loop) return;
  pecent = ~~(100 * e.loaded / e.total) / 2;
  $li.find(".progress span").css('width', pecent + "%");
  if (pecent == 50) {
  mockProgress();
  }
 }, false);
 //数据后50%用模拟进度
 function mockProgress() {
  if (loop) return;
  loop = setInterval(function() {
  pecent++;
  $li.find(".progress span").css('width', pecent + "%");
  if (pecent == 99) {
   clearInterval(loop);
  }
  }, 100);
 }
 xhr.send(formdata);
 }
 /**
 * 获取blob对象的兼容性写法
 * @param buffer
 * @param format
 * @returns {*}
 */
 function getBlob(buffer, format) {
 try {
  return new Blob(buffer, {type: format});
 } catch (e) {
  var bb = new (window.BlobBuilder || window.WebKitBlobBuilder || window.MSBlobBuilder);
  buffer.forEach(function(buf) {
  bb.append(buf);
  });
  return bb.getBlob(format);
 }
 }
 /**
 * 获取formdata
 */
 function getFormData() {
 var isNeedShim = ~navigator.userAgent.indexOf('Android')
  && ~navigator.vendor.indexOf('Google')
  && !~navigator.userAgent.indexOf('Chrome')
  && navigator.userAgent.match(/AppleWebKit\/(\d+)/).pop() <= 534;
 return isNeedShim ? new FormDataShim() : new FormData();
 }
 /**
 * formdata 补丁, 给不支持formdata上传blob的android机打补丁
 * @constructor
 */
 function FormDataShim() {
 console.warn('using formdata shim');
 var o = this,
  parts = [],
  boundary = Array(21).join('-') + (+new Date() * (1e16 * Math.random())).toString(36),
  oldSend = XMLHttpRequest.prototype.send;
 this.append = function(name, value, filename) {
  parts.push('--' + boundary + '\r\nContent-Disposition: form-data; name="' + name + '"');
  if (value instanceof Blob) {
  parts.push('; filename="' + (filename || 'blob') + '"\r\nContent-Type: ' + value.type + '\r\n\r\n');
  parts.push(value);
  }
  else {
  parts.push('\r\n\r\n' + value);
  }
  parts.push('\r\n');
 };
 // Override XHR send()
 XMLHttpRequest.prototype.send = function(val) {
  var fr,
   data,
   oXHR = this;
  if (val === o) {
  // Append the final boundary string
  parts.push('--' + boundary + '--\r\n');
  // Create the blob
  data = getBlob(parts);
  // Set up and read the blob into an array to be sent
  fr = new FileReader();
  fr.onload = function() {
   oldSend.call(oXHR, fr.result);
  };
  fr.onerror = function(err) {
   throw err;
  };
  fr.readAsArrayBuffer(data);
  // Set the multipart content type and boudary
  this.setRequestHeader('Content-Type', 'multipart/form-data; boundary=' + boundary);
  XMLHttpRequest.prototype.send = oldSend;
  }
  else {
  oldSend.call(this, val);
  }
 };
 }
</script>

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ page import="java.util.*,java.io.*" %>
<%@ page import="java.text.SimpleDateFormat" %>
<%@ page import="org.apache.commons.fileupload.*" %>
<%@ page import="org.apache.commons.fileupload.disk.*" %>
<%@ page import="org.apache.commons.fileupload.servlet.*" %>
<%@ page
 import="org.apache.struts2.dispatcher.multipart.MultiPartRequestWrapper"%>
<%@ page import="org.json.simple.*" %>
<%

/**
 * KindEditor JSP
 * 
 * 本JSP程序是演示程序，建议不要直接在实际项目中使用。
 * 如果您确定直接使用本程序，使用之前请仔细确认相关安全设置。
 * 
 */

//文件保存目录路径
String savePath = pageContext.getServletContext().getRealPath("/") + "attached/";
//String savePath = "http:\\\\192.168.1.226:8080\\qslnbase\\uploadFile/";
//String savePath = "D:/WWW/qslnADP/ADP/WebRoot/kindeditor/attached/";
//文件保存目录URL
String saveUrl = request.getContextPath() + "/attached/";
//定义允许上传的文件扩展名
HashMap<String, String> extMap = new HashMap<String, String>();
extMap.put("image", "gif,jpg,jpeg,png,bmp,blob");
extMap.put("flash", "swf,flv");
extMap.put("media", "swf,flv,mp3,wav,wma,wmv,mid,avi,mpg,asf,rm,rmvb");
extMap.put("file", "doc,docx,xls,xlsx,ppt,htm,html,txt,zip,rar,gz,bz2");

//最大文件大小
long maxSize = 1000000;

response.setContentType("text/html; charset=UTF-8");

if(!ServletFileUpload.isMultipartContent(request)){
 out.println(getError("请选择文件。"));
 return;
}
//检查目录
File uploadDir = new File(savePath);
if(!uploadDir.isDirectory()){
 out.println(getError("上传目录不存在。"));
 return;
}
//检查目录写权限
if(!uploadDir.canWrite()){
 out.println(getError("上传目录没有写权限。"));
 return;
}

String dirName = request.getParameter("dir");
if (dirName == null) {
 dirName = "image";
}
if(!extMap.containsKey(dirName)){
 out.println(getError("目录名不正确。"));
 return;
}
//创建文件夹
savePath += dirName + "/";
saveUrl += dirName + "/";
File saveDirFile = new File(savePath);
if (!saveDirFile.exists()) {
 saveDirFile.mkdirs();
}
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
String ymd = sdf.format(new Date());
savePath += ymd + "/";
saveUrl += ymd + "/";
File dirFile = new File(savePath);
if (!dirFile.exists()) {
 dirFile.mkdirs();
}
//Struts2 请求 包装过滤器
MultiPartRequestWrapper wrapper = (MultiPartRequestWrapper) request;

//获得上传 的文件名
String fileName1 = wrapper.getFileNames("upload")[0];

//获得文件过滤器
File file = wrapper.getFiles("upload")[0];

//检查文件大小
if(file.length() > maxSize){
 out.println(getError("上传文件大小超过限制。"));
 return;
}

//检查扩展名
String fileExt1 = fileName1.substring(fileName1.lastIndexOf(".") + 1).toLowerCase();
//重构上传文件名
SimpleDateFormat df1 = new SimpleDateFormat("yyyyMMddHHmmss");
String newFileName1 = df1.format(new Date()) + "_" + new Random().nextInt(1000) + "." + fileExt1;

byte[] buffer = new byte[1024];
//获取文件输出流
FileOutputStream fos = new FileOutputStream(savePath + newFileName1);
String url=savePath + newFileName1;
out.println(url);
//获取内存中当前文件输入流
InputStream in = new FileInputStream(file);

try {
 int num = 0;
 while ((num = in.read(buffer)) > 0) {
  fos.write(buffer, 0, num);
 }
} catch (Exception e) {
 e.printStackTrace(System.err);
} finally {
 in.close();
 fos.close();
}
%>
<%!
private String getError(String message) {
 JSONObject obj = new JSONObject();
 obj.put("error", 1);
 obj.put("message", message);
 return obj.toJSONString();
}
%>

<div id="div2">
 <ul class="img-list">
  <li id="wy">
   <img style="height:100%;width:100%;position:absolute;top:0px;" src="<%=request.getContextPath()%>/shequ/images/index.png;" >
  </li>
 </ul> 
</div>