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URLString 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>