java webApp异步上传图片

本文包含以下几个问题：

1.图片上传；
2.图片上传预览；
3.上传图片更改地址异步添加到数据库；
主要内容
本示例主要采用纯HTML前端和JavaScript代码作工具，查询有关demo其实现图片上传的代码范例如下：
（1）点击上传图片的div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>

(2)javaScript代码

<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>

（3）kindeditor插件的上传图片jsp页面相关代码.

<%@ 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();}%>

（3）有关kindeditor上传图片的jar包有如下所示
A.commons-fileupload-1.2.1.jar
B.commons-io-1.4.jar
C.json_simple-1.1.jar
这里没有用到有关于kindeditor的js代码

（4）有关kindeditor上传图片预览的div如下

<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>