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";

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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 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>