jsp中点击图片弹出文件上传界面及实现预览实例详解

!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 
html> 
head> 
meta http-equiv="Content-Type" content="text/html; charset=utf-8"> 
title>Insert title here/title> 
script type="text/javascript"> 
function tempClick(){ 
  
 /** 
  * 火狐浏览器实现点击图片出现文件上传界面 
  * var a=document.createEvent("MouseEvents"); 
  * a.initEvent("click", true, true); 
  * document.getElementById("upload_main_img").dispatchEvent(a); 
  */ 
  
 //IE浏览器实现点击图片出现文件上传界面 
 document.getElementById('main_img').click();   //调用main_img的onclick事件 
} 
 
/** 
 * 预览图片 
 * @param obj 
 * @returns {Boolean} 
 */ 
function PreviewImg(obj) { 
 
 var newPreview = document.getElementById("img_2"); 
 var imgPath = getPath(obj); 
 alert(imgPath); 
 if( !obj.value.match( /.jpg|.gif|.png|.bmp/i ) ){ 
  alert("图片格式错误！"); 
  return false; 
 } 
  
 newPreview.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";  
 newPreview.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgPath; 
} 
 
/** 
 * 得到图片绝对路径 
 * @param obj 
 * @returns 
 */ 
function getPath(obj){ 
 if(obj) {  
  if(navigator.userAgent.indexOf("MSIE")>0) { 
   obj.select();  
   //IE下取得图片的本地路径  
   return document.selection.createRange().text; 
  } else if(isFirefox=navigator.userAgent.indexOf("Firefox")>0) { 
    if (obj.files) { // Firefox下取得的是图片的数据  
    return files.item(0).getAsDataURL();  
    }  
    return obj.value;  
   } 
   return obj.value;  
 }  
}  
/script> 
/head> 
body> 
form> 
div>input type="file" style="position: absolute; filter: alpha(opacity = 0); opacity: 0; width: 30px;" size="1" id="main_img" name="main_img" onchange="PreviewImg(this)">/div> 
div id="img_2" style="width:133px;height:95px; cursor:pointer; background-image: url('Chrysanthemum.jpg');" onclick="tempClick()">/div> 
/form> 
/body> 
/html>