html页面实现文件上传

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因为业务的需求,需要实现一个通过浏览器把本地文件上传到服务器的功能,因为之前没有做过,所以也是经过了一番探索才实现了这个功能,这里只介绍前端的实现,后台的接收、验证和保存就不介绍了。

这个流程如下:

1、读取本地文件

2、建立和服务器的连接(使用AJAX)

3、上传一些头信息和文件流

4、等待服务器响应后,显示结果

 

读取本地文件,在页面中点击 "浏览" 后,弹出文件选择对话框,使用 标签即可,如果要过滤指定后缀的文件,添加accept属性,如只能选择rar文件

<input class="style_file_content" accept=".rar" type="file" id="upload_file_id"/>
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要通过js将文件读取出来,需要用到 FileReader

var fReader = new FileReader();
fReader.onload=function(e){
   //读取完成
   xhreq.send(fReader.result);
}
fReader.readAsArrayBuffer(uploadFile.files[0]);
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读取文件完成后,会回调onload 函数,文件内容保存在fReader.result,所以在onload 里面把数据发生到服务器即可

和服务器建立连接,js代码如下

function createHttpRequest()
 {
	 var xmlHttp=null;
     try{
 	    // Firefox, Opera 8.0+, Safari
 	    xmlHttp=new XMLHttpRequest();
 	 }catch (e){
 	    // Internet Explorer
 		try{
 	        xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
 	    }catch (e){
 		try{
 		    xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
 	        }catch (e){
 	            alert("您的浏览器不支持AJAX!");
 	        }
 	    }
 	}
    return xmlHttp;
 }
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调用open 后才会真正建立和服务器的连接,第一个参数是请求的方式,第二个参数是对应的URL

xhreq.open("POST","/upload/file",true);
xhreq.setRequestHeader("Content-type", "application/octet-stream"); //流类型
xhreq.setRequestHeader("Content-length", fwFile.files[0].size);     //文件大小
xhreq.setRequestHeader("uploadfile_name", encodeURI(fwFile.files[0].name)); //兼容中文
xhreq.send(fReader.result);
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因为调用send()调用一次之后,就会把数据发送出去,比较难在内容里面添加一些参数,比如文件名等信息,所以这里键文件名放在header里面,如 xhreq.setRequestHeader("uploadfile_name", encodeURI(fwFile.files[0].name)); //兼容中文。因为如果header里面的参数是中文的时候,后台读出来时会出现乱码,所以需要encodeURI() 做一次编码,后台读取后再做一次转码。

var xhreq=createHttpRequest();
xhreq.onreadystatechange=function(){
	if(xhreq.readyState==4){
		if(xhreq.status==200){
			uploadTip.innerText=xhreq.responseText;
			setTimeout(function(){
			hideUploadDialog()
			},2000);	//2秒后隐藏
		}else{
			uploadTip.innerText="文件上传失败了";
		}	
	 }
}
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在 请求发送给后台的过程中,可以通过 onreadystatechange 这个会调函数知道当前的状态,当 readyState 等于 4 且状态为 200 时,表示响应已就绪,响应的结果在xhreq.responseText。

完整的demo如下:

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>文件上传测试</title>
</head>
 
<style type="text/css">
	#content_div{
   	position:absolute;
		left:0px;
		top:0px;
		right:0px;
		bottom:0px;
		text-align:center
  }
  
  .upload_dialog_div{
  position:fixed;
	left:0px;
	right:0px;
	top:0px;
	bottom:0px;
	overflow:auto; 
	visibility:hidden;
	background-color: rgba(60,60,60,0.5);
	z-index:99;
  }
  .style_content_div{
  position:relative;
  margin:auto;
  margin-top:160px;
	width:400px;
	height:160px;
	background:#F5F5DC;
  }
  .style_content_upper_div{
  position:absolute;
  left:0px;
  top:0px;
	width:400px;
	height:100px;
	background:#F5F5DC;
  }
  .style_content_lower_div{
  position:absolute;
  left:0px;
  top:100px;
	width:400px;
	height:60px;
	background:#F5FFDC;
  }
  
  .style_content_file_div{
  position:absolute;
  left:15px;
  top:20px;
	width:380px;
	height:60px;
  }
  .style_file_span{
	  float:left;
	  width:120px;
	  height:36px;
	  font-size:24px;
	  text-align:right;
  }
  .style_file_content{
	  margin-top:5px;
  }
  .style_content_prog_div{
  position:absolute;
  left:18px;
  top:57px;
	width:360px;
	height:40px;
  }
  .style_prog_span_hit{
	  color:#ff0000;
  }
  .style_prog_content{
	  width:360px;
	  visibility:hidden;
  }
  .style_content_span{
  width:200px;
	height:60px;
	line-height:60px;
	display:inline-block;
	float:left;
	font-size:32px;
	text-align:center;
	cursor: pointer;
  }
 
  .style_copyright_a{
	text-decoration:none;
	color:#cc00cc;
  }
</style>
<script>
function createHttpRequest()
 {
	 var xmlHttp=null;
     try{
 	    // Firefox, Opera 8.0+, Safari
 	    xmlHttp=new XMLHttpRequest();
 	 }catch (e){
 	    // Internet Explorer
 		try{
 	        xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
 	    }catch (e){
 		try{
 		    xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
 	        }catch (e){
 	            alert("您的浏览器不支持AJAX!");
 	        }
 	    }
 	}
    return xmlHttp;
 }
 
 function uploadFileToServer(){
	var uploadFile = document.getElementById("upload_file_id");
	var uploadTip = document.getElementById("upload_tip_id");
	var uploadProgress = document.getElementById("upload_progress_id");
	
	if(uploadFile.value==""){
		 uploadTip.innerText="请选择一个文件";
	}else if(uploadFile.files[0].size>1024 &&uploadFile.files[0].size<(40*1024*1024)){ 
		try{
			if(window.FileReader){
				var fReader = new FileReader();
				var xhreq=createHttpRequest();
				 xhreq.onreadystatechange=function(){
					 if(xhreq.readyState==4){
						if(xhreq.status==200){
							 uploadTip.innerText="文件上传成功";
							 setTimeout(function(){
								hideUploadDialog()
							},2000);	//2秒后隐藏
						}else{
							uploadTip.innerText="文件上传失败了";
						}	
					 }
				 }
				fReader.onload=function(e){
					 xhreq.open("POST","/upload/file",true);
					 xhreq.setRequestHeader("Content-type", "application/octet-stream"); //流类型
					 xhreq.setRequestHeader("Content-length", fwFile.files[0].size);     //文件大小
					 xhreq.setRequestHeader("uploadfile_name", encodeURI(fwFile.files[0].name)); //兼容中文
					 xhreq.send(fReader.result);
				}
				fReader.onprogress = function(e){
					 uploadProgress.value = e.loaded*100/e.total;
				}
				fReader.readAsArrayBuffer(uploadFile.files[0]);
				uploadProgress.style.visibility="visible";
				uploadProgress.value = 0;
			}else{
				uploadTip.innerText="浏览器不支持上传文件";
			}			
		}catch(e){
			 uploadTip.innerText="文件上传失败";
		}
	}else{
		  uploadTip.innerText="文件不符合要求";
	}
}
 function showUploadDialog(){
	var up_dialog=document.getElementById("upload_dialog");
  document.getElementById("upload_tip_id").innerText="请选择要上传的文件";
  document.getElementById("upload_progress_id").style.visibility="hidden";
	up_dialog.style.visibility="visible";
	
 }
 function hideUploadDialog(){
	var up_dialog=document.getElementById("upload_dialog");
	document.getElementById("upload_progress_id").style.visibility="hidden";
	up_dialog.style.visibility="hidden";
 }
</script>
<body>
   <div id="content_div">
   	  <br>
   	  <br>
   	  <br>
   	  <br>
   	  <br>
   	  <a class="style_copyright_a" href="javascript:void(0);" onclick="showUploadDialog()">上传新文件</a>
   </div>
   
   <div id="upload_dialog" class="upload_dialog_div"> 
   	    <div class="style_content_div">
  	  	  <div class="style_content_upper_div">
  	  	  	  <div class="style_content_file_div">
  	  	  	  	 <span class="style_file_span"> 文件路径:</span>
  	  	  	  	 <input class="style_file_content" type="file" id="upload_file_id"/>
  	  	  	  </div>
  	  	  	  <div class="style_content_prog_div">
  	  	  	  	 <span class="style_prog_span_hit" id="upload_tip_id"> 请选择要上传的文件 </span>
  	  	  	     <progress class="style_prog_content" id="upload_progress_id" value="0" max="100"></progress> 
  	  	  	  </div>
  	  	  </div>
  	  	  <div class="style_content_lower_div">
  	  	  	   <span class="style_content_span" onmouseover="this.style.background='#cccccc'" onmouseout="this.style.background=''" onclick="hideUploadDialog()">取消</span>
  	  	  	   <span class="style_content_span" onmouseover="this.style.background='#F5CCDC'" onmouseout="this.style.background=''" onclick="uploadFileToServer()">确定</span>
  	  	  </div>
  	  </div>
   </div>
</body>
</html>
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