因爲業務的需求,需要實現一個通過瀏覽器把本地文件上傳到服務器的功能,因爲之前沒有做過,所以也是經過了一番探索才實現了這個功能,這裏只介紹前端的實現,後臺的接收、驗證和保存就不介紹了。
這個流程如下:
1、讀取本地文件
2、建立和服務器的連接(使用AJAX)
3、上傳一些頭信息和文件流
4、等待服務器響應後,顯示結果
讀取本地文件,在頁面中點擊 "瀏覽" 後,彈出文件選擇對話框,使用 <input type="file"/>標籤即可,如果要過濾指定後綴的文件,添加accept屬性,如只能選擇rar文件
<input class="style_file_content" accept=".rar" type="file" id="upload_file_id"/>
要通過js將文件讀取出來,需要用到 FileReader
var fReader = new FileReader();
fReader.onload=function(e){
//讀取完成
xhreq.send(fReader.result);
}
fReader.readAsArrayBuffer(uploadFile.files[0]);
讀取文件完成後,會回調onload 函數,文件內容保存在fReader.result,所以在onload 裏面把數據發生到服務器即可
和服務器建立連接,js代碼如下
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("您的瀏覽器不支持AJAX!");
}
}
}
return xmlHttp;
}
調用open 後纔會真正建立和服務器的連接,第一個參數是請求的方式,第二個參數是對應的URL
xhreq.open("POST","/upload/file",true);
xhreq.setRequestHeader("Content-type", "application/octet-stream"); //流類型
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);
因爲調用send()調用一次之後,就會把數據發送出去,比較難在內容裏面添加一些參數,比如文件名等信息,所以這裏鍵文件名放在header裏面,如 xhreq.setRequestHeader("uploadfile_name", encodeURI(fwFile.files[0].name)); //兼容中文。因爲如果header裏面的參數是中文的時候,後臺讀出來時會出現亂碼,所以需要encodeURI() 做一次編碼,後臺讀取後再做一次轉碼。
var xhreq=createHttpRequest();
xhreq.onreadystatechange=function(){
if(xhreq.readyState==4){
if(xhreq.status==200){
uploadTip.innerText=xhreq.responseText;
setTimeout(function(){
hideUploadDialog()
},2000); //2秒後隱藏
}else{
uploadTip.innerText="文件上傳失敗了";
}
}
}
在 請求發送給後臺的過程中,可以通過 onreadystatechange 這個會調函數知道當前的狀態,當 readyState 等於 4 且狀態爲 200 時,表示響應已就緒,響應的結果在xhreq.responseText。
完整的demo如下:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>文件上傳測試</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("您的瀏覽器不支持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="請選擇一個文件";
}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="文件上傳成功";
setTimeout(function(){
hideUploadDialog()
},2000); //2秒後隱藏
}else{
uploadTip.innerText="文件上傳失敗了";
}
}
}
fReader.onload=function(e){
xhreq.open("POST","/upload/file",true);
xhreq.setRequestHeader("Content-type", "application/octet-stream"); //流類型
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="瀏覽器不支持上傳文件";
}
}catch(e){
uploadTip.innerText="文件上傳失敗";
}
}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="請選擇要上傳的文件";
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()">上傳新文件</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"> 文件路徑:</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"> 請選擇要上傳的文件 </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()">確定</span>
</div>
</div>
</div>
</body>
</html>