如何在Java服务器端使用Ajax检索上传的文件? [英] How to retrieve uploaded file using ajax on java server side?

问题描述

我正在服务器端使用struts2框架.我正在使用

I am using struts2 framework on server side. I am uploading a file using

服务器端:

<s:file name="fTU" id="fTU"/>

<input type="submit" value ="ok" onclick="upload()">

客户端:

function upload(){

var file = document.getElementById("fTU");

try {
    this.xml = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
    try {
        this.xml = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (err) {
        this.xml = null;
    }
}
if(!this.xml && typeof XMLHttpRequest != "undefined")
    this.xml = new XMLHttpRequest();
if (!this.xml){
    this.failed = true; 
}

var formData = new FormData();
/* Add the file */ 
formData.append("upload", file.files[0]);

xml.open("POST"，"，true); xml.setRequestHeader("Content-Type"，"false");

xml.open("POST", "", true); xml.setRequestHeader("Content-Type", "false");

xml.send(formData);  /* Send to server */

xml.onreadystatechange = function () {
    if (xml.readyState == 4 && xml.status == 200) {
        alert(xml.statusText);
    }
}

}

如何在struts2服务器端获取上载的文件对象?

How to fetch the uploaded file object on struts2 server side?

它正在服务器端类中，我正在尝试使用request.getParameter(upload)来检索文件，但它给出的是空值.

It is going in server side class and I am trying to retrieve file by using request.getParameter(upload) but it is giving null.

推荐答案

我认为您错过了在xml.open()方法中添加操作链接的过程.看看 MDN 可以看到一些示例.

I think you missed to add the Action Link in the xml.open() method. Take a look at the MDN to see some examples.

您的Action类的外观如何?您是否已使用getter/setter定义了一个名为 upload 的File字段?

How does your Action-class look like? Have you defined a File field named upload with getter/setters?

还请检查您的浏览器是否支持FormData元素，请参见问题.

Please also check, that your browser supports the FormData element, see question.

我还建议您使用jQuery之类的库来简化Javascript代码.

I also would suggest you to use a library like jQuery to simplify the Javascript code.

操作

public class FileUpload extends ActionSupport {
   File myFile;

   public String execute() {
       //do some preparations for the upload
       return SUCCESS;
   }

   public String upload() {
       //only here the myFile is filled with data
       return SUCCESS;
   }

   public void setMyFile(File myFile) {
       this.myFile = myFile;
   }

   public File getMyFile() {
       return myFile;
   }
}

struts.xml

<!-- init method to show the form -->
<action name="fileForm" class="...FileUpload">
    <result name="success">fileupload.jsp</result>
</action>

<!-- upload method to upload the file -->
<action name="fileUpload" class="...FileUpload" method="upload">
    <result name="success">fileupload.jsp</result>
</action>

JSP

<s:form enctype="multipart/form-data" method="post" name="fileinfo" action="fileUpload">
    <s:file name="myFile"/>
</s:form>

<input type="submit" onClick="upload()" value="OK"> 

JavaScript(摘自上面的MDN示例)

function upload() {
   var fd = new FormData(document.querySelector("form"));
   $.ajax({
       url : "fileUpload", //this is the actionName
       type: "POST",
       data: fd,
       processData: false,
       contentType: false
   });

   return false; //to stop submitting the form
}

我尚未测试此代码，因此请对其进行更改或在某些操作无效的情况下添加注释.

I have not tested this code, so please change it or add comments if something doesn't work.

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