Struts 2 File Upload
In this section you will learn how to write program in
Struts 2 to upload the file on the server. In this example we are also providing
the code to save the uploaded file in any directory on the server machine.
The Struts 2 FileUpload component can be used to upload
the multipart file in your Struts 2 application. In this section you will learn
about the code to upload file on the server.
How File Upload Works in Struts 2?
Struts 2 utilizes the service of File Upload
Interceptor to add the support for uploading files in the Struts
applications. The Struts 2 File Upload Interceptor is based on
MultiPartRequestWrapper, which is automatically applied to the request if it
contains the file element. Then it adds the following parameters to the request
(assuming the uploaded file name is MyFile).
- [MyFile] : File - the actual File
- [MyFile]ContentType : String - the content type of the file
- [File Name]FileName : String - the actual name of the file uploaded (not the HTML name)
In the action class you can get the file, the uploaded
file name and content type by just creating getter and setters. For example,
setMyfile(File file), setMyFileContentType(String contentType), getMyFile(),
etc..
The file upload interceptor also does the validation
and adds errors, these error messages are stored in the struts-messsages.properties
file. The values of the messages can be overridden by providing the text for the
following keys:
- struts.messages.error.uploading - error when uploading
of file fails
- struts.messages.error.file.too.large - error
occurs when file size is large
- struts.messages.error.content.type.not.allowed -
when the content type is not allowed
Parameters
You can use the following parameters to control the file upload functionality.
- maximumSize This parameter is optional. The
default value of this is 2MB.
- allowedTypes This parameter is also optional.
It allows you to specify the allowed content type.
Writing Example code to upload file
Now we will write the code to upload the file on
server.
Action Class
In the action class we will define four properties to
facilitate the file upload.
private
File upload; // The
actual file
private
String uploadContentType;//
The content type of the file
private
String uploadFileName;//
The uploaded file name and path
private
String fileCaption;//
The caption of the file entered by user.
Here is the full code of action class StrutsFileUpload.java
package net.roseindia;
import java.util.Date;
import java.io.File;
import com.opensymphony.xwork2.ActionSupport;
public class StrutsFileUpload extends ActionSupport {
private File upload;//The actual file
private String uploadContentType; //The content type of the file
private String uploadFileName; //The uploaded file name
private String fileCaption;//The caption of the file entered by user
public String execute() throws Exception {
return SUCCESS;
}
public String getFileCaption() {
return fileCaption;
}
public void setFileCaption(String fileCaption) {
this.fileCaption = fileCaption;
}
public File getUpload() {
return upload;
}
public void setUpload(File upload) {
this.upload = upload;
}
public String getUploadContentType() {
return uploadContentType;
}
public void setUploadContentType(String uploadContentType) {
this.uploadContentType = uploadContentType;
}
public String getUploadFileName() {
return uploadFileName;
}
public void setUploadFileName(String uploadFileName) {
this.uploadFileName = uploadFileName;
}
}
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Here we have not shown the code to save the uploaded file. But it can be done easily
using the following code in execute(..) method of action class. Here is code
snippet.
//Following code can be
used to save the uploaded file
try
{
String fullFileName = "c:/upload/myfile.txt";
File theFile = new
File(fullFileName);
FileUtils.copyFile( upload,
theFile);
} catch
(Exception e) {
addActionError(e.getMessage());
return
INPUT;
}
Writing JSP page
Here is the code of jsp file (upload.jsp) that
displays the file upload form to the user.
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>File Upload Example</title>
<link href="<s:url value="/css/main.css"/>" rel="stylesheet" type="text/css"/>
</head>
<body>
<s:actionerror />
<s:fielderror />
<s:form action="doUpload" method="POST" enctype="multipart/form-data">
<tr>
<td colspan="2"><h1>File Upload Example</h1></td>
</tr>
<s:file name="upload" label="File"/>
<s:textfield name="caption" label="Caption"/>
<s:submit />
</s:form>
</body>
</html>
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In the above code the form encrypt type is "multipart/form-data"
and <s:file ../> tag renders the html file tag.
File upload success page
Here is the code of file upload(upload-success.jsp)
success page.
<%@ page
language="java"
contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<html>
<head>
<title>Showcase</title>
<link href="<s:url value="/css/main.css"/>" rel="stylesheet" type="text/css"/>
</head>
<body>
<table class="wwFormTable">
<tr>
<td colspan="2"><h1>File Upload Example</h1></td>
</tr>
<tr>
<td class="tdLabel"><label for="doUpload_upload" class="label">Content Type:</label></td>
<td><s:property value="uploadContentType" /></td>
</tr>
<tr>
<td class="tdLabel"><label for="doUpload_upload" class="label">File Name:</label></td>
<td ><s:property value="uploadFileName" /></td>
</tr>
<tr>
<td class="tdLabel"><label for="doUpload_upload" class="label">File:</label></td>
<td><s:property value="upload" /></td>
</tr>
<tr>
<td class="tdLabel"><label for="doUpload_upload" class="label">File Caption:</label></td>
<td><s:property value="caption" /></td>
</tr>
</table>
</body>
</html>
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Adding mapping in struts.xml file
Add the following mapping in the struts.xml file.
<!-- File Upload -->
<action name="showUpload">
<result>/pages/upload.jsp</result>
</action>
<action name="doUpload" class="net.roseindia.StrutsFileUpload">
<result name="input">/pages/upload.jsp</result>
<result>/pages/upload-success.jsp</result>
</action>
<!-- End File Upload -->
The "showUpload" action displays the upload
form and "doUpload" action actually uploads the file.
Running the example
To test the application compile code and then run the
tomcat. Type http://localhost:8080/struts2tutorial/roseindia/showUpload.action
in your browser. You browser should show the following form:
Now browse the file, enter caption and then click on
the "Submit" button. Application will upload your file and then
following success screen will be displayed.
There is one important point to be noted about File
Upload Interceptor. The File Upload Interceptor actually deletes the the upload,
once the action is executed. Here is the screen shot of tomcat that shows the
file delete message:
INFO: Removing file upload C:\apache-tomcat-6.0.10Struts2\apache-tomcat-6.0.10\work\Catalina\
localhost\struts2tutorial\upload__13f532f7_1132e1d4754__8000_00000000.tmp
In this section you learnt the concept of file upload
in struts 2.
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