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;
|
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> |
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. 0
| <%@ 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> |
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 -->
1
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: 2
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.
3
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. 4