Uploading File to server using Servlet and JSP is a common task in Java
web application. Before coding your Servlet or JSP to handle file upload request,
you need to know little bit about File upload support in HTML and HTTP protocol.
If you want your user to choose files from file system and upload to server
than you need to use . This will
enable to choose any file form file system and upload to server. Next thing is
that form method should be HTTP
POST with enctype as multipart/form-data,
which makes file data available in parts inside request body. Now in order to
read those file parts and create a File inside Servlet can be done by using ServletOutputStream. It's
better to use Apache commons FileUpload, an open source library. Apache
FileUpload handles all low details of parsing HTTP request which confirm to RFC
1867 or "Form based File upload in
HTML”, when you set form method post and content type as "multipart/form-data".
Apace Commons FileUpload - Important points:
1) DiskFileItemFactory is default Factory
class for FileItem. When Apache commons read
multipart content and generates FileItem, this implementation keep
file content either in memory or in disk as temporary file, depending upon threshold size. By default DiskFileItemFactory has threshold size of 10KB and generates temporary files in temp directory,
returned by System.getProperty("java.io.tmpdir"). Both of
these values are configurable and it's best to configure these for production
usage. You may get permission issues if user account used for running Server
doesn't have sufficient permission to write files into temp directory.
2) Choose threshold size carefully based upon memory usage, keeping large
content in memory may result in java.lang.OutOfMemory, while
having too small values may result in lot's of temporary files.
3) Apache commons file upload also provides FileCleaningTracker to delete
temporary files created by DiskFileItemFactory. FileCleaningTracker deletes
temporary files as soon as corresponding File
instance is garbage collected. It accomplish this by a cleaner thread which
is created when FileCleaner is loaded. If you use this
feature, than remember to terminate this Thread when your web application ends.
4) Keep configurable details e.g. upload directory, maximum file size, threshold size etc in config files and use reasonable default values in case
they are not configured.
5) It's good to validate size, type and other details of Files based upon
your project requirement e.g. you may wants to allow upload only images of certain size and certain
types e.g. JPEG, PNG etc.
File Upload Example in Java Servlet and JSP
Here is the complete code for uploading files in Java web application
using Servlet and JSP. This File Upload Example needs four files :
1. index.jsp which contains HTML content to
setup a form, which allows user to select and upload file to server.
2. FileUploader Servlet which handles file upload
request and uses Apache FileUpload library to parse multipart form
data
3. web.xml to configure servlet and JSP in
Java web application.
4. result.jsp for showing result of file upload
operation.
FileUploadHandler.java
import java.io.File;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
/**
* Servlet to handle File upload request from
Client
* @author Javin Paul
*/
public class FileUploadHandler
extends HttpServlet {
private
final String UPLOAD_DIRECTORY = "C:/uploads";
@Override
protected
void doPost(HttpServletRequest request, HttpServletResponse response)
throws
ServletException, IOException {
//process
only if its multipart content
if(ServletFileUpload.isMultipartContent(request)){
try
{
List<FileItem> multiparts =
new ServletFileUpload(
new
DiskFileItemFactory()).parseRequest(request);
for(FileItem item :
multiparts){
if(!item.isFormField()){
String name = new
File(item.getName()).getName();
item.write( new
File(UPLOAD_DIRECTORY + File.separator +
name));
}
}
//File
uploaded successfully
request.setAttribute("message",
"File Uploaded Successfully");
}
catch (Exception
ex) {
request.setAttribute("message",
"File Upload Failed due to " + ex);
}
}else{
request.setAttribute("message",
"Sorry this Servlet only handles file upload
request");
}
request.getRequestDispatcher("/result.jsp").forward(request, response);
}
}
index.jsp
<%@page
contentType="text/html" pageEncoding="UTF-8"%>
HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
http-equiv="Content-Type"
content="text/html;
charset=UTF-8">
Choose File to Upload in Server
action="upload"
method="post"
enctype="multipart/form-data">
type="file"
name="file"
/>
type="submit"
value="upload"
/>
result.jsp
<%@page
contentType="text/html" pageEncoding="UTF-8"%>
HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
http-equiv="Content-Type"
content="text/html;
charset=UTF-8">
id="result">
${requestScope["message"]}
web.xml
version="1.0" encoding="UTF-8"?>
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
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In summary just keep three things in mind while uploading files using
Java web application
1) Use HTML form input type as File to browse files to upload
2) Use form method as post and enctype as multipart/form-data
Dependency
In order to compile and run this Java web application in any web server
e.g. Tomcat,
you need to include following dependency JAR in WEB-INF lib folder.
commons-fileupload-1.2.2.jar
commons-io-2.4.jar
If you are using Maven than you can also use following dependencies :
That's all on How to upload Files using Servlet and JSP in Java web
application. This File Upload example can be written using JSP, Filter or Servlet because
all three are request’s entry point in Java web application. I have used
Servlet for handling File upload request for simplicity. By the way from
Servlet 3.0 API, Servlet is supporting multipart form data and you can use getPart() method of HttpServletRequest to handle
file upload.
Thanks, this is generally helpful.
BalasHapusStill, I followed step-by-step your method in this Java online training
Java course