The Commons FileUpload package makes it easy to add robust, high-performance, file upload capability to your servlets and web applications.
要想利用Commons FileUpload實現文件上傳功能，可以參考官網的“User guide”。簡而言之，需要一個Form表單提交文件上傳請求，然後在後臺通過servlet等技術使用Commons FileUpload來實現文件上傳功能。如果需要實現上傳進度條功能，則還需要實現ProgerssListener。
示例如下：
FileUploadForm.jsp 利用Form表單提交一個上傳文件的請求
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>文件上傳</title>
</head>
<body>
<form action="../FileUpload" method="post" enctype="multipart/form-data" name="book">
<table>
<tr>
<th colspan="2" align="center">錄入書籍信息</th>
</tr>
<tr>
<td>書名：</td>
<td><input type="text" name="bookname" /></td>
</tr>
<tr>
<td>封面：</td>
<td><input type="file" name="cover" /></td>
</tr>
<tr>
<td>作者：</td>
<td><input type="text" name="author" /></td>
</tr>
<tr>
<td colspan="2"><input type="submit" value="提交" /></td>
</tr>
</table>
</form>
</body>
</html>FileUpload.java 通過servlet使用Commons FileUpload實現文件上傳功能
package fileupload;
import java.io.File;
import java.io.IOException;
import java.util.Iterator;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
/**
* Servlet implementation class FileUpload
*/
@WebServlet("/FileUpload")
public class FileUpload extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public FileUpload() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
// Check that we have a file upload requestss
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
if (!isMultipart) {
return;
}
// Create a factory for disk-based file items
DiskFileItemFactory factory = new DiskFileItemFactory();
// Set factory constraintsx
factory.setSizeThreshold(1024); //yourMaxMemorySize
factory.setRepository(new File("E:/Downloads/tmp")); //yourTempDirectory
// Create a new file upload handler
ServletFileUpload upload = new ServletFileUpload(factory);
//setProgressListener
upload.setProgressListener(new FileUploadProgressListener());
// Parse the request
List items = null;
try {
items = upload.parseRequest(request);
} catch (FileUploadException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
// Process the uploaded items
Iterator iter = items.iterator();
while (iter.hasNext()) {
FileItem item = (FileItem)iter.next();
//整個表單的所有域都會被解析，要先判斷一下是普通表單域還是文件上傳域
if (item.isFormField()) {
String name = item.getFieldName();
String value = item.getString();
System.out.println(name + ":" + value);
} else {
String fieldName = item.getFieldName();
String fileName = item.getName();
String contentType = item.getContentType();
boolean isInMem = item.isInMemory();
long sizeInBytes = item.getSize();
System.out.println(fieldName + ":" + fileName);
System.out.println("類型：" + contentType);
System.out.println("是否在內在：" + isInMem);
System.out.println("文件大小" + sizeInBytes);
File uploadedFile = new File("E:/Downloads/upload/" + fileName);
try {
item.write(uploadedFile);
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
this.doGet(request, response);
}
}
FileUploadProgressListener.java 實現進度條監聽器
package fileupload;
import org.apache.commons.fileupload.ProgressListener;
public class FileUploadProgressListener implements ProgressListener {
public FileUploadProgressListener() {
super();
// TODO Auto-generated constructor stub
System.out.println("Progress Listened!");
}
@Override
public void update(long pBytesRead, long pContentLength, int pItems) {
// TODO Auto-generated method stub
System.out.println("現在已經處理了" + pBytesRead
+ "數據，總數據量" + pContentLength
+ "正在處理" + pItems);
}
}