Servlet 文件上傳
Servlet 可以與 HTML form 標籤一起使用，來允許用戶上傳文件到服務器。上傳的文件可以是文本文件或圖像文件或任何文檔。
1.工程配置
需要引入的 jar 文件：commons-fileupload-1.3.2、commons-io-2.5.jar
2.upload.jsp
<%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2020/6/21
Time: 17:52
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>文件上傳</title>
</head>
<body>
<h1>文件上傳實例</h1>
<form method="post" action="helloworld/uploadServlet" enctype="multipart/form-data">
選擇一個文件:<input type="file" name="uploadFile" />
<br/><br/><input type="submit" value="上傳" />
</form>
</body>
</html>
3.message.jsp
<%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2020/6/21
Time: 18:00
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>文件上傳結果</title>
</head>
<body>
<center>
<h2>${message}</h2>
</center>
</body>
</html>
4.uploadServlet
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
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 java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import static org.apache.commons.fileupload.servlet.ServletFileUpload.*;
@WebServlet(name = "uploadServlet")
public class uploadServlet extends HttpServlet {
// 上傳文件存儲目錄
private static final String UPLOAD_DIRECTORY = "upload";
// 上傳配置
private static final int MEMORY_THRESHOLD = 1024 * 1024 * 3; // 3MB
private static final int MAX_FILE_SIZE = 1024 * 1024 * 40; // 40MB
private static final int MAX_REQUEST_SIZE = 1024 * 1024 * 50; // 50MB
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 檢測是否爲多媒體上傳
if (!isMultipartContent(request)) {
// 如果不是則停止
PrintWriter writer = response.getWriter();
writer.println("Error: 表單必須包含 enctype=multipart/form-data");
writer.flush();
return;
}
// 配置上傳參數
DiskFileItemFactory factory = new DiskFileItemFactory();
// 設置內存臨界值 - 超過後將產生臨時文件並存儲於臨時目錄中
factory.setSizeThreshold(MEMORY_THRESHOLD);
// 設置臨時存儲目錄
factory.setRepository(new File(System.getProperty("java.io.tmpdir")));
ServletFileUpload upload = new ServletFileUpload(factory);
// 設置最大文件上傳值
upload.setFileSizeMax(MAX_FILE_SIZE);
// 設置最大請求值 (包含文件和表單數據)
upload.setSizeMax(MAX_REQUEST_SIZE);
// 中文處理
upload.setHeaderEncoding("UTF-8");
// 構造臨時路徑來存儲上傳的文件
// 這個路徑相對當前應用的目錄
String uploadPath = request.getServletContext().getRealPath("./") + File.separator + UPLOAD_DIRECTORY;
// 如果目錄不存在則創建
File uploadDir = new File(uploadPath);
if (!uploadDir.exists()) {
uploadDir.mkdir();
}
try {
// 解析請求的內容提取文件數據
@SuppressWarnings("unchecked")
List<FileItem> formItems = upload.parseRequest(request);
if (formItems != null && formItems.size() > 0) {
// 迭代表單數據
for (FileItem item : formItems) {
// 處理不在表單中的字段
if (!item.isFormField()) {
String fileName = new File(item.getName()).getName();
String filePath = uploadPath + File.separator + fileName;
File storeFile = new File(filePath);
// 在控制檯輸出文件的上傳路徑
System.out.println(filePath);
// 保存文件到硬盤
item.write(storeFile);
request.setAttribute("message","文件上傳成功!");
}
}
}
} catch (Exception ex) {
request.setAttribute("message","錯誤信息: " + ex.getMessage());
}
// 跳轉到 message.jsp
request.getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
5.效果圖
