2.8

今天探索了Java Web开发中的文件上传功能。在Web应用中，经常需要允许用户上传文件，如头像上传等。
使用Apache Commons FileUpload库可以方便地实现文件上传功能。首先需要在项目中引入该库的依赖。
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;
import javax.servlet.ServletException;
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.util.List;

public class FileUploadServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
if (ServletFileUpload.isMultipartContent(request)) {
DiskFileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
try {
List items = upload.parseRequest(request);
for (FileItem item : items) {
if (!item.isFormField()) {
String fileName = item.getName();
File uploadedFile = new File("uploads/" + fileName);
item.write(uploadedFile);
}
}
} catch (FileUploadException | java.io.IOException e) {
e.printStackTrace();
}
}
}
}
这里将上传的文件保存到名为uploads的目录下，当然在实际应用中需要更多的错误处理和安全检查。