JSP和Servlet实现文件上传_上传文件的jsp与servlet核心代码-优快云博客

本文详细介绍了如何使用Servlet实现文件上传，并通过Java代码解释了文件上传的基本流程及关键步骤，包括配置解析类、设置最大文件大小、解析请求、处理上传文件并记录到数据库。

servlet代码：

package test.servlet;

import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletContext;
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;

public class UpLoad extends HttpServlet {
@SuppressWarnings("unchecked")
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
resp.setContentType("text/html;charset=utf-8");
// 为解析类提供配置信息
DiskFileItemFactory factory = new DiskFileItemFactory();
// 创建解析类的实例
ServletFileUpload sfu = new ServletFileUpload(factory);
// 开始解析
sfu.setFileSizeMax(1024 * 400);
// 每个表单域中数据会封装到一个对应的FileItem对象上
try {
List<FileItem> items = sfu.parseRequest(req);
// 区分表单域
for (int i = 0; i < items.size(); i++) {
FileItem item = items.get(i);
// isFormField为true，表示这不是文件上传表单域
if (!item.isFormField()) {
ServletContext sctx = getServletContext();
// 获得存放文件的物理路径
// upload下的某个文件夹得到当前在线的用户找到对应的文件夹

String path = sctx.getRealPath("/upload");
System.out.println(path);
// 获得文件名
String fileName = item.getName();
System.out.println(fileName);
// 该方法在某些平台(操作系统),会返回路径+文件名
fileName = fileName
.substring(fileName.lastIndexOf("/") + 1);
File file = new File(path + "\\" + fileName);
if (!file.exists()) {
item.write(file);
// 将上传图片的名字记录到数据库中

resp.sendRedirect("ok.jsp");
}
}
}
} catch (Exception e) {
e.printStackTrace();
}

}

}

index.jsp代码：

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'upload.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

</head>
<body>
<form action="upload" method="post" enctype="multipart/form-data">
请选择上传的图片或文件:<input type="file" name="fileName"/><input type="submit" value="上传"/>
</form>
</body>
</html>