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Servlet+Jsp implements the specific ideas and code for uploading pictures or files
Servlet+Jsp implements the specific ideas and code for uploading pictures or files
现在不管是博客论坛还是企业办公，都离不开资源的共享。通过文件上传的方式，与大家同分享，从而达到大众间广泛的沟通和交流，我们既可以从中获得更多的知识和经验，也能通过他人的反馈达到自我改进和提升的目的。
下面我就为大家介绍 web项目中的这一上传功能，那么文件是如何从本地发送到服务器的呢？看我慢慢道来：
首先，我们创建一个新的web工程，在工程的WebRoot目录下新建一个upload文件夹，这样当我们将该工程部署到服务器上时，服务器便也生成个upload文件夹，用来存放上传的资源。
然后，在WebRoot目录下新建一个jsp文件，主要实现的作用就是选择上传的文件，提交至servlet来进行处理
详细代码如下：一个form将文件信息通过post方式传送到指定的servlet
<%@ 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"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> </head> <body> <form action="/upload/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>
可以看到，我们将数据提交到工程下的upload/UpLoad。
之后，我们就来编写这个servlet——UpLoad.java
package load;
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.FileUploadException;
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("/upload/ok.html");
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}因为已对 代码做了详细的注释，所以相信大家也能基本上传的这个过程。要注意的一点是解析实例空间大小的设置。我们希望上传的文件不会是无限大，因此，设置
.setFileSizeMax(1024*400);
在这儿我们也可以将其设置成一个条件，当文件大于最大值时向页面 提交错误提示。此外，也可以读取选择文件的后缀来筛选出可以上传的类型。这些代码大家自己扩展，不再细谈。
通过servlet， 将正确的文件传送到服务端的upload文件夹中。这儿要注意，如果以后将工程从tomcat移除后，这些文件就会被自动删除。
上传结束之后，使页面转到上传成功页面ok.html。 当用户看到此页面时，说明你已实现文件的上传功能。
更多Servlet+Jsp实现图片或文件的上传功能具体思路及代码相关文章请关注PHP中文网！
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