Web项目(二) ————上传文件

小编做这个项目之前先做了一个上传文件的功能,这个功能在后面的项目中,有可能会用到。

  • 本项目用到的基础知识,不会再介绍相关的基础知识,如果想要学习HTML的相关知识可以到 Web开发基础学习笔记. 去看相应的章节
    本文的代码 原文链接:
    https://blog.csdn.net/javae100/article/details/79938923

先给出代码文件

UpLoad.html


<html>
    <head>
        <meta charset="UTF-8">
        <title>文件上传title>
    head>
    <body>
        <form action="" method="get" enctype="multipart/form-data">
            <input type="text" name="username">
            <input type="file" name="upload" >
            <input type="submit" value="提交">

        form>
    body>
html>

UpLoad.jsp

<%@ 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>文件上传</title>
</head>
<body>
 # 
<form action="${pageContext.request.contextPath }/UploadServlet" method="post" enctype="multipart/form-data">
	<input type="text" name="username">
	<input type="file" name="upload">
	<input type="submit" value="提交">
</form>
 
 
</body>
</html>
package demo;
 
 
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.List;
import java.util.Map;
 
 
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;
import org.apache.commons.io.IOUtils;
 
 
public class UploadServlet extends HttpServlet {
	
 
 
	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		try {
			//1、创建磁盘文件项工厂
			//获取web根目录下放置缓存文件的文件夹“temp”的物理路径
			String path_temp = this.getServletContext().getRealPath("temp");
			File file =  new File(path_temp) ;
			DiskFileItemFactory factory = new DiskFileItemFactory(1024*1024, file);//1024*1024为设置文件缓存大小
			//也可以new一个空参的factory,随后再设置缓存大小,和缓存位置
			//DiskFileItemFactory factory = new DiskFileItemFactory();
			//factory.setSizeThreshold(1024*1024);
			//factory.setRepository(file);
				
			//2、创建文件上传的核心类
			ServletFileUpload upload = new ServletFileUpload(factory);
			//设置上传文件名称的编码为UTF-8,不设置有可能会出现中文乱码,编码规范要进行设置。
			upload.setHeaderEncoding("UTF-8");
			//判断表单是否是文件上传表单,只是为了演示需要,实际开发中开发人员肯定知道这是不是文件上传表单
			boolean multipartContent = upload.isMultipartContent(request);
			if(multipartContent) {
				//是文件上传的表单,解析request获得文件项集合
				List<FileItem> parseRequest = upload.parseRequest(request);
				if(parseRequest!=null) {
					for(FileItem item :parseRequest) {
						//判断是不是普通表单项
						boolean formField = item.isFormField();
						if(formField) {
							//如果是普通表单项
							String fieldName = item.getFieldName();
							String fieldValue = item.getString("UTF-8");//对普通表单项的内容进行编码
							//当表单是enctype="multipart/form-data"时,request.getParameter相关的方法都失效,所以要用上面的方法获得值
							//String parameter = request.getParameter("username");//获取不到,失效!
							System.out.println("表单值为:"+fieldName+"="+fieldValue);
						}else {
							//如果是文件上传项							
							String name = item.getName();
							System.out.println("文件名为:"+name);
							System.out.println(item);
							//加入判断文件是否上传,如果不加判断,前台没有选择文件,提交后会报IO空指针异常
							if(item.getSize()==0L) {
								response.setContentType("text/html;charset=UTF-8");
								response.getWriter().write("请上传文件");
								return;
							}
							if(name=="") {
								response.setContentType("text/html;charset=UTF-8");
								response.getWriter().write("文件名不能为空");
								return;
							}
							InputStream in = item.getInputStream();
							String path_store = this.getServletContext().getRealPath("upload");
							OutputStream out = new FileOutputStream(path_store+"/"+name);
							IOUtils.copy(in, out);
							in.close();
							out.close();
							//删除临时文件
							item.delete();
						}
						
					}					
				}
				response.setContentType("text/html;charset=UTF-8");
				response.getWriter().write("是文件上传");
				
			}else {
				//不是文件上传表单,可以使用原始的获取表单数据方式request.getParameter();
				//只是为了演示需要,实际开发中开发人员肯定知道这是不是文件上传表单
				Map<String, String[]> parameterMap = request.getParameterMap();
				response.setContentType("text/html;charset=UTF-8");
				response.getWriter().write("不是文件上传表单");
			}
		} catch (FileUploadException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
 
 
	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
} 

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