java:(监听,上传,下载)

1.监听:

  index.jsp:

<%@ 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 'index.jsp' starting page</title>
</head>

<body>

    <%
        session.setAttribute("username", "zhangsan");// attributeAdded
        session.setAttribute("pwd", "123456");// attributeAdded
        session.setAttribute("username", "lisi");// attributeReplaced
        session.removeAttribute("username");// attributeRemoved
    %>

    <h1>监听器</h1>
    <pre>
              
              在web项目中,监听器也是监听比较重要的事件或者对象
                  监听作用域
                      1.监听作用域的生命周期
                      2.监听作用域的值传递

                    **当监听器开始监听的时候,绝对是监听已经被创建后      
                    
                    监听的原则:
                        **作用一定要单一                
                      
                      三个作用域两个监听:每一个作用域都会有两个监听,一共有三个作用域,就会有六个监听
                      request:请求和所有请求转发的跳转的页面
                          ServletRequestListener:sre.getServletRequest();
                          ServletContextAttributeListener:
                              srae.getName();
                              srae.getValue();
                              srae.getServletRequest();
                      session:一次会话
                          HttpSessionListener:se.getSession();
                          HttpSessionAttributeListener:
                              event.getName();
                            event.getValue();
                            event.getSession();
                      application:作用于整个项目
                          ServletContextListener:sce.getServletContext()
                          ServletContextAttributeListener:
                              event.getName();
                            event.getValue();
                            event.getServletContext();
                      
                      
                      pageContext:虽然是作用域,但是作用范围很小,只作用于当前页面,所有两个servlet之间的值传递会失效,没有必要监听
                          四大作用域中,唯一一个没有监听的作用域
              
          
          </pre>

</body>
</html>

 

  web.xml:

  

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
    <display-name>20170807_listener</display-name>

    <listener>
        <listener-class>cn.zzsxt.lee.web.listener.HelloListener</listener-class>
    </listener>

    <listener>
        <listener-class>cn.zzsxt.lee.web.listener.HiListener</listener-class>
    </listener>

    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

  HelloListener:

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class HelloListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        // 系统默认加载的数据
        System.out.println("我是初始化方法,我被调用了");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        System.out.println("我是销毁方法,我被调用了");
    }

}

 

  HiListener:

import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;

public class HiListener implements HttpSessionAttributeListener {

    @Override
    public void attributeAdded(HttpSessionBindingEvent event) {
        System.out.println("添加会被调用");
    }

    @Override
    public void attributeRemoved(HttpSessionBindingEvent event) {
        System.out.println("移除时会被调用");
    }

    @Override
    public void attributeReplaced(HttpSessionBindingEvent event) {
        System.out.println("替换时会被调用");
    }

}

 

  ManyListener:

  

import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class ManyListener implements ServletContextListener, ServletContextAttributeListener, HttpSessionListener, HttpSessionAttributeListener, ServletRequestListener, ServletRequestAttributeListener {

    @Override
    public void attributeAdded(ServletRequestAttributeEvent srae) {
        srae.getServletRequest().getAttribute("username");
        // TODO Auto-generated method stub
        
    }

    @Override
    public void attributeRemoved(ServletRequestAttributeEvent srae) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void attributeReplaced(ServletRequestAttributeEvent srae) {
        
    }

    @Override
    public void requestDestroyed(ServletRequestEvent sre) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void requestInitialized(ServletRequestEvent sre) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void attributeAdded(HttpSessionBindingEvent event) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void attributeRemoved(HttpSessionBindingEvent event) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void attributeReplaced(HttpSessionBindingEvent event) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void sessionCreated(HttpSessionEvent se) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent se) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void attributeAdded(ServletContextAttributeEvent arg0) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void attributeRemoved(ServletContextAttributeEvent arg0) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void attributeReplaced(ServletContextAttributeEvent event) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void contextDestroyed(ServletContextEvent event) {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void contextInitialized(ServletContextEvent event) {
        // TODO Auto-generated method stub
        
    }

}

2.上传:

  jar:

 

 

  index.jsp:

<%@ 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 'index.jsp' starting page</title>
</head>

<body>

    <form action="upload.sxt" enctype="multipart/form-data" method="post">
        上传头像:
        <input type="file" name="headPhoto" />
        用户名:<input type="text" name="username" />
        <input type="submit" value="提交" />
    </form>

    <!--
      
          上传必须遵循以下规则:
              文件的上传需要在form表单添加enctype属性,值必须为multipart/form-data
              请求方式一定要是post,不能使用get
              enctype="multipart/form-data" method="post"
                  会把需要上传的文件转换为字节流
                  所以在servlet中无法使用request.getParameter()获取
              
              在上传成功后,文件头部会出现:
                  ------WebKitFormBoundaryG5qMELzS6gD7bSK6
                        Content-Disposition: form-data; name="headPhoto"; filename="meinv.jpg"
                        Content-Type: image/jpeg
              
              上传流程:
                  1.首先把需要上传的图片转换为字节流enctype="multipart/form-data" method="post"
                  2.在servlet接收:request.getInputStream();字节流
                  3.客户端向服务器端上传相对于服务器来说是输入流
                  4.服务器要把字节流转换为文件格式
                  5.关闭资源(为空判定)
      
       -->

</body>
</html>

 

  UploadServlet:

package cn.zzsxt.lee.web.servlet;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.UUID;

import javax.servlet.ServletContext;
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 org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;

@WebServlet("/upload.sxt")
public class UploadServlet extends HttpServlet {

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // File.separator:/
        // 在windows中E:\\,但是在mac中/Desctop/,在linux中也是
        // 获取项目全局作用域:application
        ServletContext context = this.getServletContext();// ServletContext就是application
        // context.getRealPath:zzsxt/
        // tempDirectory:zzsxt/temp
        // fileDirectory:zzsxt/upload
        // 满64K写入的路径
        String tempDirectory = context.getRealPath(File.separator + "temp");
        // 最终上传到服务器上的路径
        String fileDirectory = context.getRealPath(File.separator + "picture");

        try {
            // 写满该大小的缓存后,存入硬盘中。
            int sizeThreshold = 1024 * 64;// 设置每几K写入一次
            // 创建临时文件夹目录
            File repositoryFile = new File(tempDirectory);// 创建临时文件夹
            // 首先创建一个文件工厂:每64k就往临时文件夹写入一次数据
            FileItemFactory factory = new DiskFileItemFactory(sizeThreshold, repositoryFile);
            // jar给创建好了一个servlet来处理上传功能-->需要传入一个参数:factory
            ServletFileUpload upload = new ServletFileUpload(factory);
            // 设置上传文件的大小限制
            upload.setSizeMax(500 * 1024 * 1024);// 文件最大上传大小,文件最大上传500M,多于500M就报错给你看
            // 开始解析请求数据,将输入写到临时文件夹(一个表单域就是list的一个对象)
            List items = upload.parseRequest(request);//request也就是相当于request.getInputStream();
            // 开始遍历获取数据
            Iterator iter = items.iterator();// 遍历list集合(客户端上传的字节流)
            while (iter.hasNext()) {
                // 获取一个表单域资源
                FileItem item = (FileItem) iter.next(); // FileItem就是表示一个表单域:所谓表单域就是<form></form>标签面的东西
                // 判断当前资源是否是一个文件(isFormField方法用于判断FileItem是否代表一个普通表单域(即非file表单域))
                if (item.isFormField()) {// 判断客户端传过来的数据是否为一个普通表单域(所谓普通表单域就是非file的表单域text password select radio checkbox...)
                    // 返回表单域的名字
                    System.out.println("普通表单域的名字---------------" + item.getFieldName());
                    // 返回表单域的值
                    System.out.println("普通表单域的值----------------" + item.getString("utf-8"));
                    // 比如说要通过username进行查询
                    request.getParameter("username");
                    // 从数据库查询数据
                    // 调用service-->dao-->sql-->最终从数据库查询出值
                } else {
                    // 就是file类型
                    // 获取表单域name属性的值
                    String fieldName = item.getFieldName();// headPhoto
                    System.out.println(fieldName);
                    // 返回该文件在客户机上的文件名。e.g: e:\dianying\\video\1.wmv
                    String fileName = item.getName();// 才是文件名(包含了服务器的路径)
                    // 获取文件的类型
                    String fileType = fileName.substring(fileName.lastIndexOf("."));// 从获取的文件名中截取出该文件的类型.txt;.jpg;.java.zip...
                    // System.out.println("文件域的名字--*****" + fieldName);
                    // System.out.println("上传文件的名字*****" + fileName);
                    // System.out.println("上传文件的类型*****" + fileType);
                    // 创建一个真实的文件目录
                    // 只有这才是真正上传,前面其他的东西都是为了这一步做铺垫
                    // zzsxt/upload/201707084132141321321fjdhfjdsh4718467363217.jpg
                    File uploadedFile = new File(fileDirectory + File.separator + new Date().getTime()
                            + UUID.randomUUID().toString() + fileType);
                    // 将临时文件写入到真实文件夹里面去
                    item.write(uploadedFile);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void ioUpload(HttpServletRequest request, HttpServletResponse response) throws Exception {
        // 上传和下载功能,一般情况下使用IO流
        InputStream ip = request.getInputStream();
        // System.out.println(ip.available());// 接收到数量
        OutputStream os = new FileOutputStream("E:\\java_tools\\meinv" + UUID.randomUUID().toString() + ".jpg");
        byte[] bytes = new byte[1024 * 8];// 每8k写入一次
        int len = 0;
        while ((len = ip.read(bytes)) != -1) {
            os.write(bytes, 0, len);
        }
        os.flush();
        if (os != null) {
            os.close();
        }
        if (ip != null) {
            ip.close();
        }

        // 要把上传记录保存在数据库中
        // insert into语句
        // 首先要保存路径
        // 然后需要保存客户上传的文件名
        // 最后还需要保存文件在服务器上的名字
    }

}

 

3.下载:

 

 

  .txt:

  

几年前,他无助时,她救了他,他那时候觉得他对她有一点好感,却不知道,自己已经已经陷入爱情的深渊,那个散发着纯净气息的无辜眼神,令他沦陷。几年后,她在闺蜜榕衫介绍的工作下,无意中当上了他的女仆,他发现了,她就是几年前的她……她娇弱的靠在他怀里,他的心,乱了。

 

  index.jsp:

<%@ 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 'index.jsp' starting page</title>
</head>

<body>

    <a href="dowload.sxt?fileName=bdzcasw.txt">霸道总裁爱上我-简介</a>

</body>
</html>

 

  DownloadServlet:

  

package cn.zzsxt.lee.web.servlet;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/dowload.sxt")
public class DownloadServlet extends HttpServlet {

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        // 获取需要下载的文件名
        String fileName = request.getParameter("fileName");
        // zzsxt/upload/需要下载的文件名
        InputStream ip = new FileInputStream(
                this.getServletContext().getRealPath(File.separator + "upload" + File.separator + fileName));
        // 清空response
        response.reset();
        // 文件名中有可能存在中文-->中文乱码
        // 把中文的文件名转换为字节数组
        // UTF-8就是为了统一编码集
        // ISO-8859-1:就是为了能发送字节流,默认情况下UTF-8是不能发送字节流
        /*fileName.getBytes("UTF-8");
        String str = new String(fileName.getBytes("UTF-8"), "IOS-8859-1");*/
        response.addHeader("Content-Disposition",
                "attachment;filename=" + new String(fileName.getBytes("utf-8"), "ISO-8859-1"));
        response.addHeader("Content-Length", "" + ip.available());
        // 服务器把客户端需要下载文件写出(转换成流的方式写出)
        OutputStream op = response.getOutputStream();
        byte[] bytes = new byte[1024 * 8];
        int len = 0;
        while ((len = ip.read(bytes)) != -1) {
            op.write(bytes, 0, len);
        }
        op.flush();
        if (op != null) {
            op.close();
        }
        if (ip != null) {
            ip.close();
        }

    }

}

 

 

posted @ 2017-08-08 12:17  咫尺天涯是路人丶  阅读(498)  评论(0编辑  收藏  举报