2021.3.15 JavaEE2 JSP 笔记 - 《Java学习笔记---武伟》

《学习内容》：

//========学习内容=========
EL表达式语言（域对象取值）
EL表达式语言（参数值+运算）
JSTL核心标签
JSTL标签+练习
JSTL自定义
文件上传（1）
文件上传（2）
文件下载

《知识点—笔记》
//=========================
EL域对象取值：
${requestScope.存的key}
${sessionScope.存的key}
${applicationScope.存的key}

JSTL遍历集合数组

中间内容进行拼接等操作

文件上传
//创建一个工厂
DiskFileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(//需要Factory工厂);
List fileItems = upload.parseRequest(request);可以解析当前的request对象返回值是FileItems集合存着每个组件

《代码内容》：

TestEL项目
Index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <script>
      window.onload = function () {
          window.location.href = "test"
      }
  </script>
  <body>
  </body>
</html>

TestCont**roller**

package controller;
import domain.User;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
public class TestController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        String uname = "武伟";
        request.setAttribute("uname",uname);
        User user = new User("李雅芬","520");
        request.setAttribute("user",user);
        String[] unames = new String[]{"武伟","李雅芬","二胖"};
        request.setAttribute("unames",unames);
        ArrayList<User> list = new ArrayList<>();
        list.add(user);
        list.add(user);
        request.setAttribute("list",list);
        ArrayList<String> data = new ArrayList<>();
        data.add("'name'");data.add("'age'");data.add("'sex'");data.add("'value'");data.add("'dink'");
        request.setAttribute("data",data);
        ArrayList<Integer> echars = new ArrayList<>();
        echars.add(1);echars.add(2);echars.add(19);echars.add(25);echars.add(26);
        request.setAttribute("echars",echars);
        request.getRequestDispatcher("newJsp.jsp").forward(request,response);
    }
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }
}

newJsp.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page isELIgnored="false"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<html>
<head>
    <script type="text/javascript" src="./static/echarts-en.min.js"></script>
</head>
<body>
<div align="center" id="main" style="width: 600px;height:400px;"></div>
</body>
<script>
    var myChart = echarts.init(document.getElementById("main"));
        option =  {
            xAxis: {
                type: 'category',
                data: ${requestScope.data}
            },
            yAxis: {
                type: 'value'
            },
            series: [{
                data: ${requestScope.echars},
                type: 'line'
            }]
        };
        myChart.setOption(option)
</script>
</html>

上传文件和下载文件项目
downLoa**d.jsp**

<%--
  Created by IntelliJ IDEA.
  User: ATanmo
  Date: 2021/3/16
  Time: 8:57
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>下载产品</title>
    <meta charset="UTF-8">
</head>
<body>
        <a href="download?filename=bj.png">下载</a>
</body>
</html>

index.js**p**

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <meta charset="UTF-8">
    <title>文件上传与下载</title>
  </head>
  <body>
  <table align="center" width="60%" height="60%">
    <form action="testfile" method="post" enctype="multipart/form-data">
      <tr>
      <p>
        用户名：<input type="text" name="username" value="">
      </p>
      <p>
        请您选择上传的文件：<input type="file" name="filename" value="">
      </p>
        <p>
          <input type="submit" value="确认">
        </p>
    </form>
    </tr>
  </table>
  </body>
</html>

DownLoad**Controller**

package controller;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URL;
import java.net.URLEncoder;
public class DownLoadController extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            request.setCharacterEncoding("UTF-8");
            String filename = request.getParameter("filename");
            FileInputStream inputStream = new FileInputStream("D://test/" + filename);
            byte[] stream = new byte[1024];
            int length = inputStream.read(stream);
        String encode = URLEncoder.encode(filename, "UTF-8");
        System.out.println(encode);
        response.setContentType("application/x-msdownLoad");
        response.setHeader("Content-disposition","attachment;filename="+filename);
        //循环读取全部的字节 然后输出流写出去
            ServletOutputStream outputStream = response.getOutputStream();
            while (length != -1){
            outputStream.write(stream);
            outputStream.flush();
            length = inputStream.read(stream);
        }
    }
}

TestFileCo**ntroller**

package controller;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileItemFactory;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.taglibs.standard.lang.jstl.test.beans.Factory;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.util.List;
public class TestFileController extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //创建一个工厂
        DiskFileItemFactory factory = new DiskFileItemFactory();
        //创建一个文件加载
        ServletFileUpload upload = new ServletFileUpload(factory);
        //加载request对象 进行包装
        try {
            System.out.println("文件上传中...");
            //解析后 里面有前端全部的组件
            List<FileItem> fileItems = upload.parseRequest(request);
            for (FileItem item : fileItems){
                //来判断他是一个普通的组件还是一个文件组件
                if (item.isFormField()){//如果他是一个普通的组件
                    String fieldName = item.getFieldName();
                    String paramValue = item.getString("UTF-8");
                    System.out.println(fieldName+"===="+paramValue);
                }else {
                    //如果走到了这里  那么说明他是一个文件组件
                    request.setCharacterEncoding("UTF-8");
                    String fieldName = item.getFieldName();
                    String value = item.getString("UTF-8");
                    String realFileName = item.getName();
                    System.out.println(fieldName+"==="+value+"==="+realFileName);
                    item.write(new File("D://test/"+realFileName));
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

学习总结：
学懂的：
可以熟练的使用EL和JSTL,文件上传下载的具体写法，当时写的时候挺熟练的。
有问题的地方：
虽然写的功能没有什么问题，但是文件上传和下载虽然流程功能没有什么问题
但是其中的设置缓存，最大多少，最小多少，进度条，自己没有去尝试，等待
后期项目的时候用的时候勾起印象，进行进一步加深，JSTL的自定义标签和自定义EL
都没有去练习。**