學習筆記專區

• 先做一隻程式(class)，一輸入的參數隨機生出一組數字來，回傳這一組數字(是一個list)，這個class叫LotteryBean
• 再做一隻程式(servlet)名叫LotteryServlet，他被召喚後會呼叫LotteryBean、傳入值域(最大49最小值1、一組要幾個數字6)後獲得一組數字，他會把獲得的list放入一個Collection中，再用setAttribute把這個Collection傳入JSP裡。用getRequestDispatcher跟forward來設定要傳到哪一個JSP中跟傳甚麼(/ch01/goodLuck.jsp)

再來著作接收跟傳入資訊的JSP檔

• 第一個queryLottery.jsp，也就是傳出資料的頁面有一個表單form，<Form action="LotteryServlet" method="POST">，表示將表單的資料傳給LotteryServlet這個Servlet來執行
• 第二個goodLuck.jsp，接收LotteryServlet計算好的資料並顯示於螢幕，用${visitName}、${luckyNumber}來抓標記把值放出來

package ch01;

import java.util.ArrayList;

import java.util.Collection;

import java.util.HashSet;

import java.util.List;

import java.util.Set;

import java.util.TreeSet;

public class LotteryBean {

    private int lowerBound;

    private int upperBound;

    private int ballNumber;

     public LotteryBean() {

     }

     public void setLowerBound(int lowerBound) {

         this.lowerBound = lowerBound;

     }

     public void setUpperBound(int upperBound) {

         this.upperBound = upperBound;

     }

     public void setBallNumber(int ballNumber) {

         this.ballNumber = ballNumber;

     }

     public Collection<Integer> getLuckyNumbers() {

         Set<Integer> set = new TreeSet<Integer>();

         //TreeSet是一个有序集合，她的元素按照升序排列，默认是按照自然顺序排列

         while (set.size() < ballNumber ) {

         int num = (int)(Math.random()* (upperBound-lowerBound+1) + lowerBound);

         set.add(num);

         }

         return set;

     }

     public Collection<Integer> getFourStars() {

         List<Integer> list = new ArrayList<Integer>();

         while (list.size() < ballNumber ) {

         int num = (int)(Math.random()* (upperBound-lowerBound+1) + lowerBound);

         list.add(num);

         }

         return list;

     }

}

package ch01;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.util.Collection;

import javax.servlet.RequestDispatcher;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class LotteryServlet

 * HttpServlet繼承自GenericServlet，GenericServlet是Servlet這個Interface的實作

 */

@WebServlet("/ch01/LotteryServlet")//別人呼叫這個class時需要使用的關鍵字?

public class LotteryServlet extends HttpServlet {

     private static final long serialVersionUID = 1L;//不懂這句用意

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         processRequest(request,response);

     }

     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

         processRequest(request,response);

     }

     private void processRequest(HttpServletRequest request,//為何自動生成private?

              HttpServletResponse response) throws ServletException, IOException {

         try {request.setCharacterEncoding("UTF-8");//說明傳送到本程式的資料內碼

         String name=request.getParameter("visitor");//讀取瀏覽器送來的資料?

         if(name==null||name.trim().length()==0){

              //String java.lang.String.trim()

//            Returns a string whose value is this string,

//            with any leading and trailing whitespace removed.

              name="訪客";

              }

         //如果讀不到使用者傳送的資料，將name設為"訪客"

         LotteryBean lottery = new LotteryBean();

         lottery.setLowerBound(1);//最小數字1

         lottery.setUpperBound(49);//最大數字49

         lottery.setBallNumber(6);//出現六個數字一組

         Collection coll = lottery.getLuckyNumbers();//產生所需結果

         request.setAttribute("visitName", name);

         request.setAttribute("luckyNumber", coll);//把用servlet算好的結果放入HttpServletRequest的request中

         RequestDispatcher rd = request.getRequestDispatcher("/ch01/goodLuck.jsp");

         //再建一個goodLuck.jsp檔

         //Dispatcher：發送者

         rd.forward(request, response);

         //Forward：發送

         return;//forward之後會有一個return敘述←?

         }catch (UnsupportedEncodingException e) {

              throw new ServletException(e);

         }

     }

}

<%@ 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>查詢明牌</title>

</head>

<body>

<h2>查詢明牌</h2>

<Form action="LotteryServlet" method="POST">

<!-- action是表單(form)專用的方法，用以連結到接受資料的程式

method有post跟get，GET的資料會顯示在url上、post的不會-->

訪客姓名：<input type="text" name="visitor" size="10"><p/>

<!-- name主要是用於獲取提交表單的某表單域信息， 作為可與伺服器交互數據的HTML元素的服務器端的標記 -->

<input type="submit" value="確定"><p/>

</Form>

</body>

</html>

<%@ 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>報明牌</title><!-- 這是結果回傳頁 -->

</head>

<body>

<H2>卜籤求明牌</H2>

${visitName}，您好，<BR>

您的明牌為：${luckyNumber}<!-- 金錢符號用法類似window.onload，就是先載入執行再繼續的意思 -->

</body>

</html>