JSP入门教程

dn001 2014-01-12 12:31:12

<%! Circle a = new circle(2.0) ; %>;

在页面中使用变量和方法之前必须声明;

声明的范围通常是JSP页，但如果页面中使用INCLUDE指令包含其他页面，范围应变得扩展到被包含的页面。;

表达式<%=……%>可以在页面中包含任何合法的语言表达式，不用分号。;

例：<%= Math.sqrt(2) %>;

<%= item[I] %>;

<%= a+b+c %>;

<%= new java.util.date() %>;

表达式和脚本的一个关键的不同点就是不需要分号。如果你需要在脚本中使用表达式就必须加分号。;

脚本<%……%>允许你写的任何数量的脚本语言;

例：<% String name=null ;;

If (request.getParmeter("name")==null{;

%>;

记住在脚本中必须使用分号结尾。;

猜数字游戏;

猜数字游戏非常的有趣，而且从这里你还可以学到很多表达式的用法。;

代码;

显示用的主屏幕（numguess.jsp）;

<!--;

Number Guess Game;

Written by Jason Hunter, CTO, K&A Software;

jasonh@kasoftware.com, http://www.servlets.com;

Distributed by Sun Microsystems with permission;

-->;

<%@ page import = "num.NumberGuessBean" %>;

<jsp:useBean id="numguess" class="num.NumberGuessBean" scope="session" />;

<jsp:setProperty name="numguess" property="*" />;

<html>;

<head><title>Number Guess</title></head>;

<body bgcolor="white">;

<font size=4>;

<% if (numguess.getSuccess() ) { %>;

Congratulations! You got it.;

And after just <%= numguess.getNumGuesses() %>tries.<p>;

<% numguess.reset(); %>;

Care to <a href="numguess.jsp">try again</a>?;

<% } else if (numguess.getNumGuesses() == 0) { %>;

Welcome to the Number Guess game.<p>;

I'm thinking of a number between 1 and 100.<p>;

<form method=get>;

What's your guess? <input type=text name=guess>;

<input type=submit value="Submit">;

</form>;

<% } else { %>;

Good guess, but nope. Try <b><%= numguess.getHint() %></b>.;

You have made <%= numguess.getNumGuesses() %> guesses.;

<p>I'm thinking of a number between 1 and 100.;

<p><form method=get>;

What's your guess? <input type=text name=guess>;

<input type=submit value="Submit">;

</form>;

<% } %>;

</font>;

</body>;

</html>;

操作程序(NumberGuessBean.java);

// Number Guess Game;

// Written by Jason Hunter, CTO, K&A Software;

// jasonh@kasoftware.com, http://www.servlets.com;

// Distributed by Sun Microsystems with permission;

package num;;

import java.util.*;;

public class NumberGuessBean {;

int answer;;

boolean success;;

String hint;;

int numGuesses;;

public NumberGuessBean() {;

reset();;

};

public void setGuess(String guess) {;

numGuesses++;;

int g;;

try {;

g = Integer.parseInt(guess);;

};

catch (NumberFormatException e) {;

g = -1;;

};

if (g == answer) {;

success = true;;

};

else if (g == -1) {;

hint = "a number next time";;

};

else if (g < answer) {;

hint = "higher";;

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