JSP开发入门(二)----JSP语法的基本原理_MySQL
安装之后，接下来我们要讨论JSP的语法.如果要偷懒，你可以下载语法卡而如果你不熟悉 Java的程序设计，你可能会想要参考Sun的使用手册；然而，网站建立者不应该做太多的Java发展。除了几个函式呼叫之外，出现在你JSP网页上的Java程序代码应该将它减到最少;
记住这点之后，现在让我们先来看看JSP的编译器指引与指令组件，之后我们将解释JavaBeans与内部对象. JSP编译器指引与指令组件有五种型态.JSP 1.0之后，大部分的JSP是包含在以作为结束的单一卷标里.新的 JSP 1.1规格已经发表了，它同时也与XML兼容.
JSP的编译器指引与指令组件
编译器指示
声明
表达式
程序代码段/小型指令
注释
编译器指示
JSP的编译器指示是针对JSP引擎。它们并不会直接产生任何看得见的输出；相反的，它们是在告诉引擎如何处理其它的JSP网页。它们永远包含在 卷标里。两个主要的指引是 page与include。我们不会讨论taglib编译器指引但它可以在JSP1.1里用来建立自订卷标。
你几乎可以在你所有的JSP网页最上面找到page编译器指示。虽然这不是必须的，但它可以让你指定到哪里可以找到支持的Java类别这类的事：
，
当发生Java问题的事件时应该将讯息传送到哪里：
，
以及你是?需要为使用者管理通话期的信息，可能存取多个网页(稍后在JavaBeans里会有更多通话期的讨论):
。
include编译器指示让你将你的内容分成几个可管理的组件，就像那些有表头或脚注的网页。所包含的网页可以是固定格式的HTML网页或者是JSP内容的网页:
。
宣告
JSP声明让你定义网页层的变量，来储存信息或定义支持的函式，让JSP网页的其余部分能够使用。如果你发现自己有太多的程序代码，你最好将它们放在不同的Java类别里。你可以在 卷标里找到声明。记住要在变量声明的后面加上分号，就跟任何有效的Java叙述的形式一样: 。
表达式
JSP里有表达式，评估表达式的结果可以转换成字符串并且直接使用在输出网页上。JSP运算是属于 卷标里，并不包含分号，加引号字符串的无用部分。
。
程序代码段/小型指令文件
JSP程序代码片段或小型指令文件是包含在 卷标里。当网络服务器接受这段请求时，这段Java程序代码会执行。小型指令文件可以是原始的HTML或XML，其内部的程序代码片段可以让你建立有条件的执行程序代码，或者只是一些使用另一块程序代码的东西。举例来说，下列的程序代码结合了表达式与小型指令文件，在H1，H2，H3，以及H4卷标里显示字符串"Hello"。小型指令文件不限于一行的原始程序代码 :
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