syntaxref.fm3.html

来自「这是java源码。」· HTML 代码 · 共 61 行

<html><head><title></title></head>
<body bgcolor=#ffffff>
 
<a href="tags.html">[Top]</a> <a href="syntaxref.fm2.html">[Prev]</a> <a href="syntaxref.fm4.html">[Next]</a> <a href="Copyright.fm.html">[Bottom]</a>
<hr><br>
 
<a name="10983"> </a>
<h2 align="center"> Declaration</h2>
<p><a name="10984"> </a>
Declares a variable or method valid in the page scripting language.
</p><a name="10985"> </a>
<h4> JSP Syntax</h4>
<blockquote><pre><code>&lt;%! </code><em>declarations</em><code> %&gt;
</code></pre></blockquote><a name="10987"> </a>
<h4> Examples</h4>
<blockquote><pre>&lt;%! int i = 0; %&gt;
&lt;%! int a, b, c; %&gt;
&lt;%! Circle a = new Circle(2.0); %&gt;
</pre></blockquote><a name="10989"> </a>
<h4> Description</h4>
<p><a name="16594"> </a>
A declaration declares one or more variables or methods for use later in the JSP source file. 
</p><p><a name="15971"> </a>
A declaration must contain at least one complete declarative statement. You can declare any number of variables or methods within one declaration tag, as long as they are separated by semicolons. The declaration must be valid in the scripting language used in the JSP file. In JSP 1.0, you must use the JavaTM programming language for scripting, and declarations must conform to the <em>Java Language Specification</em>.
</p><p><a name="16636"> </a>
When you use the Java programming language for scripting, remember these rules:
</p><ul><a name="16640"> </a>
<li>You must end the declaration with a semicolon (the same rule as for a <a href="syntaxref.fm5.html#10996">Scriptlet</a>, but the opposite of an <a href="syntaxref.fm4.html#11258">Expression</a>). 
<a name="16644"> </a>
<li>You must declare the variable or method <em>before</em> you use it in the JSP file.
<a name="16645"> </a>
<li>You can already use variables or methods that are declared in packages imported by the <a href="syntaxref.fm7.html#15653">Page Directive</a>, so there is no need to declare them.
</ul><p><a name="15972"> </a>
In general, a declaration has page scope, so it is valid in scriptlets, expressions, and other declarations within the same JSP source file. But if a JSP file includes other files, the rules of scope become a bit trickier. The rules of scope for declarations are described below:
</p><ul><a name="15907"> </a>
<li>If the JSP source file does not include any other files, declarations have page scope.
<a name="16609"> </a>
<li>If the JSP source file includes a dynamic file with <code><a href="syntaxref.fm11.html#8828">&lt;jsp:include&gt;</a></code>, declarations have page scope.
<a name="16613"> </a>
<li>If the JSP source file includes static files with <code><a href="syntaxref.fm11.html#8828">&lt;jsp:include&gt;</a></code> or the <a href="syntaxref.fm6.html#8772">Include Directive</a>, declarations have translation unit scope. A translation unit is the JSP source file plus all of its static include files, but without any dynamic include files.
</ul><a name="10991"> </a>
<h4> See Also</h4>
<ul><a name="10992"> </a>
<li><a href="syntaxref.fm5.html#10996">Scriptlet</a>
<a name="10993"> </a>
<li><a href="syntaxref.fm4.html#11258">Expression</a>
</ul>
<hr><br>
 
<a href="tags.html">[Top]</a> <a href="syntaxref.fm2.html">[Prev]</a> <a href="syntaxref.fm4.html">[Next]</a> <a href="Copyright.fm.html">[Bottom]</a>
<hr><br>



<i>Copyright  &#169; 1999, Sun Microsystems, Inc.   All rights
reserved.</i>


</body>
</html>