j-customtags-3-5.html

这是用java编写自定义标签的一些源码和笔记

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<a name="navskip"></a><td height="25" colspan="4"><img alt="3.简单标签" src="imagemaster/titlebar3.jpg" border="0" height="25" width="562"></td>
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<td width="90%"><font size="4" face="Verdana, Arial, Helvetica"><b>第 3 步：在标签处理程序 Java 类中创建属性</b></font></td><td width="200" align="right"><font size="1" face="Verdana, Arial, Helvetica"><nobr>   第 5 页（共9 页）</nobr></font></td>
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<p>
          

 我们希望为 <code>mapDefine</code> 标签指定三个属性，如下所示：
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<th width="225pt">属性说明</th>
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								<code>id</code>
							</td><td width="225pt">新 scriptlet 变量的名字。</td>
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								<code>scope</code>
							</td><td width="225pt">新 scriptlet 变量所在的范围。 </td>
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								<code>type</code>
							</td><td width="225pt">新 scriptlet 变量的类型 （<code>HashMap</code>、<code>FastHashMap</code>、<code>TreeMap</code> 或者 <code>FastTreeMap</code>）。

         如果 <code>type</code> 设置为 <code>hash</code>，那么就会创建一个 <code>HashMap</code>。如果 <code>type</code> 设置为 <code>fasthash</code>，那么将创建 <code>FastHashMap</code>。 </td>
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 在 JSP 页中使用这个标签时，它看起来将像下面这样：

 

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<code style="font-family: Courier New, Courier, monospace; font-size: 12">
  

 &lt;map:mapDefine id="editParams" scope="session" type="hash"&gt;          

     ...

 &lt;/map:mapDefine&gt;

 

 </code>
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 这个标签将在会话范围内创建一个名为 <code>editParams</code> 的 <code>HashMap</code>。 

 

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 为了在标签处理程序中创建属性，需要定义相应的 JavaBean 属性。 

 因此，每一个属性在标签处理程序中都有对应的 setter 方法，如下所示：

 

 </p>
<pre>
<code style="font-family: Courier New, Courier, monospace; font-size: 12">
  

 public class MapDefineTag extends TagSupport {

 

     ...

     private String type = FASTTREE;

     private String id;

     private String scope;

 

 

     public void setType(String string) {

         type = string;

     }

 

     public void setId(String string) {

         id = string;

     }

     

 

     public void setScope(String string) {

         scope = string;

     }

 

 </code>
</pre>
<p>
  

 

 转换引擎将用硬编码的配置数据或者运行时表达式设置这个标签的属性。

 我们将在 <a href="j-customtags-3-6.html">第 4 步：在 TLD 文件中定义属性</a> 中对此做更详细的讨论。</p>
<p>在 <a href="j-customtags-3-7.html">第 5 步：实现 doStartTag() 方法</a> 中，我们将在标签处理程序的 <code>doStartTag()</code> 方法中使用这些属性。

 

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