j2ee_08_ custom label

1. Tag language features
   <attribute start tag = "attribute value"> tag body </ tag end>

   Empty tag
   
   

   ---

   
   <Start label> </ end label>
   <label start />

2. Since the development and use steps to define the label
   2.1 to create a label helper class (inherited BodyTagSupport)
   tag attributes must attribute the corresponding helper class, and to provide the corresponding get / set methods
   rtexprvalue

2.2 Creating a tag library descriptor (tld), add a custom tag configuration
Note: tld files must be saved to the WEB-INF directory or its subdirectories
jstl tag library
my label provides a description file, you can copy the past to create the file extension instead .tld

<!DOCTYPE taglib
  PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN"
   "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd">
<!-- 标签库描述符 -->
<taglib xmlns="http://java.sun.com/JSP/TagLibraryDescriptor">
	<!-- 代表标签库的版本号 -->
	<tlib-version>1.0</tlib-version>
	<!-- 代表jsp的版本 -->
	<jsp-version>1.2</jsp-version>
	<!-- 你的标签库的简称 -->
	<short-name>test</short-name>
	<!-- 你标签库的引用uri -->
	<uri>/zking</uri>

	<tag>
		<!-- 标签名 -->
		<name>yy</name>
		<!-- 标签工具类 -->
		<tag-class>com.zking.TestTag</tag-class>
		<!-- 标签的内容类型：empty表示空标签，jsp表示可以为任何合法的JSP元素 -->
		<body-content>jsp</body-content>
		<!-- 自定义标签的属性定义,请注意一定要在标签类中提供对应的get/set方法 -->
		<attribute>
			<!-- 自定义标签的属性名称 -->
			<name>name</name>
			<!-- true表示必填 -->
			<required>true</required>
			<!-- true支持动态值,可以向值里面填jsp表达式、EL表达式,false则不支持 -->
			<rtexprvalue>false</rtexprvalue>
		</attribute>
	</tag>
</taglib>

2.3 taglib introduced by instruction tag library JSP, and accessed by the suffix to specify custom label

3. Label Lifecycle

SKIP_BODY: not Skip body is calculated content
EVAL_BODY_INCLUDE: calculated tag's body and [Output]
EVAL_PAGE: calculating subsequent portion of the page
SKIP_PAGE: skipping subsequent portions are not connected the tab page
EVAL_BODY_AGAIN: a body recalculation