JSP2.x自定义标签的创建

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不同于JSP1.x，2.0开始，JSP提供了一套简化的标签，SimpleTag()接口，实现doTag()方法。

示例：

1、不带标签体的标签

taglib.tld配置

<tag>        <name>table</name>        <tagclass>my.Table</tagclass>        <bodycontent>JSP</bodycontent>        <info>Love Rabbit So Much.</info>        <attribute>            <name>items</name>            <required>true</required>            <rtexprvalue>true</rtexprvalue>        </attribute>        <attribute>            <name>url</name>            <required>false</required>            <rtexprvalue>true</rtexprvalue>        </attribute>    </tag>

MultiTag.java 标签实现类

package my;import java.io.IOException;import javax.servlet.jsp.JspException;import javax.servlet.jsp.tagext.SimpleTagSupport;public class MultiTag extends SimpleTagSupport{private int num1;private int num2;@Overridepublic void doTag() throws JspException, IOException{this.getJspContext().getOut().write("" + num1 + " * " + num2 + " = " + (num1 * num2));}public int getNum1(){return num1;}public void setNum1(int num1){this.num1 = num1;}public int getNum2(){return num2;}public void setNum2(int num2){this.num2 = num2;}}

multi.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"%><%@ taglib uri="http://www.loverabbit.com/tags" prefix="taglib"%><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body>    <taglib:multi num1="3" num2="4" /></body></html>

运行结果：

2、带标签体的标签

taglib.tld配置

<tag>        <name>toUpperCase</name>        <tagclass>my.ToUpperCaseTag</tagclass>        <bodycontent>tagdependent</bodycontent>        <info>Love Rabbit So Much.</info>    </tag>

ToUpperCaseTag.java 标签实现类

package my;import java.io.IOException;import java.io.StringWriter;import javax.servlet.jsp.JspException;import javax.servlet.jsp.tagext.JspFragment;import javax.servlet.jsp.tagext.SimpleTagSupport;public class ToUpperCaseTag extends SimpleTagSupport{@Overridepublic void doTag() throws JspException, IOException{// 将 标签体内容读入该 writerStringWriter writer = new StringWriter();// 标签体 为 JspFragment 的形式JspFragment jspFragment = this.getJspBody();// 通过 invoke 输出到指定的 writer 中。// 如果参数为 null，将输出到默认的 writer 中，即 getJspContext().getOut() 输出到HTML中jspFragment.invoke(writer);String content = writer.getBuffer().toString();this.getJspContext().getOut().print(content.toUpperCase());}}

toUpperCase.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"%><%@ taglib uri="http://www.loverabbit.com/tags" prefix="taglib"%><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body>    <taglib:toUpperCase>This is a to upper case tag. </taglib:toUpperCase></body></html>

运行结果：

3、带多个标签体的标签

taglib.tld配置

<tag>        <name>multiAttribute</name>        <tagclass>my.MultiAttributeTag</tagclass>        <bodycontent>tagdependent</bodycontent>        <info>Love Rabbit So Much.</info>        <attribute>            <name>body1</name>            <required>false</required>            <fragment>true</fragment>        </attribute>        <attribute>            <name>body2</name>            <required>false</required>            <fragment>true</fragment>        </attribute>    </tag>

MultiAttributeTag.java 标签实现类

package my;import java.io.IOException;import java.io.StringWriter;import javax.servlet.jsp.JspException;import javax.servlet.jsp.tagext.JspFragment;import javax.servlet.jsp.tagext.SimpleTagSupport;public class MultiAttributeTag extends SimpleTagSupport{private JspFragment body1;private JspFragment body2;public void setBody1(JspFragment body1){this.body1 = body1;}public void setBody2(JspFragment body2){this.body2 = body2;}@Overridepublic void doTag() throws JspException, IOException{StringWriter writer1 = new StringWriter();StringWriter writer2 = new StringWriter();for(int i = 0; i < 5; i++){// body1 调用 5 次body1.invoke(writer1);}for(int i = 0; i < 3; i++){// body2 调用 3 次body2.invoke(writer2);}this.getJspContext().getOut().print("3 次调用 body2 后的结果：" + writer2.getBuffer().toString()+ "<br/><br/>");this.getJspContext().getOut().print("5 次调用 body1 后的结果：" + writer1.getBuffer().toString()+ "<br/><br/>");}}

multiAttribute.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"%><%@ taglib uri="http://www.loverabbit.com/tags" prefix="taglib"%><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title><style type="text/css">body {font-size: 12px;}</style></head><body>    <taglib:multiAttribute><jsp:attribute name="body1">标签体一, </jsp:attribute><jsp:attribute name="body2">标签体二, </jsp:attribute></taglib:multiAttribute></body></html>

运行结果：

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