自定义标签 (choose)

public class ChooseTag extends SimpleTagSupport {
    public Boolean tag = true;

    public Boolean getTag() {
        return tag;
    }

    public void setTag(Boolean tag) {
        this.tag = tag;
    }

    @Override
    public void doTag() throws JspException, IOException {
        JspFragment jspBody = this.getJspBody();
        jspBody.invoke(null);
        super.doTag();
    }

}

public class WhenTag extends SimpleTagSupport {
    public Boolean test;

    public Boolean getTest() {
        return test;
    }

    public void setTest(Boolean test) {
        this.test = test;
    }

    @Override
    public void doTag() throws JspException, IOException {
        ChooseTag chooseTag = (ChooseTag) this.getParent();
        Boolean tag = chooseTag.getTag();
        if (tag && this.getTest()) {
            chooseTag.setTag(false);
            JspFragment jspBody = this.getJspBody();
            jspBody.invoke(null);
        }
        super.doTag();
    }
}

public class OtherwiseTag extends SimpleTagSupport{
    
    @Override
    public void doTag() throws JspException, IOException {
        ChooseTag  chooseTag = (ChooseTag) this.getParent();
        Boolean tag = chooseTag.getTag();
        if(tag){
            JspFragment jspBody = this.getJspBody();
            jspBody.invoke(null);
        }
        super.doTag();
    }

}

<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>

    <tlibversion>1.2</tlibversion>
    <jspversion>1.1</jspversion>


    <shortname>mylib</shortname>
    <uri>http://www.fz.song.myLib</uri>



    <tag>
        <name>choose</name>
        <tagclass>fz.song.tag.ifelse.ChooseTag</tagclass>
        <bodycontent>scriptless</bodycontent>
    </tag>

    <tag>
        <name>when</name>
        <tagclass>fz.song.tag.ifelse.WhenTag</tagclass>
        <bodycontent>scriptless</bodycontent>
        <attribute>
            <name>test</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
    
    <tag>
        <name>otherwise</name>
        <tagclass>fz.song.tag.ifelse.OtherwiseTag</tagclass>
        <bodycontent>scriptless</bodycontent>
    </tag>


    <tag>
        <name>foreach</name>
        <tagclass>fz.song.tag.foreach.ForeachTag</tagclass>
        <bodycontent>scriptless</bodycontent>
        <attribute>
            <name>items</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
        <attribute>
            <name>var</name>
            <required>true</required>
            <rtexprvalue>false</rtexprvalue>
        </attribute>
    </tag>

</taglib>

<%@ taglib uri="http://www.fz.song.myLib" prefix="x"%>




    <x:choose>
        <x:when test="${10>1}">true</x:when>
        <x:otherwise>false</x:otherwise>
    </x:choose>