jstl c:choose>、 和 標簽的自定義開發

<c:choose>
<c:when test="${param.age>24}">大學畢業</c:when>
<c:when test="${param.age>20}">高中畢業</c:when>
<c:otherwise>高中以下學歷</c:otherwise>
</c:choose>

 

》開發三個標簽 choose when otherwise

》其中when標簽中有一個Boolean類型的屬性：test

》choose是when和otherwise的父標簽，when在otherwise之前使用

》在父標簽中定義一個“全局”的Boolean類型的flag：用於判斷子標簽在滿足條件的情況下是否執行

      >若when的test為true，且when的父標簽flag也為true，則執行when的標簽體（正常輸出標簽體內容）同時將flag設置為false

      >若when的test為true，且when的父標簽flag為false，則不執行標簽體

      >若flag為true，otherwise執行標簽體

 

choose類

public class ChooseTag extends SimpleTagSupport {
    private boolean flag = true;
    public void setFlag(boolean flag) {
        this.flag = flag;
    }
    public boolean isFlag() {
        return flag;
    }
    @Override
    public void doTag() throws JspException, IOException {
        getJspBody().invoke(null);
    }

when類

public class WhenTag extends SimpleTagSupport {
    private boolean test;
    public void setTest(boolean test) {
        this.test = test;
    }
    @Override
    public void doTag() throws JspException, IOException {
        if(test){
            //得到父標簽的引用
            ChooseTag chooseTag = (ChooseTag) getParent();
            Boolean flag = chooseTag.isFlag();
            if(flag){
                getJspBody().invoke(null);
                chooseTag.setFlag(false);
            }
        }
    }

otherwise類

public class OtherWiseTag extends SimpleTagSupport {
    @Override
    public void doTag() throws JspException, IOException {
        ChooseTag chooseTag = (ChooseTag) getParent();
        if(chooseTag.isFlag()){
            getJspBody().invoke(null);
        }
    }

test.jsp

<!-- 導入標簽庫文件(自定義) -->
<%@taglib uri="http://www.wlc.com/myTag/core" prefix="wlc"%>

<wlc:choose>
        <wlc:when test="${param.age>24}">大學畢業</wlc:when>
        <wlc:when test="${param.age>20}">高中畢業</wlc:when>
        <wlc:otherwise>高中以下學歷</wlc:otherwise>
    </wlc:choose>

tld文件

<tag>
        <name>choose</name>
        <tag-class>cn.stud.wlc.tag.ChooseTag</tag-class>
        <body-content>scriptless</body-content>
    </tag>

    <tag>
        <name>when</name>
        <tag-class>cn.stud.wlc.tag.WhenTag</tag-class>
        <body-content>scriptless</body-content>
        <attribute>
            <name>test</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>

    <tag>
        <name>otherwise</name>
        <tag-class>cn.stud.wlc.tag.OtherWiseTag</tag-class>
        <body-content>scriptless</body-content>
    </tag>