JSP：自定义标签之开发标签

练习有父标签的和两个标签之间通信（通过父标签） <fix:choose>          <fix:when test="${user==null }">                                           未登陆. <br>          </fix:when>          <fix:otherwith>               welcome用户已经登录. <br>          </fix:otherwith> </fix:choose> <fix:choose>          <fix:when test="${2==2}">         2==2<br>          </fix:when>          <fix:otherwith>             2!=2<br>          </fix:otherwith> </fix:choose>   <fix:choose>          <fix:when test="${1==1}">          1==1 <br>          </fix:when>          <fix:otherwith>              1<>1 <br>          </fix:otherwith> </fix:choose>

public class Choose extends SimpleTagSupport {          private boolean isDo;          public boolean isDo() {                    return isDo;          }          public void setDo(boolean isDo) {                    this.isDo = isDo;          }          @Override          public void doTag() throws JspException, IOException {                    this.getJspBody().invoke(null);          } }

public class WhenTag extends SimpleTagSupport {            private boolean test;                   public void setTest(boolean test) {                    this.test = test;          }            @Override          public void doTag() throws JspException, IOException {                    Choose parent=(Choose) this.getParent();                    if(test && !parent.isDo())                    {                             this.getJspBody().invoke(null);                             parent.setDo(true);                    }                          } }

public class OtherwithTag extends SimpleTagSupport {            @Override          public void doTag() throws JspException, IOException {                   Choose parent=(Choose) this.getParent();                    if(!parent.isDo())                    {                             this.getJspBody().invoke(null);                             parent.setDo(true);                    }                          } }