JSP 简单标签extends SimpleTagSupport

1.控制JSP页面某一部分内容是否执行

public void doTag()

this.getJspBody().invoke(null);执行

空白，不执行

2.控制JSP页面内容重复执行

 package cn.itcast.web.simpletag;

 import java.io.IOException;

 import javax.servlet.jsp.JspException;
 import javax.servlet.jsp.tagext.JspFragment;
 import javax.servlet.jsp.tagext.SimpleTagSupport;

 public class SimpleTagDemo2 extends SimpleTagSupport {

     @Override
     public void doTag() throws JspException, IOException {
         // TODO Auto-generated method stub
         JspFragment jf = this.getJspBody();

         for (int i = 0; i < 10; i++) {
             jf.invoke(null);
         }
     }

 }

3.修改JSP页面内容输出

 package cn.itcast.web.simpletag;

 import java.io.IOException;
 import java.io.StringWriter;

 import javax.servlet.jsp.JspContext;
 import javax.servlet.jsp.JspException;
 import javax.servlet.jsp.tagext.JspFragment;
 import javax.servlet.jsp.tagext.SimpleTagSupport;

 public class SimpleTagDemo3 extends SimpleTagSupport {

     @Override
     public void doTag() throws JspException, IOException {
         // TODO Auto-generated method stub

         JspFragment jf = this.getJspBody();
         StringWriter sw = new StringWriter();
         jf.invoke(sw);

         String content = sw.getBuffer().toString();

         content = content.toUpperCase();

         JspContext pageContent = this.getJspContext();
         pageContent.getOut().write(content);
     }

 }

4.控制标签余下的JSP不执行

 package cn.itcast.web.simpletag;

 import java.io.IOException;

 import javax.servlet.jsp.JspException;
 import javax.servlet.jsp.SkipPageException;
 import javax.servlet.jsp.tagext.SimpleTagSupport;

 public class SimpleTagDemo4 extends SimpleTagSupport {

     @Override
     public void doTag() throws JspException, IOException {
         // TODO Auto-generated method stub
         throw new SkipPageException();
     }

 }

开发带属性的标签

要想让一个自定义标签具有属性，通常需要完成两个任务：

在标签处理器中编写每个属性对应的setter方法

 package cn.itcast.web.simpletag;

 import java.io.IOException;

 import javax.servlet.jsp.JspException;
 import javax.servlet.jsp.tagext.SimpleTagSupport;

 public class SimpleTagDemo5 extends SimpleTagSupport {

     private int count;

     public void setCount(int count) {
         this.count = count;
     }

     @Override
     public void doTag() throws JspException, IOException {
         // TODO Auto-generated method stub

         for (int i = 0; i < count; i++) {
             this.getJspBody().invoke(null);
         }
     }

 }

在tld文件中描述标签的属性

     <tag>
         <name>demo5</name>
         <tag-class>cn.itcast.web.simpletag.SimpleTagDemo5</tag-class>
         <body-content>scriptless</body-content>
         <attribute>
             <name>count</name>
             <required>true</required>
             <rtexprvalue>true</rtexprvalue>
         </attribute>
     </tag>