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>