JSP自定义标签(3)


八、SimpleTagSupport类


在JSP2.0后,为了简化标签开发的难度,就可以使用SimpleTagSupport进行开发;


1.开发一般标签


注意点:

(1)需要继承SimpleTagSupport类;

(2)实现public void doTag()throws JspException,IOException;

(3)super.getJspContext().getOut().write("....");   进行输出;

(4)在SimpleTagSupport中,tld中的<body-content>内容不能为JSP,如果标签体不为空,则只能为scriptless


代码:

SimpleTagSupportDemo.java

package org.tagext;
import javax.servlet.jsp.tagext.*;
import javax.servlet.jsp.*;
import java.io.*;
public class SimpleTagSupportDemo extends SimpleTagSupport{
	private String name;
	public String getName(){
		return name;
	}
	public void setName(String name){
		this.name = name;
	}
	public void doTag()throws JspException,IOException{
		super.getJspContext().getOut().write("<h3>"+name+"</h3>");
	}
}


2.开发迭代标签


通过super.getJspBody().invoke(null);能够执行标签体内容;

SimpleTagSupportDemo.java
package org.tagext;
import javax.servlet.jsp.tagext.*;
import javax.servlet.jsp.*;
import java.io.*;
import java.util.*;
public class SimpleTagSupportDemo extends SimpleTagSupport{
	private String name;
	private String id;
	public String getName(){
		return name;
	}
	public void setName(String name){
		this.name = name;
	}
	public String getId(){
		return id;
	}
	public void setId(String id){
				this.id = id;
	}
	public void doTag()throws JspException,IOException{
		Object value = super.getJspContext().getAttribute(name,PageContext.PAGE_SCOPE);
		Iterator<String> iter = ((List<String>)value).iterator();
		while(iter.hasNext()){
			super.getJspContext().setAttribute(id,iter.next());
			super.getJspBody().invoke(null);
		}

	}
}

综合看来,SimpleTagSupport比起前面的TagSupport,BodyTagSupport,简单了许多,不需要任何返回值;


九、常见问题


1.区分是否有标签体

<xiazdong:hello name="">

</xiazdong:hello>

是属于有标签体的,只是标签体为空;

<xiazdong:hello name=""/>为标签体为空;



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