JSP 简单标签extends SimpleTagSupport

Posted 2020-10-19 邓戈麟

 

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

 

 1 package cn.itcast.web.simpletag;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.jsp.JspException;
 6 import javax.servlet.jsp.tagext.JspFragment;
 7 import javax.servlet.jsp.tagext.SimpleTagSupport;
 8 
 9 public class SimpleTagDemo2 extends SimpleTagSupport {
10 
11     @Override
12     public void doTag() throws JspException, IOException {
13         // TODO Auto-generated method stub
14         JspFragment jf = this.getJspBody();
15 
16         for (int i = 0; i < 10; i++) {
17             jf.invoke(null);
18         }
19     }
20 
21 }

 

3.修改JSP页面内容输出

 

 1 package cn.itcast.web.simpletag;
 2 
 3 import java.io.IOException;
 4 import java.io.StringWriter;
 5 
 6 import javax.servlet.jsp.JspContext;
 7 import javax.servlet.jsp.JspException;
 8 import javax.servlet.jsp.tagext.JspFragment;
 9 import javax.servlet.jsp.tagext.SimpleTagSupport;
10 
11 public class SimpleTagDemo3 extends SimpleTagSupport {
12 
13     @Override
14     public void doTag() throws JspException, IOException {
15         // TODO Auto-generated method stub
16 
17         JspFragment jf = this.getJspBody();
18         StringWriter sw = new StringWriter();
19         jf.invoke(sw);
20 
21         String content = sw.getBuffer().toString();
22 
23         content = content.toUpperCase();
24 
25         JspContext pageContent = this.getJspContext();
26         pageContent.getOut().write(content);
27     }
28 
29 }

 

4.控制标签余下的JSP不执行

 

 1 package cn.itcast.web.simpletag;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.jsp.JspException;
 6 import javax.servlet.jsp.SkipPageException;
 7 import javax.servlet.jsp.tagext.SimpleTagSupport;
 8 
 9 public class SimpleTagDemo4 extends SimpleTagSupport {
10 
11     @Override
12     public void doTag() throws JspException, IOException {
13         // TODO Auto-generated method stub
14         throw new SkipPageException();
15     }
16 
17 }

 

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

 

 1 package cn.itcast.web.simpletag;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.jsp.JspException;
 6 import javax.servlet.jsp.tagext.SimpleTagSupport;
 7 
 8 public class SimpleTagDemo5 extends SimpleTagSupport {
 9 
10     private int count;
11 
12     public void setCount(int count) {
13         this.count = count;
14     }
15 
16     @Override
17     public void doTag() throws JspException, IOException {
18         // TODO Auto-generated method stub
19 
20         for (int i = 0; i < count; i++) {
21             this.getJspBody().invoke(null);
22         }
23     }
24 
25 }

 

在tld文件中描述标签的属性

 

 1     <tag>
 2         <name>demo5</name>
 3         <tag-class>cn.itcast.web.simpletag.SimpleTagDemo5</tag-class>
 4         <body-content>scriptless</body-content>
 5         <attribute>
 6             <name>count</name>
 7             <required>true</required>
 8             <rtexprvalue>true</rtexprvalue>
 9         </attribute>
10     </tag>

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