jsp自定义标签

package com.itheima.web.tag;import java.io.IOException;import javax.servlet.http.HttpServletRequest;import javax.servlet.jsp.JspException;import javax.servlet.jsp.JspWriter;import javax.servlet.jsp.tagext.TagSupport;public class ViewIPTag extends TagSupport {@Overridepublic int doStartTag() throws JspException {HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();JspWriter out = this.pageContext.getOut();String ip = request.getRemoteAddr();   try {out.print(ip);} catch (IOException e) {throw new RuntimeException();}return super.doStartTag();}}

0,移除jsp中的java代码

[java] view plaincopy

1. public class ViewIPTag extends TagSupport {  
2.   
3.     @Override  
4.     public int doStartTag() throws JspException {  
5.         HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();  
6.         JspWriter out = this.pageContext.getOut();  
7.           
8.         String ip = request.getRemoteAddr();  
9.         try {  
10.             out.print(ip);  
11.         } catch (IOException e) {  
12.             throw new RuntimeException();  
13.         }  
14.         return super.doStartTag();  
15.     }  
16.       
17. }  

1,控制标签内的文本是否输出

[java] view plaincopy

1. public class TagDemo extends TagSupport {  
2.   
3.     @Override  
4.     public int doStartTag() throws JspException {  
5.           
6.           
7.         return Tag.EVAL_BODY_INCLUDE;//输出,不输出SKIP_TAGE  
8.     }  
9.   
10. }  

2,控制标签后面的文本是否输出

[java] view plaincopy

1. public class TagDemo2 extends TagSupport {  
2.   
3.     @Override  
4.     public int doEndTag() throws JspException {  
5.           
6.         return Tag.EVAL_PAGE;  
7.     }  
8.   
9. }  

3,控制标签体内的文本循环输出

[java] view plaincopy

1. public class TagDemo3 extends TagSupport {  
2.     static int num = 0;  
3.       
4.     @Override  
5.     public int doStartTag() throws JspException {  
6.         // TODO Auto-generated method stub  
7.         return Tag.EVAL_BODY_INCLUDE;  
8.     }  
9.   
10.     @Override  
11.     public int doAfterBody() throws JspException {  
12.         if(++num<5){  
13.             return IterationTag.EVAL_BODY_AGAIN;  
14.         }else{  
15.             return IterationTag.SKIP_BODY;  
16.         }  
17.           
18.     }  
19.   
20. }  

4,修改标签体内的文件

[java] view plaincopy

1. public class TagDemo4 extends SimpleTagSupport {  
2.   
3.     @Override  
4.     public void doTag() throws JspException, IOException {  
5.         JspFragment jf = this.getJspBody();  
6.         StringWriter writer = new StringWriter();  
7.         jf.invoke(writer);  
8.         String str = writer.getBuffer().toString().toUpperCase();  
9.         this.getJspContext().getOut().write(str);  
10.           
11.     }  

5,防盗链

<itheima:refererDemo site="http://localhost" page="/day11/index.jsp" />

public class refererDemo extends SimpleTagSupport {private String site;private String page;public void setSite(String site) {this.site = site;}public void setPage(String page) {this.page = page;}@Overridepublic void doTag() throws JspException, IOException {PageContext context = (PageContext) this.getJspContext();HttpServletRequest request = (HttpServletRequest) context.getRequest();HttpServletResponse response = (HttpServletResponse) context.getResponse();String referer = request.getHeader("referer");if(referer !=null && referer.startsWith(site)){//request.getRequestDispatcher("/7.jsp");}else{response.sendRedirect(page);}}}

tld文件

[html] view plaincopy

1. <tag>  
2.   
3.     <name>ViewIP</name>  
4.     <tag-class>com.itheima.web.tag.ViewIPTag</tag-class>  
5.     <body-content>empty</body-content>  
6. </tag>  
7. <tag>  
8.   
9.     <name>TagDemo</name>  
10.     <tag-class>com.itheima.web.tag.TagDemo</tag-class>  
11.     <body-content>JSP</body-content>  
12. </tag>  
13. <tag>  
14.   
15.     <name>TagDemo3</name>  
16.     <tag-class>com.itheima.web.tag.TagDemo3</tag-class>  
17.     <body-content>JSP</body-content>  
18. </tag>  
19. <tag>  
20.   
21.     <name>TagDemo4</name>  
22.     <tag-class>com.itheima.web.tag.TagDemo4</tag-class>  
23.     <body-content>scriptless</body-content>  
24. </tag>  
25. <tag>  
26.   
27.     <name>TagDemo2</name>  
28.     <tag-class>com.itheima.web.tag.TagDemo2</tag-class>  
29.     <body-content>empty</body-content>  
30. </tag> 
    
31. <tag>
            <name>refererDemo</name>
            <tag-class>com.itheima.web.tag.referer.refererDemo</tag-class>
            <body-content>empty</body-content>
            <attribute>
            <name>site</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
            </attribute>
            <attribute>
            <name>page</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
            </attribute>
        </tag>
    
32.