标签案例

时间：2015-03-31 14:19:05 阅读：294 评论：0 收藏：0 [点我收藏+]

标签：

<?xml version="1.0" encoding="UTF-8" ?>
<taglib xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    
    <description>A tag library exercising SimpleTag handlers.</description>
    <tlib-version>1.0</tlib-version>
    <short-name>SimpleTagLibrary</short-name>
    <uri>/lcp</uri>
    
    
    <tag>
        <name>referer</name>  <!-- 为标签处理器类配一个标签名 -->
        <tag-class>cn.lcp.web.tag.RefererTag</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>
    
        
    <tag>
        <name>if</name>  <!-- 为标签处理器类配一个标签名 -->
        <tag-class>cn.lcp.web.tag.IfTag</tag-class>
        <body-content>scriptless</body-content>
        
        <attribute>
            <name>test</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
    
    
    <tag>
        <name>choose</name>  <!-- 为标签处理器类配一个标签名 -->
        <tag-class>cn.lcp.web.tag.ChooseTag</tag-class>
        <body-content>scriptless</body-content>
    </tag>
    
    <tag>
        <name>when</name>  <!-- 为标签处理器类配一个标签名 -->
        <tag-class>cn.lcp.web.tag.WhenTag</tag-class>
        <body-content>scriptless</body-content>
        
        <attribute>
            <name>test</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
    
    <tag>
        <name>otherwise</name>  <!-- 为标签处理器类配一个标签名 -->
        <tag-class>cn.lcp.web.tag.OtherwiseTag</tag-class>
        <body-content>scriptless</body-content>
    </tag>
    
    
    
    <tag>
        <name>foreach</name>  <!-- 为标签处理器类配一个标签名 -->
        <tag-class>cn.lcp.web.tag.ForEachTag</tag-class>
        <body-content>scriptless</body-content>
        
        <attribute>
            <name>var</name>
            <required>true</required>
            <rtexprvalue>false</rtexprvalue>
        </attribute>
        
        <attribute>
            <name>items</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
    
    
    <tag>
        <name>foreach2</name>  <!-- 为标签处理器类配一个标签名 -->
        <tag-class>cn.lcp.web.tag.ForEachTag2</tag-class>
        <body-content>scriptless</body-content>
        <attribute>
            <name>var</name>
            <required>true</required>
            <rtexprvalue>false</rtexprvalue>
        </attribute>
        <attribute>
            <name>items</name>
            <required>true</required>
            <rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
    
    <tag>
        <name>htmlFilter</name>  <!-- 为标签处理器类配一个标签名 -->
        <tag-class>cn.lcp.web.tag.HtmlFilter</tag-class>
        <body-content>scriptless</body-content>
    </tag> 
</taglib>

•开发防盗链标签

index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>My JSP ‘index.jsp‘ starting page</title>
  </head>
  
  <body>
    <a href="${pageContext.request.contextPath }/1.jsp">ahahah</a>
  </body>
</html>

1.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="/lcp" prefix="lcp"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<itcast:referer site="http://localhost:8080/" page="/index.jsp"/>

<html>
  <head>
    <title>防盗链</title>
  </head>
  <body> 
    ahhah 
  </body>
</html>

RefererTag.java


public class RefererTag extends SimpleTagSupport {

    private String site;
    private String page;
    public void setSite(String site) {
        this.site = site;
    }
    public void setPage(String page) {
        this.page = page;
    }
    
    
    @Override
    public void doTag() throws JspException, IOException {
        //看来访问者是从哪个页面来的
        PageContext pageContext = (PageContext)this.getJspContext();
        HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
        String referer = request.getHeader("referer");  //http://www.sina.com/index.html
        
        //判断
        if(referer==null || !referer.startsWith(site)){
            HttpServletResponse response = (HttpServletResponse) pageContext.getResponse();
            String webroot = request.getContextPath();
            if(page.startsWith(webroot)){
                response.sendRedirect(page);
            }else{
                response.sendRedirect(webroot + page);
            }
            //重定向后，控制保护的页面不要执行
            throw new SkipPageException();  
        }    
    }    
}

•开发<c:if>标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="/example" prefix="c" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>c:if标签，是否执行标签体</title>
  </head>
  
  <body>
    <c:if test="${user==null }">
        xxxx
    </c:if>
    
    <c:if test="${user !=null }">
        xxxx
    </c:if>   
  </body>
</html>

package cnl.lcp.web.tag.example;

import java.io.IOException;

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

//if标签
public class IfTag extends SimpleTagSupport {

    private boolean test;

    public void setTest(boolean test) {
        this.test = test;
    }

    @Override
    public void doTag() throws JspException, IOException {
        if(test){
            this.getJspBody().invoke(null);
        }
    }    
}

•开发<c:if><c:else>标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="/example" prefix="c" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head> 
    <title>if...else标签</title>
  </head>
  
  <body>
    
   <c:choose>   
           <c:when test="${user!=null}"> 
               xxxx
           </c:when>
           
           <c:otherwise>  
               yyyy
           </c:otherwise>
   </c:choose> 
  </body>
</html>

package cnl.lcp.web.tag.example;

import java.io.IOException;

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

public class OtherwiseTag extends SimpleTagSupport {

    @Override
    public void doTag() throws JspException, IOException {
        //拿到父标签
        ChooseTag parent = (ChooseTag) this.getParent();
        if(parent.isOk()==false){
            this.getJspBody().invoke(null);
            parent.setOk(true);
        }
        
    }
}

package cnl.lcp.web.tag.example;

import java.io.IOException;

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

public class WhenTag extends SimpleTagSupport {
    
    private boolean test; //这个值由服务器赋值

    public void setTest(boolean test) {
        this.test = test;
    }

    @Override
    public void doTag() throws JspException, IOException {
        //得到父标签，已经通过setParent吧父标签传递进来了。
        ChooseTag parent = (ChooseTag) this.getParent();
        //test并且父标签没有执行过， 
        if(test==true && parent.isOk()==false){
            this.getJspBody().invoke(null);  //执行标签体
            parent.setOk(true);  //控制兄弟不要执行
        }   
    }    
}

package cnl.lcp.web.tag.example;

import java.io.IOException;

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

public class ChooseTag extends SimpleTagSupport {
    
    private boolean isOk;

    public boolean isOk() {   //相当于get方法
        return isOk;
    }

    public void setOk(boolean isOk) {    //相当于set方法
        this.isOk = isOk;
    }

    @Override
    public void doTag() throws JspException, IOException {
        this.getJspBody().invoke(null);   //控制标签体执行
    }
}

•开发迭代标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="/example" prefix="c" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>foreach标签，重复执行标签体</title>
  </head>
  
  <body>
    
    <!-- 迭代list集合 -->
    <% 
        List list = new ArrayList();
        list.add("a");
        list.add("b");
        request.setAttribute("list",list);
    %>
    <c:foreach var="str" items="${list}">
        ${str }
    </c:foreach>
    <br/><hr><br/><br/>
    
    
    
    <!-- 迭代map集合 -->
    <%         
        Map map = new HashMap();
        map.put("a","aaaa");
        map.put("b","bbbb");
        request.setAttribute("map",map);
    %>
    <c:foreach2 items="${map}" var="entry">
         ${entry.key }=${entry.value }<br/>
    </c:foreach2>
    <br/><hr><br/><br/>
   
     
     
     <!-- 迭代数组 -->
     <%
         Integer num[] = {1, 2, 3, 4};
         request.setAttribute("num", num);
     %>
     <c:foreach2 items="${num}" var="i">
         ${i }
    </c:foreach2>
    
    <!-- 迭代数组 -->
     <%
         int num1[] = {1, 2, 3, 4};
         request.setAttribute("num", num1);
     %>
     <c:foreach2 items="${num}" var="i">
         ${i }
    </c:foreach2>
  </body>
</html>

package cnl.lcp.web.tag.example;

import java.io.IOException;
import java.util.Iterator;
import java.util.List;

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

public class ForEachTag extends SimpleTagSupport {

    private List items;
    private String var;
    public void setItems(List items) {
        this.items = items;
    }
    public void setVar(String var) {
        this.var = var;
    }
    
    @Override
    //迭代集合
    public void doTag() throws JspException, IOException {
        
        PageContext context = (PageContext) this.getJspContext();
        
        Iterator it = items.iterator();
        while(it.hasNext()){
            Object obj = it.next();
            //
            context.setAttribute(var, obj);
            this.getJspBody().invoke(null);  
            
        }
    }
}

package cnl.lcp.web.tag.example;

import java.io.IOException;
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;

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

public class ForEachTag2 extends SimpleTagSupport {

    private Object items;
    private String var;
    private Collection collection;   //记住集合类型
    
    public void setItems(Object items) {  //int[]
        
        this.items = items;        
        if(items instanceof Collection){  //判断是否是单链集合
            collection = (Collection) items;  //list set
        }
        
        if(items instanceof Map){    //如果是双链集合，先强转为map，再转成单链集合
            Map map = (Map) items;
            collection = map.entrySet();  //set
        }        
        
        //对任意数组进行操作。
        if(items.getClass().isArray()){
            
            this.collection  = new ArrayList();
            int len = Array.getLength(items);
            for(int i = 0; i < len; i ++){
                Object obj = Array.get(items, i);
                this.collection.add(obj);
            }
        }
        
    }
    
    
    public void setVar(String var) {
        this.var = var;
    }
    
    @Override
    public void doTag() throws JspException, IOException {
        
        PageContext pageContext = (PageContext) this.getJspContext();
        
        Iterator it = collection.iterator();  //null.iterator
        while(it.hasNext()){
            Object obj = it.next();   //
            pageContext.setAttribute(var, obj);
            this.getJspBody().invoke(null);
        }
    }
}

•开发html转义标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib uri="/example" prefix="c" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>html转移标签，修改标签体</title>
  </head>
  
  <body>
   <a href="">点点</a>
   
   <!-- 对标签内容进行转义  -->
   <c:htmlFilter>
           <a href="">点点</a>
   </c:htmlFilter>
  </body>
</html>

package cnl.lcp.web.tag.example;

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

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

public class HtmlFilter extends SimpleTagSupport {

    @Override
    public void doTag() throws JspException, IOException {
        
        //invoke写到容器里面需要缓冲流
        StringWriter sw = new StringWriter();
        this.getJspBody().invoke(sw);   //得到标签体，再把标签体写到一个容器里面去。
        
        //得到标签体的内容
        String content = sw.getBuffer().toString();
        content = filter(content);
        
        
        this.getJspContext().getOut().write(content);
    }
    //转义字符串，是Apache里面的代码
    private String filter(String message) {

        if (message == null)
            return (null);

        char content[] = new char[message.length()];
        message.getChars(0, message.length(), content, 0);
        StringBuffer result = new StringBuffer(content.length + 50);
        for (int i = 0; i < content.length; i++) {
            switch (content[i]) {
            case ‘<‘:
                result.append("&lt;");
                break;
            case ‘>‘:
                result.append("&gt;");
                break;
            case ‘&‘:
                result.append("&amp;");
                break;
            case ‘"‘:
                result.append("&quot;");
                break;
            default:
                result.append(content[i]);
            }
        }
        return (result.toString());
    }
}

标签案例

标签：

原文地址：http://www.cnblogs.com/lcpholdon/p/4380668.html

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