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  • 自定义标签

    JSP自定义标签

    一般我们说自定义标签是指JSP自定义标签。自定义标签在功能上逻辑上与javaBean 类似,都封装Java 代码。自定义标签是可重用的组件代码，并且允许开发人员为复杂的操作提供逻辑名称。

    ①使用Jsp自定义标签写一个HelloWorld.

    先要写一个tld文件：

     1 <?xml version="1.0" encoding="utf-8" ?>
 2 <taglib xmlns="http://java.sun.com/xml/ns/javaee"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
 5     version="2.1">
 6     <tlib-version>1.0</tlib-version>
 7     <short-name>java1234Tag</short-name>
 8     <tag>
 9         <name>helloWorld</name>
10         <tag-class>com.java1234.tag.HelloWorldTag</tag-class>
11     <body-content>empty</body-content>
12     </tag>
13 </taglib>
    java.tld
     1 package com.java1234.tag;
 2 import java.io.IOException;
 3 import javax.servlet.jsp.JspException;
 4 import javax.servlet.jsp.JspWriter;
 5 import javax.servlet.jsp.tagext.TagSupport;
 6 public class HelloWorldTag extends TagSupport{
 7     private static final long serialVersionUID = 1L;
 8     @Override
 9     public int doStartTag() throws JspException {
10         JspWriter out=this.pageContext.getOut();
11         try {
12             out.print("Jsp自定义标签HelloWorld");
13 
14         } catch (IOException e) {
15             // TODO Auto-generated catch block
16             e.printStackTrace();
17         }
18         return TagSupport.SKIP_BODY;//直接跳出jsp标签（最简单的标签）
19     }
20 }
    HelloWorldTag

    页面：

    在HelloWorldTag.jsp文件的标头我们引入tld文件。<%@ taglib prefix="java1234" uri="/WEB-INF/java1234.tld" %> 

    <%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<%@ taglib prefix="java1234" uri="/WEB-INF/java1234.tld" %> 
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>helloWorldTag</title>
</head>
<body>
<java1234:helloWorld/>
</body>
</html>
    HelloWorldTag.jsp

    ②自定义标签有属性的标签

    传递一个参数name,需要在配置文件里面设置如下：(<required>yes</required><!-- 表示该属性，一定要使用 --> <rtexprvalue>true</rtexprvalue><!-- 属性是否能用表达式 -->)

     1 <tag>
 2         <name>helloWorld2</name>
 3         <tag-class>com.java1234.tag.HelloWorldTag2</tag-class>
 4         <body-content>empty</body-content>
 5         <attribute>
 6             <name>name</name>//带有name
 7             <required>true</required>//为了在页面
 8             <rtexprvalue>true</rtexprvalue>
 9         </attribute>
10     </tag>
     1 package com.java1234.tag;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.jsp.JspException;
 6 import javax.servlet.jsp.JspWriter;
 7 import javax.servlet.jsp.tagext.TagSupport;
 8 public class HelloWorldTag2 extends TagSupport{
 9     private String name;//定义name属性
10     // set & get 方法
11     public String getName() {
12         return name;
13     }
14     public void setName(String name) {
15         this.name = name;
16     }
17     
18     
19     private static final long serialVersionUID = 1L;
20     @Override
21     public int doStartTag() throws JspException {
22         JspWriter out=this.pageContext.getOut();
23         try {
24             out.print(name+"Jsp自定义标签");
25 
26         } catch (IOException e) {
27             // TODO Auto-generated catch block
28             e.printStackTrace();
29         }
30         return TagSupport.SKIP_BODY;//直接跳出jsp标签（最简单的标签）
31     }
32 }

     页面部分

     1 <%@ page language="java" contentType="text/html; charset=utf-8"
 2     pageEncoding="utf-8"%>
 3 <%@ taglib prefix="java1234" uri="/WEB-INF/java1234.tld" %> //引入部分
 4 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 5 <html>
 6 <head>
 7 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
 8 <title>helloWorldTag2</title>
 9 </head>
10 <body>
11 <java1234:helloWorld2 name="带属性的jsp自定义标签屌爆了！"/>
12 </body>
13 </html>

    ③有标签体的自定义标签

    我们在设置属性“集合”，“元素”，“遍历器”。操作如下

     1 package com.java1234.tag;
 2 import java.util.Iterator;
 3 import java.util.List;
 4 import javax.servlet.jsp.JspException;
 5 import javax.servlet.jsp.tagext.TagSupport;
 6 public class Iterate extends TagSupport{
 7     private String var;//集合中的每一个元素
 8     private String items;//"集合"
 9     private Iterator iter;//遍历器用来放置数据的。
10     
11     public String getVar() {
12         return var;
13     }
14     public void setVar(String var) {
15         this.var = var;
16     }
17     public String getItems() {
18         return items;
19     }
20     public void setItems(String items) {
21         this.items = items;
22     }
23     public Iterator getIter() {
24         return iter;
25     }
26     public void setIter(Iterator iter) {
27         this.iter = iter;
28     }
29     private static final long serialVersionUID = 1L;
30     @Override
31     public int doStartTag() throws JspException {
32         //获取集合数据items----->监测数据是否存在   ----->存在并且是List  --->搞成遍历器 调用方法  ----如果有值-->我进行遍历执行标签体
33         Object value=this.pageContext.getAttribute(items);
34         if(value!=null && value instanceof List ){    //判断value是不是List
35             this.iter=((List)value).iterator();
36             if(iter.hasNext()){
37                 this.pageContext.setAttribute(var, iter.next());
38                 return TagSupport.EVAL_BODY_INCLUDE;//跳到标签体去执行操作。
39             }else{
40                 return TagSupport.SKIP_BODY;//直接跳出标签体，结束任务
41             }
42         }else{
43             return TagSupport.SKIP_BODY;//跳出标签体，结束任务。
44         }
45     }
46     @Override
47     //如果iter还没有执行完，我就在执行一次标签体！
48     public int doAfterBody() throws JspException {
49          if(iter.hasNext()){
50              this.pageContext.setAttribute(var, iter.next());
51              return TagSupport.EVAL_BODY_AGAIN;//在执行一次标签体
52          }else{
53              return TagSupport.SKIP_BODY;//直接跳出标签体
54          }
55     }
56     
57 }

    配置文件tld；

     1 <?xml version="1.0" encoding="utf-8" ?>
 2 <taglib xmlns="http://java.sun.com/xml/ns/javaee"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
 5     version="2.1">
 6     <tlib-version>1.0</tlib-version>
 7     <short-name>java1234Tag</short-name>
 8     <tag>
 9         <name>iterate</name>
10         <tag-class>com.java1234.tag.Iterate</tag-class>
11         <body-content>JSP</body-content>
12         <attribute>
13             <name>items</name>
14             <required>true</required>
15             <rtexprvalue>true</rtexprvalue>
16         </attribute>
17         <attribute>
18             <name>var</name>
19             <required>true</required>
20             <rtexprvalue>true</rtexprvalue>
21         </attribute>
22     </tag>
23 
24 </taglib>

    页面 iterate.jsp

     1 <%@ page language="java" contentType="text/html; charset=utf-8"
 2     pageEncoding="utf-8"%>
 3 <%@ page import="java.util.*"%>
 4 <%@ taglib prefix="java1234" uri="/WEB-INF/java1234.tld" %>
 5 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 6 <html>
 7 <head>
 8 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
 9 <title>iterate</title>
10 </head>
11 <body>
12     <%
13     List people =new ArrayList();
14         people.add("张三丰2");
15         people.add("丝丝光2");
16         people.add("王二小2");
17         pageContext.setAttribute("people", people);
18     %>
19 <java1234:iterate2 var="p" iteams="people">
20 ${p }
21 </java1234:iterate2>    
22 </body>
23 </html>

    ④简单标签

    配置文件：

     1 <?xml version="1.0" encoding="utf-8" ?>
 2 <taglib xmlns="http://java.sun.com/xml/ns/javaee"
 3     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 4     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
 5     version="2.1">
 6     <tlib-version>1.0</tlib-version>
 7     <short-name>java1234Tag</short-name>
 8     <tag>
 9         <name>iterate2</name>
10         <tag-class>com.java1234.tag.IterateSimple</tag-class>
11         <body-content>scriptless</body-content>
12         <attribute>
13             <name>var</name>
14             <required>true</required>
15             <rtexprvalue>true</rtexprvalue>
16         </attribute>
17         <attribute>
18         <name>iteams</name>
19             <required>true</required>
20             <rtexprvalue>true</rtexprvalue>
21         </attribute>
22     </tag>
23 </taglib>

    处理部分：

     1 package com.java1234.tag;
 2 
 3 import java.io.IOException;
 4 import java.util.Iterator;
 5 import java.util.List;
 6 
 7 import javax.servlet.jsp.JspException;
 8 import javax.servlet.jsp.tagext.SimpleTagSupport;
 9 
10 public class IterateSimple extends SimpleTagSupport{
11     private String var;
12     private String iteams;
13     
14     public String getVar() {
15         return var;
16     }
17     public void setVar(String var) {
18         this.var = var;
19     }
20     public String getIteams() {
21         return iteams;
22     }
23     public void setIteams(String iteams) {
24         this.iteams = iteams;
25     }
26     @Override
27     public void doTag() throws JspException, IOException {
28         Object value=this.getJspContext().getAttribute("iteams");
29         if(value !=null && value instanceof List){
30          Iterator iter=((List)value).iterator();//构造遍历器
31             while(iter.hasNext()){
32                 this.getJspContext().setAttribute(var, iter.next());
33                 this.getJspBody().invoke(null);//响应页面！
34             }
35         }
36     }
37 }

    页面：

     1 <%@ page language="java" contentType="text/html; charset=utf-8"
 2     pageEncoding="utf-8"%>
 3 <%@ page import="java.util.*"%>
 4 <%@ taglib prefix="java1234" uri="/WEB-INF/java1234.tld" %>
 5 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 6 <html>
 7 <head>
 8 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
 9 <title>iterate</title>
10 </head>
11 <body>
12     <%
13     List people =new ArrayList();
14         people.add("张三丰");
15         people.add("丝丝光");
16         people.add("王二小");
17         pageContext.setAttribute("people", people);
18     %>
19 <java1234:iterate items="people" var="p">
20     <h1>${p }</h1>
21 </java1234:iterate>    
22 </body>
23 </html>

    勤加练习！加油
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  • 原文地址：https://www.cnblogs.com/zyxsblogs/p/9747750.html
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