jstl标签库的配置
* 将jstl.jar和standard.jar拷贝到WEB-INF/lib下（如果使用el表达式，不用拷贝这两个jar）
注意：jstl必须在能够支持j2ee1.4/servlet2.4/jsp2.0版本上的容器才能运行，这个环境
是目前较为常用的环境
标签库的使用
* 采用taglib指令引入
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<%@ taglib prefix= "c" uri= "http://java.sun.com/jsp/jstl/core " %> |
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<%@ taglib prefix= "fmt" uri= "http://java.sun.com/jsp/jstl/fmt " %> |
自定义函数库：
1、定义类和方法（方法必须是public static）
2、编写自定义tld文件，并且将此文件放到WEB-INF或WEB-INF任意子目录下
3、在jsp中采用taglib指令引入自定义函数库
4、采用 前缀+冒号（:）+函数名 调用即可
MyFunctions.java
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Myfunctions.java代码 |
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public class MyFunctions { |
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|
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public static String sayHello(String name) { |
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return "Hello " + name; |
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} |
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|
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} |
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public class MyFunctions { |
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|
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public static String sayHello(String name) { |
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return "Hello " + name; |
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} |
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|
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} |
myfunctions.tld
自定义标签
Xml代码
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<? xml version = "1.0" encoding = "UTF-8" ?> |
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|
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< taglib xmlns = "http://java.sun.com/xml/ns/j2ee " |
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xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance " |
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xsi:schemaLocation = "http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd " |
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version = "2.0" > |
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|
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< description >my functions library</ description > |
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< display-name >my functions</ display-name > |
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< tlib-version >1.0</ tlib-version > |
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< short-name >my</ short-name > |
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< uri >http://www.bjsxt.com/functions</ uri > |
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|
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< function > |
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< name >sayHello</ name > |
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< function-class >com.bjsxt.struts.MyFunctions</ function-class > |
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< function-signature >java.lang.String sayHello(java.lang.String)</ function-signature > |
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</ function > |
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|
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</ taglib > |
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<? xml version = "1.0" encoding = "UTF-8" ?> |
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< taglib xmlns = "http://java.sun.com/xml/ns/j2ee " |
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xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance " |
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xsi:schemaLocation = "http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd " |
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version = "2.0" > |
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|
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< description >my functions library</ description > |
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< display-name >my functions</ display-name > |
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< tlib-version >1.0</ tlib-version > |
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< short-name >my</ short-name > |
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< uri >http://www.bjsxt.com/functions</ uri > |
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|
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< function > |
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< name >sayHello</ name > |
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< function-class >com.bjsxt.struts.MyFunctions</ function-class > |
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< function-signature >java.lang.String sayHello(java.lang.String)</ function-signature > |
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</ function > |
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|
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</ taglib > |
jstl_fn.jsp
注意与前面的配置文件myfunctions.tld相对应，
prefix对应<short-name>my</short-name>
uri对应 <uri>http://www.bjsxt.com/functions</uri>
可使用以下面两种方式给name赋值：
1、${my:sayHello("David") }
2、request.setAttribute("name", "David");
Java代码
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<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%> |
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<%@ taglib uri="http://www.bjsxt.com/functions " prefix="my" %> |
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|
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<% |
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request.setAttribute("name", "David"); |
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%> |
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|
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
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< html > |
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< head > |
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< title >testTemplate</ title > |
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</ head > |
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< body > |
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${my:sayHello(name) } |
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</ body > |
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</ html > |
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<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%> |
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<%@ taglib uri="http://www.bjsxt.com/functions " prefix="my" %> |
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<% |
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request.setAttribute("name", "David"); |
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%> |
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
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< html > |
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< head > |
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< title >testTemplate</ title > |
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</ head > |
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< body > |
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${my:sayHello(name) } |
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</ body > |
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</ html > |
补充：web-app version="2.4"
有时也需要在web.xml中添加对标签的定义：
Xml代码
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< jsp-config > |
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< taglib > |
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< taglib-uri >www.bjsxt.com/functions</ taglib-uri > |
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< taglib-location >/WEB-INF/my.tld</ taglib-location > |
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</ taglib > |
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</ jsp-config > |
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< jsp-config > |
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< taglib > |
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< taglib-uri >www.bjsxt.com/functions</ taglib-uri > |
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< taglib-location >/WEB-INF/my.tld</ taglib-location > |
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</ taglib > |
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</ jsp-config > |
注意：
可能出现的异常
1、The function xxx must be used with a prefix when a default namespace is not specified
--- 在jsp页面中调用方式不正确，可能将 ":" 写成了 "."
2、The function xxx cannot be located with the specified prefix
--- a) 类中定义的方法不是 public static 的方法
b) 类中的方法名称和jsp自带的标签元素冲突，重名等