JSP - JSTL 如何自定义标签库
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
1
|
<%@ taglib prefix=
"c"
uri=
"http://java.sun.com/jsp/jstl/core
"
%>
|
2
|
<%@ 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
02
|
public
class
MyFunctions {
|
04
|
public
static
String sayHello(String name) {
|
05
|
return
"Hello "
+ name;
|
09
|
public
class
MyFunctions {
|
11
|
public
static
String sayHello(String name) {
|
12
|
return
"Hello "
+ name;
|
myfunctions.tld
自定义标签
Xml代码
01
|
<?
xml
version
=
"1.0"
encoding
=
"UTF-8"
?>
|
03
|
<
taglib
xmlns
=
"http://java.sun.com/xml/ns/j2ee
"
|
04
|
xmlns:xsi
=
"http://www.w3.org/2001/XMLSchema-instance
"
|
05
|
xsi:schemaLocation
=
"http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd
"
|
08
|
<
description
>my functions library</
description
>
|
09
|
<
display-name
>my functions</
display-name
>
|
10
|
<
tlib-version
>1.0</
tlib-version
>
|
11
|
<
short-name
>my</
short-name
>
|
12
|
<
uri
>http://www.bjsxt.com/functions</
uri
>
|
15
|
<
name
>sayHello</
name
>
|
16
|
<
function-class
>com.bjsxt.struts.MyFunctions</
function-class
>
|
17
|
<
function-signature
>java.lang.String sayHello(java.lang.String)</
function-signature
>
|
21
|
<?
xml
version
=
"1.0"
encoding
=
"UTF-8"
?>
|
23
|
<
taglib
xmlns
=
"http://java.sun.com/xml/ns/j2ee
"
|
24
|
xmlns:xsi
=
"http://www.w3.org/2001/XMLSchema-instance
"
|
25
|
xsi:schemaLocation
=
"http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-jsptaglibrary_2_0.xsd
"
|
28
|
<
description
>my functions library</
description
>
|
29
|
<
display-name
>my functions</
display-name
>
|
30
|
<
tlib-version
>1.0</
tlib-version
>
|
31
|
<
short-name
>my</
short-name
>
|
32
|
<
uri
>http://www.bjsxt.com/functions</
uri
>
|
35
|
<
name
>sayHello</
name
>
|
36
|
<
function-class
>com.bjsxt.struts.MyFunctions</
function-class
>
|
37
|
<
function-signature
>java.lang.String sayHello(java.lang.String)</
function-signature
>
|
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
01
|
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
|
02
|
<%@ taglib uri="http://www.bjsxt.com/functions
" prefix="my" %>
|
05
|
request.setAttribute("name", "David");
|
08
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
11
|
<
title
>testTemplate</
title
>
|
17
|
<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
|
18
|
<%@ taglib uri="http://www.bjsxt.com/functions
" prefix="my" %>
|
21
|
request.setAttribute("name", "David");
|
24
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
|
27
|
<
title
>testTemplate</
title
>
|
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
03
|
<
taglib-uri
>www.bjsxt.com/functions</
taglib-uri
>
|
04
|
<
taglib-location
>/WEB-INF/my.tld</
taglib-location
>
|
09
|
<
taglib-uri
>www.bjsxt.com/functions</
taglib-uri
>
|
10
|
<
taglib-location
>/WEB-INF/my.tld</
taglib-location
>
|
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