标签库由三个部分组成:标签处理程序类(提供功能)、标签库描述符(TLD文件,描述标签并将标签与处理程序匹配)、标签库指示(放在JSP文件,通过它使用标签)
相应的,JSP提供三种接口可以利用:Tag,IterationTag和BodyTag,也可以利用TagSupport类或者BodyTagSupport类扩展
6、1 基本的使用方法
例子:显示时间
传统的方式是利用JavaBean分离数据
Time.java文件为:
package javabeans;
import java.text.SimpleDateFormat;
public class Time {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年M月d日HH点mm分ss秒");
String time = sdf.format(new java.util.Date());
public String getTime() {
return time;
}
}
index.jsp文件:
<%@page c%>
<html>
<head>
</head>
<body>
<jsp:useBean id="time" class="javabeans.Time" />
<jsp:getProperty name="time" property="time" />
</body>
</html>
但是网页的格式化信息难以有效的结合进行JavaBean中
package javabeans;
import java.text.SimpleDateFormat;
public class Time {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年M月d日HH点mm分ss秒");
String time = sdf.format(new java.util.Date());
public String getTime() {
StringBuffer result = new StringBuffer();
result.append("<span style = 'background-color: black;color: cyan;'>");
result.append(time);
result.append("</span>");
return result.toString();
}
}
事实上,JavaBean只负责数据,不仅可以给Web程序提供数据,还可以给其他诸如窗体程序提供数据,所以也不应该嵌入HTML的格式代码
利用标签可以完成该项任务
TimeTag文件为:
package taglib;
import javabeans.Time;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class TimeTag extends TagSupport {
Time time = new Time();
public int doEndTag() throws JspException {
try {
pageContext.getOut().print(
"<span style = 'background-color: black;color: cyan;'>");
pageContext.getOut().print(time.getTime());
pageContext.getOut().print("</span>");
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
}
注意:pageContext属性用于代表Web应用中的PageContext对象,它里面还有setAttribute方法和getAttribute方法可以保存和访问Web应用中的共享数据,两个方法都需要指定scope参数来说明属性存在的范围。这个属性不能在TagSupport构造函数中使用,因为此时还没初始化pageContext属性。除此外,还有一个parent属性代表嵌套了当前标签的上层标签的处理类,但是必须通过getParent方法获得引用
time.tld文件为:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.2</jspversion>
<shortname></shortname>
<uri></uri>
<info></info>
<tag>
<name>time</name>
<tagclass>taglib.TimeTag</tagclass>
</tag>
</taglib>
放入Web应用程序根目录
index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="time.tld"%>
<html>
<head>
</head>
<body>
<mytag:time />
</body>
</html>
注意:
1)如果time.tld文件不在当前目录,如在WEB-INF下,则可以换成:
<%@ taglib prefix="mytag" uri="../WEB-INF/time.tld" %>
2)这里直接使用实际uri,也可以使用web.xml进行路径转换
<jsp-config>
<taglib>
<taglib-uri>time</taglib-uri>
<taglib-location>/time.tld</taglib-location>
</taglib>
</jsp-config>
3)一般JSP容器先把uri作为路径进行查找,如不可行,则检查web.xml文件进行查找
此时的网页为:
<%@page c%>
<%@ taglib prefix="mytag" uri="time"%>
<html>
<head>
</head>
<body>
<mytag:time />
</body>
</html>
注意:可能由于Tomcat服务器缓存的原因,导致不能及时刷新,解决方法有:
1)让JSP不缓存方法网页头部加上
<%
response.setHeader("Pragma","No-cache");//HTTP 1.1
response.setHeader("Cache-Control","no-cache");//HTTP 1.0
response.setHeader("Expires","0");//防止被proxy
%>
2)修改conf/server.xml 文件Context path 中间加上 reloadable="true"
例如:<Context path="" docBase="E:\MYJSP\" debug="0" reloadable="true" />
6、2 标签类的方法
在标签处理程序类中,重要的是实现doStartTag()和doEndTag(),程序读到<mytag:time>开始部分,调用doStartTag(),程序读到</mytag:time>结束部分,调用doEndTag()
遇到开始标签,调用doStartTag(),返回值为EVAL_BODY_INCLUDE或是SKIP_BODY,前者将引起标签体的计算,后者不计算
遇到结束标签,调用doEndTag(),如是空标签也会执行,返回值为EVAL_PAGE和SKIP_PAGE,前者继续执行标签后的JSP代码,后者结束JSP网页的生成,直接将现有内容发向客户端
修改TimeTag.java文件:
package taglib;
import javabeans.Time;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class TimeTag extends TagSupport {
Time time = new Time();
public int doStartTag() throws JspException {
try {
pageContext.getOut().print("[");
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
public int doEndTag() throws JspException {
try {
pageContext.getOut().print(
"<span style = 'background-color: black;color: cyan;'>");
pageContext.getOut().print(time.getTime());
pageContext.getOut().print("</span>");
pageContext.getOut().print("]");
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
}
index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="time.tld"%>
<html>
<head>
</head>
<body>
<mytag:time>Some text</mytag:time>
</body>
</html>
再次修改TimeTag.java文件:
package taglib;
import javabeans.Time;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class TimeTag extends TagSupport {
Time time = new Time();
public int doStartTag() throws JspException {
try {
pageContext.getOut().print("[");
} catch (Exception e) {
throw new JspException(e.toString());
}
return SKIP_BODY;// 注意
}
public int doEndTag() throws JspException {
try {
pageContext.getOut().print(
"<span style = 'background-color: black;color: cyan;'>");
pageContext.getOut().print(time.getTime());
pageContext.getOut().print("</span>");
pageContext.getOut().print("]");
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
}
此时将忽略标签体的内容
再次修改TimeTag.java文件:
package taglib;
import javabeans.Time;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class TimeTag extends TagSupport {
Time time = new Time();
public int doStartTag() throws JspException {
try {
pageContext.getOut().print("[");
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
public int doEndTag() throws JspException {
try {
pageContext.getOut().print(
"<span style = 'background-color: black;color: cyan;'>");
pageContext.getOut().print(time.getTime());
pageContext.getOut().print("</span>");
pageContext.getOut().print("]");
} catch (Exception e) {
throw new JspException(e.toString());
}
return SKIP_PAGE;// 注意
}
}
index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="time.tld"%>
<html>
<head>
</head>
<body>
<mytag:time>Some text</mytag:time>
<%=new java.util.Date()%>
</body>
</html>
此时将忽略网页中后续代码的计算
总结:
EVAL_BODY_INCLUDE:把Body读入存在的输出流中,doStartTag()函数可用
EVAL_PAGE:继续处理页面,doEndTag()函数可用
SKIP_BODY:忽略对Body的处理,doStartTag()和doAfterBody()函数可用
SKIP_PAGE:忽略对余下页面的处理,doEndTag()函数可用
EVAL_BODY_TAG:已经废止,由EVAL_BODY_BUFFERED取代
EVAL_BODY_BUFFERED:申请缓冲区,由setBodyContent()函数得到的BodyContent对象来处理tag的body,如果类实现了BodyTag,那么doStartTag()可用,否则非法
6、3 标签的属性
6、3、1 利用页面变量传递属性(也被称为代码段变量,使用标签处理程序创建的变量被称为代码段变量)
修改标签文件为:
package taglib;
import javabeans.Time;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class TimeTag extends TagSupport {
Time time = new Time();
public int doEndTag() throws JspException {
try {
String fgColor = pageContext.getRequest().getParameter("fgColor");
String bgColor = pageContext.getRequest().getParameter("bgColor");
if (fgColor == null)
fgColor = "black";
if (bgColor == null)
bgColor = "white";
pageContext.getOut().print(
"<span style = 'background-color: " + bgColor + ";color: "
+ fgColor + ";'>");
pageContext.getOut().print(time.getTime());
pageContext.getOut().print("</span>");
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
}
index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="time.tld"%>
<html>
<head>
</head>
<body>
<mytag:time />
<form action="index.jsp" method="Post">前景色:<select name='fgColor'>
<option value="red" style="background-color: red">red</option>
<option value="blue" style="background-color: blue">blue</option>
<option value="cyan" style="background-color: cyan" selected>cyan</option>
<option value="black" style="background-color: black; color: white">black</option>
</select> <br>
背景色: <select name='bgColor'>
<option value="gray" style="background-color: gray; color: white">gray</option>
<option value="yellow" style="background-color: yellow">yellow</option>
<option value="black" style="background-color: black" selected>black</option>
<option value="white" style="background-color: white">white</option>
</select> <br>
<input type="submit" name="submit" value="确认"></form>
</body>
</html>
运行观察效果
http://localhost:8088/myweb/index.jsp?fgColor=yellow&bgColor=blue
6、3、2 利用标签属性
修改标签为:
package taglib;
import javabeans.Time;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class TimeTag extends TagSupport {
Time time = new Time();
String fgColor = "black";
String bgColor = "white";
public void setTime(Time time) {
this.time = time;
}
public void setFgColor(String fgColor) {
this.fgColor = fgColor;
}
public void setBgColor(String bgColor) {
this.bgColor = bgColor;
}
public int doEndTag() throws JspException {
try {
pageContext.getOut().print(
"<span style = 'background-color: " + bgColor + ";color: "
+ fgColor + ";'>");
pageContext.getOut().print(time.getTime());
pageContext.getOut().print("</span>");
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
}
相应的time.tld文件为:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.2</jspversion>
<shortname></shortname>
<uri></uri>
<info></info>
<tag>
<name>time</name>
<tagclass>taglib.TimeTag</tagclass>
<attribute>
<name>fgColor</name>
<rtexprvalue>true</rtexprvalue>
</attribute>
<attribute>
<name>bgColor</name>
<rtexprvalue>true</rtexprvalue>
</attribute>
</tag>
</taglib>
注意:rtexprvalue的全称是 Run-time Expression Value,表示是否可以在运行时动态生成属性值,默认为false
index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="time.tld"%>
<html>
<head>
</head>
<body>
<mytag:time fgColor="red" bgColor="yellow" />
</body>
</html>
6、4 IterationTag接口的使用
和Tag相似,能够重复计算标签组成的代码体。IterationTag通过扩展Tag实现doAfterBody来进行循环,它只有在doStartTag返回值为EVAL_BODY_INCLUDE后才调用,而且doAfterBody返回值为EVAL_BODY_AGAIN才进行下一轮循环,直至SKIP_BODY或者EVAL_BODY_INCLUDE才停止
标签类仍然可以使用TagSupport类扩展得到,如:
package taglib;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class IterationTag extends TagSupport {
private int count = 0;
private String[] strings = null;
public int doStartTag() {
strings = (String[]) pageContext.getAttribute("strings");
return EVAL_BODY_INCLUDE;
}
public int doAfterBody() throws JspException {
try {
pageContext.getOut().print(strings[count].toString() + "<br>");
} catch (Exception e) {
throw new JspException(e.toString());
}
count++;
if (count >= strings.length)
return SKIP_BODY;
return EVAL_BODY_AGAIN;
}
}
mytags.tld文件为:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.2</jspversion>
<shortname></shortname>
<uri></uri>
<info></info>
<tag>
<name>iteration</name>
<tagclass>taglib.IterationTag</tagclass>
</tag>
</taglib>
index.jsp文件为:
<%@page c%>
<%@ taglib prefix="iterator" uri="mytags.tld"%>
<html>
<head>
</head>
<body>
<h1>
<%
String[] str = new String[] { "Apple", "Banana", "Orange" };
pageContext.setAttribute("strings", str);
%> <iterator:iteration>The string is:</iterator:iteration></h1>
</body>
</html>
6、5 BodyTag接口
是三个标签接口中最大,最通用的接口,扩展了IterationTag接口,允许标签改变网页内容
6、6 通过TLD文件使用代码段变量
使用标签处理程序创建的对象称为代码段变量,与<jsp:useBean>和<scriptlet>创建的效果一样,但是更加简单方便,如标签创建的对象可以被合作标签使用和scriptlet使用
具体的使用方式是通过网页或者会话的参数属性来传递
6、6、1 一般的方法
标签为:
package taglib;
import javax.servlet.jsp.tagext.TagSupport;
public class DataSeedTag extends TagSupport {
public int doStartTag() {
String[] str = new String[] { "Apple", "Banana", "Orange" };
pageContext.setAttribute("strings", str);
return EVAL_PAGE;
}
}
mytags.tld文件为:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.2</jspversion>
<shortname></shortname>
<uri></uri>
<info></info>
<tag>
<name>array</name>
<tagclass>taglib.DataSeedTag</tagclass>
</tag>
</taglib>
index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>
<h1><mytag:array /> <%
String[] strings = (String[]) pageContext.getAttribute("strings");
%>There are <%=strings.length%> variables!
<p>
<%
for (int i = 0; i < strings.length; i++)
out.println("The value is " + strings[i] + "<P>");
%>
</h1>
</body>
</html>
6、6、2 使用代码段变量
修改mytags.tld文件为:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.2</jspversion>
<shortname></shortname>
<uri></uri>
<info></info>
<tag>
<name>array</name>
<tagclass>taglib.DataSeedTag</tagclass>
<variable>
<name-given>strings</name-given>
<variable-class>java.lang.String [] </variable-class>
<declare>true</declare>
<scope>AT_END</scope>
</variable>
</tag>
</taglib>
注意:tld文件中使用了<variable>子元素来定义代码段变量,使得下面的JSP文件的变量声明可以省略。文件中的各个元素说明如下:
<name-given>名称
<variable-class>类型
<declare>判断代码段变量是新定义的(true)还是已经存在的(false,前面的网页中已经声明过)
<scope>定义代码段的使用范围,AT_BEGIN表示在起始标签处创建代码段变量,AT_END表示在结束标签处创建代码段变量,NESTED表示代码段变量只在自定义标签的起始标签和结束标签之间有效
修改index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>
<h1><mytag:array />There are <%=strings.length%> variables!
<p>
<%
for (int i = 0; i < strings.length; i++)
out.println("The value is " + strings[i] + "<P>");
%>
</h1>
</body>
</html>
注意:此时无需获取strings变量,可以直接使用
再次修改标签文件为:
package taglib;
import javax.servlet.jsp.tagext.TagSupport;
public class DataSeedTag extends TagSupport {
public int doStartTag() {
String[] str = new String[] { "Apple", "Banana", "Orange" };
pageContext.setAttribute("strings", str);
pageContext.setAttribute("length",new Integer(str.length));
return EVAL_PAGE;
}
}
修改mytags.tld文件,增加为:
<variable>
<name-given>length</name-given>
<variable-class>java.lang.Integer</variable-class>
<declare>true</declare>
<scope>NESTED</scope>
</variable>
修改index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>
<h1><%--Total:<%=length%><P>--%> <mytag:array>The string length is <%=length%></mytag:array>
</h1>
</body>
</html>
注意:
1)如果将注释去除则会异常
2)如果使用一般的注释也会异常,如<!--和-->,因为<%--和--%>注释编译后在servlet中看不见
此时观察JSP生成的Servlet源码会看到内容,如:
out.write("<!--Total:");
out.print(length);
out.write("<P>-->\r\n");
6、6、3 例子
1)一个结合循环标签和代码段变量的例子
增加循环标签为:
package taglib;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class IterationTag extends TagSupport {
private int index = 0;
private String[] strings = null;
public int doStartTag() {
strings = (String[]) pageContext.getAttribute("strings");
pageContext.setAttribute("current", strings[index]);
pageContext.setAttribute("index", new Integer(index));
return EVAL_PAGE;
}
public int doAfterBody() throws JspException {
index++;
if (index >= strings.length)
return SKIP_BODY;
pageContext.setAttribute("current", strings[index]);
pageContext.setAttribute("index", new Integer(index));
return EVAL_BODY_AGAIN;
}
}
修改mytags.tld文件为:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.2</jspversion>
<shortname></shortname>
<uri></uri>
<info></info>
<tag>
<name>iteration</name>
<tag-class>taglib.IterationTag</tag-class>
<variable>
<name-given>current</name-given>
<variable-class>java.lang.String</variable-class>
<declare>true</declare>
<scope>NESTED</scope>
</variable>
<variable>
<name-given>index</name-given>
<variable-class>java.lang.Integer</variable-class>
<declare>true</declare>
<scope>NESTED</scope>
</variable>
</tag>
<tag>
<name>array</name>
<tag-class>taglib.DataSeedTag</tag-class>
<variable>
<name-given>strings</name-given>
<variable-class>java.lang.String [] </variable-class>
<declare>true</declare>
<scope>AT_END</scope>
</variable>
</tag>
</taglib>
修改index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>
<h1><mytag:array></mytag:array> <mytag:iteration>
The string is: <%=current%> at <%=index%><p>
</mytag:iteration></h1>
</body>
</html>
2)完全使用标签的改进例子
增加标签IndexTag为:
package taglib;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class IndexTag extends TagSupport {
public int doEndTag() throws JspException {
int index = ((Integer) (pageContext.getAttribute("index"))).intValue();
try {
pageContext.getOut().print(index);
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
}
增加标签TextTag为:
package taglib;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class TextTag extends TagSupport {
public int doEndTag() throws JspException {
String current = (String) (pageContext.getAttribute("current"));
try {
pageContext.getOut().print(current);
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
}
修改mytags.tld文件为:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.2</jspversion>
<shortname></shortname>
<uri></uri>
<info></info>
<tag>
<name>iteration</name>
<tag-class>taglib.IterationTag</tag-class>
</tag>
<tag>
<name>array</name>
<tag-class>taglib.DataSeedTag</tag-class>
</tag>
<tag>
<name>array.index</name>
<tag-class>taglib.IndexTag</tag-class>
</tag>
<tag>
<name>array.text</name>
<tag-class>taglib.TextTag</tag-class>
</tag>
</taglib>
修改index.jsp文件为:
<%@page c%>
<%@ taglib prefix="mytag" uri="mytags.tld"%>
<html>
<head>
</head>
<body>
<h1><mytag:array /> <mytag:iteration>
The string is:<mytag:array.text /> at <mytag:array.index />
<p>
</mytag:iteration></h1>
</body>
</html>
6、7 标签库的JAR文件
具体做法:
1)生成标签类
package taglib;
import java.text.SimpleDateFormat;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.TagSupport;
public class TimeTag extends TagSupport {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy年M月d日HH点mm分ss秒");
String time = sdf.format(new java.util.Date());
public int doEndTag() throws JspException {
try {
pageContext.getOut().print(
"<span style = 'background-color: black;color: cyan;'>");
pageContext.getOut().print(time);
pageContext.getOut().print("</span>");
} catch (Exception e) {
throw new JspException(e.toString());
}
return EVAL_PAGE;
}
}
2)生成标签的TLD文件(如mytags.tld),确保里面有<uri>http://www.njmars.net</uri>节点,并将此文件放入META-INF目录下
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN" "http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1.dtd">
<taglib>
<tlibversion>1.0</tlibversion>
<jspversion>1.2</jspversion>
<shortname></shortname>
<uri>http://www.njmars.net</uri>
<info></info>
<tag>
<name>time</name>
<tag-class>taglib.TimeTag</tag-class>
</tag>
</taglib>
3)将完整的标签类包文件和tld文件复制到其他工作目录下,命令提示符下使用指令:
jar cvf time.jar taglib/*.class META-INF/mytags.tld
4)新建其他Web应用程序,将jar文件放入当前应用程序的WEB-INF\lib文件夹下
相应的index.jsp网页为:
<%@page c%>
<%@ taglib prefix="mytags" uri="http://www.njmars.net"%>
<html>
<head>
</head>
<body>
<h1><mytags:time/></h1>
</body>
</html>
注意:<%@ taglib prefix="mytags" uri="http://www.njmars.net"%>中的uri既非真实路径,也非web.xml中的信息,而是tld文件中的<uri>信息
6、8 JSP2.0提供的TAG标签定义方法
也被称为Simple Tag,它继承的类为SimpleTagSupport
1)新建WEB-INF/tags目录,新建hello.tag文件,内容为:
<table border="1">
<tr><td>Hello! World!</td></tr>
</table>
2)新建index.jsp文件为:
<%@page c%>
<%@taglib prefix="demo" tagdir="/WEB-INF/tags"%>
<html>
<body>
<demo:hello />
</body>
</html>
注意:
在Tag File中也可以使用out、config、request、response、session、application、jspContext等对象,如:
<table border="1">
<tr>
<td>
<%
java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat(
"yyyy年M月d日HH点mm分ss秒");
String time = new String(sdf.format(new java.util.Date()).getBytes(
"ISO-8859-1"), "GBK");
out.print("<span style = 'background-color: black;color: cyan;'>");
out.print(time);
out.print("</span>");
%></td>
</tr>
</table>
此时可能要修改Eclipse的JSP Tag Definition默认字符集
[此贴子已经被作者于2010-11-25 10:26:22编辑过]