JSP——（JSTL标签库）

jstl：JSP标准标签库。主要提供一些标签简化JSP代码。这些标签都有特定的功能。

一，使用JSTL标签

• 第一步：引入jstl的jar包；

---

jstl-1.2.jar

standard-1.1.2.jar

---

• 第二步：在JSP页面使用taglib指令引入标签库文件；

核心标签库：http://java.sun.com/jsp/jstl/core 推荐前缀名：c

格式化标签库：http://java.sun.com/jsp/jstl/fmt 推荐前缀名：fmt

函数标签库：http://java.sun.com/jsp/jstl/functions 推荐前缀名：fn

<%@taglib uri="标签库的url" prefix="前缀名" %>

标签库的url自己指定的，可以是任意的url路径。

如果要访问jstl标签库的标签，必须要通过“前缀名”进行访问。而前缀名可以是任意名字。

---

• 第三步：在JSP页面中使用jstl标签。

通过查看jstl.jar/META-INF/xxx.tld，tld文件就是jstl标签定义文件。每一个标签库都有一个标签定义文件。比如核心标签库有一个c.tld文件。

<taglib xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">
  
  <description>JSTL 1.1 core librarydescription>
  
  <display-name>JSTL coredisplay-name>
  
  <tlib-version>1.1tlib-version>
  
  <short-name>cshort-name>
  
  <uri>http://java.sun.com/jsp/jstl/coreuri>

  
  <tag>
    
    <description>
        Catches any Throwable that occurs in its body and optionally
        exposes it.
    description>
    
    <name>catchname>
    
    <tag-class>org.apache.taglibs.standard.tag.common.core.CatchTagtag-class>
    
    <body-content>JSPbody-content>
    
    <attribute>
        
        <description>
Name of the exported scoped variable for the
exception thrown from a nested action. The type of the
scoped variable is the type of the exception thrown.
        description>
        
        <name>varname>
        
        <required>falserequired>
        
        <rtexprvalue>falsertexprvalue>
    attribute>
  tag>
taglib>

二，常用标签的使用

2.1 核心标签

• if标签：条件判断

	body...

• forEach标签：循环数组或集合

	${pageCope.属性名}

forEach标签遍历数组或集合的时候，它会把遍历出来的每一个元素都保存在pageContext域对象的属性中。属性名就是使用var来指定的。

注意：遍历Map集合的时候，遍历出来的每一个元素是一个Entry对象。

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.util.*" %>

<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<% 
	//String[] books = {"三国演义", "西游记", "红楼梦"};
	//pageContext.setAttribute("books", books);
	
	
	//List books = new ArrayList();
	//books.add("西游记");
	//books.add("海底总动员");
	//books.add("海底三万里");
	//pageContext.setAttribute("books", books);
	
	Map books = new HashMap();
	books.put("西游记", 99);
	books.put("海底总动员", 199);
	books.put("海底三万里", 79);
	pageContext.setAttribute("books", books);
%>







	
	
	
	
		<%-- ${pageScope.book.getKey()} --> ${pageScope.book.getValue()}
 --%>
		${pageScope.book.key} --> ${pageScope.book.value}

	
	
	

2.2 格式化标签

日期格式化标签：

日期模式与SimpleDateFormat对象所使用模式一样。

<%@ page language="java" import="java.util.*" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>

<%@taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt"%>
<% 
	Date d = new Date();
	pageContext.setAttribute("currentDate", d);
%>







	当前时间：	

2.3 函数标签

定义格式：

${fn:函数名（参数列表）}

函数可以在jstl文件下的/META-INF/fn.tld文件下查看。下面是该文件内容：

    
  JSTL 1.1 functions library
  JSTL functions
  1.1
  fn
  http://java.sun.com/jsp/jstl/functions

  
    
      Tests if an input string contains the specified substring.
    
    contains
    org.apache.taglibs.standard.functions.Functions
    boolean contains(java.lang.String, java.lang.String)
    
      <c:if test="${fn:contains(name, searchString)}">
    
  

  
    
      Tests if an input string contains the specified substring in a case insensitive way.
    
    containsIgnoreCase
    org.apache.taglibs.standard.functions.Functions
    boolean containsIgnoreCase(java.lang.String, java.lang.String)
    
      <c:if test="${fn:containsIgnoreCase(name, searchString)}">
    
  

  
    
      Tests if an input string ends with the specified suffix.
    
    endsWith
    org.apache.taglibs.standard.functions.Functions
    boolean endsWith(java.lang.String, java.lang.String)
    
      <c:if test="${fn:endsWith(filename, ".txt")}">
    
  

  
    
      Escapes characters that could be interpreted as XML markup.
    
    escapeXml
    org.apache.taglibs.standard.functions.Functions
    java.lang.String escapeXml(java.lang.String)
    
      ${fn:escapeXml(param:info)}
    
  

  
    
      Returns the index withing a string of the first occurrence of a specified substring.
    
    indexOf
    org.apache.taglibs.standard.functions.Functions
    int indexOf(java.lang.String, java.lang.String)
    
      ${fn:indexOf(name, "-")}
    
  

  
    
      Joins all elements of an array into a string.
    
    join
    org.apache.taglibs.standard.functions.Functions
    java.lang.String join(java.lang.String[], java.lang.String)
    
      ${fn:join(array, ";")}
    
  

  
    
      Returns the number of items in a collection, or the number of characters in a string.
    
    length
    org.apache.taglibs.standard.functions.Functions
    int length(java.lang.Object)
    
      You have ${fn:length(shoppingCart.products)} in your shopping cart.
    
  

  
    
      Returns a string resulting from replacing in an input string all occurrences
      of a "before" string into an "after" substring.
    
    replace
    org.apache.taglibs.standard.functions.Functions
    java.lang.String replace(java.lang.String, java.lang.String, java.lang.String)
    
      ${fn:replace(text, "-", "•")}
    
  

  
    
      Splits a string into an array of substrings.
    
    split
    org.apache.taglibs.standard.functions.Functions
    java.lang.String[] split(java.lang.String, java.lang.String)
    
      ${fn:split(customerNames, ";")}
    
  

  
    
      Tests if an input string starts with the specified prefix.
    
    startsWith
    org.apache.taglibs.standard.functions.Functions
    boolean startsWith(java.lang.String, java.lang.String)
    
      <c:if test="${fn:startsWith(product.id, "100-")}">
    
  

  
    
      Returns a subset of a string.
    
    substring
    org.apache.taglibs.standard.functions.Functions
    java.lang.String substring(java.lang.String, int, int)
    
      P.O. Box: ${fn:substring(zip, 6, -1)}
    
  

  
    
      Returns a subset of a string following a specific substring.
    
    substringAfter
    org.apache.taglibs.standard.functions.Functions
    java.lang.String substringAfter(java.lang.String, java.lang.String)
    
      P.O. Box: ${fn:substringAfter(zip, "-")}
    
  

  
    
      Returns a subset of a string before a specific substring.
    
    substringBefore
    org.apache.taglibs.standard.functions.Functions
    java.lang.String substringBefore(java.lang.String, java.lang.String)
    
      Zip (without P.O. Box): ${fn:substringBefore(zip, "-")}
    
  

  
    
      Converts all of the characters of a string to lower case.
    
    toLowerCase
    org.apache.taglibs.standard.functions.Functions
    java.lang.String toLowerCase(java.lang.String)
    
      Product name: ${fn.toLowerCase(product.name)}
    
  

  
    
      Converts all of the characters of a string to upper case.
    
    toUpperCase
    org.apache.taglibs.standard.functions.Functions
    java.lang.String toUpperCase(java.lang.String)
    
      Product name: ${fn.UpperCase(product.name)}
    
  

  
    
      Removes white spaces from both ends of a string.
    
    trim
    org.apache.taglibs.standard.functions.Functions
    java.lang.String trim(java.lang.String)
    
      Name: ${fn.trim(name)}
      
  

下面列举了一些常用函数：

• toLowerCase()：把字符串全部转换小写；
• toUpperCase()：把字符串全部转化大写；
• length()：截取字符串；
• substring()：截取字符串；

<%@ page language="java" import="java.util.*" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn"%>
<% 
	String name = "ChinaSoft";
	pageContext.setAttribute("name", name);
%>







	
	${fn:toLowerCase(name)}	

	
	${fn:toUpperCase(name)}	

	
	${fn:length(name)}	

	
	${fn:substring(name, 1, 5)}	

三，自定义标签

第一步：创建一个类，继承SimpleTagSupport

package com.eight.utils;

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

public class FormatDateTag extends SimpleTagSupport{
	

}

第二步：重写doTag方法。举例：创建修改时间格式标签

public class FormatDateTag extends SimpleTagSupport{
	Date date;

	@Override
	public void doTag() throws JspException, IOException {
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		if(date != null){
			String dateStr = sdf.format(date);
			// 把系统时间输出到JSP页面上
			this.getJspContext().getOut().write(dateStr);
		}
	}

	public Date getDate() {
		return date;
	}

	public void setDate(Date date) {
		this.date = date;
	}

}

第三步：在WEB-INF目录下创建一个 .tld文件，配置short-name和uri

<taglib xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">
    
  <description>JSTL 1.1 core librarydescription>
  <display-name>JSTL coredisplay-name>
  <tlib-version>1.1tlib-version>
  
  <short-name>lmcshort-name>
  
  <uri>/mytagsuri>

	
  <tag>
  	
    <name>formatDateTagname>
    
    <tag-class>com.eight.utils.FormatDateTagtag-class>
    <body-content>scriptlessbody-content>
    <attribute>
        
        <name>datename>
        
        <required>truerequired>
        
        <rtexprvalue>truertexprvalue>
    attribute>
  tag>
  
  <tag>
  	
    <name>statusname>
    
    <tag-class>com.eight.utils.StatusTagtag-class>
    <body-content>scriptlessbody-content>
    <attribute>
        <name>typename>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>statusname>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
  tag>
  

taglib>

第四步：在jsp页面引入自定义标签库：

<%@ page language="java" import="java.util.*,com.eight.beans.*" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="/mytags" prefix="lmc" %>

第五步：使用自定义标签

3.1 自定义分页标签

第一步：创建类

package com.eight.utils;

import java.io.IOException;
import java.text.SimpleDateFormat;

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

public class PageTag2 extends SimpleTagSupport{
	String url;
	String arg1Name;
	String arg1Value;
	String arg2Name;
	String arg2Value;
	Integer curPage;
	Integer totalPage;
	Integer total;
	
	@Override
	public void doTag() throws JspException, IOException {
		StringBuilder html = new StringBuilder("");
		//首页
		html.append("首页");
		//上一页
		html.append("上一页");
		//下一页
		html.append("下一页");
		//尾页
		html.append("尾页共");
		//其他
		html.append(total);
		html.append("条纪录，当前第");
		html.append(curPage);
		html.append("/");
		html.append(totalPage);
		html.append("页，每页5条纪录 ");
		
		this.getJspContext().getOut().write(html.toString());
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	

	public String getArg1Name() {
		return arg1Name;
	}

	public void setArg1Name(String arg1Name) {
		this.arg1Name = arg1Name;
	}

	public String getArg1Value() {
		return arg1Value;
	}

	public void setArg1Value(String arg1Value) {
		this.arg1Value = arg1Value;
	}

	public String getArg2Name() {
		return arg2Name;
	}

	public void setArg2Name(String arg2Name) {
		this.arg2Name = arg2Name;
	}

	public String getArg2Value() {
		return arg2Value;
	}

	public void setArg2Value(String arg2Value) {
		this.arg2Value = arg2Value;
	}

	public Integer getCurPage() {
		return curPage;
	}

	public void setCurPage(Integer curPage) {
		this.curPage = curPage;
	}

	public Integer getTotalPage() {
		return totalPage;
	}

	public void setTotalPage(Integer totalPage) {
		this.totalPage = totalPage;
	}

	public Integer getTotal() {
		return total;
	}

	public void setTotal(Integer total) {
		this.total = total;
	}
	
	

}

第二步：在 .tld上配置

<taglib xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">
    
  <description>JSTL 1.1 core librarydescription>
  <display-name>JSTL coredisplay-name>
  <tlib-version>1.1tlib-version>
  
  <short-name>lmcshort-name>
  
  <uri>/mytagsuri>

  
  <tag>
  	
    <name>statusname>
    
    <tag-class>com.eight.utils.StatusTagtag-class>
    <body-content>scriptlessbody-content>
    <attribute>
        <name>typename>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>statusname>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
  tag>
  
  <tag>
    <name>pagename>
    
    <tag-class>com.eight.utils.PageTag2tag-class>
    <body-content>scriptlessbody-content>
    <attribute>
        <name>urlname>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>arg1Namename>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>arg1Valuename>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>arg2Namename>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>arg2Valuename>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>curPagename>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>totalPagename>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
    <attribute>
        <name>totalname>
        <required>truerequired>
        <rtexprvalue>truertexprvalue>
    attribute>
  tag>

taglib>

第三步：在jsp页面上引用：