JSP标准标记库（JSTL）教程

发布于 2015-08-17 14:47:29 | 235 次阅读 | 评论: 0 | 来源: 网络整理

在JSP标准标记库（JSTL）是很有用的JSP标签的集合，它封装常见的许多JSP应用程序的核心功能。

JSTL具有如迭代和条件，标签为操纵XML文档，国际化标签，和SQL标签常见，结构任务的支持。它还提供了集成现有的自定义标签与JSTL标记框架。

JSTL标记可以进行分类，根据其功能，进入下面可以创建一个JSP页面时，可以使用JSTL标签库组：

安装JSTL库：

如果您使用的是Apache Tomcat容器，那么按照下面两个简单的步骤：

从Apache标准标签库下载二进制分发和解压的压缩文件。
若要从Jakarta Taglibs中使用的标准标签库，只需在分布的'lib'目录复制JAR文件到您的应用程序的webappsROOTWEB-INFlib目录中。

使用任何库，必须包括<taglib>指令在每个JSP中使用该库的顶部。

标签的核心小组是最常用的JSTL标记。以下是语法包括JSTL core库在JSP：


<%@ taglib prefix="c" 
           uri="http://java.sun.com/jsp/jstl/core" %>

有以下核心JSTL标签：

标签	描述
<c:out >	Like <%= ... >, but for expressions.
<c:set >	Sets the result of an expression evaluation in a 'scope'
<c:remove >	Removes a scoped variable (from a particular scope, if specified).
<c:catch>	Catches any Throwable that occurs in its body and optionally exposes it.
<c:if>	Simple conditional tag which evalutes its body if the supplied condition is true.
<c:choose>	Simple conditional tag that establishes a context for mutually exclusive conditional operations, marked by <when> and <otherwise>
<c:when>	Subtag of <choose> that includes its body if its condition evalutes to 'true'.
<c:otherwise >	Subtag of <choose> that follows <when> tags and runs only if all of the prior conditions evaluated to 'false'.
<c:import>	Retrieves an absolute or relative URL and exposes its contents to either the page, a String in 'var', or a Reader in 'varReader'.
<c:forEach >	The basic iteration tag, accepting many different collection types and supporting subsetting and other functionality .
<c:forTokens>	Iterates over tokens, separated by the supplied delimeters.
<c:param>	Adds a parameter to a containing 'import' tag's URL.
<c:redirect >	Redirects to a new URL.
<c:url>	Creates a URL with optional query parameters

在JSTL格式标签用于格式化和国际化的网站显示文本，日期，时间和数字。以下是语法，包括格式化库在JSP：


<%@ taglib prefix="fmt" 
           uri="http://java.sun.com/jsp/jstl/fmt" %>

以下是格式化的JSTL标签的列表：

标签	描述
<fmt:formatNumber>	To render numerical value with specific precision or format.
<fmt:parseNumber>	Parses the string representation of a number, currency, or percentage.
<fmt:formatDate>	Formats a date and/or time using the supplied styles and pattern
<fmt:parseDate>	Parses the string representation of a date and/or time
<fmt:bundle>	Loads a resource bundle to be used by its tag body.
<fmt:setLocale>	Stores the given locale in the locale configuration variable.
<fmt:setBundle>	Loads a resource bundle and stores it in the named scoped variable or the bundle configuration variable.
<fmt:timeZone>	Specifies the time zone for any time formatting or parsing actions nested in its body.
<fmt:setTimeZone>	Stores the given time zone in the time zone configuration variable
<fmt:message>	To display an internationalized message.
<fmt:requestEncoding>	Sets the request character encoding

JSTL的SQL标记库提供标签为关系型数据库（RDBMS），如Oracle，MySQL等，或Microsoft SQL Server进行交互。

以下是语法包括JSTL SQL库在JSP：


<%@ taglib prefix="sql" 
           uri="http://java.sun.com/jsp/jstl/sql" %>

以下是SQL JSTL标签的列表：

标签	描述
<sql:setDataSource>	Creates a simple DataSource suitable only for prototyping
<sql:query>	Executes the SQL query defined in its body or through the sql attribute.
<sql:update>	Executes the SQL update defined in its body or through the sql attribute.
<sql:param>	Sets a parameter in an SQL statement to the specified value.
<sql:dateParam>	Sets a parameter in an SQL statement to the specified java.util.Date value.
<sql:transaction >	Provides nested database action elements with a shared Connection, set up to execute all statements as one transaction.

JSTL的XML标记提供了创建和操作XML文档的JSP为中心的方式。以下是语法包括JSTL的XML库在JSP。

JSTL的XML标记库有自定义标签用于处理XML数据进行交互。这包括解析XML，转换XML数据，流程和基于XPath表达式控制。


<%@ taglib prefix="x" 
           uri="http://java.sun.com/jsp/jstl/xml" %>

在继续之前的例子，你需要下面的两个XML和XPath相关的库文件复制到您的<Tomcat安装目录> lib中：

以下是XML的JSTL标签列表：

标签	描述
<x:out>	Like <%= ... >, but for XPath expressions.
<x:parse>	Use to parse XML data specified either via an attribute or in the tag body.
<x:set >	Sets a variable to the value of an XPath expression.
<x:if >	Evaluates a test XPath expression and if it is true, it processes its body. If the test condition is false, the body is ignored.
<x:forEach>	To loop over nodes in an XML document.
<x:choose>	Simple conditional tag that establishes a context for mutually exclusive conditional operations, marked by <when> and <otherwise>
<x:when >	Subtag of <choose> that includes its body if its expression evalutes to 'true'
<x:otherwise >	Subtag of <choose> that follows <when> tags and runs only if all of the prior conditions evaluated to 'false'
<x:transform >	Applies an XSL transformation on a XML document
<x:param >	Use along with the transform tag to set a parameter in the XSLT stylesheet

JSTL包含了一些标准函数，其中大部分是常用的字符串操作函数。以下是语法包括JSTL函数库在JSP：


<%@ taglib prefix="fn" 
           uri="http://java.sun.com/jsp/jstl/functions" %>

下面是JSTL函数的列表：

Function	描述
fn:contains()	Tests if an input string contains the specified substring.
fn:containsIgnoreCase()	Tests if an input string contains the specified substring in a case insensitive way.
fn:endsWith()	Tests if an input string ends with the specified suffix.
fn:escapeXml()	Escapes characters that could be interpreted as XML markup.
fn:indexOf()	Returns the index withing a string of the first occurrence of a specified substring.
fn:join()	Joins all elements of an array into a string.
fn:length()	Returns the number of items in a collection, or the number of characters in a string.
fn:replace()	Returns a string resulting from replacing in an input string all occurrences with a given string.
fn:split()	Splits a string into an array of substrings.
fn:startsWith()	Tests if an input string starts with the specified prefix.
fn:substring()	Returns a subset of a string.
fn:substringAfter()	Returns a subset of a string following a specific substring.
fn:substringBefore()	Returns a subset of a string before a specific substring.
fn:toLowerCase()	Converts all of the characters of a string to lower case.
fn:toUpperCase()	Converts all of the characters of a string to upper case.
fn:trim()	Removes white spaces from both ends of a string.