jstl教程

JavaServer Pages标准标记库（JSTL）是一个有用的JSP标签的集合，它封装了许多JSP应用程序通用的核心功能。

JSTL支持常见的，结构性任务，如迭代和条件，标签为操纵XML文件，国际化标签和SQL标签。它还提供了一个框架，将现有的自定义标签和JSTL标签。

JSTL标签进行分类，根据其功能分为以下，可用于创建一个JSP页面时，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：

要使用JSTL库，要在每一个JSP的顶部，使用该库必须包括一个<taglib>指令。

核心组的标签是最常用的JSTL标签。以下是在您的JSP的语法包括JSTL核心库：

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

有以下核心JSTL标签：

Tag	Description
<c:out >	和<%= ... >标签一样功能, 但对于表达式。
<c:set >	设置表达式求值的结果在一个'范围'
<c:remove >	删除一个范围的变量（从一个特定的范围内，如果已指定）。
<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

使用JSTL格式标签来格式化和显示文本，日期，时间和数字的，国际化的网站。以下是在您的JSP的语法，包括格式化库：

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

以下是格式化JSTL标签列表：

Tag	Description
<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标签库标签可以交互关系型数据库（如Oracle，MySQL或Microsoft SQL Server的关系数据库管理系统）。

以下是在您的JSP语法包括JSTL SQL库：

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

以下是SQL JSTL标签的列表：

Tag	Description
<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 XML标记提供了一种创建和操作XML文档的JSP为中心的方式。以下是在您的JSP的语法包括JSTL XML库。

JSTL XML标记库具有自定义标签与XML数据交互。这包括XML解析，转换XML数据，流控制，基于XPath表达式。

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

在继续之前的例子中，将需要复制下面的两个XML和XPath相关的库到<Tomcat安装目录> 的lib目录：

以下是XML JSTL标签列表：

Tag	Description
<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包括一些标准功能，其中大部分是常见的字符串操作函数。以下是在JSP的语法包函JSTL函数库：

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

以下是JSTL函数列表：

Function	Description
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.