Jakarta Standard Tag Library API Introduction Tutorial
Jakarta Standard Tag Library (JSTL) API entry tutorial
Overview:
Jakarta Standard Tag Library (JSTL) is a standard label library on the Java platform for simplifying the development of JSP pages.JSTL provides a set of commonly used labels and functions to make the JSP page more concise and maintenance.This tutorial will introduce the basic concepts and usage of JSTL API and provide some Java code examples.
1. JSTL API Introduction
JSTL API contains many labels and functions to handle various common tasks, such as logical control, iteration, formatting, and internationalization.The JSTL API is published as part of the JSP specification, so it can be used without additional configuration.To use JSTL API, you only need to add the related jar file to your project.
2. JSTL tag
The JSTL label is used to perform various tasks on the JSP page.Here are some commonly used JSTL tags:
-` <C: if> `: Used to perform conditional judgments, control the display and hiding of the page according to the results of the expression.
-`<C: Foreach>`: For iterative collection or array, the same code block can be generated on the page.
-`<C: Choose>` and `<C: WHEN>`: It is used to achieve multi -branch conditional judgment and execute the corresponding code block according to the conditions.
-` <C: set> `: It is used to set the value of a variable and can be used in subsequent code.
3. JSTL function
In addition to labels, the JSTL API also provides some practical functions to perform various operations.Here are some commonly used JSTL functions:
-` Fn: LENGTH () `: The length of the collection or string is obtained.
-` Fn: Substring () `: Used to intercept part of the string.
-` Fn: Touppercase () and `Fn: TOLOWERCASE ()`: It is used to convert the string into uppercase or lowercase.
-` FMT: Formatnumber () `: For formatting numbers.
-` FMT: Bundle`: Used to load the value in the international resource package to the JSP page.
4. JSTL example
Below is a simple example of using JSTL API:
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
<html>
<head>
<Title> JSTL Example </Title>
</head>
<body>
<c:if test="${num > 0}">
<H1> This is a positive number!</h1>
</c:if>
<c:forEach var="item" items="${list}">
<p>${item}</p>
</c:forEach>
<fmt:formatNumber value="${price}" type="currency" currencyCode="USD" var="formattedPrice" />
<p> Price: $ {formattedprice} </p>
</body>
</html>
In the above example, we use the `<C: if>` tag to determine whether the title is displayed based on the value of the `num` variable.Use the `<C: Foreach>` tags to traverse the `List` collection, and display each element as the` <p> `paragraph.Finally, we use the `fmt: formatnumber>` tag to format the `Price` variable into a currency format, and store the result in the` FormattedPrice` variable.
This is just a simple example. The JSTL API also provides many other labels and functions, which can be used according to actual needs.
Through the above entry tutorial, you should have a basic understanding of the Jakarta Standard Tag Library (JSTL) API.You can continue to learn the advanced characteristics and more usage of the JSTL API to improve the development efficiency and maintenance of the JSP page.I wish you success in JSTL's learning and use!
