Jakarta Standard Tag Library API Frequently Asked Question (Frequently Asked Questions)

Jakarta Standard Tag Library (JSTL) is a standard label library for writing simple and maintainable code on the JSP page.It provides a series of labels and functions that can be used to process and display data, and simplify the development process of the JSP page.The following is a common answer about Jakarta Standard Tag Library API: Question 1: What is JSTL?What is its role? Answer: JSTL is the abbreviation of Jakarta Standard Tag Library.It is a standard labeling library for JavaseerVer Pages (JSP) technology, which provides a more concise and easier -maintaining way to process and display data for the JSP page.JSTL provides a series of labels and functions for common operations such as circulation, conditional judgment, and formatting dates, reducing the needs of writing a large number of Java code in JSP code, and improving development efficiency and code quality. Question 2: How to use JSTL in the project? Answer: To use JSTL in the project, you first need to add the dependencies of the JSTL library.We can introduce the JSTL library by adding the following dependencies to the construction file of the project: <dependency> <groupId>javax.servlet</groupId> <artifactId>jstl</artifactId> <version>1.2</version> </dependency> In the JSP page, we can use the ` %@ taglib %>` instruction to introduce the JSTL label library.For example, to introduce the core label library of JSTL, you can use the following instructions: jsp <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> After the label library is introduced, we can use JSTL labels and functions on the JSP page. Question 3: What core labels JSTL provides? Answer: The Core Tag Library of JSTL provides some commonly used tags and functions to control and process data.The following are several commonly used core tags: 1. `<C: FOREACH>`: It is used to cycle the collection or array, and perform the corresponding operation at each iteration. Example: jsp <c:forEach var="item" items="${myList}"> ${item} </c:forEach> 2. <C: if> `: Used to perform the corresponding branch according to the given conditions. Example: jsp <c:if test="${myVar > 10}"> Greater than 10 </c:if> <c:else> Less than equal to 10 </c:else> 3. <C: Choose> `,` <C: When> `and` <C: Otherwise> `: Used to achieve multiple conditional judgments. Example: jsp <c:choose> <c:when test="${myVar == 1}"> Equal to 1 </c:when> <c:when test="${myVar == 2}"> Equal to 2 </c:when> <c:otherwise> Not 1 nor 2 nor 2 </c:otherwise> </c:choose> Question 4: How does JSTL formatting the date? Answer: JSTL provides a function formatting function `<FMT: Formatdate>`, which can convert the date object in the specified format into a string. Example: jsp <%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %> <fmt:formatDate value="${myDate}" pattern="yyyy-MM-dd HH:mm:ss" /> This will convert the `mydate` object in the format of" Yyyy-MM-DD HH: MM: SS "to a string. The above is a common answer to Jakarta Standard Tag Library API.By using JSTL, developers can easily write simple and maintained code on the JSP page.Hope this article will help you!