Jakarta Standard Tag Library API Frequently Asked Questions (Frequently Asked Questions Regarding Jakarta Standard Tag Library API

Jakarta Standard Tag Library (JSTL) is a standard library for the general task on the JSP (Javaseerver Pages) page.It provides a set of JSP tags to simplify and enhance the development of JSP pages, including common tasks such as cycle, condition control, and formatting output.The following is a common answer about Jakarta Standard Tag Library API. Question 1: What is JSTL? Answer: JSTL is a standard label library for simplifying and enhancing the development of JSP pages.It includes core label libraries, formatting tag libraries (FMT), database access label library (SQL) and XML tag library (XML). Question 2: How to use JSTL? Answer: To use JSTL, first of all, you need to introduce related JSTL jar files in the project.Then use the JSTL label on the JSP page to reference different label libraries through the tag front.For example, use the Core label library Foreach tag: jsp <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> ... <c:forEach items="${users}" var="user"> <tr> <td>${user.name}</td> <td>${user.email}</td> </tr> </c:forEach> Question 3: What are the commonly used labels of the core label library of JSTL? Answer: The core label library of JSTL includes labels such as commonly used cycles, conditions (IF, Choose), output (out), and URL jumps (Redirect).These tags provide the main control structure and data display function. Question 4: How to judge and select execution? Answer: JSTL provides `<C: if>` labels for conditional judgment, which can determine whether the corresponding content can be performed according to the results of the expression.At the same time, you can use `<C: Choose>` and `<C: WHEN>` `tags to implement multiple conditions.The following is an example: jsp <c:choose> <c:when test="${age >= 18}"> <p> Adults </p> </c:when> <c:otherwise> <p> Minor </p> </c:otherwise> </c:choose> Question 5: How to traverse the collection or array? Answer: Using JSTL's Foreach tag can traverse a collection or array and perform corresponding content for each element.For example: jsp <c:forEach items="${users}" var="user"> <p>${user.name}</p> </c:forEach> Question 6: Does JSTL support internationalization and formatting? Answer: Yes, JSTL provides formatting tag library (FMT) for internationalization and formatting operations.You can use the language environment of different areas to set the language environment in different areas, and use the labels such as `Form: Formatdate>` and `<FMT: Formatnumber>` to format the date and numbers. Question 7: What other common functions are there in the JSTL tag library? Answer: In addition to the core and formatting label library, the JSTL also includes the database access label library (SQL) and XML tag library (XML).The database access label library provides support for adding, delete, modified, and checked the database. The XML label library provides the function of processing and conversion of XML data. The above is a common answer about Jakarta Standard Tag Library API. I hope to help you better understand and use JSTL.If you have more questions, please refer to the official documentation or search for relevant information.