Jakarta Standard Tag Library API Quick Start Guide

Jakarta Standard Tag Library is a technology used to simplify page development in Java Web applications.JSTL provides a series of labels that can be used to operate data, control processes, and formatting.This article will provide you with a fast entry guide for Jakarta Standard Tag Library API, and use the Java code example to help you better understand. Jstl classification JSTL can be divided into four main label libraries: core label library (Core), formatting tag library (FMT), XML tag library (XML), and SQL tag library (SQL).Each label library provides a set of specific tags, which can be selected and applied as needed. Quick Getting Started Guide The following is the fast entry step of JSTL: Step 1: Download and add JSTL library First, you need to download the JSTL library file from the Apache official website.Once the download is completed, unzip the file and add the jar file to the class path of your Java Web application.This can be implemented by copying jar files to the "Web-INF/Lib" folder. Step 2: Introduce the label library At the top of the JSP page, you need to use the Taglib instruction to introduce the corresponding label library. <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> This is an example of introducing the core label library.You can specify a different name for the label library by changing "Prefix". Step 3: Use the JSTL tag Once the label library is introduced, you can use JSTL labels on the JSP page.The following is a simple example of using the core label library: html <c:set var="name" value="Java"> <c:if test="${name eq 'Java'}"> <p>Welcome to the world of Java!</p> </c:if> <c:forEach items="${languages}" var="language"> <p>${language}</p> </c:forEach> In the above example, we first use the <C: Set> tag to set a variable called "name" to "Java".Then, in the <C: If> tag, we check whether this variable is equal to "java".If it is true, we will output a welcome message.Finally, in the <c: Foreach> tag, we traversed a collection called "Languages" and output each element. By using different labels and expressions, you can handle data, conditional judgments, and iterative sets of data. Step 4: Run web application After completing the above steps, you can deploy the JSP page to any compatible Java Web container and visit the page in the browser.The JSTL label will be parsed and executed on the server side, and the corresponding HTML code will eventually generate. Java Code Examples The following is a simple Java code example to demonstrate how to use the JSTL API in Java: import javax.servlet.jsp.JspException; import javax.servlet.jsp.JspWriter; import javax.servlet.jsp.tagext.SimpleTagSupport; public class HelloWorldTag extends SimpleTagSupport { @Override public void doTag() throws JspException { JspWriter out = getJspContext().getOut(); try { out.println("Hello, World!"); } catch (IOException e) { e.printStackTrace(); } } } This is a simple custom tag called HelloWorldTag, which expands the SimpletagSupport class.In the dotag () method, we obtained the JSPWriter object and output the news of "Hello, World!". This is just the basic entry guide and example of JSTL.By learning more JSTL tags and APIs, you will be able to better use this powerful technology to simplify your Java Web application development.