JSP Standard Tag Library (JSTL) Principles commonly used in Java development
JSP Standard Tag Library (JSTL) is a commonly used technology in Java development. It is used to perform some common logical operations on the JSP page, such as cycle, conditional judgment, and formatting date.JSTL provides a more concise and more readable way by introducing a set of labels to handle these logical operations.
JSTL consists of four core libraries, namely the core label library (Core), formatting tag library (FMT), XML tag library (XML) and SQL tag library (SQL).Each library contains a set of labels that can be used for different purposes.
The principle of JSTL is to introduce the label of the label library to the JSP page by introducing the statement of the label library.These tags are translated into standard Java code during the compilation and execution, thereby achieving corresponding logical operations.
The following is a simple example, demonstrating the use of the core label library in JSTL:
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<Title> Use JSTL Example </Title>
</head>
<body>
<c: set var = "name" value = "alice" /> <!-Set a variable->
<c: if test = "$ {name eq 'alice'}"> <!-Condition judgment->
<p>Welcome, ${name}!</p>
</c:if>
<c: FOREACH VAR = "I" begin = "1" END = "5"> <!-Cycle->
<p>Number: ${i}</p>
</c:forEach>
</body>
</html>
In the above example, first pass the JSTL core label library through ` %@ taglib prefix =" c "uri =" http://java.sun.com/jsp/jstl/core " %>` `` `` `` `` `` `` `` sentences introduced JSTL core tag libraries.Then use the `<C: Set>` tag to set a variable called `name`, which is` Alice`.Then use the `<C: if>` tag for conditional judgment. If the value of the `name` is equal to` alice`, the welcome message is displayed.Finally, use the `<C: Foreach> label to circulate, and output the variable` I` from 1 to 5.
By using JSTL, we can abstract some common logical operations, making the code of the JSP page more concise and easy to read.This can not only improve development efficiency, but also make the code easier to maintain and modify.
To sum up, JSTL is a commonly used technology in Java development. By introducing the label library, it provides a simple and highly readable way to handle common logical operations.Its principle is to translate labels to java code during compilation and execution.By learning and using JSTL, we can better develop and maintain the JSP page.
