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In-depth understanding of the core knowledge points of JSP syntax structure

王林
王林Original
2024-01-31 15:35:061181browse

In-depth understanding of the core knowledge points of JSP syntax structure

JSP syntax structure: core knowledge point analysis

JSP (JavaServer Pages) is a server-side scripting language used to create dynamic web pages. The JSP syntax structure is simple and easy to learn, but it is powerful and can meet various complex web development needs.

1. JSP page structure

A JSP page usually consists of the following parts:

  • Directives: Directives Used to tell the JSP container how to process the page. Common instructions are:

    • : used to set the properties of the page, such as page encoding, content type, etc.
    • : used to include another JSP page.
    • : used to import JSP tag library.

  • Script Elements: Script elements are used to embed Java code in JSP pages. Common script elements are:

    • <script></script>: used to write Java code blocks.
    • : used to write Java expressions.
    • : Used to output the results of Java expressions.

  • JSP Tags: JSP tags are used to insert dynamic content into JSP pages. Common JSP tags are:

    • <if></if>: used to determine whether the condition is true.
    • <foreach></foreach>: used to traverse the collection.
    • <out></out>: used to output content.
  • HTML code: HTML code is used to create static content in JSP pages.

2. JSP instructions

JSP instructions are used to tell the JSP container how to process the page. Common JSP instructions are:

  • : used to set the properties of the page, such as page encoding, content type, etc. 
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
  • : Used to include another JSP page. 
<%@ include file="header.jsp" %>
  • : used to import JSP tag library. 
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

3. JSP script element

JSP script element is used to embed Java code in JSP pages. Common JSP script elements are:

  • <script></script>: used to write Java code blocks. 
<script>
    int sum = 1 + 2;
    out.println("The sum is: " + sum);
</script>
  • : Used to write Java expressions. 
<%
    int sum = 1 + 2;
%>
  • : Used to output the results of Java expressions. 
<%= 1 + 2 %>

4. JSP tag

JSP tag is used to insert dynamic content in JSP pages. Common JSP tags are:

  • <if></if>: used to determine whether the condition is true. 
<c:if test="${user != null}">
    Welcome, ${user.name}!
</c:if>
  • <foreach></foreach>: Used to traverse the collection. 
<c:forEach var="item" items="${items}">
    <li>${item}</li>
</c:forEach>
  • <out></out>: Used to output content. 
<c:out value="${user.name}" />

5. HTML code

HTML code is used to create static content in JSP pages. 

<!DOCTYPE html>
<html>
<head>
    <title>My JSP Page</title>
</head>
<body>
    <h1>Hello, world!</h1>
</body>
</html>

6. JSP code example

The following is a simple JSP code example:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>



    My JSP Page


    
Hello, world!

    <%
        int sum = 1 + 2;
        out.println("The sum is: " + sum);
    %>

This JSP code example will output the following:

<!DOCTYPE html>
<html>
<head>
    <title>My JSP Page</title>
</head>
<body>
    <h1>Hello, world!</h1>
    The sum is: 3
</body>
</html>

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