Basic knowledge of jsp and El expressions, and jspel expressions

Basic knowledge of jsp and El expressions, and jspel expressions
1. jsp BASIC script and syntax format

Jsp script <% String name = "Tubo"; // java code %> jsp expression <% = name %>

2. jsp execution Principle

Jsp execution principle:

1) a jsp file -? Translate into a Java file -? _ 01_hello.java

2) Compile: a java file is compiled into a class file.

3) Call method: tomcat execute _ jspService (): jsp service method

3. Nine built-in jsp objects

PageContext // jsp context Object HttpRequest // request Object HttpSession // session Object (session) ServletContext // application Page // Object Throwable // exception JspWriter // outServletConfig // config

4. EL built-in object

PageContext -- not only the built-in objects in EL, but also the built-in jsp object pageScoperquestScopesessionScopeapplicationScopeparam. the built-in object for obtaining parameters <% String name = "Tubo"; % >$ {param ['name']}

5. jstl Technology

Use of jstl: You must import jar packages -- jstl-1.2.jar-to use these labels

<% @ Taglib uri = "https://java.sun.com/jstl/core" prefix = "c" %> // uri is the file ending with tld associated with the jar package
 
  
Content here
 // The prefix is
 
  
Content here
 

 
  
Page --> page domain request-> request domain session-> session domain application-> application domain
 

 
  
// When the boolean Type in test is true, the statement or code here is executed.
 

 
  
   
// Logic code
  
  
   
// Logic code