Java Enterprise-level development--jsp,el,jstl (14)

Three, El expression language

EL full name is Expression Language. An expression language. Jsp2.0 was introduced after the

El main role: substitution: <%=%> out.print ();

Get data: The most common is to get data from 4 domain objects (page,request,session,application (ServletContext)).

El expressions are primarily used to replace script expressions <%=%>in JSP pages to retrieve from various types of Web domains Java objects, fetching data. (objects in a web domain, accessing JavaBean properties, accessing the list collection, accessing the map collection, accessing an array)

Main replacement <%=%>

Perform the operation:

The EL expression allows you to perform some basic relational, logical, and arithmetic operations on a JSP page to accomplish some simple logic operations in a JSP page. ${user==null}

Get Web Development Common objects

EL expressions define implicit objects that make it easy for web developers to get a reference to a common Web object to get the data in those objects.

Calling the Java method

The EL expression allows the user to develop a custom El function that invokes a method of the Java class through an El expression in a JSP page.

Java Enterprise-level development--jsp,el,jstl (14)