Introduction:-
The Spring Expression Language is a powerful expression language that supports
querying and manipulating an object graph at runtime. SpEL
expressions can be used with XML or annotation based configuration
metadata for defining BeanDefinitions. In both cases the syntax to define the
expression is of the form:
#{ <expression string>
There are several existing expression languages like MVEL, OGNL and
JBoss EL. Every EL is developed with some purpose in mind. SpEL is created
to help the Spring porfolio products. The syntax used for the SpEL is same like
Unified EL.
SpEL serves as the foundation for expression evaluation within the Spring
portfolio, it is not directly tied to Spring and can be used independently. In
order to be self contained, many of the examples in this chapter use SpEL as if
it were an independent expression language. This requires creating a few
bootstrapping infrastructure classes such as the parser.
Another advantage of SpEL is it can work independently without
depending on the Spring environment. In the following sections, you will read
the complete details on SpEL API and Features the Spring Expression Language.
SpEL API:-
The SpEL API provides many interfaces and classes. They are as follows:
1 Expression interface
2 SpelExpression class
3 ExpressionParser interface
4 SpelExpressionParser class
5 EvaluationContext interface
6 StandardEvaluationContext class