OGNL

Object -Graph Navigation Language, abbreviated as OGNL is an expression language for reading and writing of properties in Java objects. To be used to set and read the value of a property of the same terms. Can be used OGNL for example, when binding a presentation layer ( GUI) to an object in a data model. It also allows OGNL "projection", "selection" and pseudo- lambda expressions.

In a "projection" the same method is invoked or accessed on the same property and the result of this operation (s ) in turn stored in a collection of all elements of a collection.

In a "selection" are a set of elements of a vector specific items that meet the stated condition, saved as a result in a new vector.

OGNL has a simplified lambda expression syntax, which allows you to write simple functions.

Examples

An OGNL expression

Code.toLowerCase (). getBytes (). intValue.toString ()

• Retrieves the property "code",
• Calls the toLowerCase () method on the resulting string,
• Calls the method getBytes () on the resulting string
• Byte is extracted from the resulting array to the first value, that encapsulates a byte object
• For which in turn the intValue property is determined ( by calling the method intValue ()),
• The resulting int is in turn encapsulated in an Integer object, which is obtained by calling the toString () method is converted to a string.

Projectiondesign

Listeners. { delegate }

A list of all the delegates Collection listeners back.

Selection

Listeners. {? # this instanceof KeyListener }

Is a vector back all of the listener, which are KeyListener.