Object Graph Navigation Language

Object Graph Navigation Language (OGNL) is a powerful expression language used in Java-based applications, particularly associated with [[Apache Struts 2]] and other frameworks. OGNL provides a concise and flexible syntax for navigating and manipulating object graphs in [[Java]].

OGNL serves as an expression language for evaluating expressions on object graphs. OGNL allows developers to navigate complex object structures, accessing and manipulating properties of objects within the graph.

OGNL expressions are concise and resemble a combination of Java and [[XPath]] syntax. An example may be: person.address.city.

OGNL supports various arithmetic and logical operations, enabling developers to perform calculations and make decisions within expressions. OGNL supports conditional expressions, allowing developers to create expressions with conditions like ternary operators.

OGNL provides capabilities for working with collections, including iterating over lists and maps. OGNL is often integrated into frameworks like Apache Struts 2 for handling dynamic content and interactions in web applications. Developers can use OGNL expressions in configurations, form validations, and other aspects of a framework.

In Apache Struts 2, OGNL is a key component for handling data binding, form submissions, and interactions between the view and the underlying Java code. Due to its powerful capabilities, OGNL usage should be carefully controlled to prevent security vulnerabilities, such as remote code execution.

Developers can extend OGNL to support custom operations and functions, providing additional flexibility. OGNL supports null-safe navigation, allowing developers to safely navigate object graphs even when certain properties are null.