To evaluate an Expression , an ELContext must be provided. The ELContext holds:

• a reference to the base ELResolver that will be consulted to resolve model objects and their properties
• a reference to FunctionMapper that will be used to resolve EL Functions.
• a reference to VariableMapper that will be used to resolve EL Variables.
• a collection of all the relevant context objects for use by ELResolvers
• state information during the evaluation of an expression, such as whether a property has been resolved yet

The collection of context objects is necessary because each ELResolver may need access to a different context object. For example, JSP and Faces resolvers need access to a JspContext and a FacesContext , respectively.

Creation of ELContext objects is controlled through the underlying technology. For example, in JSP the JspContext.getELContext() factory method is used. Some technologies provide the ability to add an ELContextListener so that applications and frameworks can ensure their own context objects are attached to any newly created ELContext.

Because it stores state during expression evaluation, an ELContext object is not thread-safe. Care should be taken to never share an ELContext instance between two or more threads.