## javax.el
Class ELContext

    java.lang.Object
      javax.el.ELContext

Direct Known Subclasses:
  ELContextImpl, EvaluationContext

    public abstract class ELContext

extends Object

Context information for expression evaluation.

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 `ELResolver`s
- 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.

Since:
  JSP 2.1
See Also:
  `ELContextListener`, `ELContextEvent`, `ELResolver`, `FunctionMapper`, `VariableMapper`, `JspContext`

Constructor Summary
`ELContext()`

Method Summary
`Object` `getContext(Class key)` Returns the context object associated with the given key.
`abstract ELResolver` `getELResolver()` Retrieves the `ELResolver` associated with this context.
`abstract FunctionMapper` `getFunctionMapper()` Retrieves the `FunctionMapper` associated with this `ELContext`.
`Locale` `getLocale()` Get the `Locale` stored by a previous invocation to `setLocale(java.util.Locale)`.
`abstract VariableMapper` `getVariableMapper()` Retrieves the `VariableMapper` associated with this `ELContext`.
`boolean` `isPropertyResolved()` Returns whether an `ELResolver` has successfully resolved a given (base, property) pair.
`void` `putContext(Class key, Object contextObject)` Associates a context object with this `ELContext`.
`void` `setLocale(Locale locale)` Set the `Locale` for this instance.
`void` `setPropertyResolved(boolean resolved)` Called to indicate that a `ELResolver` has successfully resolved a given (base, property) pair.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### ELContext

    public ELContext()

Method Detail

### setPropertyResolved

    public void setPropertyResolved(boolean resolved)

  Called to indicate that a `ELResolver` has successfully resolved a given (base, property) pair.

  The `CompositeELResolver` checks this property to determine whether it should consider or skip other component resolvers.

  Parameters:
    `resolved` - true if the property has been resolved, or false if not.
  See Also:
    `CompositeELResolver`

### isPropertyResolved

    public boolean isPropertyResolved()

  Returns whether an `ELResolver` has successfully resolved a given (base, property) pair.

  The `CompositeELResolver` checks this property to determine whether it should consider or skip other component resolvers.

  Returns:
    true if the property has been resolved, or false if not.
  See Also:
    `CompositeELResolver`

### putContext

    public void putContext(Class key,
                           Object contextObject)

  Associates a context object with this `ELContext`.

  The `ELContext` maintains a collection of context objects relevant to the evaluation of an expression. These context objects are used by `ELResolver`s. This method is used to add a context object to that collection.

  By convention, the `contextObject` will be of the type specified by the `key`. However, this is not required and the key is used strictly as a unique identifier.

  Parameters:
    `key` - The key used by an @{link ELResolver} to identify this context object.
    `contextObject` - The context object to add to the collection.
  Throws:
    `NullPointerException` - if key is null or contextObject is null.

### getContext

    public Object getContext(Class key)

  Returns the context object associated with the given key.

  The `ELContext` maintains a collection of context objects relevant to the evaluation of an expression. These context objects are used by `ELResolver`s. This method is used to retrieve the context with the given key from the collection.

  By convention, the object returned will be of the type specified by the `key`. However, this is not required and the key is used strictly as a unique identifier.

  Parameters:
    `key` - The unique identifier that was used to associate the context object with this `ELContext`.
  Returns:
    The context object associated with the given key, or null if no such context was found.
  Throws:
    `NullPointerException` - if key is null.

### getELResolver

    public abstract ELResolver getELResolver()

  Retrieves the `ELResolver` associated with this context.

  The `ELContext` maintains a reference to the `ELResolver` that will be consulted to resolve variables and properties during an expression evaluation. This method retrieves the reference to the resolver.

  Once an `ELContext` is constructed, the reference to the `ELResolver` associated with the context cannot be changed.

  Returns:
    The resolver to be consulted for variable and property resolution during expression evaluation.

### getFunctionMapper

    public abstract FunctionMapper getFunctionMapper()

  Retrieves the `FunctionMapper` associated with this `ELContext`.

  Returns:
    The function mapper to be consulted for the resolution of EL functions.

### getLocale

    public Locale getLocale()

  Get the `Locale` stored by a previous invocation to `setLocale(java.util.Locale)`. If this method returns non `null`, this `Locale` must be used for all localization needs in the implementation. The `Locale` must not be cached to allow for applications that change `Locale` dynamically.

  Returns:
    The `Locale` in which this instance is operating. Used primarily for message localization.

### setLocale

    public void setLocale(Locale locale)

  Set the `Locale` for this instance. This method may be called by the party creating the instance, such as JavaServer Faces or JSP, to enable the EL implementation to provide localized messages to the user. If no `Locale` is set, the implementation must use the locale returned by `Locale.getDefault( )`.

### getVariableMapper

    public abstract VariableMapper getVariableMapper()

  Retrieves the `VariableMapper` associated with this `ELContext`.

  Returns:
    The variable mapper to be consulted for the resolution of EL variables.

Copyright © 2008 Mort Bay Consulting. All Rights Reserved.