javax.el: abstract public class: ELContext

javax.el
abstract public class: ELContext [javadoc | source]

java.lang.Object
   javax.el.ELContext

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 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 javax.servlet.jsp.JspContext and a javax.faces.context.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.

Also see:

javax.servlet.jsp.JspContext

since: JSP - 2.1

Method from javax.el.ELContext Summary:
getContext, getELResolver, getFunctionMapper, getLocale, getVariableMapper, isPropertyResolved, putContext, setLocale, setPropertyResolved

Methods from java.lang.Object:
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from javax.el.ELContext Detail:
public Object getContext(Class key) { if(key == null) { throw new NullPointerException(); } return map.get(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.
abstract public 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.
abstract public FunctionMapper getFunctionMapper() Retrieves the `FunctionMapper` associated with this `ELContext`.
public Locale getLocale() { return this.locale; } Get the `Locale` stored by a previous invocation to #setLocale . 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.
abstract public VariableMapper getVariableMapper() Retrieves the `VariableMapper` associated with this `ELContext`.
public boolean isPropertyResolved() { return resolved; } 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.
public void putContext(Class key, Object contextObject) { if((key == null) \|\| (contextObject == null)) { throw new NullPointerException(); } map.put(key, 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.
public void setLocale(Locale locale) { this.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( )`.
public void setPropertyResolved(boolean resolved) { this.resolved = 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.

Method from javax.el.ELContext Detail:

 public Object getContext(Class key) {
        if(key == null) {
            throw new NullPointerException();
        }
        return map.get(key);
}

The ELContext maintains a collection of context objects relevant to the evaluation of an expression. These context objects are used by ELResolvers. 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.

 abstract public 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.

 abstract public FunctionMapper getFunctionMapper()Retrieves the FunctionMapper associated with this
ELContext.

 public Locale getLocale() {
        return this.locale;
}

Locale

#setLocale

null

Locale

 abstract public VariableMapper getVariableMapper()Retrieves the VariableMapper associated with this
ELContext.

 public boolean isPropertyResolved() {
        return resolved;
}

ELResolver

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

 public  void putContext(Class key,
    Object contextObject) {
        if((key == null) || (contextObject == null)) {
            throw new NullPointerException();
        }
        map.put(key, contextObject);
}

ELContext

The ELContext maintains a collection of context objects relevant to the evaluation of an expression. These context objects are used by ELResolvers. 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.

 public  void setLocale(Locale locale) {
        this.locale = locale;
}

Locale

Locale.getDefault( )

 public  void setPropertyResolved(boolean resolved) {
        this.resolved = resolved;
}

ELResolver

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