Class ELContext
- java.lang.Object
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- javax.el.ELContext
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public abstract class ELContext extends java.lang.Object
Context information for expression evaluation.To evaluate an
Expression
, anELContext
must be provided. TheELContext
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 ajavax.servlet.jsp.JspContext
and ajavax.faces.context.FacesContext
, respectively.Creation of
ELContext
objects is controlled through the underlying technology. For example, in JSP theJspContext.getELContext()
factory method is used. Some technologies provide the ability to add anELContextListener
so that applications and frameworks can ensure their own context objects are attached to any newly createdELContext
.Because it stores state during expression evaluation, an
ELContext
object is not thread-safe. Care should be taken to never share anELContext
instance between two or more threads.- Since:
- JSP 2.1
- See Also:
ELContextListener
,ELContextEvent
,ELResolver
,FunctionMapper
,VariableMapper
,javax.servlet.jsp.JspContext
- a reference to the base
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Constructor Summary
Constructors Constructor Description ELContext()
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description java.lang.Object
getContext(java.lang.Class key)
Returns the context object associated with the given key.abstract ELResolver
getELResolver()
Retrieves theELResolver
associated with this context.abstract FunctionMapper
getFunctionMapper()
Retrieves theFunctionMapper
associated with thisELContext
.java.util.Locale
getLocale()
Get theLocale
stored by a previous invocation tosetLocale(java.util.Locale)
.abstract VariableMapper
getVariableMapper()
Retrieves theVariableMapper
associated with thisELContext
.boolean
isPropertyResolved()
Returns whether anELResolver
has successfully resolved a given (base, property) pair.void
putContext(java.lang.Class key, java.lang.Object contextObject)
Associates a context object with thisELContext
.void
setLocale(java.util.Locale locale)
Set theLocale
for this instance.void
setPropertyResolved(boolean resolved)
Called to indicate that aELResolver
has successfully resolved a given (base, property) pair.
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Method Detail
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setPropertyResolved
public void setPropertyResolved(boolean resolved)
Called to indicate that aELResolver
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
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isPropertyResolved
public boolean isPropertyResolved()
Returns whether anELResolver
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
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putContext
public void putContext(java.lang.Class key, java.lang.Object contextObject)
Associates a context object with thisELContext
.The
ELContext
maintains a collection of context objects relevant to the evaluation of an expression. These context objects are used byELResolver
s. This method is used to add a context object to that collection.By convention, the
contextObject
will be of the type specified by thekey
. 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:
java.lang.NullPointerException
- if key is null or contextObject is null.
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getContext
public java.lang.Object getContext(java.lang.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 byELResolver
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 thisELContext
.- Returns:
- The context object associated with the given key, or null if no such context was found.
- Throws:
java.lang.NullPointerException
- if key is null.
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getELResolver
public abstract ELResolver getELResolver()
Retrieves theELResolver
associated with this context.The
ELContext
maintains a reference to theELResolver
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 theELResolver
associated with the context cannot be changed.- Returns:
- The resolver to be consulted for variable and property resolution during expression evaluation.
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getFunctionMapper
public abstract FunctionMapper getFunctionMapper()
Retrieves theFunctionMapper
associated with thisELContext
.- Returns:
- The function mapper to be consulted for the resolution of EL functions.
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getLocale
public java.util.Locale getLocale()
Get theLocale
stored by a previous invocation tosetLocale(java.util.Locale)
. If this method returns nonnull
, thisLocale
must be used for all localization needs in the implementation. TheLocale
must not be cached to allow for applications that changeLocale
dynamically.- Returns:
- The
Locale
in which this instance is operating. Used primarily for message localization.
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setLocale
public void setLocale(java.util.Locale locale)
Set theLocale
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 noLocale
is set, the implementation must use the locale returned byLocale.getDefault( )
.
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getVariableMapper
public abstract VariableMapper getVariableMapper()
Retrieves theVariableMapper
associated with thisELContext
.- Returns:
- The variable mapper to be consulted for the resolution of EL variables.
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