| java.lang.Object
 javax.el.ELResolver
javax.el.MapELResolver
| MapELResolver | | public class MapELResolver extends ELResolver (Code) | | Defines property resolution behavior on instances of
java.util.Map .
This resolver handles base objects of type java.util.Map.
It accepts any object as a property and uses that object as a key in
the map. The resulting value is the value in the map that is associated with
that key.
This resolver can be constructed in read-only mode, which means that
MapELResolver.isReadOnly will always return true and
MapELResolver.setValue will always throw
PropertyNotWritableException.
ELResolvers are combined together using
CompositeELResolver s, to define rich semantics for evaluating
an expression. See the javadocs for
ELResolver for details.
See Also: CompositeELResolver
See Also: ELResolver
See Also: java.util.Map
since:
JSP 2.1 |
| Constructor Summary | |
| public | MapELResolver()
Creates a new read/write MapELResolver. | | public | MapELResolver(boolean isReadOnly)
Creates a new MapELResolver whose read-only status is
determined by the given parameter. |
| Method Summary | |
| public Class | getCommonPropertyType(ELContext context, Object base)
If the base object is a map, returns the most general type that
this resolver accepts for the property argument.
Otherwise, returns null.
Assuming the base is a Map, this method will always
return Object.class. | | public Iterator<FeatureDescriptor> | getFeatureDescriptors(ELContext context, Object base)
If the base object is a map, returns an Iterator
containing the set of keys available in the Map. | | public Class | getType(ELContext context, Object base, Object property)
If the base object is a map, returns the most general acceptable type
for a value in this map.
If the base is a Map, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. | | public Object | getValue(ELContext context, Object base, Object property)
If the base object is a map, returns the value associated with the
given key, as specified by the property argument. | | public boolean | isReadOnly(ELContext context, Object base, Object property)
If the base object is a map, returns whether a call to
MapELResolver.setValue will always fail.
If the base is a Map, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. | | public void | setValue(ELContext context, Object base, Object property, Object val)
If the base object is a map, attempts to set the value associated with
the given key, as specified by the property argument.
If the base is a Map, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. |
| MapELResolver | | public MapELResolver()(Code) | | Creates a new read/write MapELResolver.
|
| MapELResolver | | public MapELResolver(boolean isReadOnly)(Code) | | Creates a new MapELResolver whose read-only status is
determined by the given parameter.
Parameters:
isReadOnly - true if this resolver cannot modifymaps; false otherwise. |
| getCommonPropertyType | | public Class getCommonPropertyType(ELContext context, Object base)(Code) | | If the base object is a map, returns the most general type that
this resolver accepts for the property argument.
Otherwise, returns null.
Assuming the base is a Map, this method will always
return Object.class. This is because Maps
accept any object as a key.
Parameters:
context - The context of this evaluation.
Parameters:
base - The map to analyze. Only bases of type Mapare handled by this resolver. null if base is not a Map; otherwiseObject.class. |
| getFeatureDescriptors | | public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)(Code) | | If the base object is a map, returns an Iterator
containing the set of keys available in the Map.
Otherwise, returns null.
The Iterator returned must contain zero or more
instances of
java.beans.FeatureDescriptor . Each info object
contains information about a key in the Map, and is initialized as
follows:
displayName - The return value of calling the
toString method on this key, or
"null" if the key is null.
name - Same as displayName property.
shortDescription - Empty string
expert - false
hidden - false
preferred - true
In addition, the following named attributes must be set in the
returned FeatureDescriptors:
ELResolver.TYPE - The return value of calling the getClass()
method on this key, or null if the key is
null.
ELResolver.RESOLVABLE_AT_DESIGN_TIME - true
Parameters:
context - The context of this evaluation.
Parameters:
base - The map whose keys are to be iterated over. Only bases of type Map are handled by this resolver. An Iterator containing zero or more (possiblyinfinitely more) FeatureDescriptor objects, eachrepresenting a key in this map, or null if the base object is not a map. |
| getType | | public Class getType(ELContext context, Object base, Object property)(Code) | | If the base object is a map, returns the most general acceptable type
for a value in this map.
If the base is a Map, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. If this property
is not true after this method is called, the caller
should ignore the return value.
Assuming the base is a Map, this method will always
return Object.class. This is because Maps
accept any object as the value for a given key.
Parameters:
context - The context of this evaluation.
Parameters:
base - The map to analyze. Only bases of type Mapare handled by this resolver.
Parameters:
property - The key to return the acceptable type for.Ignored by this resolver. If the propertyResolved property of ELContext was set to true, thenthe most general acceptable type; otherwise undefined.
throws:
NullPointerException - if context is null
throws:
ELException - if an exception was thrown while performingthe property or variable resolution. The thrown exceptionmust be included as the cause property of this exception, ifavailable. |
| getValue | | public Object getValue(ELContext context, Object base, Object property)(Code) | | If the base object is a map, returns the value associated with the
given key, as specified by the property argument. If the
key was not found, null is returned.
If the base is a Map, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. If this property
is not true after this method is called, the caller
should ignore the return value.
Just as in
java.util.Map.get , just because null
is returned doesn't mean there is no mapping for the key; it's also
possible that the Map explicitly maps the key to
null.
Parameters:
context - The context of this evaluation.
Parameters:
base - The map to be analyzed. Only bases of type Mapare handled by this resolver.
Parameters:
property - The key whose associated value is to be returned. If the propertyResolved property of ELContext was set to true, thenthe value associated with the given key or nullif the key was not found. Otherwise, undefined.
throws:
ClassCastException - if the key is of an inappropriate type for this map (optionally thrown by the underlying Map).
throws:
NullPointerException - if context is null, or if the key is null and this map does not permit null keys (thelatter is optionally thrown by the underlying Map).
throws:
ELException - if an exception was thrown while performingthe property or variable resolution. The thrown exceptionmust be included as the cause property of this exception, ifavailable. |
| isReadOnly | | public boolean isReadOnly(ELContext context, Object base, Object property)(Code) | | If the base object is a map, returns whether a call to
MapELResolver.setValue will always fail.
If the base is a Map, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. If this property
is not true after this method is called, the caller
should ignore the return value.
If this resolver was constructed in read-only mode, this method will
always return true.
If a Map was created using
java.util.Collections.unmodifiableMap , this method must
return true. Unfortunately, there is no Collections API
method to detect this. However, an implementation can create a
prototype unmodifiable Map and query its runtime type
to see if it matches the runtime type of the base object as a
workaround.
Parameters:
context - The context of this evaluation.
Parameters:
base - The map to analyze. Only bases of type Mapare handled by this resolver.
Parameters:
property - The key to return the read-only status for.Ignored by this resolver. If the propertyResolved property of ELContext was set to true, thentrue if calling the setValue methodwill always fail or false if it is possible thatsuch a call may succeed; otherwise undefined.
throws:
NullPointerException - if context is null
throws:
ELException - if an exception was thrown while performingthe property or variable resolution. The thrown exceptionmust be included as the cause property of this exception, ifavailable. |
| setValue | | public void setValue(ELContext context, Object base, Object property, Object val)(Code) | | If the base object is a map, attempts to set the value associated with
the given key, as specified by the property argument.
If the base is a Map, the propertyResolved
property of the ELContext object must be set to
true by this resolver, before returning. If this property
is not true after this method is called, the caller
can safely assume no value was set.
If this resolver was constructed in read-only mode, this method will
always throw PropertyNotWritableException.
If a Map was created using
java.util.Collections.unmodifiableMap , this method must
throw PropertyNotWritableException. Unfortunately,
there is no Collections API method to detect this. However, an
implementation can create a prototype unmodifiable Map
and query its runtime type to see if it matches the runtime type of
the base object as a workaround.
Parameters:
context - The context of this evaluation.
Parameters:
base - The map to be modified. Only bases of type Mapare handled by this resolver.
Parameters:
property - The key with which the specified value is to beassociated.
Parameters:
val - The value to be associated with the specified key.
throws:
ClassCastException - if the class of the specified key or value prevents it from being stored in this map.
throws:
NullPointerException - if context is null, or if this map does not permit null keys or values, andthe specified key or value is null.
throws:
IllegalArgumentException - if some aspect of this key or value prevents it from being stored in this map.
throws:
ELException - if an exception was thrown while performingthe property or variable resolution. The thrown exceptionmust be included as the cause property of this exception, ifavailable.
throws:
PropertyNotWritableException - if this resolver was constructedin read-only mode, or if the put operation is not supported by the underlying map. |
| Methods inherited from javax.el.ELResolver | abstract public Class getCommonPropertyType(ELContext context, Object base)(Code)(Java Doc)
abstract public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)(Code)(Java Doc)
abstract public Class getType(ELContext context, Object base, Object property)(Code)(Java Doc)
abstract public Object getValue(ELContext context, Object base, Object property)(Code)(Java Doc)
abstract public boolean isReadOnly(ELContext context, Object base, Object property)(Code)(Java Doc)
abstract public void setValue(ELContext context, Object base, Object property, Object value)(Code)(Java Doc)
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