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java.lang.Object javax.el.ELResolver javax.el.MapELResolver
public class MapELResolver
Defines property resolution behavior on instances of 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
isReadOnly
will always return true
and
setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
will always throw
PropertyNotWritableException
.
ELResolver
s are combined together using
CompositeELResolver
s, to define rich semantics for evaluating
an expression. See the javadocs for ELResolver
for details.
CompositeELResolver
,
ELResolver
,
Map
Field Summary | |
---|---|
private boolean |
isReadOnly
|
private static java.lang.Class<?> |
theUnmodifiableMapClass
|
Fields inherited from class javax.el.ELResolver |
---|
RESOLVABLE_AT_DESIGN_TIME, TYPE |
Constructor Summary | |
---|---|
MapELResolver()
Creates a new read/write MapELResolver . |
|
MapELResolver(boolean isReadOnly)
Creates a new MapELResolver whose read-only status is
determined by the given parameter. |
Method Summary | |
---|---|
java.lang.Class<?> |
getCommonPropertyType(ELContext context,
java.lang.Object base)
If the base object is a map, returns the most general type that this resolver accepts for the property argument. |
java.util.Iterator<java.beans.FeatureDescriptor> |
getFeatureDescriptors(ELContext context,
java.lang.Object base)
If the base object is a map, returns an Iterator
containing the set of keys available in the Map . |
java.lang.Class<?> |
getType(ELContext context,
java.lang.Object base,
java.lang.Object property)
If the base object is a map, returns the most general acceptable type for a value in this map. |
java.lang.Object |
getValue(ELContext context,
java.lang.Object base,
java.lang.Object property)
If the base object is a map, returns the value associated with the given key, as specified by the property argument. |
boolean |
isReadOnly(ELContext context,
java.lang.Object base,
java.lang.Object property)
If the base object is a map, returns whether a call to setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) will always fail. |
void |
setValue(ELContext context,
java.lang.Object base,
java.lang.Object property,
java.lang.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. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
---|
private static java.lang.Class<?> theUnmodifiableMapClass
private boolean isReadOnly
Constructor Detail |
---|
public MapELResolver()
MapELResolver
.
public MapELResolver(boolean isReadOnly)
MapELResolver
whose read-only status is
determined by the given parameter.
isReadOnly
- true
if this resolver cannot modify
maps; false
otherwise.Method Detail |
---|
public java.lang.Class<?> getType(ELContext context, java.lang.Object base, java.lang.Object property)
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 Map
s
accept any object as the value for a given key.
getType
in class ELResolver
context
- The context of this evaluation.base
- The map to analyze. Only bases of type Map
are handled by this resolver.property
- The key to return the acceptable type for.
Ignored by this resolver.
propertyResolved
property of
ELContext
was set to true
, then
the most general acceptable type; otherwise undefined.
java.lang.NullPointerException
- if context is null
ELException
- if an exception was thrown while performing
the property or variable resolution. The thrown exception
must be included as the cause property of this exception, if
available.public java.lang.Object getValue(ELContext context, java.lang.Object base, java.lang.Object property)
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 Map.get(java.lang.Object)
, 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
.
getValue
in class ELResolver
context
- The context of this evaluation.base
- The map to be analyzed. Only bases of type Map
are handled by this resolver.property
- The key whose associated value is to be returned.
propertyResolved
property of
ELContext
was set to true
, then
the value associated with the given key or null
if the key was not found. Otherwise, undefined.
java.lang.ClassCastException
- if the key is of an inappropriate type
for this map (optionally thrown by the underlying Map
).
java.lang.NullPointerException
- if context is null
, or if
the key is null and this map does not permit null keys (the
latter is optionally thrown by the underlying Map
).
ELException
- if an exception was thrown while performing
the property or variable resolution. The thrown exception
must be included as the cause property of this exception, if
available.public void setValue(ELContext context, java.lang.Object base, java.lang.Object property, java.lang.Object val)
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
Collections.unmodifiableMap(java.util.Map extends K, ? extends V>)
, 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.
setValue
in class ELResolver
context
- The context of this evaluation.base
- The map to be modified. Only bases of type Map
are handled by this resolver.property
- The key with which the specified value is to be
associated.val
- The value to be associated with the specified key.
java.lang.ClassCastException
- if the class of the specified key or
value prevents it from being stored in this map.
java.lang.NullPointerException
- if context is null
, or if
this map does not permit null
keys or values, and
the specified key or value is null
.
java.lang.IllegalArgumentException
- if some aspect of this key or
value prevents it from being stored in this map.
ELException
- if an exception was thrown while performing
the property or variable resolution. The thrown exception
must be included as the cause property of this exception, if
available.
PropertyNotWritableException
- if this resolver was constructed
in read-only mode, or if the put operation is not supported by
the underlying map.public boolean isReadOnly(ELContext context, java.lang.Object base, java.lang.Object property)
setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
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
Collections.unmodifiableMap(java.util.Map extends K, ? extends V>)
, 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.
isReadOnly
in class ELResolver
context
- The context of this evaluation.base
- The map to analyze. Only bases of type Map
are handled by this resolver.property
- The key to return the read-only status for.
Ignored by this resolver.
propertyResolved
property of
ELContext
was set to true
, then
true
if calling the setValue
method
will always fail or false
if it is possible that
such a call may succeed; otherwise undefined.
java.lang.NullPointerException
- if context is null
ELException
- if an exception was thrown while performing
the property or variable resolution. The thrown exception
must be included as the cause property of this exception, if
available.public java.util.Iterator<java.beans.FeatureDescriptor> getFeatureDescriptors(ELContext context, java.lang.Object base)
Iterator
containing the set of keys available in the Map
.
Otherwise, returns null
.
The Iterator
returned must contain zero or more
instances of FeatureDescriptor
. Each info object
contains information about a key in the Map, and is initialized as
follows:
toString
method on this key, or
"null"
if the key is null
.false
false
true
FeatureDescriptor
s:
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
getFeatureDescriptors
in class ELResolver
context
- The context of this evaluation.base
- The map whose keys are to be iterated over. Only bases
of type Map
are handled by this resolver.
Iterator
containing zero or more (possibly
infinitely more) FeatureDescriptor
objects, each
representing a key in this map, or null
if
the base object is not a map.FeatureDescriptor
public java.lang.Class<?> getCommonPropertyType(ELContext context, java.lang.Object base)
property
argument.
Otherwise, returns null
.
Assuming the base is a Map
, this method will always
return Object.class
. This is because Map
s
accept any object as a key.
getCommonPropertyType
in class ELResolver
context
- The context of this evaluation.base
- The map to analyze. Only bases of type Map
are handled by this resolver.
null
if base is not a Map
; otherwise
Object.class
.
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