public class MapELResolver extends ELResolver
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
RESOLVABLE_AT_DESIGN_TIME, TYPE
Constructor and Description |
---|
MapELResolver()
Creates a new read/write
MapELResolver . |
MapELResolver(boolean isReadOnly)
Creates a new
MapELResolver whose read-only status is determined by the given parameter. |
Modifier and Type | Method and Description |
---|---|
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. |
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 . |
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.
|
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. |
boolean |
isReadOnly(ELContext context,
Object base,
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,
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. |
convertToType, invoke
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.public Class<?> getType(ELContext context, Object base, 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.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 Object getValue(ELContext context, Object base, 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.ClassCastException
- if the key is of an inappropriate type for this map (optionally thrown by the underlying
Map
).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, Object base, Object property, 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.ClassCastException
- if the class of the specified key or value prevents it from being stored in this map.NullPointerException
- if context is null
, or if this map does not permit null
keys
or values, and the specified key or value is null
.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, Object base, 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.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 Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, 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 Class<?> getCommonPropertyType(ELContext context, 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
.Comments to: el-dev@eclipse.org.
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Use is subject to license terms.