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java.lang.Object javax.el.ELResolver javax.el.ListELResolver
public class ListELResolver
Defines property resolution behavior on instances of List
.
This resolver handles base objects of type java.util.List
.
It accepts any object as a property and coerces that object into an
integer index into the list. The resulting value is the value in the list
at that index.
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
,
List
Field Summary |
---|
Fields inherited from class javax.el.ELResolver |
---|
RESOLVABLE_AT_DESIGN_TIME, TYPE |
Constructor Summary | |
---|---|
ListELResolver()
Creates a new read/write ListELResolver . |
|
ListELResolver(boolean isReadOnly)
Creates a new ListELResolver whose read-only status is
determined by the given parameter. |
Method Summary | |
---|---|
Class<?> |
getCommonPropertyType(ELContext context,
Object base)
If the base object is a list, returns the most general type that this resolver accepts for the property argument. |
Iterator<FeatureDescriptor> |
getFeatureDescriptors(ELContext context,
Object base)
Always returns null , since there is no reason to
iterate through set set of all integers. |
Class<?> |
getType(ELContext context,
Object base,
Object property)
If the base object is a list, returns the most general acceptable type for a value in this list. |
Object |
getValue(ELContext context,
Object base,
Object property)
If the base object is a list, returns the value at the given index. |
boolean |
isReadOnly(ELContext context,
Object base,
Object property)
If the base object is a list, 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 list, attempts to set the value at the given index with the given value. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
---|
public ListELResolver()
ListELResolver
.
public ListELResolver(boolean isReadOnly)
ListELResolver
whose read-only status is
determined by the given parameter.
isReadOnly
- true
if this resolver cannot modify
lists; false
otherwise.Method Detail |
---|
public Class<?> getType(ELContext context, Object base, Object property)
If the base is a List
, 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 List
, this method will always
return Object.class
. This is because List
s
accept any object as an element.
getType
in class ELResolver
context
- The context of this evaluation.base
- The list to analyze. Only bases of type List
are handled by this resolver.property
- The index of the element in the list to return the
acceptable type for. Will be coerced into an integer, but
otherwise ignored by this resolver.
propertyResolved
property of
ELContext
was set to true
, then
the most general acceptable type; otherwise undefined.
PropertyNotFoundException
- if the given index is out of
bounds for this list.
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, and
coerced into an integer. If the coercion could not be performed,
an IllegalArgumentException
is thrown. If the index is
out of bounds, null
is returned.
If the base is a List
, 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.
getValue
in class ELResolver
context
- The context of this evaluation.base
- The list to be analyzed. Only bases of type
List
are handled by this resolver.property
- The index of the value to be returned. Will be coerced
into an integer.
propertyResolved
property of
ELContext
was set to true
, then
the value at the given index or null
if the index was out of bounds. Otherwise, undefined.
IllegalArgumentException
- if the property could not be coerced
into an integer.
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 void setValue(ELContext context, Object base, Object property, Object val)
property
argument, and coerced into an integer. If the
coercion could not be performed, an
IllegalArgumentException
is thrown. If the index is
out of bounds, a PropertyNotFoundException
is thrown.
If the base is a List
, 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 List
was created using
Collections.unmodifiableList(java.util.List extends T>)
, this method must
throw PropertyNotWritableException
. Unfortunately,
there is no Collections API method to detect this. However, an
implementation can create a prototype unmodifiable List
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 list to be modified. Only bases of type
List
are handled by this resolver.property
- The index of the value to be set. Will be coerced
into an integer.val
- The value to be set at the given index.
ClassCastException
- if the class of the specified element
prevents it from being added to this list.
NullPointerException
- if context is null
, or
if the value is null
and this List
does not support null
elements.
IllegalArgumentException
- if the property could not be coerced
into an integer, or if some aspect of the specified element
prevents it from being added to this list.
PropertyNotWritableException
- if this resolver was constructed
in read-only mode, or if the set operation is not supported by
the underlying list.
PropertyNotFoundException
- if the given index is out of
bounds for this list.
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 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 List
, 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 List
was created using
Collections.unmodifiableList(java.util.List extends T>)
, this method must
return true
. Unfortunately, there is no Collections API
method to detect this. However, an implementation can create a
prototype unmodifiable List
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 list to analyze. Only bases of type List
are handled by this resolver.property
- The index of the element in the list to return the
acceptable type for. Will be coerced into an integer, but
otherwise 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.
PropertyNotFoundException
- if the given index is out of
bounds for this list.
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)
null
, since there is no reason to
iterate through set set of all integers.
The getCommonPropertyType(javax.el.ELContext, java.lang.Object)
method returns sufficient
information about what properties this resolver accepts.
getFeatureDescriptors
in class ELResolver
context
- The context of this evaluation.base
- The list. Only bases of type List
are
handled by this resolver.
null
.FeatureDescriptor
public Class<?> getCommonPropertyType(ELContext context, Object base)
property
argument.
Otherwise, returns null
.
Assuming the base is a List
, this method will always
return Integer.class
. This is because List
s
accept integers as their index.
getCommonPropertyType
in class ELResolver
context
- The context of this evaluation.base
- The list to analyze. Only bases of type List
are handled by this resolver.
null
if base is not a List
; otherwise
Integer.class
.
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Copyright 2007 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.