public class ListELResolver extends ELResolver
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.
ELResolvers are combined together using CompositeELResolvers, to define rich semantics for
evaluating an expression. See the javadocs for ELResolver for details.
CompositeELResolver,
ELResolver,
ListRESOLVABLE_AT_DESIGN_TIME, TYPE| Constructor and Description |
|---|
ListELResolver()
Creates a new read/write
ListELResolver. |
ListELResolver(boolean isReadOnly)
Creates a new
ListELResolver whose read-only status is determined by the given parameter. |
| Modifier and Type | Method and Description |
|---|---|
java.lang.Class<?> |
getCommonPropertyType(ELContext context,
java.lang.Object base)
If the base object is a list, 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)
Always returns
null, since there is no reason to iterate through set set of all integers. |
java.lang.Class<?> |
getType(ELContext context,
java.lang.Object base,
java.lang.Object property)
If the base object is a list, returns the most general acceptable type for a value in this list.
|
java.lang.Object |
getValue(ELContext context,
java.lang.Object base,
java.lang.Object property)
If the base object is a list, returns the value at the given index.
|
boolean |
isReadOnly(ELContext context,
java.lang.Object base,
java.lang.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,
java.lang.Object base,
java.lang.Object property,
java.lang.Object val)
If the base object is a list, attempts to set the value at the given index with the given value.
|
convertToType, invokepublic 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.public java.lang.Class<?> getType(ELContext context, java.lang.Object base, java.lang.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
Lists accept any object as an element.
getType in class ELResolvercontext - 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.java.lang.NullPointerException - if context is nullELException - 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, 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 ELResolvercontext - 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.java.lang.IllegalArgumentException - if the property could not be coerced into an integer.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 void setValue(ELContext context, java.lang.Object base, java.lang.Object property, java.lang.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 ELResolvercontext - 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.java.lang.ClassCastException - if the class of the specified element prevents it from being added to this list.java.lang.NullPointerException - if context is null, or if the value is null and this
List does not support null elements.java.lang.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, 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 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 ELResolvercontext - 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.java.lang.NullPointerException - if context is nullELException - 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)
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 ELResolvercontext - The context of this evaluation.base - The list. Only bases of type List are handled by this resolver.null.FeatureDescriptorpublic java.lang.Class<?> getCommonPropertyType(ELContext context, java.lang.Object base)
property
argument. Otherwise, returns null.
Assuming the base is a List, this method will always return Integer.class. This is because
Lists accept integers as their index.
getCommonPropertyType in class ELResolvercontext - 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.