Top Description Fields Constructors Methods
jakarta.el

public Class ListELResolver

extends ELResolver
Class Inheritance
Imports
java.util.ArrayList, .Collections, .List

Defines property resolution behavior on instances of java.util.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 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.

Since
Jakarta Server Pages 2.1
See Also
CompositeELResolver, ELResolver, java.util.List

Field Summary

Modifier and TypeField and Description
private boolean
private static Class<?>

Constructor Summary

AccessConstructor and Description
public
ListELResolver()

Creates a new read/write ListELResolver.

public
ListELResolver(boolean
true if this resolver cannot modify lists; false otherwise.
isReadOnly
)

Creates a new ListELResolver whose read-only status is determined by the given parameter.

Method Summary

Modifier and TypeMethod and Description
public Class<?>

Returns:

null if base is not a List; otherwise Integer.class.
getCommonPropertyType
(ELContext
The context of this evaluation.
context
,
Object
The list to analyze. Only bases of type List are handled by this resolver.
base
)

Implements abstract jakarta.el.ELResolver.getCommonPropertyType.

If the base object is a list, returns the most general type that this resolver accepts for the property argument.

public Class<?>

Returns:

If the propertyResolved property of ELContext was set to true, then the most general acceptable type which must be null if the either the property or the resolver is read-only; otherwise undefined
getType
(ELContext
The context of this evaluation.
context
,
Object
The list to analyze. Only bases of type List are handled by this resolver.
base
,
Object
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.
property
)

Implements abstract jakarta.el.ELResolver.getType.

If the base object is a list, returns the most general acceptable type for a value in this list.

public Object

Returns:

If the 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.
getValue
(ELContext
The context of this evaluation.
context
,
Object
The list to be analyzed. Only bases of type List are handled by this resolver.
base
,
Object
The index of the value to be returned. Will be coerced into an integer.
property
)

Implements abstract jakarta.el.ELResolver.getValue.

If the base object is a list, returns the value at the given index.

public boolean

Returns:

If the 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.
isReadOnly
(ELContext
The context of this evaluation.
context
,
Object
The list to analyze. Only bases of type List are handled by this resolver.
base
,
Object
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.
property
)

Implements abstract jakarta.el.ELResolver.isReadOnly.

If the base object is a list, returns whether a call to setValue will always fail.

public void
setValue(ELContext
The context of this evaluation.
context
,
Object
The list to be modified. Only bases of type List are handled by this resolver.
base
,
Object
The index of the value to be set. Will be coerced into an integer.
property
,
Object
The value to be set at the given index.
val
)

Implements abstract jakarta.el.ELResolver.setValue.

If the base object is a list, attempts to set the value at the given index with the given value.

private int
Inherited from jakarta.el.ELResolver:
convertToTypeinvoke

Field Detail

isReadOnlyback to summary
private boolean isReadOnly
theUnmodifiableListClassback to summary
private static Class<?> theUnmodifiableListClass

Constructor Detail

ListELResolverback to summary
public ListELResolver()

Creates a new read/write ListELResolver.

ListELResolverback to summary
public ListELResolver(boolean isReadOnly)

Creates a new ListELResolver whose read-only status is determined by the given parameter.

Parameters
isReadOnly:boolean

true if this resolver cannot modify lists; false otherwise.

Method Detail

getCommonPropertyTypeback to summary
public Class<?> getCommonPropertyType(ELContext context, Object base)

Implements abstract jakarta.el.ELResolver.getCommonPropertyType.

If the base object is a list, returns the most general type that this resolver accepts for the 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.

Parameters
context:ELContext

The context of this evaluation.

base:Object

The list to analyze. Only bases of type List are handled by this resolver.

Returns:Class<?>

null if base is not a List; otherwise Integer.class.

Annotations
@Override
getTypeback to summary
public Class<?> getType(ELContext context, Object base, Object property)

Implements abstract jakarta.el.ELResolver.getType.

If the base object is a list, returns the most general acceptable type for a value in this list.

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 return Object.class unless the resolver is constructed in read-only mode in which case null will be returned. This is because Lists accept any object as an element.

Parameters
context:ELContext

The context of this evaluation.

base:Object

The list to analyze. Only bases of type List are handled by this resolver.

property:Object

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.

Returns:Class<?>

If the propertyResolved property of ELContext was set to true, then the most general acceptable type which must be null if the either the property or the resolver is read-only; otherwise undefined

Annotations
@Override
Exceptions
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.
getValueback to summary
public Object getValue(ELContext context, Object base, Object property)

Implements abstract jakarta.el.ELResolver.getValue.

If the base object is a list, returns the value at the given index. The index is specified by the 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.

Parameters
context:ELContext

The context of this evaluation.

base:Object

The list to be analyzed. Only bases of type List are handled by this resolver.

property:Object

The index of the value to be returned. Will be coerced into an integer.

Returns:Object

If the 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.

Annotations
@Override
Exceptions
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.
isReadOnlyback to summary
public boolean isReadOnly(ELContext context, Object base, Object property)

Implements abstract jakarta.el.ELResolver.isReadOnly.

If the base object is a list, returns whether a call to setValue 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 java.util.Collections#unmodifiableList, 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.

Parameters
context:ELContext

The context of this evaluation.

base:Object

The list to analyze. Only bases of type List are handled by this resolver.

property:Object

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.

Returns:boolean

If the 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.

Annotations
@Override
Exceptions
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.
setValueback to summary
public void setValue(ELContext context, Object base, Object property, Object val)

Implements abstract jakarta.el.ELResolver.setValue.

If the base object is a list, attempts to set the value at the given index with the given value. The index is specified by the 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 java.util.Collections#unmodifiableList, 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.

Parameters
context:ELContext

The context of this evaluation.

base:Object

The list to be modified. Only bases of type List are handled by this resolver.

property:Object

The index of the value to be set. Will be coerced into an integer.

val:Object

The value to be set at the given index.

Annotations
@Override
Exceptions
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.
toIntegerback to summary
private int toInteger(Object p)