Top Description Fields Constructors Methods
javax.el

public Class MapELResolver

extends ELResolver
Class Inheritance
Imports
java.beans.FeatureDescriptor, java.util.Map, .Iterator, .Collections, .HashMap, .List, .ArrayList
Defines property resolution behavior on instances of java.util.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 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
JSP 2.1
See Also
CompositeELResolver, ELResolver, java.util.Map

Field Summary

Modifier and TypeField and Description
private boolean
isReadOnly

private static Class<?>
theUnmodifiableMapClass

Inherited from javax.el.ELResolver:
RESOLVABLE_AT_DESIGN_TIMETYPE

Constructor Summary

AccessConstructor and Description
public
MapELResolver()

Creates a new read/write MapELResolver.

public
MapELResolver(boolean
true if this resolver cannot modify maps; false otherwise.
isReadOnly)

Creates a new MapELResolver 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 Map; otherwise Object.class.
getCommonPropertyType(ELContext
The context of this evaluation.
context, Object
The map to analyze. Only bases of type Map are handled by this resolver.
base)

Implements abstract javax.el.ELResolver.getCommonPropertyType.

If the base object is a map, returns the most general type that this resolver accepts for the property argument.
public Iterator<FeatureDescriptor>

Returns:

An 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.
getFeatureDescriptors(ELContext
The context of this evaluation.
context, Object
The map whose keys are to be iterated over. Only bases of type Map are handled by this resolver.
base)

Implements abstract javax.el.ELResolver.getFeatureDescriptors.

If the base object is a map, returns an Iterator containing the set of keys available in the Map.
public Class<?>

Returns:

If the propertyResolved property of ELContext was set to true, then the most general acceptable type; otherwise undefined.
getType(ELContext
The context of this evaluation.
context, Object
The map to analyze. Only bases of type Map are handled by this resolver.
base, Object
The key to return the acceptable type for. Ignored by this resolver.
property)

Implements abstract javax.el.ELResolver.getType.

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

Returns:

If the 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.
getValue(ELContext
The context of this evaluation.
context, Object
The map to be analyzed. Only bases of type Map are handled by this resolver.
base, Object
The key whose associated value is to be returned.
property)

Implements abstract javax.el.ELResolver.getValue.

If the base object is a map, returns the value associated with the given key, as specified by the property argument.
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 map to analyze. Only bases of type Map are handled by this resolver.
base, Object
The key to return the read-only status for. Ignored by this resolver.
property)

Implements abstract javax.el.ELResolver.isReadOnly.

If the base object is a map, returns whether a call to setValue will always fail.
public void
setValue(ELContext
The context of this evaluation.
context, Object
The map to be modified. Only bases of type Map are handled by this resolver.
base, Object
The key with which the specified value is to be associated.
property, Object
The value to be associated with the specified key.
val)

Implements abstract javax.el.ELResolver.setValue.

If the base object is a map, attempts to set the value associated with the given key, as specified by the property argument.
Inherited from javax.el.ELResolver:
convertToTypeinvoke

Field Detail

isReadOnlyback to summary
private boolean isReadOnly
theUnmodifiableMapClassback to summary
private static Class<?> theUnmodifiableMapClass

Constructor Detail

MapELResolverback to summary
public MapELResolver()

Creates a new read/write MapELResolver.

MapELResolverback to summary
public MapELResolver(boolean isReadOnly)

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

Parameters
isReadOnly:boolean

true if this resolver cannot modify maps; false otherwise.

Method Detail

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

Implements abstract javax.el.ELResolver.getCommonPropertyType.

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

Assuming the base is a Map, this method will always return Object.class. This is because Maps accept any object as a key.

Parameters
context:ELContext

The context of this evaluation.

base:Object

The map to analyze. Only bases of type Map are handled by this resolver.

Returns:Class<?>

null if base is not a Map; otherwise Object.class.

getFeatureDescriptorsback to summary
public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)

Implements abstract javax.el.ELResolver.getFeatureDescriptors.

If the base object is a map, returns an Iterator containing the set of keys available in the Map. Otherwise, returns null.

The Iterator returned must contain zero or more instances of java.beans.FeatureDescriptor. Each info object contains information about a key in the Map, and is initialized as follows:

  • displayName - The return value of calling the toString method on this key, or "null" if the key is null.
  • name - Same as displayName property.
  • shortDescription - Empty string
  • expert - false
  • hidden - false
  • preferred - true
    • In addition, the following named attributes must be set in the returned FeatureDescriptors:
  • 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

    • Parameters
    context:ELContext

    The context of this evaluation.

    base:Object

    The map whose keys are to be iterated over. Only bases of type Map are handled by this resolver.

    Returns:Iterator<FeatureDescriptor>

    An 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.

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

    Implements abstract javax.el.ELResolver.getType.

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

    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 Maps accept any object as the value for a given key.

    Parameters
    context:ELContext

    The context of this evaluation.

    base:Object

    The map to analyze. Only bases of type Map are handled by this resolver.

    property:Object

    The key to return the acceptable type for. Ignored by this resolver.

    Returns:Class<?>

    If the propertyResolved property of ELContext was set to true, then the most general acceptable type; otherwise undefined.

    Exceptions
    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 javax.el.ELResolver.getValue.

    If the base object is a map, returns the value associated with the given key, as specified by the 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 java.util.Map#get, 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.

    Parameters
    context:ELContext

    The context of this evaluation.

    base:Object

    The map to be analyzed. Only bases of type Map are handled by this resolver.

    property:Object

    The key whose associated value is to be returned.

    Returns:Object

    If the 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.

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

    Implements abstract javax.el.ELResolver.isReadOnly.

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

    Parameters
    context:ELContext

    The context of this evaluation.

    base:Object

    The map to analyze. Only bases of type Map are handled by this resolver.

    property:Object

    The key to return the read-only status for. 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.

    Exceptions
    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 javax.el.ELResolver.setValue.

    If the base object is a map, attempts to set the value associated with the given key, as specified by the 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 java.util.Collections#unmodifiableMap, 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.

    Parameters
    context:ELContext

    The context of this evaluation.

    base:Object

    The map to be modified. Only bases of type Map are handled by this resolver.

    property:Object

    The key with which the specified value is to be associated.

    val:Object

    The value to be associated with the specified key.

    Exceptions
    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.