public abstract class TypeConverter extends ELResolver
For example, to convert a String to an instance of MyDate, one can write
ELProcessor elp = new ELProcessor(); elp.getELManager().addELResolver(new TypeConverter() { Object convertToType(ELContext context, Object obj, Class> type) { if ((obj instanceof String) && type == MyDate.class) { context.setPropertyResolved(obj, type); return (obj == null)? null: new MyDate(obj.toString()); } return null; } };
RESOLVABLE_AT_DESIGN_TIME, TYPE
Constructor and Description |
---|
TypeConverter() |
Modifier and Type | Method and Description |
---|---|
abstract Object |
convertToType(ELContext context,
Object obj,
Class<?> targetType)
Converts an object to a specific type.
|
Class<?> |
getCommonPropertyType(ELContext context,
Object base)
Returns the most general type that this resolver accepts for the
property argument, given a base object. |
Iterator<FeatureDescriptor> |
getFeatureDescriptors(ELContext context,
Object base)
Returns information about the set of variables or properties that
can be resolved for the given
base object. |
Class<?> |
getType(ELContext context,
Object base,
Object property)
For a given
base and property , attempts to
identify the most general type that is acceptable for an object to be
passed as the value parameter in a future call
to the ELResolver.setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) method. |
Object |
getValue(ELContext context,
Object base,
Object property)
Attempts to resolve the given
property object on the given
base object. |
boolean |
isReadOnly(ELContext context,
Object base,
Object property)
For a given
base and property , attempts to
determine whether a call to ELResolver.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 value)
Attempts to set the value of the given
property
object on the given base object. |
invoke
public Object getValue(ELContext context, Object base, Object property)
ELResolver
property
object on the given
base
object.
If this resolver handles the given (base, property) pair,
the propertyResolved
property of the
ELContext
object must be set to true
by the 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 base object whose property value is to be returned,
or null
to resolve a top-level variable.property
- The property or variable to be resolved.propertyResolved
property of
ELContext
was set to true
, then
the result of the variable or property resolution; otherwise
undefined.public Class<?> getType(ELContext context, Object base, Object property)
ELResolver
base
and property
, attempts to
identify the most general type that is acceptable for an object to be
passed as the value
parameter in a future call
to the ELResolver.setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
method.
If this resolver handles the given (base, property) pair,
the propertyResolved
property of the
ELContext
object must be set to true
by the resolver, before returning. If this property is not
true
after this method is called, the caller should ignore
the return value.
This is not always the same as getValue().getClass()
.
For example, in the case of an ArrayELResolver
, the
getType
method will return the element type of the
array, which might be a superclass of the type of the actual
element that is currently in the specified array element.
getType
in class ELResolver
context
- The context of this evaluation.base
- The base object whose property value is to be analyzed,
or null
to analyze a top-level variable.property
- The property or variable to return the acceptable
type for.propertyResolved
property of
ELContext
was set to true
, then
the most general acceptable type; otherwise undefined.public void setValue(ELContext context, Object base, Object property, Object value)
ELResolver
property
object on the given base
object.
If this resolver handles the given (base, property) pair,
the propertyResolved
property of the
ELContext
object must be set to true
by the resolver, before returning. If this property is not
true
after this method is called, the caller can
safely assume no value has been set.
setValue
in class ELResolver
context
- The context of this evaluation.base
- The base object whose property value is to be set,
or null
to set a top-level variable.property
- The property or variable to be set.value
- The value to set the property or variable to.public boolean isReadOnly(ELContext context, Object base, Object property)
ELResolver
base
and property
, attempts to
determine whether a call to ELResolver.setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
will always fail.
If this resolver handles the given (base, property) pair,
the propertyResolved
property of the
ELContext
object must be set to true
by the resolver, before returning. If this property is not
true
after this method is called, the caller should ignore
the return value.
isReadOnly
in class ELResolver
context
- The context of this evaluation.base
- The base object whose property value is to be analyzed,
or null
to analyze a top-level variable.property
- The property or variable to return the read-only status
for.propertyResolved
property of
ELContext
was set to true
, then
true
if the property is read-only or
false
if not; otherwise undefined.public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)
ELResolver
base
object. One use for
this method is to assist tools in auto-completion.
If the base
parameter is null
, the
resolver must enumerate the list of top-level variables it can
resolve.
The Iterator
returned must contain zero or more
instances of FeatureDescriptor
, in no guaranteed
order. In the case of primitive types such as int
, the
value null
must be returned. This is to prevent the
useless iteration through all possible primitive values. A
return value of null
indicates that this resolver does
not handle the given base
object or that the results
are too complex to represent with this method and the
ELResolver.getCommonPropertyType(javax.el.ELContext, java.lang.Object)
method should be used instead.
Each FeatureDescriptor
will contain information about
a single variable or property. In addition to the standard
properties, the FeatureDescriptor
must have two
named attributes (as set by the setValue
method):
ELResolver.TYPE
- The value of this named attribute must be
an instance of java.lang.Class
and specify the
runtime type of the variable or property.ELResolver.RESOLVABLE_AT_DESIGN_TIME
- The value of this
named attribute must be an instance of
java.lang.Boolean
and indicates whether it is safe
to attempt to resolve this property at design-time. For
instance, it may be unsafe to attempt a resolution at design
time if the ELResolver
needs access to a resource
that is only available at runtime and no acceptable simulated
value can be provided.The caller should be aware that the Iterator
returned might iterate through a very large or even infinitely large
set of properties. Care should be taken by the caller to not get
stuck in an infinite loop.
This is a "best-effort" list. Not all ELResolver
s
will return completely accurate results, but all must be callable
at both design-time and runtime (i.e. whether or not
Beans.isDesignTime()
returns true
),
without causing errors.
The propertyResolved
property of the
ELContext
is not relevant to this method.
The results of all ELResolver
s are concatenated
in the case of composite resolvers.
getFeatureDescriptors
in class ELResolver
context
- The context of this evaluation.base
- The base object whose set of valid properties is to
be enumerated, or null
to enumerate the set of
top-level variables that this resolver can evaluate.Iterator
containing zero or more (possibly
infinitely more) FeatureDescriptor
objects, or
null
if this resolver does not handle the given
base
object or that the results are too complex to
represent with this methodFeatureDescriptor
public Class<?> getCommonPropertyType(ELContext context, Object base)
ELResolver
property
argument, given a base
object.
One use for this method is to assist tools in auto-completion.
This assists tools in auto-completion and also provides a
way to express that the resolver accepts a primitive value,
such as an integer index into an array. For example, the
ArrayELResolver
will accept any int
as a
property
, so the return value would be
Integer.class
.
getCommonPropertyType
in class ELResolver
context
- The context of this evaluation.base
- The base object to return the most general property
type for, or null
to enumerate the set of
top-level variables that this resolver can evaluate.null
if this ELResolver
does not
know how to handle the given base
object; otherwise
Object.class
if any type of property
is accepted; otherwise the most general property
type accepted for the given base
.public abstract Object convertToType(ELContext context, Object obj, Class<?> targetType)
An ELException
is thrown if an error occurs during
the conversion.
convertToType
in class ELResolver
context
- The context of this evaluation.obj
- The object to convert.targetType
- The target type for the conversion.ELException
- thrown if errors occur.Copyright © 1996-2013, Oracle and/or its affiliates. All Rights Reserved. Use is subject to license terms.