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Oracle Fusion Middleware Java API Reference for Oracle ADF Mobile Client 11g Release 1 (11.1.1) E17503-02 |
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public interface ELResolver
Enables customization of variable and property resolution behavior for EL expression evaluation.
While evaluating an expression, the ELResolver
associated with the
ELContext
is consulted to do the initial resolution of the first variable of an
expression. It is also consulted when a .
or []
operator is
encountered, except for the last such operator in a method expression, in which case the
resultion rules are hard coded.
For example, in the EL expression ${employee.lastName}
, the
ELResolver
determines what object employee
refers to, and what it
means to get the lastName
property on that object.
Most methods in this class accept a base
and property
parameter. In
the case of variable resolution (e.g. determining what employee
refers to in
${employee.lastName}
), the base
parameter will be
null
and the property
parameter will always be of type
String
. In this case, if the property
is not a String
,
the behavior of the ELResolver
is undefined.
In the case of property resolution, the base
parameter identifies the base object
and the property
object identifies the property on that base. For example, in the
expression ${employee.lastName}
, base
is the result of the
variable resolution for employee
and property
is the string
"lastName"
. In the expression ${y[x]}
, base
is the
result of the variable resolution for y
and property
is the result
of the variable resolution for x
.
Though only a single ELResolver
is associated with an ELContext
,
there are usually multiple resolvers considered for any given variable or property resolution.
ELResolver
s are combined together using CompositeELResolver
s, to define
rich semantics for evaluating an expression.
For the getValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object)
, getType(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object)
, setValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
and isReadOnly(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object)
methods,
an ELResolver
is not responsible for resolving all possible (base, property)
pairs. In fact, most resolvers will only handle a base
of a single type. To
indicate that a resolver has successfully resolved a particular (base, property) pair, it must
set the propertyResolved
property of the ELContext
to
true
. If it could not handle the given pair, it must leave this property alone.
The caller must ignore the return value of the method if propertyResolved
is
false
.
The #getFeatureDescriptors
and #getCommonPropertyType
methods are primarily
designed for design-time tool support, but must handle invocation at runtime as well. The
java.beans.Beans#isDesignTime
method can be used to determine if the resolver is being
consulted at design-time or runtime.
CompositeELResolver
,
ELContext.getELResolver()
Field Summary | |
---|---|
static java.lang.String |
RESOLVABLE_AT_DESIGN_TIME
The attribute name of the named attribute in the FeatureDescriptor that
specifies whether the variable or property can be resolved at runtime. |
static java.lang.String |
TYPE
The attribute name of the named attribute in the FeatureDescriptor that
specifies the runtime type of the variable or property. |
Method Summary | |
---|---|
java.lang.Class |
getType(ELContext context,
java.lang.Object base,
java.lang.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 setValue(oracle.adfnmc.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object) method. |
java.lang.Object |
getValue(ELContext context,
java.lang.Object base,
java.lang.Object property)
Attempts to resolve the given property object on the given base
object. |
boolean |
isReadOnly(ELContext context,
java.lang.Object base,
java.lang.Object property)
For a given base and property , attempts to determine whether a
call to setValue(oracle.adfnmc.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 value)
Attempts to set the value of the given property object on the given
base object. |
Field Detail |
---|
static final java.lang.String TYPE
The attribute name of the named attribute in the FeatureDescriptor
that
specifies the runtime type of the variable or property.
static final java.lang.String RESOLVABLE_AT_DESIGN_TIME
The attribute name of the named attribute in the FeatureDescriptor
that
specifies whether the variable or property can be resolved at runtime.
Method Detail |
---|
java.lang.Object getValue(ELContext context, java.lang.Object base, java.lang.Object property)
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.
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.
java.lang.NullPointerException
- if context is null
PropertyNotFoundException
- if the given (base, property) pair is handled by this ELResolver
but the specified variable or property does not exist or is not readable.
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.java.lang.Class getType(ELContext context, java.lang.Object base, java.lang.Object property)
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 setValue(oracle.adfnmc.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.
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.
java.lang.NullPointerException
- if context is null
PropertyNotFoundException
- if the given (base, property) pair is handled by this ELResolver
but the specified variable or property does not exist or is not readable.
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.void setValue(ELContext context, java.lang.Object base, java.lang.Object property, java.lang.Object value)
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.
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.
java.lang.NullPointerException
- if context is null
PropertyNotFoundException
- if the given (base, property) pair is handled by this ELResolver
but the specified variable or property does not exist.
PropertyNotWritableException
- if the given (base, property) pair is handled by this ELResolver
but the specified variable or property is not writable.
ELException
- if an exception was thrown while attempting to set the property or variable. The
thrown exception must be included as the cause property of this exception, if
available.boolean isReadOnly(ELContext context, java.lang.Object base, java.lang.Object property)
base
and property
, attempts to determine whether a
call to setValue(oracle.adfnmc.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.
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.
java.lang.NullPointerException
- if context is null
PropertyNotFoundException
- if the given (base, property) pair is handled by this ELResolver
but the specified variable or property does not exist.
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.
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Oracle Fusion Middleware Java API Reference for Oracle ADF Mobile Client 11g Release 1 (11.1.1) E17503-02 |
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