public class CompositeELResolver extends ELResolver
ELResolver
s.
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 a CompositeELResolver
, to define rich semantics for evaluating an expression.
For the getValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object)
, getType(jakarta.el.ELContext, java.lang.Object, java.lang.Object)
, setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
and isReadOnly(jakarta.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 CompositeELResolver
initializes the ELContext.propertyResolved
flag to
false
, and uses it as a stop condition for iterating through its component resolvers.
The ELContext.propertyResolved
flag is not used for the design-time methods
getFeatureDescriptors(jakarta.el.ELContext, java.lang.Object)
and getCommonPropertyType(jakarta.el.ELContext, java.lang.Object)
. Instead, results are collected and combined from
all child ELResolver
s for these methods.
ELContext
,
ELResolver
RESOLVABLE_AT_DESIGN_TIME, TYPE
Constructor and Description |
---|
CompositeELResolver() |
Modifier and Type | Method and Description |
---|---|
void |
add(ELResolver elResolver)
Adds the given resolver to the list of component resolvers.
|
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 setValue(jakarta.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 by querying all
component resolvers. |
Object |
invoke(ELContext context,
Object base,
Object method,
Class<?>[] paramTypes,
Object[] params)
Attempts to resolve and invoke the given
method on the given base object by querying all
component resolvers. |
boolean |
isReadOnly(ELContext context,
Object base,
Object property)
For a given
base and property , attempts to determine whether a call to setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
will always fail. |
void |
setValue(ELContext context,
Object base,
Object property,
Object val)
Attempts to set the value of the given
property object on the given base object. |
public void add(ELResolver elResolver)
Resolvers are consulted in the order in which they are added.
elResolver
- The component resolver to add.NullPointerException
- If the provided resolver is null
.public Object getValue(ELContext context, Object base, Object property)
property
object on the given base
object by querying all
component resolvers.
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.
First, propertyResolved
is set to false
on the provided ELContext
.
Next, for each component resolver in this composite:
getValue()
method is called, passing in the provided context
, base
and
property
.ELContext
's propertyResolved
flag is false
then iteration
continues.getValue()
is returned by this method.
If none of the component resolvers were able to perform this operation, the value null
is returned and
the propertyResolved
flag remains set to false
.
Any exception thrown by component resolvers during the iteration is propagated to the caller of this method.
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.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.public Object invoke(ELContext context, Object base, Object method, Class<?>[] paramTypes, Object[] params)
method
on the given base
object by querying all
component resolvers.
If this resolver handles the given (base, method) 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.
First, propertyResolved
is set to false
on the provided ELContext
.
Next, for each component resolver in this composite:
invoke()
method is called, passing in the provided context
, base
,
method
, paramTypes
, and params
.ELContext
's propertyResolved
flag is false
then iteration
continues.getValue()
is returned by this method.
If none of the component resolvers were able to perform this operation, the value null
is returned and
the propertyResolved
flag remains set to false
Any exception thrown by component resolvers during the iteration is propagated to the caller of this method.
invoke
in class ELResolver
context
- The context of this evaluation.base
- The bean on which to invoke the methodmethod
- The simple name of the method to invoke. Will be coerced to a String
.paramTypes
- An array of Class objects identifying the method's formal parameter types, in declared order. Use
an empty array if the method has no parameters. Can be null
, in which case the method's formal parameter
types are assumed to be unknown.params
- The parameters to pass to the method, or null
if no parameters.null
if the method has a void
return type).public Class<?> getType(ELContext context, Object base, 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(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
method. The result is obtained by querying all component resolvers.
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.
First, propertyResolved
is set to false
on the provided ELContext
.
Next, for each component resolver in this composite:
getType()
method is called, passing in the provided context
, base
and
property
.ELContext
's propertyResolved
flag is false
then iteration
continues.getType()
is returned by this method.
If none of the component resolvers were able to perform this operation, the value null
is returned and
the propertyResolved
flag remains set to false
.
Any exception thrown by component resolvers during the iteration is propagated to the caller of this method.
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.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.public void setValue(ELContext context, Object base, Object property, Object val)
property
object on the given base
object. All
component resolvers are asked to attempt to set the value.
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.
First, propertyResolved
is set to false
on the provided ELContext
.
Next, for each component resolver in this composite:
setValue()
method is called, passing in the provided context
, base
,
property
and value
.ELContext
's propertyResolved
flag is false
then iteration
continues.
If none of the component resolvers were able to perform this operation, the propertyResolved
flag
remains set to false
.
Any exception thrown by component resolvers during the iteration is propagated to the caller of this method.
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.val
- The value to set the property or variable to.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.public boolean isReadOnly(ELContext context, Object base, Object property)
base
and property
, attempts to determine whether a call to setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
will always fail. The result is obtained by querying all component resolvers.
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.
First, propertyResolved
is set to false
on the provided ELContext
.
Next, for each component resolver in this composite:
isReadOnly()
method is called, passing in the provided context
, base
and property
.ELContext
's propertyResolved
flag is false
then iteration
continues.isReadOnly()
is returned by this method.
If none of the component resolvers were able to perform this operation, the value false
is returned and
the propertyResolved
flag remains set to false
Any exception thrown by component resolvers during the iteration is propagated to the caller of this method.
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.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.public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base)
base
object. One use for this method is to assist tools in auto-completion. The results are collected from all component
resolvers.
The propertyResolved
property of the ELContext
is not relevant to this method. The results
of all ELResolver
s are concatenated.
The Iterator
returned is an iterator over the collection of FeatureDescriptor
objects
returned by the iterators returned by each component resolver's getFeatureDescriptors
method. If
null
is returned by a resolver, it is skipped.
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)
property
argument, given a
base
object. One use for this method is to assist tools in auto-completion. The result is obtained by
querying all component resolvers.
The Class
returned is the most specific class that is a common superclass of all the classes returned by
each component resolver's getCommonPropertyType
method. If null
is returned by a resolver,
it is skipped.
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 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 convertion.targetType
ELException
- thrown if errors occur.Copyright © 2018,2020 Eclipse Foundation.
Use is subject to license terms.