Class CompositeELResolver
- java.lang.Object
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- org.camunda.bpm.engine.impl.javax.el.ELResolver
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- org.camunda.bpm.engine.impl.javax.el.CompositeELResolver
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public class CompositeELResolver extends ELResolver
Maintains an ordered composite list of child ELResolvers. Though only a single ELResolver is associated with an ELContext, there are usually multiple resolvers considered for any given variable or property resolution. ELResolvers are combined together using a CompositeELResolver, to define rich semantics for evaluating an expression. For thegetValue(ELContext, Object, Object)
,getType(ELContext, Object, Object)
,setValue(ELContext, Object, Object, Object)
andisReadOnly(ELContext, Object, 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 methodsgetFeatureDescriptors(ELContext, Object)
andgetCommonPropertyType(ELContext, Object)
. Instead, results are collected and combined from all child ELResolvers for these methods.
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Field Summary
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Fields inherited from class org.camunda.bpm.engine.impl.javax.el.ELResolver
RESOLVABLE_AT_DESIGN_TIME, TYPE
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Constructor Summary
Constructors Constructor Description CompositeELResolver()
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
add(ELResolver elResolver)
Adds the given resolver to the list of component resolvers.java.lang.Class<?>
getCommonPropertyType(ELContext context, java.lang.Object base)
Returns the most general type that this resolver accepts for the property argument, given a base object.java.util.Iterator<java.beans.FeatureDescriptor>
getFeatureDescriptors(ELContext context, java.lang.Object base)
Returns information about the set of variables or properties that can be resolved for the given base object.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 thesetValue(ELContext, Object, Object, 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 by querying all component resolvers.java.lang.Object
invoke(ELContext context, java.lang.Object base, java.lang.Object method, java.lang.Class<?>[] paramTypes, java.lang.Object[] params)
Attempts to resolve and invoke the givenmethod
on the givenbase
object by querying all component resolvers.boolean
isReadOnly(ELContext context, java.lang.Object base, java.lang.Object property)
For a given base and property, attempts to determine whether a call tosetValue(ELContext, Object, Object, 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.
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Method Detail
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add
public void add(ELResolver elResolver)
Adds the given resolver to the list of component resolvers. Resolvers are consulted in the order in which they are added.- Parameters:
elResolver
- The component resolver to add.- Throws:
java.lang.NullPointerException
- If the provided resolver is null.
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getCommonPropertyType
public java.lang.Class<?> getCommonPropertyType(ELContext context, java.lang.Object base)
Returns the most general type that this resolver accepts for the 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.- Specified by:
getCommonPropertyType
in classELResolver
- Parameters:
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.- Returns:
- 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.
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getFeatureDescriptors
public java.util.Iterator<java.beans.FeatureDescriptor> getFeatureDescriptors(ELContext context, java.lang.Object base)
Returns information about the set of variables or properties that can be resolved for the given 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 ELResolvers 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.- Specified by:
getFeatureDescriptors
in classELResolver
- Parameters:
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.- Returns:
- An 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 method
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getType
public 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 thesetValue(ELContext, Object, Object, 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:- The getType() method is called, passing in the provided context, base and property.
- If the ELContext's propertyResolved flag is false then iteration continues.
- Otherwise, iteration stops and no more component resolvers are considered. The value returned by getType() is returned by this method.
- Specified by:
getType
in classELResolver
- Parameters:
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.property
- The property or variable to return the acceptable type for.- Returns:
- If the propertyResolved property of ELContext was set to true, then the most general acceptable type; otherwise undefined.
- Throws:
java.lang.NullPointerException
- if context is nullPropertyNotFoundException
- if base is not null and the specified 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.
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getValue
public 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 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:- The getValue() method is called, passing in the provided context, base and property.
- If the ELContext's propertyResolved flag is false then iteration continues.
- Otherwise, iteration stops and no more component resolvers are considered. The value returned by getValue() is returned by this method.
- Specified by:
getValue
in classELResolver
- Parameters:
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.property
- The property or variable to return the acceptable type for.- Returns:
- If the propertyResolved property of ELContext was set to true, then the result of the variable or property resolution; otherwise undefined.
- Throws:
java.lang.NullPointerException
- if context is nullPropertyNotFoundException
- if base is not null and the specified 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.
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isReadOnly
public boolean isReadOnly(ELContext context, java.lang.Object base, java.lang.Object property)
For a given base and property, attempts to determine whether a call tosetValue(ELContext, Object, Object, 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:- The isReadOnly() method is called, passing in the provided context, base and property.
- If the ELContext's propertyResolved flag is false then iteration continues.
- Otherwise, iteration stops and no more component resolvers are considered. The value returned by isReadOnly() is returned by this method.
- Specified by:
isReadOnly
in classELResolver
- Parameters:
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.property
- The property or variable to return the acceptable type for.- Returns:
- If the propertyResolved property of ELContext was set to true, then true if the property is read-only or false if not; otherwise undefined.
- Throws:
java.lang.NullPointerException
- if context is nullPropertyNotFoundException
- if base is not null and the specified 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.
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setValue
public 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. 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:- The setValue() method is called, passing in the provided context, base, property and value.
- If the ELContext's propertyResolved flag is false then iteration continues.
- Otherwise, iteration stops and no more component resolvers are considered.
- Specified by:
setValue
in classELResolver
- Parameters:
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.property
- The property or variable to return the acceptable type for.value
- The value to set the property or variable to.- Throws:
java.lang.NullPointerException
- if context is nullPropertyNotFoundException
- if base is not null and the specified property does not exist or is not readable.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.
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invoke
public java.lang.Object invoke(ELContext context, java.lang.Object base, java.lang.Object method, java.lang.Class<?>[] paramTypes, java.lang.Object[] params)
Attempts to resolve and invoke the givenmethod
on the givenbase
object by querying all component resolvers.If this resolver handles the given (base, method) pair, the
propertyResolved
property of theELContext
object must be set totrue
by the resolver, before returning. If this property is nottrue
after this method is called, the caller should ignore the return value.First,
propertyResolved
is set tofalse
on the providedELContext
.Next, for each component resolver in this composite:
- The
invoke()
method is called, passing in the providedcontext
,base
,method
,paramTypes
, andparams
. - If the
ELContext
'spropertyResolved
flag isfalse
then iteration continues. - Otherwise, iteration stops and no more component resolvers are considered. The value
returned by
getValue()
is returned by this method.
If none of the component resolvers were able to perform this operation, the value
null
is returned and thepropertyResolved
flag remains set tofalse
Any exception thrown by component resolvers during the iteration is propagated to the caller of this method.
- Overrides:
invoke
in classELResolver
- Parameters:
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 aString
. If method is "<init>"or "<clinit>" a NoSuchMethodException is raised.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 benull
, in which case the method's formal parameter types are assumed to be unknown.params
- The parameters to pass to the method, ornull
if no parameters.- Returns:
- The result of the method invocation (
null
if the method has avoid
return type). - Since:
- 2.2
- The
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