groovy.lang
[Java] Interface MetaClass

groovy.lang.MetaClass
  groovy.lang.MetaObjectProtocol

All Superinterfaces:

MetaObjectProtocol

public interface MetaClass
extends MetaObjectProtocol

A MetaClass within Groovy defines the behaviour of any given Groovy or Java class. The MetaClass interface defines two parts. The client API, which is defined via the extend MetaObjectProtocol interface and the contract with the Groovy runtime system. In general the compiler and Groovy runtime engine interact with methods on this class whilst MetaClass clients interact with the method defined by the MetaObjectProtocol interface

Authors:

John Wilson

Graeme Rocher

See Also:

MetaClassImpl

MetaObjectProtocol

getAttribute

public java.lang.Object getAttribute(java.lang.Class sender, java.lang.Object receiver, java.lang.String messageName, boolean useSuper)

Retrieves the value of an attribute (field). This method is to support the Groovy runtime and not for general client API usage.

Parameters:

sender - The class of the object that requested the attribute

receiver - The instance

messageName - The name of the attribute

useSuper - Whether to look-up on the super class or not

Returns:

The attribute value

getClassNode

public ClassNode getClassNode()

Obtains a reference to the original AST for the MetaClass if it is available at runtime

Returns:

The original AST or null if it cannot be returned

getMetaMethods

public java.util.List getMetaMethods()

Retrieves a list of MetaMethods held by this class

Returns:

A list of MetaMethods

getMethods

public java.util.List getMethods()

Retrieves a list of MetaMethods held by the class

Returns:

A list of MetaMethods

getProperties

public java.util.List getProperties()

Retrieves a list of MetaProperty instances that the MetaClass has

Returns:

A list of MetaProperty instances

See Also:

MetaProperty

getProperty

public java.lang.Object getProperty(java.lang.Class sender, java.lang.Object receiver, java.lang.String property, boolean isCallToSuper, boolean fromInsideClass)

Retrieves a property on the given receiver for the specified arguments. The sender is the class that is requesting the property from the object. The MetaClass will attempt to establish the method to invoke based on the name and arguments provided.

The isCallToSuper and fromInsideClass help the Groovy runtime perform optimisations on the call to go directly to the super class if necessary

Parameters:

sender - The java.lang.Class instance that requested the property

receiver - The Object which the property is being retrieved from

property - The name of the property

isCallToSuper - Whether the call is to a super class property

fromInsideClass - ??

Returns:

The properties value

initialize

public void initialize()

complete the initialisation process. After this method is called no methods should be added to the meta class. Invocation of methods or access to fields/properties is forbidden unless this method is called. This method should contain any initialisation code, taking a longer time to complete. An example is the creation of the Reflector. It is suggested to synchronize this method.

invokeMethod

public java.lang.Object invokeMethod(java.lang.Class sender, java.lang.Object receiver, java.lang.String methodName, java.lang.Object[] arguments, boolean isCallToSuper, boolean fromInsideClass)

Invokes a method on the given receiver for the specified arguments. The sender is the class that invoked the method on the object. The MetaClass will attempt to establish the method to invoke based on the name and arguments provided.

The isCallToSuper and fromInsideClass help the Groovy runtime perform optimisations on the call to go directly to the super class if necessary

Parameters:

sender - The java.lang.Class instance that invoked the method

receiver - The object which the method was invoked on

methodName - The name of the method

arguments - The arguments to the method

isCallToSuper - Whether the method is a call to a super class method

fromInsideClass - Whether the call was invoked from the inside or the outside of the class

Returns:

The return value of the method

invokeMissingMethod

public java.lang.Object invokeMissingMethod(java.lang.Object instance, java.lang.String methodName, java.lang.Object[] arguments)

Attempts to invoke the methodMissing method otherwise throws a MissingMethodException

Parameters:

instance - The instance to invoke methodMissing on

methodName - The name of the method

arguments - The arguments to the method

Returns:

The results of methodMissing or throws MissingMethodException

See Also:

MissingMethodException

invokeMissingProperty

public java.lang.Object invokeMissingProperty(java.lang.Object instance, java.lang.String propertyName, java.lang.Object optionalValue, boolean isGetter)

Invokes the propertyMissing method otherwise throws a MissingPropertyException

Parameters:

instance - The instance of the class

propertyName - The name of the property

optionalValue - The value of the property which could be null in the case of a getter

isGetter - Whether the missing property event was the result of a getter or a setter

Returns:

The result of the propertyMissing method or throws MissingPropertyException

pickMethod

public MetaMethod pickMethod(java.lang.String methodName, java.lang.Class[] arguments)

Selects a method by name and argument classes. This method does not search for an exact match, it searches for a compatible method. For this the method selection mechanism is used as provided by the implementation of this MetaClass. pickMethod may or may not be used during the method selection process when invoking a method. There is no warranty for that.

throws:

GroovyRuntimeException if there is more than one matching method

Parameters:

methodName - the name of the method to pick

arguments - the method arguments

Returns:

a matching MetaMethod or null

selectConstructorAndTransformArguments

public int selectConstructorAndTransformArguments(int numberOfConstructors, java.lang.Object[] arguments)

Internal method to support Groovy runtime. Not for client usage.

Parameters:

numberOfConstructors - The number of constructors

arguments - The arguments

Returns:

selected index

setAttribute

public void setAttribute(java.lang.Class sender, java.lang.Object receiver, java.lang.String messageName, java.lang.Object messageValue, boolean useSuper, boolean fromInsideClass)

Sets the value of an attribute (field). This method is to support the Groovy runtime and not for general client API usage.

Parameters:

sender - The class of the object that requested the attribute

receiver - The instance

messageName - The name of the attribute

messageValue - The value of the attribute

useSuper - Whether to look-up on the super class or not

fromInsideClass - Whether the call happened from the inside or the outside of a class

setProperty

public void setProperty(java.lang.Class sender, java.lang.Object receiver, java.lang.String property, java.lang.Object value, boolean isCallToSuper, boolean fromInsideClass)

Retrieves a property on the given receiver for the specified arguments. The sender is the class that is requesting the property from the object. The MetaClass will attempt to establish the method to invoke based on the name and arguments provided.

The isCallToSuper and fromInsideClass help the Groovy runtime perform optimisations on the call to go directly to the super class if necessary

Parameters:

sender - The java.lang.Class instance that is mutating the property

receiver - The Object which the property is being set on

property - The name of the property

value - The new value of the property to set

isCallToSuper - Whether the call is to a super class property

fromInsideClass - ??

Groovy Documentation