groovy.lang
[Java] Interface MetaObjectProtocol

public interface MetaObjectProtocol

An interface that defines the API usable by clients of Groovy's Meta Object Protocol (MOP). These methods are implemented by the reference implementation of the MetaClass interface.

Authors:

John Wilson

Graeme Rocher

See Also:

MetaClassImpl

getAttribute

public Object getAttribute(Object object, String attribute)

Retrieves an attribute of an instance of the class returned by the getTheClass() method.

What this means is largely down to the MetaClass implementation, however the default case would result in attempt to read a field of the instance.

Parameters:

object - An instance of the class returned by the getTheClass() method

attribute - The name of the attribute to retrieve the value for

Returns:

The attribute value

See Also:

MetaClassImpl

getMetaMethod

public MetaMethod getMetaMethod(String name, Object[] args)

Retrieves an instance MetaMethod for the given name and argument values, using the types of the argument values to establish the chosen MetaMethod

Parameters:

name - The name of the MetaMethod

args - Array containing - 1) the argument values (using which their types are then inferred), or 2) the corresponding argument types

Returns:

A MetaMethod or null if it doesn't exist

getMetaProperty

public MetaProperty getMetaProperty(String name)

Returns a MetaProperty for the given name or null if it doesn't exist

Parameters:

name - The name of the MetaProperty

Returns:

A MetaProperty or null

getMethods

public List getMethods()

Obtain a list of all the meta methods available on this meta class

Returns:

A list of MetaMethod instances

See Also:

MetaMethod

getProperties

public List getProperties()

Obtain a list of all meta properties available on this meta class

Returns:

A list of MetaProperty instances

See Also:

MetaProperty

getProperty

public Object getProperty(Object object, String property)

Retrieves a property of an instance of the class returned by the getTheClass() method.

What this means is largely down to the MetaClass implementation, however the default case would result in an attempt to invoke a JavaBean getter, or if no such getter exists a public field of the instance.

Parameters:

object - An instance of the class returned by the getTheClass() method

property - The name of the property to retrieve the value for

Returns:

The properties value

See Also:

MetaClassImpl

getStaticMetaMethod

public MetaMethod getStaticMetaMethod(String name, Object[] args)

Retrieves a static MetaMethod for the given name and argument values, using the types of the arguments to establish the chosen MetaMethod

Parameters:

name - The name of the MetaMethod

args - The argument types

Returns:

A MetaMethod or null if it doesn't exist

getTheClass

public Class getTheClass()

Retrieves that Java Class that the attached Meta behaviours apply to

Returns:

The java.lang.Class instance

hasProperty

public MetaProperty hasProperty(Object obj, String name)

Returns true of the implementing MetaClass has a property of the given name

Note that this method will only return true for realised properties and does not take into account implementation of getProperty or propertyMissing

Parameters:

obj - The object to inspect

name - The name of the property

Returns:

The MetaProperty or null if it doesn't exist

invokeConstructor

public Object invokeConstructor(Object[] arguments)

Invokes a constructor for the given arguments. The MetaClass will attempt to pick the best argument which matches the types of the objects passed within the arguments array

Parameters:

arguments - The arguments to the constructor

Returns:

An instance of the java.lang.Class that this MetaObjectProtocol object applies to

invokeMethod

public Object invokeMethod(Object object, String methodName, Object[] arguments)

Invokes a method on the given Object with the given name and arguments. The MetaClass will attempt to pick the best method for the given name and arguments. If a method cannot be invoked a MissingMethodException will be thrown.

Parameters:

object - The instance which the method is invoked on

methodName - The name of the method

arguments - The arguments to the method

Returns:

The return value of the method which is null if the return type is void

See Also:

MissingMethodException

invokeMethod

public Object invokeMethod(Object object, String methodName, Object arguments)

Invokes a method on the given object, with the given name and single argument.

Parameters:

object - The Object to invoke the method on

methodName - The name of the method

arguments - The argument to the method

Returns:

The return value of the method which is null if the return type is void

See Also:

invokeMethod(Object, String, Object[])

invokeStaticMethod

public Object invokeStaticMethod(Object object, String methodName, Object[] arguments)

Invokes a static method on the given Object with the given name and arguments.

The Object can either be an instance of the class that this MetaObjectProtocol instance applies to or the java.lang.Class instance itself. If a method cannot be invoked a MissingMethodException is will be thrown

Parameters:

object - An instance of the class returned by the getTheClass() method or the class itself

methodName - The name of the method

arguments - The arguments to the method

Returns:

The return value of the method which is null if the return type is void

See Also:

MissingMethodException

respondsTo

public List respondsTo(Object obj, String name, Object[] argTypes)

Returns an object satisfying Groovy truth if the implementing MetaClass responds to a method with the given name and arguments types.

Note that this method's return value is based on realised methods and does not take into account objects or classes that implement invokeMethod or methodMissing

This method is "safe" in that it will always return a value and never throw an exception

Parameters:

obj - The object to inspect

name - The name of the method of interest

argTypes - The argument types to match against

Returns:

A List of MetaMethods matching the argument types which will be empty if no matching methods exist

respondsTo

public List respondsTo(Object obj, String name)

Returns an object satisfying Groovy truth if the implementing MetaClass responds to a method with the given name regardless of arguments. In other words this method will return for foo() and foo(String).

Note that this method's return value is based on realised methods and does not take into account objects or classes that implement invokeMethod or methodMissing

This method is "safe" in that it will always return a value and never throw an exception

Parameters:

obj - The object to inspect

name - The name of the method of interest

Returns:

A List of MetaMethods which will be empty if no methods with the given name exist

setAttribute

public void setAttribute(Object object, String attribute, Object newValue)

Sets an attribute of an instance of the class returned by the getTheClass() method.

What this means is largely down to the MetaClass implementation, however the default case would result in an attempt to set a field of the instance.

Parameters:

object - An instance of the class returned by the getTheClass() method

attribute - The name of the attribute to set

newValue - The new value of the attribute

See Also:

MetaClassImpl

setProperty

public void setProperty(Object object, String property, Object newValue)

Sets a property of an instance of the class returned by the getTheClass() method.

What this means is largely down to the MetaClass implementation, however the default case would result in an attempt to invoke a JavaBean setter, or if no such setter exists to set a public field of the instance.

Parameters:

object - An instance of the class returned by the getTheClass() method

property - The name of the property to set

newValue - The new value of the property

See Also:

MetaClassImpl

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