org.springframework.util

Class MethodInvoker

java.lang.Object

org.springframework.util.MethodInvoker

Direct Known Subclasses:

ArgumentConvertingMethodInvoker

public class MethodInvoker
extends Object

Helper class that allows for specifying a method to invoke in a declarative fashion, be it static or non-static.

Usage: Specify "targetClass"/"targetMethod" or "targetObject"/"targetMethod", optionally specify arguments, prepare the invoker. Afterwards, you may invoke the method any number of times, obtaining the invocation result.

Since:

19.02.2004

Author:

Colin Sampaleanu, Juergen Hoeller

See Also:

prepare(), invoke()

Field Summary

Fields

Modifier and Type	Field and Description
protected Class<?>	targetClass

Constructor Summary

Constructors

Constructor and Description
MethodInvoker()

Method Summary

Modifier and Type	Method and Description
protected Method	findMatchingMethod() Find a matching method with the specified name for the specified arguments.
Object[]	getArguments() Return the arguments for the method invocation.
Method	getPreparedMethod() Return the prepared Method object that will be invoked.
Class<?>	getTargetClass() Return the target class on which to call the target method.
String	getTargetMethod() Return the name of the method to be invoked.
Object	getTargetObject() Return the target object on which to call the target method.
static int	getTypeDifferenceWeight(Class<?>[] paramTypes, Object[] args) Algorithm that judges the match between the declared parameter types of a candidate method and a specific list of arguments that this method is supposed to be invoked with.
Object	invoke() Invoke the specified method.
boolean	isPrepared() Return whether this invoker has been prepared already, i.e.
void	prepare() Prepare the specified method.
protected Class<?>	resolveClassName(String className) Resolve the given class name into a Class.
void	setArguments(Object... arguments) Set arguments for the method invocation.
void	setStaticMethod(String staticMethod) Set a fully qualified static method name to invoke, e.g.
void	setTargetClass(Class<?> targetClass) Set the target class on which to call the target method.
void	setTargetMethod(String targetMethod) Set the name of the method to be invoked.
void	setTargetObject(Object targetObject) Set the target object on which to call the target method.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

targetClass

@Nullable
protected Class<?> targetClass

Constructor Detail

MethodInvoker

public MethodInvoker()

Method Detail

setTargetClass

public void setTargetClass(@Nullable
                           Class<?> targetClass)

Set the target class on which to call the target method. Only necessary when the target method is static; else, a target object needs to be specified anyway.

See Also:

setTargetObject(java.lang.Object), setTargetMethod(java.lang.String)

getTargetClass

@Nullable
public Class<?> getTargetClass()

Return the target class on which to call the target method.

setTargetObject

public void setTargetObject(@Nullable
                            Object targetObject)

Set the target object on which to call the target method. Only necessary when the target method is not static; else, a target class is sufficient.

See Also:

setTargetClass(java.lang.Class<?>), setTargetMethod(java.lang.String)

getTargetObject

@Nullable
public Object getTargetObject()

Return the target object on which to call the target method.

setTargetMethod

public void setTargetMethod(@Nullable
                            String targetMethod)

Set the name of the method to be invoked. Refers to either a static method or a non-static method, depending on a target object being set.

See Also:

setTargetClass(java.lang.Class<?>), setTargetObject(java.lang.Object)

getTargetMethod

@Nullable
public String getTargetMethod()

Return the name of the method to be invoked.

setStaticMethod

public void setStaticMethod(String staticMethod)

Set a fully qualified static method name to invoke, e.g. "example.MyExampleClass.myExampleMethod". This is a convenient alternative to specifying targetClass and targetMethod.

See Also:

setTargetClass(java.lang.Class<?>), setTargetMethod(java.lang.String)

setArguments

public void setArguments(Object... arguments)

Set arguments for the method invocation. If this property is not set, or the Object array is of length 0, a method with no arguments is assumed.

getArguments

public Object[] getArguments()

Return the arguments for the method invocation.

prepare

public void prepare()
             throws ClassNotFoundException,
                    NoSuchMethodException

Prepare the specified method. The method can be invoked any number of times afterwards.

Throws:

ClassNotFoundException

NoSuchMethodException

See Also:

getPreparedMethod(), invoke()

resolveClassName

protected Class<?> resolveClassName(String className)
                             throws ClassNotFoundException

Resolve the given class name into a Class.

The default implementations uses ClassUtils.forName, using the thread context class loader.

Parameters:

className - the class name to resolve

Returns:

the resolved Class

Throws:

ClassNotFoundException - if the class name was invalid

findMatchingMethod

@Nullable
protected Method findMatchingMethod()

Find a matching method with the specified name for the specified arguments.

Returns:

a matching method, or null if none

See Also:

getTargetClass(), getTargetMethod(), getArguments()

getPreparedMethod

public Method getPreparedMethod()
                         throws IllegalStateException

Return the prepared Method object that will be invoked.

Can for example be used to determine the return type.

Returns:

the prepared Method object (never null)

Throws:

IllegalStateException - if the invoker hasn't been prepared yet

See Also:

prepare(), invoke()

isPrepared

public boolean isPrepared()

Return whether this invoker has been prepared already, i.e. whether it allows access to getPreparedMethod() already.

invoke

@Nullable
public Object invoke()
                        throws InvocationTargetException,
                               IllegalAccessException

Invoke the specified method.

The invoker needs to have been prepared before.

Returns:

the object (possibly null) returned by the method invocation, or null if the method has a void return type

Throws:

InvocationTargetException - if the target method threw an exception

IllegalAccessException - if the target method couldn't be accessed

See Also:

prepare()

getTypeDifferenceWeight

public static int getTypeDifferenceWeight(Class<?>[] paramTypes,
                                          Object[] args)

Algorithm that judges the match between the declared parameter types of a candidate method and a specific list of arguments that this method is supposed to be invoked with.

Determines a weight that represents the class hierarchy difference between types and arguments. A direct match, i.e. type Integer → arg of class Integer, does not increase the result - all direct matches means weight 0. A match between type Object and arg of class Integer would increase the weight by 2, due to the superclass 2 steps up in the hierarchy (i.e. Object) being the last one that still matches the required type Object. Type Number and class Integer would increase the weight by 1 accordingly, due to the superclass 1 step up the hierarchy (i.e. Number) still matching the required type Number. Therefore, with an arg of type Integer, a constructor (Integer) would be preferred to a constructor (Number) which would in turn be preferred to a constructor (Object). All argument weights get accumulated.

Note: This is the algorithm used by MethodInvoker itself and also the algorithm used for constructor and factory method selection in Spring's bean container (in case of lenient constructor resolution which is the default for regular bean definitions).

Parameters:

paramTypes - the parameter types to match

args - the arguments to match

Returns:

the accumulated weight for all arguments