org.apache.commons.beanutils
Class MethodUtils

java.lang.Object
  |
  +--org.apache.commons.beanutils.MethodUtils

public class MethodUtils

extends java.lang.Object

Utility reflection methods focussed on methods in general rather than properties in particular.

Known Limitations

Accessing Public Methods In A Default Access Superclass

There is an issue when invoking public methods contained in a default access superclass. Reflection locates these methods fine and correctly assigns them as public. However, an IllegalAccessException is thrown if the method is invoked.

MethodUtils contains a workaround for this situation. It will attempt to call setAccessible on this method. If this call succeeds, then the method can be invoked as normal. This call will only succeed when the application has sufficient security privilages. If this call fails then a warning will be logged and the method may fail.

Author:

Craig R. McClanahan, Ralph Schaer, Chris Audley, Rey François, Gregor Raıman, Jan Sorensen, Robert Burrell Donkin

Nested Class Summary

private static class

MethodUtils.MethodDescriptor Represents the key to looking up a Method by reflection.

Field Summary

private static java.util.WeakHashMap	cache Stores a cache of Methods against MethodDescriptors, in a WeakHashMap.
private static java.lang.Class[]	emptyClassArray An empty class array
private static java.lang.Object[]	emptyObjectArray An empty object array
private static org.apache.commons.logging.Log	log All logging goes through this logger
private static boolean	loggedAccessibleWarning Only log warning about accessibility work around once

Constructor Summary

MethodUtils()

Method Summary

static java.lang.reflect.Method	getAccessibleMethod(java.lang.Class clazz, java.lang.String methodName, java.lang.Class parameterType) Return an accessible method (that is, one that can be invoked via reflection) with given name and a single parameter.
static java.lang.reflect.Method	getAccessibleMethod(java.lang.Class clazz, java.lang.String methodName, java.lang.Class[] parameterTypes) Return an accessible method (that is, one that can be invoked via reflection) with given name and parameters.
static java.lang.reflect.Method	getAccessibleMethod(java.lang.reflect.Method method) Return an accessible method (that is, one that can be invoked via reflection) that implements the specified Method.
private static java.lang.reflect.Method	getAccessibleMethodFromInterfaceNest(java.lang.Class clazz, java.lang.String methodName, java.lang.Class[] parameterTypes) Return an accessible method (that is, one that can be invoked via reflection) that implements the specified method, by scanning through all implemented interfaces and subinterfaces.
static java.lang.reflect.Method	getMatchingAccessibleMethod(java.lang.Class clazz, java.lang.String methodName, java.lang.Class[] parameterTypes) Find an accessible method that matches the given name and has compatible parameters.
static java.lang.Class	getPrimitiveType(java.lang.Class wrapperType) Gets the class for the primitive type corresponding to the primitive wrapper class given.
static java.lang.Class	getPrimitiveWrapper(java.lang.Class primitiveType) Gets the wrapper object class for the given primitive type class.
static java.lang.Object	invokeExactMethod(java.lang.Object object, java.lang.String methodName, java.lang.Object arg) Invoke a method whose parameter type matches exactly the object type.
static java.lang.Object	invokeExactMethod(java.lang.Object object, java.lang.String methodName, java.lang.Object[] args) Invoke a method whose parameter types match exactly the object types.
static java.lang.Object	invokeExactMethod(java.lang.Object object, java.lang.String methodName, java.lang.Object[] args, java.lang.Class[] parameterTypes) Invoke a method whose parameter types match exactly the parameter types given.
static java.lang.Object	invokeMethod(java.lang.Object object, java.lang.String methodName, java.lang.Object arg) Invoke a named method whose parameter type matches the object type.
static java.lang.Object	invokeMethod(java.lang.Object object, java.lang.String methodName, java.lang.Object[] args) Invoke a named method whose parameter type matches the object type.
static java.lang.Object	invokeMethod(java.lang.Object object, java.lang.String methodName, java.lang.Object[] args, java.lang.Class[] parameterTypes) Invoke a named method whose parameter type matches the object type.
static boolean	isAssignmentCompatible(java.lang.Class parameterType, java.lang.Class parameterization) Determine whether a type can be used as a parameter in a method invocation.
static java.lang.Class	toNonPrimitiveClass(java.lang.Class clazz) Find a non primitive representation for given primitive class.

Methods inherited from class java.lang.Object

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

Field Detail

log

private static org.apache.commons.logging.Log log

All logging goes through this logger

loggedAccessibleWarning

private static boolean loggedAccessibleWarning

Only log warning about accessibility work around once

emptyClassArray

private static final java.lang.Class[] emptyClassArray

An empty class array

emptyObjectArray

private static final java.lang.Object[] emptyObjectArray

An empty object array

cache

private static java.util.WeakHashMap cache

Stores a cache of Methods against MethodDescriptors, in a WeakHashMap.

Constructor Detail

MethodUtils

public MethodUtils()

Method Detail

invokeMethod

public static java.lang.Object invokeMethod(java.lang.Object object,
                                            java.lang.String methodName,
                                            java.lang.Object arg)
                                     throws java.lang.NoSuchMethodException,
                                            java.lang.IllegalAccessException,
                                            java.lang.reflect.InvocationTargetException

Invoke a named method whose parameter type matches the object type.

The behaviour of this method is less deterministic than invokeExactMethod(java.lang.Object, java.lang.String, java.lang.Object). It loops through all methods with names that match and then executes the first it finds with compatable parameters.

This method supports calls to methods taking primitive parameters via passing in wrapping classes. So, for example, a Boolean class would match a boolean primitive.

This is a convenient wrapper for invokeMethod(Object object,String methodName,Object [] args).

Parameters:

object - invoke method on this object

methodName - get method with this name

arg - use this argument

Throws:

java.lang.NoSuchMethodException - if there is no such accessible method

java.lang.reflect.InvocationTargetException - wraps an exception thrown by the method invoked

java.lang.IllegalAccessException - if the requested method is not accessible via reflection

invokeMethod

public static java.lang.Object invokeMethod(java.lang.Object object,
                                            java.lang.String methodName,
                                            java.lang.Object[] args)
                                     throws java.lang.NoSuchMethodException,
                                            java.lang.IllegalAccessException,
                                            java.lang.reflect.InvocationTargetException

Invoke a named method whose parameter type matches the object type.

The behaviour of this method is less deterministic than invokeExactMethod(Object object,String methodName,Object [] args). It loops through all methods with names that match and then executes the first it finds with compatable parameters.

This method supports calls to methods taking primitive parameters via passing in wrapping classes. So, for example, a Boolean class would match a boolean primitive.

This is a convenient wrapper for invokeMethod(Object object,String methodName,Object [] args,Class[] parameterTypes).

Parameters:

object - invoke method on this object

methodName - get method with this name

args - use these arguments - treat null as empty array

Throws:

java.lang.NoSuchMethodException - if there is no such accessible method

java.lang.reflect.InvocationTargetException - wraps an exception thrown by the method invoked

java.lang.IllegalAccessException - if the requested method is not accessible via reflection

invokeMethod

public static java.lang.Object invokeMethod(java.lang.Object object,
                                            java.lang.String methodName,
                                            java.lang.Object[] args,
                                            java.lang.Class[] parameterTypes)
                                     throws java.lang.NoSuchMethodException,
                                            java.lang.IllegalAccessException,
                                            java.lang.reflect.InvocationTargetException

Invoke a named method whose parameter type matches the object type.

The behaviour of this method is less deterministic than invokeExactMethod(Object object,String methodName,Object [] args,Class[] parameterTypes). It loops through all methods with names that match and then executes the first it finds with compatable parameters.

This method supports calls to methods taking primitive parameters via passing in wrapping classes. So, for example, a Boolean class would match a boolean primitive.

Parameters:

object - invoke method on this object

methodName - get method with this name

args - use these arguments - treat null as empty array

parameterTypes - match these parameters - treat null as empty array

Throws:

java.lang.NoSuchMethodException - if there is no such accessible method

java.lang.reflect.InvocationTargetException - wraps an exception thrown by the method invoked

java.lang.IllegalAccessException - if the requested method is not accessible via reflection

invokeExactMethod

public static java.lang.Object invokeExactMethod(java.lang.Object object,
                                                 java.lang.String methodName,
                                                 java.lang.Object arg)
                                          throws java.lang.NoSuchMethodException,
                                                 java.lang.IllegalAccessException,
                                                 java.lang.reflect.InvocationTargetException

Invoke a method whose parameter type matches exactly the object type.

This is a convenient wrapper for invokeExactMethod(Object object,String methodName,Object [] args).

Parameters:

object - invoke method on this object

methodName - get method with this name

arg - use this argument

Throws:

java.lang.NoSuchMethodException - if there is no such accessible method

java.lang.reflect.InvocationTargetException - wraps an exception thrown by the method invoked

java.lang.IllegalAccessException - if the requested method is not accessible via reflection

invokeExactMethod

public static java.lang.Object invokeExactMethod(java.lang.Object object,
                                                 java.lang.String methodName,
                                                 java.lang.Object[] args)
                                          throws java.lang.NoSuchMethodException,
                                                 java.lang.IllegalAccessException,
                                                 java.lang.reflect.InvocationTargetException

Invoke a method whose parameter types match exactly the object types.

This uses reflection to invoke the method obtained from a call to getAccessibleMethod(java.lang.Class, java.lang.String, java.lang.Class).

Parameters:

object - invoke method on this object

methodName - get method with this name

args - use these arguments - treat null as empty array

Throws:

java.lang.NoSuchMethodException - if there is no such accessible method

java.lang.reflect.InvocationTargetException - wraps an exception thrown by the method invoked

java.lang.IllegalAccessException - if the requested method is not accessible via reflection

invokeExactMethod

public static java.lang.Object invokeExactMethod(java.lang.Object object,
                                                 java.lang.String methodName,
                                                 java.lang.Object[] args,
                                                 java.lang.Class[] parameterTypes)
                                          throws java.lang.NoSuchMethodException,
                                                 java.lang.IllegalAccessException,
                                                 java.lang.reflect.InvocationTargetException

Invoke a method whose parameter types match exactly the parameter types given.

This uses reflection to invoke the method obtained from a call to getAccessibleMethod(java.lang.Class, java.lang.String, java.lang.Class).

Parameters:

object - invoke method on this object

methodName - get method with this name

args - use these arguments - treat null as empty array

parameterTypes - match these parameters - treat null as empty array

Throws:

java.lang.NoSuchMethodException - if there is no such accessible method

java.lang.reflect.InvocationTargetException - wraps an exception thrown by the method invoked

java.lang.IllegalAccessException - if the requested method is not accessible via reflection

getAccessibleMethod

public static java.lang.reflect.Method getAccessibleMethod(java.lang.Class clazz,
                                                           java.lang.String methodName,
                                                           java.lang.Class parameterType)

Return an accessible method (that is, one that can be invoked via reflection) with given name and a single parameter. If no such method can be found, return null. Basically, a convenience wrapper that constructs a Class array for you.

Parameters:

clazz - get method from this class

methodName - get method with this name

parameterType - taking this type of parameter

getAccessibleMethod

public static java.lang.reflect.Method getAccessibleMethod(java.lang.Class clazz,
                                                           java.lang.String methodName,
                                                           java.lang.Class[] parameterTypes)

Return an accessible method (that is, one that can be invoked via reflection) with given name and parameters. If no such method can be found, return null. This is just a convenient wrapper for getAccessibleMethod(Method method).

Parameters:

clazz - get method from this class

methodName - get method with this name

parameterTypes - with these parameters types

getAccessibleMethod

public static java.lang.reflect.Method getAccessibleMethod(java.lang.reflect.Method method)

Return an accessible method (that is, one that can be invoked via reflection) that implements the specified Method. If no such method can be found, return null.

Parameters:

method - The method that we wish to call

getAccessibleMethodFromInterfaceNest

private static java.lang.reflect.Method getAccessibleMethodFromInterfaceNest(java.lang.Class clazz,
                                                                             java.lang.String methodName,
                                                                             java.lang.Class[] parameterTypes)

Return an accessible method (that is, one that can be invoked via reflection) that implements the specified method, by scanning through all implemented interfaces and subinterfaces. If no such method can be found, return null.

There isn't any good reason why this method must be private. It is because there doesn't seem any reason why other classes should call this rather than the higher level methods.

Parameters:

clazz - Parent class for the interfaces to be checked

methodName - Method name of the method we wish to call

parameterTypes - The parameter type signatures

getMatchingAccessibleMethod

public static java.lang.reflect.Method getMatchingAccessibleMethod(java.lang.Class clazz,
                                                                   java.lang.String methodName,
                                                                   java.lang.Class[] parameterTypes)

Find an accessible method that matches the given name and has compatible parameters. Compatible parameters mean that every method parameter is assignable from the given parameters. In other words, it finds a method with the given name that will take the parameters given.

This method is slightly undeterminstic since it loops through methods names and return the first matching method.

This method is used by invokeMethod(Object object,String methodName,Object [] args,Class[] parameterTypes).

This method can match primitive parameter by passing in wrapper classes. For example, a Boolean will match a primitive boolean parameter.

Parameters:

clazz - find method in this class

methodName - find method with this name

parameterTypes - find method with compatible parameters

isAssignmentCompatible

public static final boolean isAssignmentCompatible(java.lang.Class parameterType,
                                                   java.lang.Class parameterization)

Determine whether a type can be used as a parameter in a method invocation. This method handles primitive conversions correctly.

In order words, it will match a Boolean to a boolean, a Long to a long, a Float to a float, a Integer to a int, and a Double to a double. Now logic widening matches are allowed. For example, a Long will not match a int.

Parameters:

parameterType - the type of parameter accepted by the method

parameterization - the type of parameter being tested

Returns:

true if the assignement is compatible.

getPrimitiveWrapper

public static java.lang.Class getPrimitiveWrapper(java.lang.Class primitiveType)

Gets the wrapper object class for the given primitive type class. For example, passing boolean.class returns Boolean.class

Parameters:

primitiveType - the primitive type class for which a match is to be found

Returns:

the wrapper type associated with the given primitive or null if no match is found

getPrimitiveType

public static java.lang.Class getPrimitiveType(java.lang.Class wrapperType)

Gets the class for the primitive type corresponding to the primitive wrapper class given. For example, an instance of Boolean.class returns a boolean.class.

Parameters:

wrapperType - the

Returns:

the primitive type class corresponding to the given wrapper class, null if no match is found

toNonPrimitiveClass

public static java.lang.Class toNonPrimitiveClass(java.lang.Class clazz)

Find a non primitive representation for given primitive class.

Parameters:

clazz - the class to find a representation for, not null

Returns:

the original class if it not a primitive. Otherwise the wrapper class. Not null