public class ConstructorUtils extends Object
Utility reflection methods focused on constructors, modeled after
MethodUtils.
There is an issue when invoking public constructors
contained in a default access superclass. Reflection correctly locates these
constructors and assigns them as public. However, an
IllegalAccessException is thrown if the constructor is
invoked.
ConstructorUtils contains a workaround for this situation: it
will attempt to call AccessibleObject.setAccessible(boolean) on this constructor. If this
call succeeds, then the method can be invoked as normal. This call will only
succeed when the application has sufficient security privileges. If this call
fails then a warning will be logged and the method may fail.
| Constructor and Description |
|---|
ConstructorUtils()
ConstructorUtils instances should NOT be constructed in standard
programming.
|
| Modifier and Type | Method and Description |
|---|---|
static <T> Constructor<T> |
getAccessibleConstructor(Class<T> cls,
Class<?>... parameterTypes)
Finds a constructor given a class and signature, checking accessibility.
|
static <T> Constructor<T> |
getAccessibleConstructor(Constructor<T> ctor)
Checks if the specified constructor is accessible.
|
static <T> Constructor<T> |
getMatchingAccessibleConstructor(Class<T> cls,
Class<?>... parameterTypes)
Finds an accessible constructor with compatible parameters.
|
static <T> T |
invokeConstructor(Class<T> cls,
Object... args)
Returns a new instance of the specified class inferring the right constructor
from the types of the arguments.
|
static <T> T |
invokeConstructor(Class<T> cls,
Object[] args,
Class<?>[] parameterTypes)
Returns a new instance of the specified class choosing the right constructor
from the list of parameter types.
|
static <T> T |
invokeExactConstructor(Class<T> cls,
Object... args)
Returns a new instance of the specified class inferring the right constructor
from the types of the arguments.
|
static <T> T |
invokeExactConstructor(Class<T> cls,
Object[] args,
Class<?>[] parameterTypes)
Returns a new instance of the specified class choosing the right constructor
from the list of parameter types.
|
public ConstructorUtils()
ConstructorUtils instances should NOT be constructed in standard
programming. Instead, the class should be used as
ConstructorUtils.invokeConstructor(cls, args).
This constructor is public to permit tools that require a JavaBean
instance to operate.
public static <T> T invokeConstructor(Class<T> cls, Object... args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException
Returns a new instance of the specified class inferring the right constructor from the types of the arguments.
This locates and calls a constructor. The constructor signature must match the argument types by assignment compatibility.
T - the type to be constructedcls - the class to be constructed, not nullargs - the array of arguments, null treated as emptycls, not nullNullPointerException - if cls is nullNoSuchMethodException - if a matching constructor cannot be foundIllegalAccessException - if invocation is not permitted by securityInvocationTargetException - if an error occurs on invocationInstantiationException - if an error occurs on instantiationinvokeConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])public static <T> T invokeConstructor(Class<T> cls, Object[] args, Class<?>[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException
Returns a new instance of the specified class choosing the right constructor from the list of parameter types.
This locates and calls a constructor. The constructor signature must match the parameter types by assignment compatibility.
T - the type to be constructedcls - the class to be constructed, not nullargs - the array of arguments, null treated as emptyparameterTypes - the array of parameter types, null treated as emptycls, not nullNullPointerException - if cls is nullNoSuchMethodException - if a matching constructor cannot be foundIllegalAccessException - if invocation is not permitted by securityInvocationTargetException - if an error occurs on invocationInstantiationException - if an error occurs on instantiationConstructor.newInstance(java.lang.Object...)public static <T> T invokeExactConstructor(Class<T> cls, Object... args) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException
Returns a new instance of the specified class inferring the right constructor from the types of the arguments.
This locates and calls a constructor. The constructor signature must match the argument types exactly.
T - the type to be constructedcls - the class to be constructed, not nullargs - the array of arguments, null treated as emptycls, not nullNullPointerException - if cls is nullNoSuchMethodException - if a matching constructor cannot be foundIllegalAccessException - if invocation is not permitted by securityInvocationTargetException - if an error occurs on invocationInstantiationException - if an error occurs on instantiationinvokeExactConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])public static <T> T invokeExactConstructor(Class<T> cls, Object[] args, Class<?>[] parameterTypes) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException
Returns a new instance of the specified class choosing the right constructor from the list of parameter types.
This locates and calls a constructor. The constructor signature must match the parameter types exactly.
T - the type to be constructedcls - the class to be constructed, not nullargs - the array of arguments, null treated as emptyparameterTypes - the array of parameter types, null treated as emptycls, not nullNullPointerException - if cls is nullNoSuchMethodException - if a matching constructor cannot be foundIllegalAccessException - if invocation is not permitted by securityInvocationTargetException - if an error occurs on invocationInstantiationException - if an error occurs on instantiationConstructor.newInstance(java.lang.Object...)public static <T> Constructor<T> getAccessibleConstructor(Class<T> cls, Class<?>... parameterTypes)
Finds a constructor given a class and signature, checking accessibility.
This finds the constructor and ensures that it is accessible. The constructor signature must match the parameter types exactly.
T - the constructor typecls - the class to find a constructor for, not nullparameterTypes - the array of parameter types, null treated as emptynull if no matching accessible constructor foundNullPointerException - if cls is nullClass.getConstructor(java.lang.Class<?>...),
getAccessibleConstructor(java.lang.reflect.Constructor)public static <T> Constructor<T> getAccessibleConstructor(Constructor<T> ctor)
Checks if the specified constructor is accessible.
This simply ensures that the constructor is accessible.
T - the constructor typector - the prototype constructor object, not nullnull if no matching accessible constructor foundNullPointerException - if ctor is nullSecurityManagerpublic static <T> Constructor<T> getMatchingAccessibleConstructor(Class<T> cls, Class<?>... parameterTypes)
Finds an accessible constructor with compatible parameters.
This checks all the constructor and finds one with compatible parameters This requires that every parameter is assignable from the given parameter types. This is a more flexible search than the normal exact matching algorithm.
First it checks if there is a constructor matching the exact signature. If not then all the constructors of the class are checked to see if their signatures are assignment-compatible with the parameter types. The first assignment-compatible matching constructor is returned.
T - the constructor typecls - the class to find a constructor for, not nullparameterTypes - find method with compatible parametersNullPointerException - if cls is nullCopyright © 2001–2014 The Apache Software Foundation. All rights reserved.