Class ConstructorUtils
MethodUtils.
 Known Limitations
Accessing Public Constructors In A Default Access Superclass
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.
- Since:
- 2.5
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Constructor SummaryConstructors
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Method SummaryModifier and TypeMethodDescriptionstatic <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> TinvokeConstructor(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> TinvokeConstructor(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> TinvokeExactConstructor(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> TinvokeExactConstructor(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.
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Constructor Details- 
ConstructorUtilsDeprecated.TODO Make private in 4.0.ConstructorUtils instances should NOT be constructed in standard programming. Instead, the class should be used asConstructorUtils.invokeConstructor(cls, args).This constructor is publicto permit tools that require a JavaBean instance to operate.
 
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Method Details- 
getAccessibleConstructorFinds 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. - Type Parameters:
- T- the constructor type
- Parameters:
- cls- the class to find a constructor for, not- null
- parameterTypes- the array of parameter types,- nulltreated as empty
- Returns:
- the constructor, nullif no matching accessible constructor found
- Throws:
- NullPointerException- if- clsis- null
- See Also:
 
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getAccessibleConstructorChecks if the specified constructor is accessible.This simply ensures that the constructor is accessible. - Type Parameters:
- T- the constructor type
- Parameters:
- ctor- the prototype constructor object, not- null
- Returns:
- the constructor, nullif no matching accessible constructor found
- Throws:
- NullPointerException- if- ctoris- null
- See Also:
 
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getMatchingAccessibleConstructorpublic 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. - Type Parameters:
- T- the constructor type
- Parameters:
- cls- the class to find a constructor for, not- null
- parameterTypes- find method with compatible parameters
- Returns:
- the constructor, null if no matching accessible constructor found
- Throws:
- NullPointerException- if- clsis- null
 
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invokeConstructorpublic 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. - Type Parameters:
- T- the type to be constructed
- Parameters:
- cls- the class to be constructed, not- null
- args- the array of arguments,- nulltreated as empty
- Returns:
- new instance of cls, notnull
- Throws:
- NullPointerException- if- clsis- null
- NoSuchMethodException- if a matching constructor cannot be found
- IllegalAccessException- if invocation is not permitted by security
- InvocationTargetException- if an error occurs on invocation
- InstantiationException- if an error occurs on instantiation
- See Also:
 
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invokeConstructorpublic 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. - Type Parameters:
- T- the type to be constructed
- Parameters:
- cls- the class to be constructed, not- null
- args- the array of arguments,- nulltreated as empty
- parameterTypes- the array of parameter types,- nulltreated as empty
- Returns:
- new instance of cls, notnull
- Throws:
- NullPointerException- if- clsis- null
- NoSuchMethodException- if a matching constructor cannot be found
- IllegalAccessException- if invocation is not permitted by security
- InvocationTargetException- if an error occurs on invocation
- InstantiationException- if an error occurs on instantiation
- See Also:
 
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invokeExactConstructorpublic 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. - Type Parameters:
- T- the type to be constructed
- Parameters:
- cls- the class to be constructed, not- null
- args- the array of arguments,- nulltreated as empty
- Returns:
- new instance of cls, notnull
- Throws:
- NullPointerException- if- clsis- null
- NoSuchMethodException- if a matching constructor cannot be found
- IllegalAccessException- if invocation is not permitted by security
- InvocationTargetException- if an error occurs on invocation
- InstantiationException- if an error occurs on instantiation
- See Also:
 
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invokeExactConstructorpublic 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. - Type Parameters:
- T- the type to be constructed
- Parameters:
- cls- the class to be constructed, not- null
- args- the array of arguments,- nulltreated as empty
- parameterTypes- the array of parameter types,- nulltreated as empty
- Returns:
- new instance of cls, notnull
- Throws:
- NullPointerException- if- clsis- null
- NoSuchMethodException- if a matching constructor cannot be found
- IllegalAccessException- if invocation is not permitted by security
- InvocationTargetException- if an error occurs on invocation
- InstantiationException- if an error occurs on instantiation
- See Also:
 
 
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