java.lang.Object
- org.apache.commons.lang.reflect.ConstructorUtils

```
public class ConstructorUtils
extends Object
```
Utility reflection methods focussed on constructors, modelled after 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 locates these constructors fine and correctly assigns them as public. However, an IllegalAccessException is thrown if the constructors is invoked.

ConstructorUtils contains a workaround for this situation. It will attempt to call setAccessible 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 privilages. If this call fails then a warning will be logged and the method may fail.

Since:

2.5

Version:

$Id: ConstructorUtils.java 1056863 2011-01-09 02:00:25Z niallp $

Constructor Summary

Constructors
Constructor Description

ConstructorUtils()
ConstructorUtils instances should NOT be constructed in standard programming.

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static Constructor`	`getAccessibleConstructor(Class cls, Class parameterType)`	Returns a constructor with single argument.
`static Constructor`	`getAccessibleConstructor(Class cls, Class[] parameterTypes)`	Returns a constructor given a class and signature.
`static Constructor`	`getAccessibleConstructor(Constructor ctor)`	Returns accessible version of the given constructor.
`static Constructor`	`getMatchingAccessibleConstructor(Class cls, Class[] parameterTypes)`	Find an accessible constructor with compatible parameters.
`static Object`	`invokeConstructor(Class cls, Object arg)`	Returns new instance of `klazz` created using the actual arguments `args`.
`static Object`	`invokeConstructor(Class cls, Object[] args)`	Returns new instance of `klazz` created using the actual arguments `args`.
`static Object`	`invokeConstructor(Class cls, Object[] args, Class[] parameterTypes)`	Returns new instance of `klazz` created using constructor with signature `parameterTypes` and actual arguments `args`.
`static Object`	`invokeExactConstructor(Class cls, Object arg)`	Returns new instance of `klazz` created using the actual arguments `args`.
`static Object`	`invokeExactConstructor(Class cls, Object[] args)`	Returns new instance of `klazz` created using the actual arguments `args`.
`static Object`	`invokeExactConstructor(Class cls, Object[] args, Class[] parameterTypes)`	Returns new instance of `klazz` created using constructor with signature `parameterTypes` and actual arguments `args`.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - ConstructorUtils
```
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.
- Method Detail
  - invokeConstructor
```
public static Object invokeConstructor(Class cls,
                                       Object arg)
                                throws NoSuchMethodException,
                                       IllegalAccessException,
                                       InvocationTargetException,
                                       InstantiationException
```
    Returns new instance of klazz created using the actual arguments args. The formal parameter types are inferred from the actual values of args. See invokeExactConstructor(Class, Object[], Class[]) for more details.
    
    The signatures should be assignment compatible.
    
    Parameters:
    
    cls - the class to be constructed.
    
    arg - the actual argument
    
    Returns:
    
    new instance of klazz
    
    Throws:
    
    NoSuchMethodException - If the constructor cannot be found
    
    IllegalAccessException - If an error occurs accessing the constructor
    
    InvocationTargetException - If an error occurs invoking the constructor
    
    InstantiationException - If an error occurs instantiating the class
    
    See Also:
    
    invokeConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
  - invokeConstructor
```
public static Object invokeConstructor(Class cls,
                                       Object[] args)
                                throws NoSuchMethodException,
                                       IllegalAccessException,
                                       InvocationTargetException,
                                       InstantiationException
```
    Returns new instance of klazz created using the actual arguments args. The formal parameter types are inferred from the actual values of args. See invokeExactConstructor(Class, Object[], Class[]) for more details.
    
    The signatures should be assignment compatible.
    
    Parameters:
    
    cls - the class to be constructed.
    
    args - actual argument array
    
    Returns:
    
    new instance of klazz
    
    Throws:
    
    NoSuchMethodException - If the constructor cannot be found
    
    IllegalAccessException - If an error occurs accessing the constructor
    
    InvocationTargetException - If an error occurs invoking the constructor
    
    InstantiationException - If an error occurs instantiating the class
    
    See Also:
    
    invokeConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
  - invokeConstructor
```
public static Object invokeConstructor(Class cls,
                                       Object[] args,
                                       Class[] parameterTypes)
                                throws NoSuchMethodException,
                                       IllegalAccessException,
                                       InvocationTargetException,
                                       InstantiationException
```
    Returns new instance of klazz created using constructor with signature parameterTypes and actual arguments args.
    
    The signatures should be assignment compatible.
    
    Parameters:
    
    cls - the class to be constructed.
    
    args - actual argument array
    
    parameterTypes - parameter types array
    
    Returns:
    
    new instance of klazz
    
    Throws:
    
    NoSuchMethodException - if matching constructor cannot be found
    
    IllegalAccessException - thrown on the constructor's invocation
    
    InvocationTargetException - thrown on the constructor's invocation
    
    InstantiationException - thrown on the constructor's invocation
    
    See Also:
    
    Constructor.newInstance(java.lang.Object...)
  - invokeExactConstructor
```
public static Object invokeExactConstructor(Class cls,
                                            Object arg)
                                     throws NoSuchMethodException,
                                            IllegalAccessException,
                                            InvocationTargetException,
                                            InstantiationException
```
    Returns new instance of klazz created using the actual arguments args. The formal parameter types are inferred from the actual values of args. See invokeExactConstructor(Class, Object[], Class[]) for more details.
    
    The signatures should match exactly.
    
    Parameters:
    
    cls - the class to be constructed.
    
    arg - the actual argument
    
    Returns:
    
    new instance of klazz
    
    Throws:
    
    NoSuchMethodException - If the constructor cannot be found
    
    IllegalAccessException - If an error occurs accessing the constructor
    
    InvocationTargetException - If an error occurs invoking the constructor
    
    InstantiationException - If an error occurs instantiating the class
    
    See Also:
    
    invokeExactConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
  - invokeExactConstructor
```
public static Object invokeExactConstructor(Class cls,
                                            Object[] args)
                                     throws NoSuchMethodException,
                                            IllegalAccessException,
                                            InvocationTargetException,
                                            InstantiationException
```
    Returns new instance of klazz created using the actual arguments args. The formal parameter types are inferred from the actual values of args. See invokeExactConstructor(Class, Object[], Class[]) for more details.
    
    The signatures should match exactly.
    
    Parameters:
    
    cls - the class to be constructed.
    
    args - actual argument array
    
    Returns:
    
    new instance of klazz
    
    Throws:
    
    NoSuchMethodException - If the constructor cannot be found
    
    IllegalAccessException - If an error occurs accessing the constructor
    
    InvocationTargetException - If an error occurs invoking the constructor
    
    InstantiationException - If an error occurs instantiating the class
    
    See Also:
    
    invokeExactConstructor(java.lang.Class, java.lang.Object[], java.lang.Class[])
  - invokeExactConstructor
```
public static Object invokeExactConstructor(Class cls,
                                            Object[] args,
                                            Class[] parameterTypes)
                                     throws NoSuchMethodException,
                                            IllegalAccessException,
                                            InvocationTargetException,
                                            InstantiationException
```
    Returns new instance of klazz created using constructor with signature parameterTypes and actual arguments args.
    
    The signatures should match exactly.
    
    Parameters:
    
    cls - the class to be constructed.
    
    args - actual argument array
    
    parameterTypes - parameter types array
    
    Returns:
    
    new instance of klazz
    
    Throws:
    
    NoSuchMethodException - if matching constructor cannot be found
    
    IllegalAccessException - thrown on the constructor's invocation
    
    InvocationTargetException - thrown on the constructor's invocation
    
    InstantiationException - thrown on the constructor's invocation
    
    See Also:
    
    Constructor.newInstance(java.lang.Object...)
  - getAccessibleConstructor
```
public static Constructor getAccessibleConstructor(Class cls,
                                                   Class parameterType)
```
    Returns a constructor with single argument.
    
    Parameters:
    
    cls - the class to be constructed
    
    parameterType - The constructor parameter type
    
    Returns:
    
    null if matching accessible constructor can not be found.
    
    See Also:
    
    Class.getConstructor(java.lang.Class<?>...), getAccessibleConstructor(java.lang.reflect.Constructor)
  - getAccessibleConstructor
```
public static Constructor getAccessibleConstructor(Class cls,
                                                   Class[] parameterTypes)
```
    Returns a constructor given a class and signature.
    
    Parameters:
    
    cls - the class to be constructed
    
    parameterTypes - the parameter array
    
    Returns:
    
    null if matching accessible constructor can not be found
    
    See Also:
    
    Class.getConstructor(java.lang.Class<?>...), getAccessibleConstructor(java.lang.reflect.Constructor)
  - getAccessibleConstructor
```
public static Constructor getAccessibleConstructor(Constructor ctor)
```
    Returns accessible version of the given constructor.
    
    Parameters:
    
    ctor - prototype constructor object.
    
    Returns:
    
    null if accessible constructor can not be found.
    
    See Also:
    
    SecurityManager
  - getMatchingAccessibleConstructor
```
public static Constructor getMatchingAccessibleConstructor(Class cls,
                                                           Class[] parameterTypes)
```
    Find an accessible constructor with compatible parameters. Compatible parameters mean that every method parameter is assignable from the given parameters. In other words, it finds constructor that will take the parameters given.
    
    First it checks if there is constructor matching the exact signature. If no such, all the constructors of the class are tested if their signatures are assignment compatible with the parameter types. The first matching constructor is returned.
    
    Parameters:
    
    cls - find constructor for this class
    
    parameterTypes - find method with compatible parameters
    
    Returns:
    
    a valid Constructor object. If there's no matching constructor, returns null.

Class ConstructorUtils

Known Limitations

Accessing Public Constructors In A Default Access Superclass

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

ConstructorUtils

Method Detail

invokeConstructor

invokeConstructor

invokeConstructor

invokeExactConstructor

invokeExactConstructor

invokeExactConstructor

getAccessibleConstructor

getAccessibleConstructor

getAccessibleConstructor

getMatchingAccessibleConstructor