* a.k.a. The "ObjectMolester" *
* Here is an example of using this to access a private member:
* Given the following class MyClass:
*
*
* public class MyClass
* {
* private String name; // private attribute
*
* // private constructor
* private MyClass()
* {
* super();
* }
*
* // private method
* private void setName(String newName)
* {
* this.name = newName;
* }
* }
*
*
* We now want to access the class: * MyClass myObj = PA.instantiate(MyClass.class); * PA.invokeMethod(myObj, "setName(java.lang.String)", "myNewName"); * String name = PA.getValue(myObj, "name"); ** * This class extends {@link PrivilegedAccessor} by re-throwing checked * {@link Exception}s as {@link RuntimeException}s. * * * @see PrivilegedAccessor * * @author Sebastian Dietrich (sebastian.dietrich@e-movimento.com) * @author Lubos Bistak (lubos@bistak.sk) */ public class PA { private final Object instanceOrClass; /** * Private constructor to make it impossible to instantiate this class from * outside of PA. * * @param instanceOrClass */ private PA(Object instanceOrClass) { this.instanceOrClass = instanceOrClass; } /** * Returns a string representation of the given object. The string has the * following format: "
methodSignature could be found; or if an argument
* couldn't be converted to match the expected type
*
* @see PrivilegedAccessor#invokeMethod(Object,String,Object[])
*/
public static Object invokeMethod(final Object instanceOrClass,
final String methodSignature, final Object... arguments)
{
try
{
return PrivilegedAccessor.invokeMethod(instanceOrClass,
methodSignature, correctVarargs(arguments));
} catch (Exception e)
{
throw new IllegalArgumentException(
"Can't invoke method " + methodSignature + " on "
+ instanceOrClass + " with arguments " + arguments,
e);
}
}
/**
* Calls a method with the given arguments. Arguments can be object types or
* representations for primitives.
*
* @param methodSignature
* the name of the method and the parameters methodSignature could be found; or if an argument
* couldn't be converted to match the expected type
* @see PA#invokeMethod(Object, String, Object...)
*/
public Object invokeMethod(final String methodSignature,
final Object... arguments)
{
return PA.invokeMethod(instanceOrClass, methodSignature, arguments);
}
/**
* Corrects varargs to their initial form. If you call a method with an
* object-array as last argument the Java varargs mechanism converts this
* array in single arguments. This method returns an object array if the
* arguments are all of the same type.
*
* @param arguments
* the possibly converted arguments of a vararg method
* @return arguments possibly converted
*/
private static Object[] correctVarargs(final Object... arguments)
{
if ((arguments == null) || changedByVararg(arguments))
return new Object[] { arguments };
return arguments;
}
/**
* Tests if the arguments were changed by vararg. Arguments are changed by
* vararg if they are of a non primitive array type. E.g. arguments[] =
* Object[String[]] is converted to String[] while e.g. arguments[] =
* Object[int[]] is not converted and stays Object[int[]]
*
* Unfortunately we can't detect the difference for arg = Object[primitive]
* since arguments[] = Object[Object[primitive]] which is converted to
* Object[primitive] and arguments[] = Object[primitive] which stays
* Object[primitive]
*
* and we can't detect the difference for arg = Object[non primitive] since
* arguments[] = Object[Object[non primitive]] is converted to Object[non
* primitive] and arguments[] = Object[non primitive] stays Object[non
* primitive]
*
* @param parameters
* the parameters
* @return true if parameters were changes by varargs, false otherwise
*/
private static boolean changedByVararg(final Object[] parameters)
{
if ((parameters.length == 0) || (parameters[0] == null))
return false;
if (parameters.getClass() == Object[].class)
return false;
return true;
}
/**
* Sets the value of the named field. If fieldName denotes a static field,
* provide a class, otherwise provide an instance. If the fieldName denotes a
* final field, this method could fail with an IllegalAccessException, since
* setting the value of final fields at other times than instantiation can
* have unpredictable effects.
* String myString = "Test";
*
* //setting the private field value
* PrivilegedAccessor.setValue(myString, "value", new char[] {'T', 'e', 's', 't'});
*
* //setting the static final field serialVersionUID - MIGHT FAIL
* PrivilegedAccessor.setValue(myString.getClass(), "serialVersionUID", 1);
*
*
*
* @param instanceOrClass
* the instance or class to set the field
* @param fieldName
* the name of the field
* @param value
* the new value of the field
* @throws IllegalArgumentException
* if the value could not be set. This could be the case if no field
* with the given fieldName can be found; or if the
* field was final
*
* @see PrivilegedAccessor.setValue(Object,String,Object)
*/
public static PA setValue(final Object instanceOrClass,
final String fieldName, final Object value)
{
try
{
PrivilegedAccessor.setValue(instanceOrClass, fieldName, value);
} catch (Exception e)
{
throw new IllegalArgumentException("Can't set value " + value + " at "
+ fieldName + " in " + instanceOrClass, e);
}
return new PA(instanceOrClass);
}
/**
* Sets the value of the named field. If fieldName denotes a static field,
* provide a class, otherwise provide an instance. If the fieldName denotes a
* final field, this method could fail with an IllegalAccessException, since
* setting the value of final fields at other times than instantiation can
* have unpredictable effects.
* String myString = "Test";
*
* //setting the private field value
* PrivilegedAccessor.setValue(myString, "value", new char[] {'T', 'e', 's', 't'});
*
* //setting the static final field serialVersionUID - MIGHT FAIL
* PrivilegedAccessor.setValue(myString.getClass(), "serialVersionUID", 1);
*
*
*
* @param fieldName
* the name of the field
* @param value
* the new value of the field
* @throws IllegalArgumentException
* if the value could not be set. This could be the case if no field
* with the given fieldName can be found; or if the
* field was final
*
* @see PA.setValue(Object,String,Object)
*/
public PA setValue(final String fieldName, final Object value)
{
PA.setValue(instanceOrClass, fieldName, value);
return this;
}
}