public static <T> Constructor<T> findConstructor(Class<T> cls, boolean canFixAccess)
throws IllegalArgumentException {
try {
Constructor<T> ctor = cls.getDeclaredConstructor();
if (canFixAccess) {
checkAndFixAccess(ctor);
} else {
// Has to be public...
if (!Modifier.isPublic(ctor.getModifiers())) {
throw new IllegalArgumentException(
"Default constructor for "
+ cls.getName()
+ " is not accessible (non-public?): not allowed to try modify access via Reflection: can not instantiate type");
}
}
return ctor;
} catch (NoSuchMethodException e) {;
} catch (Exception e) {
ClassUtil.unwrapAndThrowAsIAE(
e,
"Failed to find default constructor of class "
+ cls.getName()
+ ", problem: "
+ e.getMessage());
}
return null;
}
/**
* Prints all constructors of a class
*
* @param cl a class
*/
public static void printConstructors(Class cl) {
Constructor[] constructors = cl.getDeclaredConstructors();
for (Constructor c : constructors) {
String name = c.getName();
System.out.print(" ");
String modifiers = Modifier.toString(c.getModifiers());
if (modifiers.length() > 0) System.out.print(modifiers + " ");
System.out.print(name + "(");
// print parameter types
Class[] paramTypes = c.getParameterTypes();
for (int j = 0; j < paramTypes.length; j++) {
if (j > 0) System.out.print(", ");
System.out.print(paramTypes[j].getName());
}
System.out.println(");");
}
}
/**
* Checks if a class fulfills the JavaBeans contract.
*
* @param cls the class to check
*/
public static void checkJavaBean(Class<?> cls) {
try {
Constructor<?> constructor = cls.getDeclaredConstructor();
int classModifiers = cls.getModifiers();
if (Modifier.isInterface(classModifiers))
throw new RuntimeException(cls.getName() + " is an interface");
if (Modifier.isAbstract(classModifiers))
throw new RuntimeException(
cls.getName() + " cannot be instantiated - it is an abstract class");
int modifiers = constructor.getModifiers();
if (!Modifier.isPublic(modifiers))
throw new RuntimeException("No public default constructor in " + cls);
} catch (NoSuchMethodException e) {
throw new RuntimeException("No default constructor in class " + cls);
} catch (SecurityException e) {
logger.error(
"I am not allowed to check the class by using reflection, "
+ "so I just can hope the class is alright and go on: ",
e);
}
}