/**
* 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.
*
* <p>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.
*
* @param cls find constructor for this class
* @param parameterTypes find method with compatible parameters
* @return a valid Constructor object. If there's no matching constructor, returns <code>null
* </code>.
*/
public static Constructor getMatchingAccessibleConstructor(Class cls, Class[] parameterTypes) {
// see if we can find the constructor directly
// most of the time this works and it's much faster
try {
Constructor ctor = cls.getConstructor(parameterTypes);
MemberUtils.setAccessibleWorkaround(ctor);
return ctor;
} catch (NoSuchMethodException e) {
/* SWALLOW */
}
Constructor result = null;
// search through all constructors
Constructor[] ctors = cls.getConstructors();
for (int i = 0; i < ctors.length; i++) {
// compare parameters
if (ClassUtils.isAssignable(parameterTypes, ctors[i].getParameterTypes(), true)) {
// get accessible version of method
Constructor ctor = getAccessibleConstructor(ctors[i]);
if (ctor != null) {
MemberUtils.setAccessibleWorkaround(ctor);
if (result == null
|| MemberUtils.compareParameterTypes(
ctor.getParameterTypes(), result.getParameterTypes(), parameterTypes)
< 0) {
result = ctor;
}
}
}
}
return result;
}
/**
* Gets an accessible <code>Field</code> by name breaking scope if requested.
* Superclasses/interfaces will be considered.
*
* @param cls the class to reflect, must not be null
* @param fieldName the field name to obtain
* @param forceAccess whether to break scope restrictions using the <code>setAccessible</code>
* method. <code>False</code> will only match public fields.
* @return the Field object
* @throws IllegalArgumentException if the class or field name is null
*/
public static Field getField(final Class cls, String fieldName, boolean forceAccess) {
if (cls == null) {
throw new IllegalArgumentException("The class must not be null");
}
if (fieldName == null) {
throw new IllegalArgumentException("The field name must not be null");
}
// Sun Java 1.3 has a bugged implementation of getField hence we write the
// code ourselves
// getField() will return the Field object with the declaring class
// set correctly to the class that declares the field. Thus requesting the
// field on a subclass will return the field from the superclass.
//
// priority order for lookup:
// searchclass private/protected/package/public
// superclass protected/package/public
// private/different package blocks access to further superclasses
// implementedinterface public
// check up the superclass hierarchy
for (Class acls = cls; acls != null; acls = acls.getSuperclass()) {
try {
Field field = acls.getDeclaredField(fieldName);
// getDeclaredField checks for non-public scopes as well
// and it returns accurate results
if (!Modifier.isPublic(field.getModifiers())) {
if (forceAccess) {
field.setAccessible(true);
} else {
continue;
}
}
return field;
} catch (NoSuchFieldException ex) {
// ignore
}
}
// check the public interface case. This must be manually searched for
// incase there is a public supersuperclass field hidden by a private/package
// superclass field.
Field match = null;
for (Iterator intf = ClassUtils.getAllInterfaces(cls).iterator(); intf.hasNext(); ) {
try {
Field test = ((Class) intf.next()).getField(fieldName);
if (match != null) {
throw new IllegalArgumentException(
"Reference to field "
+ fieldName
+ " is ambiguous relative to "
+ cls
+ "; a matching field exists on two or more implemented interfaces.");
}
match = test;
} catch (NoSuchFieldException ex) {
// ignore
}
}
return match;
}
