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package com.sun.xml.bind.v2;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.WeakHashMap;
import java.util.logging.Level;
import java.util.logging.Logger;
import com.sun.xml.bind.Util;
/**
* Creates new instances of classes.
*
*
* This code handles the case where the class is not public or the constructor is
* not public.
*
* @since 2.0
* @author Kohsuke Kawaguchi
*/
public final class ClassFactory {
private static final Class[] emptyClass = new Class[0];
private static final Object[] emptyObject = new Object[0];
private static final Logger logger = Util.getClassLogger();
/**
* Cache from a class to its default constructor.
*
* To avoid synchronization among threads, we use {@link ThreadLocal}.
*/
private static final ThreadLocal>> tls = new ThreadLocal>>() {
public Map> initialValue() {
return new WeakHashMap>();
}
};
/**
* Creates a new instance of the class but throw exceptions without catching it.
*/
public static T create0( final Class clazz ) throws IllegalAccessException, InvocationTargetException, InstantiationException {
Map> m = tls.get();
Constructor cons = null;
WeakReference consRef = m.get(clazz);
if(consRef!=null)
cons = consRef.get();
if(cons==null) {
try {
cons = clazz.getDeclaredConstructor(emptyClass);
} catch (NoSuchMethodException e) {
logger.log(Level.INFO,"No default constructor found on "+clazz,e);
NoSuchMethodError exp;
if(clazz.getDeclaringClass()!=null && !Modifier.isStatic(clazz.getModifiers())) {
exp = new NoSuchMethodError(Messages.NO_DEFAULT_CONSTRUCTOR_IN_INNER_CLASS.format(clazz.getName()));
} else {
exp = new NoSuchMethodError(e.getMessage());
}
exp.initCause(e);
throw exp;
}
int classMod = clazz.getModifiers();
if(!Modifier.isPublic(classMod) || !Modifier.isPublic(cons.getModifiers())) {
// attempt to make it work even if the constructor is not accessible
try {
cons.setAccessible(true);
} catch(SecurityException e) {
// but if we don't have a permission to do so, work gracefully.
logger.log(Level.FINE,"Unable to make the constructor of "+clazz+" accessible",e);
throw e;
}
}
m.put(clazz,new WeakReference(cons));
}
return cons.newInstance(emptyObject);
}
/**
* The same as {@link #create0} but with an error handling to make
* the instanciation error fatal.
*/
public static T create( Class clazz ) {
try {
return create0(clazz);
} catch (InstantiationException e) {
logger.log(Level.INFO,"failed to create a new instance of "+clazz,e);
throw new InstantiationError(e.toString());
} catch (IllegalAccessException e) {
logger.log(Level.INFO,"failed to create a new instance of "+clazz,e);
throw new IllegalAccessError(e.toString());
} catch (InvocationTargetException e) {
Throwable target = e.getTargetException();
// most likely an error on the user's code.
// just let it through for the ease of debugging
if(target instanceof RuntimeException)
throw (RuntimeException)target;
// error. just forward it for the ease of debugging
if(target instanceof Error)
throw (Error)target;
// a checked exception.
// not sure how we should report this error,
// but for now we just forward it by wrapping it into a runtime exception
throw new IllegalStateException(target);
}
}
/**
* Call a method in the factory class to get the object.
*/
public static Object create(Method method) {
Throwable errorMsg;
try {
return method.invoke(null, emptyObject);
} catch (InvocationTargetException ive) {
Throwable target = ive.getTargetException();
if(target instanceof RuntimeException)
throw (RuntimeException)target;
if(target instanceof Error)
throw (Error)target;
throw new IllegalStateException(target);
} catch (IllegalAccessException e) {
logger.log(Level.INFO,"failed to create a new instance of "+method.getReturnType().getName(),e);
throw new IllegalAccessError(e.toString());
} catch (IllegalArgumentException iae){
logger.log(Level.INFO,"failed to create a new instance of "+method.getReturnType().getName(),iae);
errorMsg = iae;
} catch (NullPointerException npe){
logger.log(Level.INFO,"failed to create a new instance of "+method.getReturnType().getName(),npe);
errorMsg = npe;
} catch (ExceptionInInitializerError eie){
logger.log(Level.INFO,"failed to create a new instance of "+method.getReturnType().getName(),eie);
errorMsg = eie;
}
NoSuchMethodError exp;
exp = new NoSuchMethodError(errorMsg.getMessage());
exp.initCause(errorMsg);
throw exp;
}
/**
* Infers the instanciable implementation class that can be assigned to the given field type.
*
* @return null
* if inference fails.
*/
public static Class inferImplClass(Class fieldType, Class[] knownImplClasses) {
if(!fieldType.isInterface())
// instanciable class?
// TODO: check if it has a default constructor
return fieldType;
for( Class impl : knownImplClasses ) {
if(fieldType.isAssignableFrom(impl))
return impl.asSubclass(fieldType);
}
// if we can't find an implementation class,
// let's just hope that we will never need to create a new object,
// and returns null
return null;
}
}