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Utility classes and methods developed for Brooklyn but not dependendent on Brooklyn or much else

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.brooklyn.util.javalang;

import static com.google.common.base.Preconditions.checkNotNull;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.lang.reflect.Array;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.TypeVariable;
import java.net.URL;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Stack;

import javax.annotation.Nullable;

import org.apache.brooklyn.util.collections.MutableList;
import org.apache.brooklyn.util.collections.MutableMap;
import org.apache.brooklyn.util.exceptions.Exceptions;
import org.apache.brooklyn.util.guava.Maybe;
import org.apache.brooklyn.util.javalang.coerce.TypeCoercer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.base.Predicate;
import com.google.common.base.Predicates;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import com.google.common.reflect.TypeToken;

/**
 * Reflection utilities
 * 
 * @author aled
 */
public class Reflections {

    private static final Logger LOG = LoggerFactory.getLogger(Reflections.class);

    public static class ReflectionNotFoundException extends RuntimeException {
        private static final long serialVersionUID = 9032835250796708037L;
        public ReflectionNotFoundException(String message, Throwable cause) {
            super(message, cause);
        }
        public ReflectionNotFoundException(String message) {
            super(message);
        }
    }

    public static class ReflectionAccessException extends RuntimeException {
        private static final long serialVersionUID = 6569605861192432009L;

        public ReflectionAccessException(String message, Throwable cause) {
            super(message, cause);
        }
    }

    private final ClassLoader classLoader;
    private final Map classRenameMap = MutableMap.of();
    
    public Reflections(ClassLoader classLoader) {
        this.classLoader = classLoader!=null ? classLoader : getClass().getClassLoader();
    }
    
    /** supply a map of known renames, of the form "old-class -> new-class" */ 
    public Reflections applyClassRenames(Map newClassRenames) {
        this.classRenameMap.putAll(newClassRenames);
        return this;
    }

    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    public Object loadInstance(String classname, Object...argValues) throws ReflectionNotFoundException, ReflectionAccessException {
        Class clazz = loadClass(classname);
        Maybe v = null;
        try {
            v = invokeConstructorFromArgs(clazz, argValues);
            if (v.isPresent()) return v.get();
        } catch (Exception e) {
            throw new IllegalStateException("Error invoking constructor for "+clazz+Arrays.toString(argValues) + ": " + Exceptions.collapseText(e));
        }
        throw new IllegalStateException("No suitable constructor for "+clazz+Arrays.toString(argValues));
    }
    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    public Object loadInstance(String classname, Class[] argTypes, Object[] argValues) throws ReflectionNotFoundException, ReflectionAccessException {
        Class clazz = loadClass(classname);
        Constructor constructor = loadConstructor(clazz, argTypes);
        return loadInstance(constructor, argValues);
    }

    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    public Object loadInstance(String classname) throws ReflectionNotFoundException, ReflectionAccessException {
        Class clazz = loadClass(classname);
        try {
            return clazz.newInstance();
        } catch (InstantiationException e) {
            throw new ReflectionAccessException("Failed to create instance of class '" + classname + "' using class loader " + classLoader + ": " + Exceptions.collapseText(e), e);
        } catch (IllegalAccessException e) {
            throw new ReflectionAccessException("Failed to create instance of class '" + classname + "' using class loader " + classLoader + ": " + Exceptions.collapseText(e), e);
        }
    }

    /** instantiates the given class from its binary name */
    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    public Class loadClass(String classname) throws ReflectionNotFoundException {
        try {
            classname = findMappedNameAndLog(classRenameMap, classname);
            return classLoader.loadClass(classname);
        } catch (ClassNotFoundException e) {
            throw new ReflectionNotFoundException("Failed to load class '" + classname + "' using class loader " + classLoader + ": " + Exceptions.collapseText(e), e);
        } catch (NoClassDefFoundError e) {
            throw new ReflectionNotFoundException("Failed to load class '" + classname + "' using class loader " + classLoader + ": " + Exceptions.collapseText(e), e);
        } catch (UnsupportedClassVersionError e) {
            throw new ReflectionNotFoundException("Failed to load class '" + classname + "' using class loader " + classLoader + ": " + Exceptions.collapseText(e), e);
        }
    }

    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    @SuppressWarnings("unchecked")
    public  Class loadClass(String classname, Class superType) throws ReflectionNotFoundException {
        return (Class) loadClass(classname);
    }

    /** given a nested part, e.g. Inner$VeryInner, this will recurse through clazz.Inner, looking for VeryInner,
     * then looking in each supertype (interface) of clazz for Inner.VeryInner;
     * 

     * so it will find Clazz.Inner.VeryInner wherever in the hierarchy it is defined
     * 

     * (as opposed to ClassLoader which requires Inner.VeryInner to be _declared_ in clazz, not in any supertype
     * 

     * returns null if not found
     */
    public static Class loadInnerClassPossiblyInheritted(Class clazz, String nestedPart) throws ReflectionNotFoundException {
        Set visited = new HashSet();
        Class result = loadInnerClassPossiblyInheritted(visited, clazz, nestedPart);
        if (result!=null) return result;
        throw new ReflectionNotFoundException("Inner class " + nestedPart + " could not be found in " + clazz + " or any of its super-types");
    }
    
    /** as 2-arg, but maintains set of  visited elements, and returns null if not found */
    private static Class loadInnerClassPossiblyInheritted(Set visited, Class clazz, String nestedPart) throws ReflectionNotFoundException {
        if (clazz==null) return null;
        if (nestedPart==null || nestedPart.length()==0) return clazz;

        int i1 = nestedPart.indexOf('$');
        int i2 = nestedPart.indexOf('.');
        int idx = (i2 > -1 && (i2 < i1 || i1==-1) ? i2 : i1);
        String thisClassToFind = nestedPart;
        String nextClassesToFind = "";
        if (idx>=0) {
            thisClassToFind = nestedPart.substring(0, idx);
            nextClassesToFind = nestedPart.substring(idx+1);
        }

        if (!visited.add(clazz.getCanonicalName()+"!"+nestedPart)) {
            //already visited
            return null;
        }

        Class[] members = clazz.getClasses();
        for (int i = 0; i < members.length; i++) {
            if (members[i].getSimpleName().equals(thisClassToFind)) {
                Class clazzI = loadInnerClassPossiblyInheritted(visited, members[i], nextClassesToFind);
                if (clazzI!=null) return clazzI;
            }
        }

        //look in supertype first (not sure if necessary)
        Class result = loadInnerClassPossiblyInheritted(visited, clazz.getSuperclass(), nestedPart);
        if (result!=null) return result;

        for (Class iface : clazz.getInterfaces()) {
            result = loadInnerClassPossiblyInheritted(visited, iface, nestedPart);
            if (result!=null) return result;
        }
        return null;
    }

    /** does not look through ancestors of outer class */
    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    public Class loadInnerClassNotInheritted(String outerClassname, String innerClassname) throws ReflectionNotFoundException {
        return loadClass(outerClassname + "$" + innerClassname);
    }

    /** does not look through ancestors of outer class
     * 

     * uses the classloader set in this class, not in the clazz supplied */
    public Class loadInnerClassNotInheritted(Class outerClazz, String innerClassname) throws ReflectionNotFoundException {
        return loadClass(outerClazz.getName() + "$" + innerClassname);
    }

    public Constructor loadConstructor(Class clazz, Class[] argTypes) throws ReflectionAccessException {
        try {
            return clazz.getConstructor(argTypes);
        } catch (SecurityException e) {
            throw new ReflectionAccessException("Failed to load constructor of class '" + clazz + " with argument types " + Arrays.asList(argTypes) + ": " + Exceptions.collapseText(e), e);
        } catch (NoSuchMethodException e) {
            throw new ReflectionAccessException("Failed to load constructor of class '" + clazz + " with argument types " + Arrays.asList(argTypes) + ": " + Exceptions.collapseText(e), e);
        }
    }

    /** @deprecated since 0.10.0 use {@link #invokeConstructorFromArgs(Class, Object...)} or one of the variants;
     * this allows null field values */ @Deprecated
    public static  Optional invokeConstructorWithArgs(ClassLoader classLoader, String className, Object...argsArray) {
        return Reflections.invokeConstructorFromArgsUntyped(classLoader, className, argsArray).toOptional();
    }
    /** @deprecated since 0.10.0 use {@link #invokeConstructorFromArgs(Class, Object...)} or one of the variants */ @Deprecated
    public static  Optional invokeConstructorWithArgs(ClassLoader classLoader, Class clazz, Object[] argsArray, boolean setAccessible) {
        return invokeConstructorFromArgs(classLoader, clazz, argsArray, setAccessible).toOptional();
    }
    /** @deprecated since 0.10.0 use {@link #invokeConstructorFromArgs(Class, Object...)} or one of the variants */ @Deprecated
    public static  Optional invokeConstructorWithArgs(Class clazz, Object...argsArray) {
        return Reflections.invokeConstructorFromArgs(clazz, argsArray).toOptional();
    }
    /** @deprecated since 0.10.0 use {@link #invokeConstructorFromArgs(Class, Object...)} or one of the variants */ @Deprecated
    public static  Optional invokeConstructorWithArgs(Class clazz, Object[] argsArray, boolean setAccessible) {
        return Reflections.invokeConstructorFromArgs(clazz, argsArray, setAccessible).toOptional();
    }
    /** @deprecated since 0.10.0 use {@link #invokeConstructorFromArgs(Class, Object...)} or one of the variants */ @Deprecated
    public static  Optional invokeConstructorWithArgs(Reflections reflections, Class clazz, Object[] argsArray, boolean setAccessible) {
        return Reflections.invokeConstructorFromArgs(reflections, clazz, argsArray, setAccessible).toOptional();
    }
    
    /** Finds and invokes a suitable constructor, supporting varargs and primitives, boxing and looking at compatible supertypes in the constructor's signature */
    public static  Maybe invokeConstructorFromArgs(Class clazz, Object...argsArray) {
        return invokeConstructorFromArgs(clazz, argsArray, false);
    }

    /** As {@link #invokeConstructorFromArgs(Class, Object...)} but allowing more configurable input */
    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    public static Maybe invokeConstructorFromArgs(ClassLoader classLoader, String className, Object...argsArray) {
        return invokeConstructorFromArgs(classLoader, null, className, argsArray);
    }
    
    /** As {@link #invokeConstructorFromArgs(Class, Object...)} but allowing more configurable input */
    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    @SuppressWarnings("unchecked")
    public static  Maybe invokeConstructorFromArgs(ClassLoader classLoader, Class optionalSupertype, String className, Object...argsArray) {
        Reflections reflections = new Reflections(classLoader);
        Class clazz = reflections.loadClass(className);
        if (optionalSupertype!=null && !optionalSupertype.isAssignableFrom(clazz)) {
            return Maybe.absent("The type requested '"+className+"' is not assignable to "+optionalSupertype);
        }
        return invokeConstructorFromArgs(reflections, (Class)clazz, argsArray, false);
    }

    /** As {@link #invokeConstructorFromArgs(Class, Object...)} but allowing more configurable input */
    /** @deprecated since 0.11.0, use {@link org.apache.brooklyn.util.core.ClassLoaderUtils} in a combination with {@link #invokeConstructorFromArgs(Class, Object...)} instead */
    public static  Maybe invokeConstructorFromArgsUntyped(ClassLoader classLoader, String className, Object...argsArray) {
        Reflections reflections = new Reflections(classLoader);
        @SuppressWarnings("unchecked")
        Class clazz = (Class)reflections.loadClass(className);
        return invokeConstructorFromArgs(reflections, clazz, argsArray, false);
    }

    /** As {@link #invokeConstructorFromArgs(Class, Object...)} but allowing more configurable input; 
     * in particular setAccessible allows private constructors to be used (not the default) */
    public static  Maybe invokeConstructorFromArgs(ClassLoader classLoader, Class clazz, Object[] argsArray, boolean setAccessible) {
        Reflections reflections = new Reflections(classLoader);
        return invokeConstructorFromArgs(reflections, clazz, argsArray, setAccessible);
    }

    /** As {@link #invokeConstructorFromArgs(Class, Object...)} but allowing more configurable input;
     * in particular setAccessible allows private constructors to be used (not the default) */
    public static  Maybe invokeConstructorFromArgs(Class clazz, Object[] argsArray, boolean setAccessible) {
        Reflections reflections = new Reflections(clazz.getClassLoader());
        return invokeConstructorFromArgs(reflections, clazz, argsArray, setAccessible);
    }

    /** As {@link #invokeConstructorFromArgs(Class, Object...)} but will use private constructors (with setAccessible = true) */
    public static  Maybe invokeConstructorFromArgsIncludingPrivate(Class clazz, Object ...argsArray) {
        return Reflections.invokeConstructorFromArgs(new Reflections(clazz.getClassLoader()), clazz, argsArray, true);
    }
    /** As {@link #invokeConstructorFromArgs(Class, Object...)} but allowing more configurable input;
     * in particular setAccessible allows private constructors to be used (not the default) */
    @SuppressWarnings("unchecked")
    public static  Maybe invokeConstructorFromArgs(Reflections reflections, Class clazz, Object[] argsArray, boolean setAccessible) {
        for (Constructor constructor : MutableList.>of().appendAll(Arrays.asList(clazz.getConstructors())).appendAll(Arrays.asList(clazz.getDeclaredConstructors()))) {
            Class[] parameterTypes = constructor.getParameterTypes();
            if (constructor.isVarArgs()) {
                if (typesMatchUpTo(argsArray, parameterTypes, parameterTypes.length-1)) {
                    Class varargType = parameterTypes[parameterTypes.length-1].getComponentType();
                    boolean varargsMatch = true;
                    for (int i=parameterTypes.length-1; i loadSingleConstructor(Class clazz) {
        Constructor[] constructors = clazz.getConstructors();
        if (constructors.length == 1) {
            return constructors[0];
        }
        throw new IllegalArgumentException("Class " + clazz + " has more than one constructor");
    }

    public  T loadInstance(Constructor constructor, Object...argValues) throws IllegalArgumentException, ReflectionAccessException {
        try {
            try {
                return constructor.newInstance(argValues);
            } catch (IllegalArgumentException e) {
                try {
                    LOG.warn("Failure passing provided arguments ("+getIllegalArgumentsErrorMessage(constructor, argValues)+"; "+e+"); attempting to reconstitute");
                    argValues = (Object[]) updateFromNewClassLoader(argValues);
                    return constructor.newInstance(argValues);
                } catch (Throwable e2) {
                    LOG.warn("Reconstitution attempt failed (will rethrow original excaption): "+e2, e2);
                    throw e;
                }
            }
        } catch (IllegalArgumentException e) {
            throw new IllegalArgumentException(getIllegalArgumentsErrorMessage(constructor, argValues)+": " + Exceptions.collapseText(e), e);
        } catch (InstantiationException e) {
            throw new ReflectionAccessException("Failed to create instance of " + constructor.getDeclaringClass() + ": " + Exceptions.collapseText(e), e);
        } catch (IllegalAccessException e) {
            throw new ReflectionAccessException("Failed to create instance of " + constructor.getDeclaringClass() + ": " + Exceptions.collapseText(e), e);
        } catch (InvocationTargetException e) {
            throw new ReflectionAccessException("Failed to create instance of " + constructor.getDeclaringClass() + ": " + Exceptions.collapseText(e), e);
        }
    }

    public Method loadMethod(Class clazz, String methodName, Class[] argTypes) throws ReflectionNotFoundException, ReflectionAccessException {
        try {
            return clazz.getMethod(methodName, argTypes);
        } catch (NoClassDefFoundError e) {
            throw new ReflectionNotFoundException("Failed to invoke method " + methodName + " on class " + clazz + " with argument types " + Arrays.asList(argTypes) + ", using class loader " + clazz.getClassLoader() + ": " + Exceptions.collapseText(e), e);
        } catch (NoSuchMethodException e) {
            throw new ReflectionNotFoundException("Failed to invoke method " + methodName + " on class " + clazz + " with argument types " + Arrays.asList(argTypes) + ": " + Exceptions.collapseText(e), e);
        } catch (SecurityException e) {
            throw new ReflectionAccessException("Failed to invoke method " + methodName + " on class " + clazz + " with argument types " + Arrays.asList(argTypes) + ": " + Exceptions.collapseText(e), e);
        }
    }

    /** returns the first method matching the given name */
    public Method loadMethod(Class clazz, String methodName) throws ReflectionNotFoundException, ReflectionAccessException {
        try {
            Method[] allmethods = clazz.getMethods();
            for (int i = 0; i < allmethods.length; i++) {
                if (allmethods[i].getName().equals(methodName)) {
                    return allmethods[i];
                }
            }
            throw new ReflectionNotFoundException("Cannot find method " + methodName + " on class " + clazz);

        } catch (SecurityException e) {
            throw new ReflectionAccessException("Failed to invoke method '" + methodName + " on class " + clazz + ": " + Exceptions.collapseText(e), e);
        }
    }

    /**
     * 
     * @throws ReflectionAccessException If invocation failed due to illegal access or the invoked method failed
     * @throws IllegalArgumentException  If the arguments were invalid
     */
    public Object invokeMethod(Method method, Object obj, Object... argValues) throws ReflectionAccessException {
        try {
            return method.invoke(obj, argValues);
        } catch (IllegalArgumentException e) {
            throw new IllegalArgumentException(getIllegalArgumentsErrorMessage(method, argValues), e);
        } catch (IllegalAccessException e) {
            throw new ReflectionAccessException("Failed to invoke method '" + method.toGenericString() + " on class " + method.getDeclaringClass() + " with argument values " + Arrays.asList(argValues) + ": " + Exceptions.collapseText(e), e);
        } catch (InvocationTargetException e) {
            throw new ReflectionAccessException("Failed to invoke method '" + method.toGenericString() + " on class " + method.getDeclaringClass() + " with argument values " + Arrays.asList(argValues) + ": " + Exceptions.collapseText(e), e);
        }
    }

    public Object invokeStaticMethod(Method method, Object... argValues) throws IllegalArgumentException, ReflectionAccessException {
        try {
            return method.invoke(null, argValues);
        } catch (IllegalArgumentException e) {
            throw new IllegalArgumentException(getIllegalArgumentsErrorMessage(method, argValues), e);
        } catch (IllegalAccessException e) {
            throw new ReflectionAccessException("Failed to invoke method '" + method.toGenericString() + " on class " + method.getDeclaringClass() + " with argument values " + Arrays.asList(argValues) + ": " + Exceptions.collapseText(e), e);
        } catch (InvocationTargetException e) {
            throw new ReflectionAccessException("Failed to invoke method '" + method.toGenericString() + " on class " + method.getDeclaringClass() + " with argument values " + Arrays.asList(argValues) + ": " + Exceptions.collapseText(e), e);
        }
    }

    public Object loadStaticField(Class clazz, String fieldname) throws ReflectionAccessException {
        return loadStaticFields(clazz, new String[] {fieldname}, null)[0];
    }

    public Object[] loadStaticFields(Class clazz, String[] fieldnamesArray, Object[] defaults) throws ReflectionAccessException {
        Object[] result = new Object[fieldnamesArray.length];
        if (defaults!=null) {
            for (int i = 0; i < defaults.length; i++) {
                result[i] = defaults[i];
            }
        }

        List fieldnames = Arrays.asList(fieldnamesArray);
        Field[] classFields = clazz.getDeclaredFields();

        for (int i = 0; i < classFields.length; i++) {
            Field field = classFields[i];
            int index = fieldnames.indexOf(field.getName());
            if (index >= 0) {
                try {
                    result[index] = field.get(null);
                } catch (IllegalArgumentException e) {
                    throw new ReflectionAccessException("Failed to load field '" + field.getName() + " from class " + clazz + ": " + Exceptions.collapseText(e), e);
                } catch (IllegalAccessException e) {
                    throw new ReflectionAccessException("Failed to load field '" + field.getName() + " from class " + clazz + ": " + Exceptions.collapseText(e), e);
                }
            }
        }
        return result;
    }

    private static String getIllegalArgumentsErrorMessage(Method method, Object[] argValues) {
        return method.toGenericString() + " not applicable for the parameters of type " + argumentTypesToString(argValues);
    }

    private static String getIllegalArgumentsErrorMessage(Constructor constructor, Object[] argValues) {
        return constructor.toGenericString() + " not applicable for the parameters of type " + argumentTypesToString(argValues);
    }

    private static String argumentTypesToString(Object[] argValues) {
        StringBuffer msg = new StringBuffer("(");
        for (int i = 0; i < argValues.length; i++) {
            if (i != 0) msg.append(", ");
            msg.append(argValues[i] != null ? argValues[i].getClass().getName() : "null");
        }
        msg.append(")");
        return msg.toString();
    }

    /** copies all fields from the source to target; very little compile-time safety checking, so use with care
     * @throws IllegalAccessException
     * @throws IllegalArgumentException */
    public static  void copyFields(T source, T target) throws IllegalArgumentException, IllegalAccessException {
        Class clazz = source.getClass();
        while (clazz!=null) {
            Field[] fields = clazz.getDeclaredFields();
            for (Field f : fields) {
                f.setAccessible(true);
                Object vs = f.get(source);
                Object vt = f.get(target);
                if ((vs==null && vt!=null) || (vs!=null && !vs.equals(vt))) {
                    f.set(target, vs);
                }
            }
            clazz = clazz.getSuperclass();
        }
    }

    /**
     * Loads class given its canonical name format (e.g. com.acme.Foo.Inner),
     * using iterative strategy (trying com.acme.Foo$Inner, then com.acme$Foo$Inner, etc).
     * @throws ReflectionNotFoundException 
     */
    public Class loadClassFromCanonicalName(String canonicalName) throws ClassNotFoundException, ReflectionNotFoundException {
        ClassNotFoundException err = null;
        String name = canonicalName;
        do {
            try {
                return classLoader.loadClass(name);
            } catch (ClassNotFoundException e) {
                if (err == null) err = e;
                int lastIndexOf = name.lastIndexOf(".");
                if (lastIndexOf >= 0) {
                    name = name.substring(0, lastIndexOf) + "$" + name.substring(lastIndexOf+1);
                }
            }
        } while (name.contains("."));
        throw err;
    }

    /** finds the resource in the classloader, if it exists; inserts or replaces leading slash as necessary
     * (i believe it should _not_ have one, but there is some inconsistency)
     * 
     * Will return null if no resource is found.
     */
    @Nullable
    public URL getResource(String r) {
        URL u = null;
        u = classLoader.getResource(r);
        if (u!=null) return u;
        
        if (r.startsWith("/")) r = r.substring(1);
        else r = "/"+r;
        return classLoader.getResource(r);
    }

    /**
     * Serialize the given object, then reload using the current class loader;
     * this removes linkages to instances with classes loaded by an older class loader.
     * 

     * (like a poor man's clone)
     * 

     * aka "reconstitute(Object)"
     */
    public final Object updateFromNewClassLoader(Object data) throws IOException, ClassNotFoundException {
        ByteArrayOutputStream bytes = new ByteArrayOutputStream();
        new ObjectOutputStream(bytes).writeObject(data);
        Object reconstituted = new ObjectInputStream(new ByteArrayInputStream(bytes.toByteArray())).readObject();
        if (LOG.isDebugEnabled()) LOG.debug("Reconstituted data: " + reconstituted + ", class loader: " + classLoader);
        return reconstituted;
    }

    public ClassLoader getClassLoader() {
        return classLoader;
    }
    
    @SuppressWarnings("unchecked")
    public static  Class findSuperType(T impl, String typeName) {
        Set> toinspect = new LinkedHashSet>();
        Set> inspected = new HashSet>();
        toinspect.add(impl.getClass());
        
        while (toinspect.size() > 0) {
            Class clazz = toinspect.iterator().next(); // get and remove the first element
            if (clazz.getName().equals(typeName)) {
                return (Class) clazz;
            }
            inspected.add(clazz);
            List> toAdd = Arrays.asList(clazz.getInterfaces());
            toinspect.addAll( toAdd );
            if (clazz.getSuperclass() != null) toinspect.add(clazz.getSuperclass());
            toinspect.removeAll(inspected);
        }
        
        return null;
    }
    
    /** whereas Class.getInterfaces() only returns interfaces directly implemented by a class,
     * this walks the inheritance hierarchy to include interfaces implemented by superclass/ancestors;
     * (note it does not include superinterfaces)
     */
    public static Set> getInterfacesIncludingClassAncestors(Class clazz) {
        Set> result = new LinkedHashSet>();
        while (clazz!=null) {
            for (Class iface: clazz.getInterfaces())
                result.add(iface);
            clazz = clazz.getSuperclass();
        }
        return result;
    }

    /** Returns any method exactly matching the given signature, including privates and on parent classes. */
    public static Maybe findMethodMaybe(Class clazz, String name, Class... parameterTypes) {
        if (clazz == null || name == null) return Maybe.absentNoTrace("class or name is null");
        Iterable result = findMethods(false, clazz, name, parameterTypes);
        if (!result.iterator().hasNext()) return Maybe.absentNoTrace("no methods matching "+clazz.getName()+"."+name+"("+Arrays.asList(parameterTypes)+")");
        return Maybe.of(result.iterator().next());
    }
    /** Returns all methods compatible with the given argument types, including privates and on parent classes and where the method takes a supertype. */
    public static Iterable findMethodsCompatible(Class clazz, String name, Class... parameterTypes) {
        return findMethods(true, clazz, name, parameterTypes);
    }
    private static Iterable findMethods(boolean allowCovariantParameterClasses, Class clazz, String name, Class... parameterTypes) {
        if (clazz == null || name == null) {
            return Collections.emptySet();
        }
        List result = MutableList.of();
        Class clazzToInspect = clazz;
        
        while (clazzToInspect != null) {
            methods: for (Method m: clazzToInspect.getDeclaredMethods()) {
                if (!name.equals(m.getName())) continue methods;
                if (m.getParameterTypes().length!=parameterTypes.length) continue methods;
                parameters: for (int i=0; i clazz, String name, Class... parameterTypes) throws NoSuchMethodException {
        if (clazz == null || name == null) {
            throw new NullPointerException("Must not be null: clazz="+clazz+"; name="+name);
        }
        Class clazzToInspect = clazz;
        NoSuchMethodException toThrowIfFails = null;
        
        while (clazzToInspect != null) {
            try {
                return clazzToInspect.getDeclaredMethod(name, parameterTypes);
            } catch (NoSuchMethodException e) {
                if (toThrowIfFails == null) toThrowIfFails = e;
                clazzToInspect = clazzToInspect.getSuperclass();
            }
        }
        throw toThrowIfFails;
    }
    
    /** Finds the field with the given name declared on the given class or any superclass,
     * using {@link Class#getDeclaredField(String)}.
     * 
 
     * If the field name contains a '.' the field is interpreted as having
     * DeclaringClassCanonicalName.FieldName format,
     * allowing a way to set a field unambiguously if some are masked.
     * 

     * @throws NoSuchFieldException if not found
     */
    public static Field findField(Class clazz, String name) throws NoSuchFieldException {
        return findFieldMaybe(clazz, name).orThrowUnwrapped();
    }
    public static Maybe findFieldMaybe(Class clazz, String originalName) {
        String name = originalName;
        if (clazz == null || name == null) {
            throw new NullPointerException("Must not be null: clazz="+clazz+"; name="+name);
        }
        Class clazzToInspect = clazz;
        NoSuchFieldException toThrowIfFails = null;

        String clazzRequired = null;
        if (name.indexOf('.')>=0) {
            int lastDotIndex = name.lastIndexOf('.');
            clazzRequired = name.substring(0, lastDotIndex);
            name = name.substring(lastDotIndex+1);
        }
        
        while (clazzToInspect != null) {
            try {
                if (clazzRequired==null || clazzRequired.equals(clazzToInspect.getCanonicalName())) {
                    return Maybe.of(clazzToInspect.getDeclaredField(name));
                }
            } catch (NoSuchFieldException e) {
                if (toThrowIfFails == null) toThrowIfFails = e;
            }
            clazzToInspect = clazzToInspect.getSuperclass();
        }
        if (toThrowIfFails==null) return Maybe.absent("Field '"+originalName+"' not found");
        return Maybe.absent(toThrowIfFails);
    }
    
    public static Maybe getFieldValueMaybe(Object instance, String fieldName) {
        try {
            if (instance==null) return null;
            Field f = findField(instance.getClass(), fieldName);
            return getFieldValueMaybe(instance, f);
        } catch (Exception e) {
            Exceptions.propagateIfFatal(e);
            return Maybe.absent(e);
        }
    }

    public static Maybe getFieldValueMaybe(Object instance, Field field) {
        try {
            if (instance==null) return null;
            if (field==null) return null;
            field.setAccessible(true);
            return Maybe.of(field.get(instance));
        } catch (Exception e) {
            Exceptions.propagateIfFatal(e);
            return Maybe.absent(e);
        }
    }

    /** Lists all public fields declared on the class or any ancestor, with those HIGHEST in the hierarchy first */
    public static List findPublicFieldsOrderedBySuper(Class clazz) {
        return findFields(clazz, new Predicate() {
            @Override public boolean apply(Field input) {
                return Modifier.isPublic(input.getModifiers());
            }}, FieldOrderings.SUB_BEST_FIELD_LAST_THEN_DEFAULT);
    }

    /** Lists all fields declared on the class, with those lowest in the hierarchy first,
     *  filtered and ordered as requested. 
     *  

     *  See {@link ReflectionPredicates} and {@link FieldOrderings} for conveniences.
     *  

     *  Default is no filter and {@link FieldOrderings#SUB_BEST_FIELD_LAST_THEN_ALPHABETICAL}
     *  */
    public static List findFields(final Class clazz, Predicate filter, Comparator fieldOrdering) {
        checkNotNull(clazz, "clazz");
        MutableList.Builder result = MutableList.builder();
        Stack> tovisit = new Stack>();
        Set> visited = Sets.newLinkedHashSet();
        tovisit.push(clazz);
        
        while (!tovisit.isEmpty()) {
            Class nextclazz = tovisit.pop();
            if (!visited.add(nextclazz)) {
                continue; // already visited
            }
            if (nextclazz.getSuperclass() != null) tovisit.add(nextclazz.getSuperclass());
            tovisit.addAll(Arrays.asList(nextclazz.getInterfaces()));
            
            result.addAll(Iterables.filter(Arrays.asList(nextclazz.getDeclaredFields()), 
                filter!=null ? filter : Predicates.alwaysTrue()));
        }
        
        List resultList = result.build();
        Collections.sort(resultList, fieldOrdering != null ? fieldOrdering : FieldOrderings.SUB_BEST_FIELD_LAST_THEN_ALPHABETICAL);
        
        return resultList;
    }
    
    // TODO I've seen strange behaviour where class.getMethods() does not include methods from interfaces.
    // Also the ordering guarantees here are useful...
    public static List findPublicMethodsOrderedBySuper(Class clazz) {
        checkNotNull(clazz, "clazz");
        MutableList.Builder result = MutableList.builder();
        Stack> tovisit = new Stack>();
        Set> visited = Sets.newLinkedHashSet();
        tovisit.push(clazz);
        
        while (!tovisit.isEmpty()) {
            Class nextclazz = tovisit.pop();
            if (!visited.add(nextclazz)) {
                continue; // already visited
            }
            if (nextclazz.getSuperclass() != null) tovisit.add(nextclazz.getSuperclass());
            tovisit.addAll(Arrays.asList(nextclazz.getInterfaces()));
            
            result.addAll(Iterables.filter(Arrays.asList(nextclazz.getDeclaredMethods()), new Predicate() {
                @Override public boolean apply(Method input) {
                    return Modifier.isPublic(input.getModifiers());
                }}));
            
        }
        
        List resultList = result.build();
        Collections.sort(resultList, new Comparator() {
            @Override public int compare(Method m1, Method m2) {
                Method msubbest = inferSubbestMethod(m1, m2);
                return (msubbest == null) ? 0 : (msubbest == m1 ? 1 : -1);
            }});
        
        return resultList;
    }
    
    /**
     * If the classes of the fields satisfy {@link #inferSubbest(Class, Class)}
     * return the field in the lower (sub-best) class, otherwise null.
     */
    public static Field inferSubbestField(Field f1, Field f2) {
        Class c1 = f1.getDeclaringClass();
        Class c2 = f2.getDeclaringClass();
        boolean isSuper1 = c1.isAssignableFrom(c2);
        boolean isSuper2 = c2.isAssignableFrom(c1);
        return (isSuper1) ? (isSuper2 ? 
            /* same field */ null : 
            /* f1 from super */ f2) : 
            (isSuper2 ? 
                /* f2 from super of f1 */ f1 : 
                /* fields are from different hierarchies */ null);
    }
    
    /**
     * If the classes of the methods satisfy {@link #inferSubbest(Class, Class)}
     * return the field in the lower (sub-best) class, otherwise null.
     */
    public static Method inferSubbestMethod(Method m1, Method m2) {
        Class c1 = m1.getDeclaringClass();
        Class c2 = m2.getDeclaringClass();
        boolean isSuper1 = c1.isAssignableFrom(c2);
        boolean isSuper2 = c2.isAssignableFrom(c1);
        return (isSuper1) ? (isSuper2 ? null : m2) : (isSuper2 ? m1 : null);
    }
    
    /**
     * If one class is a subclass of the other, return that (the lower in the type hierarchy);
     * otherwise return null (if they are the same or neither is a subclass of the other).
     */
    public static Class inferSubbest(Class c1, Class c2) {
        boolean isSuper1 = c1.isAssignableFrom(c2);
        boolean isSuper2 = c2.isAssignableFrom(c1);
        return (isSuper1) ? (isSuper2 ? null : c2) : (isSuper2 ? c1 : null);
    }
    
    /** convenience for casting the given candidate to the given type (without any coercion, and allowing candidate to be null) */
    @SuppressWarnings("unchecked")
    public static  T cast(Object candidate, Class type) {
        if (candidate==null) return null;
        if (!type.isAssignableFrom(candidate.getClass()))
            throw new IllegalArgumentException("Requires a "+type+", but had a "+candidate.getClass()+" ("+candidate+")");
        return (T)candidate;
    }

    /** @deprecated since 0.10.0 use {@link #invokeMethodFromArgs(Object, String, List)};
     * this allows null return values */ @Deprecated
    public static Optional invokeMethodWithArgs(Object clazzOrInstance, String method, List args) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
        return invokeMethodWithArgs(clazzOrInstance, method, args, false);
    }
    /** @deprecated since 0.10.0 use {@link #invokeMethodFromArgs(Object, String, List)} */ @Deprecated
    public static Optional invokeMethodWithArgs(Object clazzOrInstance, String method, List args, boolean setAccessible) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
        return invokeMethodFromArgs(clazzOrInstance, method, args, setAccessible).toOptional();
    }
    
    /** invokes the given method on the given clazz or instance, doing reasonably good matching on args etc 
     * @throws InvocationTargetException 
     * @throws IllegalAccessException 
     * @throws IllegalArgumentException */
    public static Maybe invokeMethodFromArgs(Object clazzOrInstance, String method, List args) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
        return invokeMethodFromArgs(clazzOrInstance, method, args, false);
    }
    
    /** as {@link #invokeMethodFromArgs(Object, String, List)} but giving control over whether to set it accessible */
    public static Maybe invokeMethodFromArgs(Object clazzOrInstance, String method, List args, boolean setAccessible) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
        return invokeMethodFromArgs(clazzOrInstance, method, args, setAccessible, Optional.absent());
    }
    
    /** as {@link #invokeMethodFromArgs(Object, String, List)} but giving control over whether to set it accessible */
    public static Maybe invokeMethodFromArgs(Object clazzOrInstance, String method, List args, boolean setAccessible, Optional coercer) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException {
        Maybe maybeMethod = getMethodFromArgs(clazzOrInstance, method, args);
        if (coercer.isPresent() && maybeMethod.isAbsent()) {
            maybeMethod = getMethodFromArgs(clazzOrInstance, method, args, coercer);
        }
        if (maybeMethod.isAbsent()) {
            return Maybe.absent(Maybe.getException(maybeMethod));
        }
        Method m = maybeMethod.get();

        return Maybe.of(invokeMethodFromArgs(clazzOrInstance, m, args, setAccessible, coercer));
    }

    /** searches for the given method on the given clazz or instance, doing reasonably good matching on args etc */
    public static Maybe getMethodFromArgs(Object clazzOrInstance, String method, List args) {
        return getMethodFromArgs(clazzOrInstance, method, args, Optional.absent());
    }
    
    /** searches for the given method on the given clazz or instance, doing reasonably good matching on args etc */
    public static Maybe getMethodFromArgs(Object clazzOrInstance, String method, List args, Optional coercer) {
        Preconditions.checkNotNull(clazzOrInstance, "clazz or instance");
        Preconditions.checkNotNull(method, "method");
        Preconditions.checkNotNull(args, "args to "+method);
        
        Class clazz;
        if (clazzOrInstance instanceof Class) {
            clazz = (Class)clazzOrInstance;
        } else {
            clazz = clazzOrInstance.getClass();
        }
        
        Object[] argsArray = args.toArray();

        for (Method m: clazz.getMethods()) {
            if (method.equals(m.getName())) {
                Class[] parameterTypes = m.getParameterTypes();
                if (m.isVarArgs()) {
                    if (typesMatchUpTo(argsArray, parameterTypes, parameterTypes.length-1, coercer)) {
                        Class varargType = parameterTypes[parameterTypes.length-1].getComponentType();
                        boolean varargsMatch = true;
                        for (int i=parameterTypes.length-1; i argTypes = Lists.newArrayList();
        for (Object arg : args) {
            argTypes.add(arg == null ? "" : arg.getClass().getSimpleName());
        }
        return Maybe.absent("Method '"+method+"' not found matching given args of type "+argTypes);
    }

    /** invokes the given method on the given clazz or instance, assuming that the method matches passed arguments
     * @throws InvocationTargetException 
     * @throws IllegalAccessException 
     * @throws IllegalArgumentException */
    public static Object invokeMethodFromArgs(Object clazzOrInstance, Method m, List args)
            throws IllegalAccessException, InvocationTargetException {
        return invokeMethodFromArgs(clazzOrInstance, m, args, false);
    }

    /** as {@link #invokeMethodFromArgs(Object, Method, List)} but giving control over whether to set it accessible */
    public static Object invokeMethodFromArgs(Object clazzOrInstance, Method m, List args, boolean setAccessible)
            throws IllegalAccessException, InvocationTargetException {
        return invokeMethodFromArgs(clazzOrInstance, m, args, setAccessible, Optional.absent());
    }

    /** as {@link #invokeMethodFromArgs(Object, Method, List)} but giving control over whether to set it accessible */
    public static Object invokeMethodFromArgs(Object clazzOrInstance, Method m, List args, boolean setAccessible, Optional coercer)
            throws IllegalAccessException, InvocationTargetException {
        Preconditions.checkNotNull(clazzOrInstance, "clazz or instance");
        Preconditions.checkNotNull(m, "method");
        Preconditions.checkNotNull(args, "args to "+m);

        Object instance;
        if (clazzOrInstance instanceof Class) {
            instance = null;
        } else {
            instance = clazzOrInstance;
        }

        Object[] argsArray = args.toArray();

        Class[] parameterTypes = m.getParameterTypes();
        if (m.isVarArgs()) {
            Class varargType = parameterTypes[parameterTypes.length-1].getComponentType();
            Object varargs = Array.newInstance(varargType, argsArray.length+1 - parameterTypes.length);
            for (int i=parameterTypes.length-1; i[] parameterTypes) {
        return typesMatch(argsArray, parameterTypes, Optional.absent());
    }
    
    /** true iff all args match the corresponding types */
    public static boolean typesMatch(Object[] argsArray, Class[] parameterTypes, Optional coercer) {
        if (argsArray.length != parameterTypes.length)
            return false;
        return typesMatchUpTo(argsArray, parameterTypes, argsArray.length, coercer);
    }

    /** true iff the initial N args match the corresponding types */
    public static boolean typesMatchUpTo(Object[] argsArray, Class[] parameterTypes, int lengthRequired) {
        return typesMatchUpTo(argsArray, parameterTypes, lengthRequired, Optional.absent());
    }
    
    /** true iff the initial N args match the corresponding types */
    public static boolean typesMatchUpTo(Object[] argsArray, Class[] parameterTypes, int lengthRequired, Optional coercer) {
        if (argsArray.length < lengthRequired || parameterTypes.length < lengthRequired)
            return false;
        for (int i=0; i parameterType, Optional coercer) {
        if (parameterType.isPrimitive() && arg == null) return false;
        if (arg == null) return true;
        if (Boxing.boxedType(parameterType).isInstance(arg)) return true;
        if (coercer.isPresent() && coercer.get().tryCoerce(arg, parameterType).isPresent()) return true;
        return false;
    }

    /**
     * Gets all the interfaces implemented by the given type, including its parent classes.
     *
     * @param type the class to look up
     * @return an immutable list of the interface classes
     */
    public static List> getAllInterfaces(@Nullable Class type) {
        Set> found = Sets.newLinkedHashSet();
        findAllInterfaces(type, found);
        return ImmutableList.copyOf(found);
    }

    /** Recurse through the class hierarchies of the type and its interfaces. */
    private static void findAllInterfaces(@Nullable Class type, Set> found) {
        if (type == null) return;
        for (Class i : type.getInterfaces()) {
            if (found.add(i)) { // not seen before
                findAllInterfaces(i, found);
            }
        }
        findAllInterfaces(type.getSuperclass(), found);
    }

    public static boolean hasNoArgConstructor(Class clazz) {
        try {
            clazz.getConstructor(new Class[0]);
            return true;
        } catch (NoSuchMethodException e) {
            return false;
        }
    }

    public static boolean hasNoNonObjectFields(Class clazz) {
        if (Object.class.equals(clazz)) return true;
        if (clazz.getDeclaredFields().length>0) return false;
        return hasNoNonObjectFields(clazz.getSuperclass());
    }

    /** @deprecated since 0.10.0 use {@link #findMappedNameMaybe(Map, String)} */ @Deprecated
    public static Optional tryFindMappedName(Map renames, String name) {
        return findMappedNameMaybe(renames, name).toOptional();
    }
    
    /** Takes a map of old-class-names to renames classes, and returns the mapped name if matched, or absent */
    public static Maybe findMappedNameMaybe(Map renames, String name) {
        if (renames==null) return Maybe.absent("no renames supplied");
        
        String mappedName = renames.get(name);
        if (mappedName != null) {
            return Maybe.of(mappedName);
        }
        
        // look for inner classes by mapping outer class
        if (name.contains("$")) {
            String outerClassName = name.substring(0, name.indexOf('$'));
            mappedName = renames.get(outerClassName);
            if (mappedName != null) {
                return Maybe.of(mappedName + name.substring(name.indexOf('$')));
            }
        }
        
        return Maybe.absent("mapped name not present");
    }

    public static String findMappedNameAndLog(Map renames, String name) {
        Maybe rename = Reflections.findMappedNameMaybe(renames, name);
        if (rename.isPresent()) {
            LOG.debug("Mapping class '"+name+"' to '"+rename.get()+"'");
            return rename.get();
        }
        return name;
    }

    public static boolean hasSpecialSerializationMethods(Class type) {
        if (type==null) return false;
        if (findMethodMaybe(type, "writeObject", java.io.ObjectOutputStream.class).isPresent()) return true;
        return hasSpecialSerializationMethods(type.getSuperclass());
    }

    public static List arrayToList(Object input) {
        // We can't just use Arrays.asList(), because that would return a list containing the single
        // value "input".
        List result = new ArrayList<>();
        int length = Array.getLength(input);
        for (int i = 0; i < length; i++) {
            result.add(Array.get(input, i));
        }
        return result;
    }
    
    /**
     * Attempts to find an equivalent accessible method to be invoked (or if the given method is
     * already accessible, then return it). Otherwise return absent.
     * 
     * "Accessible" means that it is a public method declared on a public type.
     * 
     * For example, if {@code method} is declared on a private sub-class, but that overides a 
     * method declared on a public super-class, then this method will return the {@link Method} 
     * instance for the public super-class (assuming the method is not static).
     * 
     * If no better method could be found, it does a log.warn (once per method signature, per 
     * jvm-invocation), and then returns absent.
     */
    public static Maybe findAccessibleMethod(Method method) {
        return MethodAccessibleReflections.findAccessibleMethod(method);
    }

    /**
     * Calls {@link Method#setAccessible(boolean)} "safely", wrapping in a try-catch block so that 
     * the exception is never propagated.
     * 

     * It will log.warn once per method signature for which we fail to set it accessible. It will
     * also log.warn if it succeeds (once per method signature) as this is discouraged!
     * 
     * @return True if setAccessible succeeded; false otherwise
     */
    public static boolean trySetAccessible(Method method) {
        return MethodAccessibleReflections.trySetAccessible(method);
    }

    public static TypeToken[] getGenericParameterTypeTokens(TypeToken t) {
        Class rawType = t.getRawType();
        TypeVariable[] pT = rawType.getTypeParameters();
        TypeToken pTT[] = new TypeToken[pT.length];
        for (int i=0; i 















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