metaclassregistry.java

来自「大名鼎鼎的java动态脚本语言。已经通过了sun的认证」· Java 代码 · 共 287 行

/*
 $Id: MetaClassRegistry.java,v 1.27 2006/05/30 18:14:45 blackdrag Exp $

 Copyright 2003 (C) James Strachan and Bob Mcwhirter. All Rights Reserved.

 Redistribution and use of this software and associated documentation
 ("Software"), with or without modification, are permitted provided
 that the following conditions are met:

 1. Redistributions of source code must retain copyright
    statements and notices.  Redistributions must also contain a
    copy of this document.

 2. Redistributions in binary form must reproduce the
    above copyright notice, this list of conditions and the
    following disclaimer in the documentation and/or other
    materials provided with the distribution.

 3. The name "groovy" must not be used to endorse or promote
    products derived from this Software without prior written
    permission of The Codehaus.  For written permission,
    please contact [e-mail].

 4. Products derived from this Software may not be called "groovy"
    nor may "groovy" appear in their names without prior written
    permission of The Codehaus. "groovy" is a registered
    trademark of The Codehaus.

 5. Due credit should be given to The Codehaus -
    http://groovy.codehaus.org/

 THIS SOFTWARE IS PROVIDED BY THE CODEHAUS AND CONTRIBUTORS
 ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
 NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
 THE CODEHAUS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 */
package groovy.lang;

import java.beans.IntrospectionException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.WeakHashMap;

import org.codehaus.groovy.runtime.DefaultGroovyMethods;
import org.codehaus.groovy.runtime.DefaultGroovyStaticMethods;
import org.codehaus.groovy.runtime.MethodHelper;
import org.codehaus.groovy.runtime.ReflectorLoader;

/**
 * A registery of MetaClass instances which caches introspection &
 * reflection information and allows methods to be dynamically added to
 * existing classes at runtime
 *
 * @author <a href="mailto:[e-mail]">James Strachan</a>
 * @version $Revision: 1.27 $
 */
/**
 * @author John Wilson
 *
 */
public class MetaClassRegistry {
    private Map metaClasses = Collections.synchronizedMap(new WeakHashMap());
    private boolean useAccessible;
    private Map loaderMap = Collections.synchronizedMap(new WeakHashMap());

    public static final int LOAD_DEFAULT = 0;
    public static final int DONT_LOAD_DEFAULT = 1;
    private static MetaClassRegistry instanceInclude;
    private static MetaClassRegistry instanceExclude;


    public MetaClassRegistry() {
        this(LOAD_DEFAULT, true);
    }

    public MetaClassRegistry(int loadDefault) {
        this(loadDefault, true);
    }

    /**
     * @param useAccessible defines whether or not the {@link java.lang.reflect.AccessibleObject.setAccessible();}
     *                      method will be called to enable access to all methods when using reflection
     */
    public MetaClassRegistry(boolean useAccessible) {
        this(LOAD_DEFAULT, useAccessible);
    }
    
    public MetaClassRegistry(final int loadDefault, final boolean useAccessible) {
        this.useAccessible = useAccessible;
        
        if (loadDefault == LOAD_DEFAULT) {
            // lets register the default methods
            lookup(DefaultGroovyMethods.class);
            registerMethods(DefaultGroovyMethods.class, true);
            lookup(DefaultGroovyStaticMethods.class);
            registerMethods(DefaultGroovyStaticMethods.class, false);
            checkInitialised();
        }
    }
    
    private void registerMethods(final Class theClass, final boolean instanceMethods) {
        Method[] methods = theClass.getMethods();
        for (int i = 0; i < methods.length; i++) {
            Method method = methods[i];
            if (MethodHelper.isStatic(method)) {
                Class[] paramTypes = method.getParameterTypes();
                if (paramTypes.length > 0) {
                    Class owner = paramTypes[0];
                    if (instanceMethods) {
                        lookup(owner).addNewInstanceMethod(method);
                    } else {
                        lookup(owner).addNewStaticMethod(method);
                    }
                }
            }
        }
    }

    public MetaClass getMetaClass(Class theClass) {
        synchronized (theClass) {
            MetaClass answer = (MetaClass) metaClasses.get(theClass);
            if (answer == null) {
                answer = getMetaClassFor(theClass);
                answer.checkInitialised();
                metaClasses.put(theClass, answer);
            }
            return answer;
        }
    }

    public void removeMetaClass(Class theClass) {
        metaClasses.remove(theClass);
    }


    /**
     * Registers a new MetaClass in the registry to customize the type
     *
     * @param theClass
     * @param theMetaClass
     */
    public void setMetaClass(Class theClass, MetaClass theMetaClass) {
        metaClasses.put(theClass, theMetaClass);
    }

    public boolean useAccessible() {
        return useAccessible;
    }

    /**
     * A helper class to load meta class bytecode into the class loader
     */
    public Class createReflectorClass(final ClassLoader parent, final String name, final byte[] bytecode) throws ClassNotFoundException {
        return (Class) AccessController.doPrivileged(new PrivilegedAction() {
            public Object run() {
                return getReflectorLoader(parent).defineClass(name, bytecode, getClass().getProtectionDomain());
            }
        });
    }

    private ReflectorLoader getReflectorLoader(final ClassLoader loader) {
        synchronized (loaderMap) {
            ReflectorLoader reflectorLoader = (ReflectorLoader) loaderMap.get(loader);
            if (reflectorLoader == null) {
                reflectorLoader = (ReflectorLoader) AccessController.doPrivileged(new PrivilegedAction() {
                    public Object run() {
                        return new ReflectorLoader(loader);
                    }
                }); 
                loaderMap.put(loader, reflectorLoader);
            }
            return reflectorLoader;
        }
    }

    /**
     * Ensures that all the registered MetaClass instances are initalized
     */
    void checkInitialised() {
        // lets copy all the classes in the repository right now 
        // to avoid concurrent modification exception
        List list = new ArrayList(metaClasses.values());
        for (Iterator iter = list.iterator(); iter.hasNext();) {
            MetaClass metaClass = (MetaClass) iter.next();
            metaClass.checkInitialised();
        }
    }

    /**
     * Used by MetaClass when registering new methods which avoids initializing the MetaClass instances on lookup
     */
    MetaClass lookup(Class theClass) {
        MetaClass answer = (MetaClass) metaClasses.get(theClass);
        if (answer == null) {
            answer = getMetaClassFor(theClass);
            metaClasses.put(theClass, answer);
        }
        return answer;
    }

    /**
     * Find a MetaClass for the class
     * If there is a custom MetaClass then return an instance of that. Otherwise return an instance of the standard MetaClass
     * 
     * @param theClass
     * @return An instace of the MetaClass which will handle this class
     */
    private MetaClass getMetaClassFor(final Class theClass) {
        try {
        final Class customMetaClass = Class.forName("groovy.runtime.metaclass." + theClass.getName() + "MetaClass");
        final Constructor customMetaClassConstructor = customMetaClass.getConstructor(new Class[]{MetaClassRegistry.class, Class.class});
            
            return (MetaClass)customMetaClassConstructor.newInstance(new Object[]{this, theClass});
        } catch (final ClassNotFoundException e) {
            try {
                return new MetaClassImpl(this, theClass);
            } catch (final IntrospectionException e1) {
                throw new GroovyRuntimeException("Could not introspect class: " + theClass.getName() + ". Reason: " + e1, e1);
            }
        } catch (final Exception e) {
            throw new GroovyRuntimeException("Could not instantiate custom Metaclass for class: " + theClass.getName() + ". Reason: " + e, e);
        }
    }

    public MetaMethod getDefinedMethod(Class theClass, String methodName, Class[] args, boolean isStatic) {
        MetaClass metaclass = this.getMetaClass(theClass);
        if (metaclass == null) {
            return null;
        }
        else {
            if (isStatic) {
                return metaclass.retrieveStaticMethod(methodName, args);
            }
            else {
                return metaclass.retrieveMethod(methodName, args);
            }
        }
    }

    public Constructor getDefinedConstructor(Class theClass, Class[] args) {
        MetaClass metaclass = this.getMetaClass(theClass);
        if (metaclass == null) {
            return null;
        }
        else {
            return metaclass.retrieveConstructor(args);
        }
    }

    /**
     * Singleton of MetaClassRegistry. Shall we use threadlocal to store the instance?
     *
     * @param includeExtension
     * @return
     */
    public static MetaClassRegistry getIntance(int includeExtension) {
        if (includeExtension != DONT_LOAD_DEFAULT) {
            if (instanceInclude == null) {
                instanceInclude = new MetaClassRegistry();
            }
            return instanceInclude;
        }
        else {
            if (instanceExclude == null) {
                instanceExclude = new MetaClassRegistry(DONT_LOAD_DEFAULT);
            }
            return instanceExclude;
        }
    }
}