objectstreamclass.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 2,026 行 · 第 1/5 页

/*
 * @(#)ObjectStreamClass.java	1.116 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.io;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.security.AccessController;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import sun.misc.SoftCache;
// import sun.misc.Unsafe;  // - Back-ported from JDK 1.4
// import sun.reflect.ReflectionFactory;  // - Back-ported from JDK 1.4 

/* Back-ported JDK 1.4 implementation  */

/**
 * Serialization's descriptor for classes.
 * It contains the name and serialVersionUID of the class.
 * <br>
 * The ObjectStreamClass for a specific class loaded in this Java VM can
 * be found/created using the lookup method.<p>
 * The algorithm to compute the SerialVersionUID is described in 
 * <a href="../../../guide/serialization/spec/class.doc4.html"> Object Serialization Specification, Section 4.4, Stream Unique Identifiers</a>.
 *
 * @author	Mike Warres
 * @author	Roger Riggs
 * @version 1.98 02/02/00
 * @see ObjectStreamField
 * @see <a href="../../../guide/serialization/spec/class.doc.html"> Object Serialization Specification, Section 4, Class Descriptors</a>
 * @since   JDK1.1
 */
public class ObjectStreamClass implements Serializable {

    /** serialPersistentFields value indicating no serializable fields */
    public static final ObjectStreamField[] NO_FIELDS = 
	new ObjectStreamField[0];
    
    private static final long serialVersionUID = -6120832682080437368L;
    private static final ObjectStreamField[] serialPersistentFields =
	NO_FIELDS;
    
    /** reflection factory for obtaining serialization constructors */
    /* // - Back-ported from JDK 1.4 
    private static final ReflectionFactory reflFactory = (ReflectionFactory)
	AccessController.doPrivileged(
	    new ReflectionFactory.GetReflectionFactoryAction());
	    */

    /** cache mapping local classes -> descriptors */
    private static final SoftCache localDescs = new SoftCache(10);
    /** cache mapping field group/local desc pairs -> field reflectors */
    private static final SoftCache reflectors = new SoftCache(10);

    /** class associated with this descriptor (if any) */
    private Class cl;
    /** name of class represented by this descriptor */
    private String name;
    /** serialVersionUID of represented class (null if not computed yet) */
    private volatile Long suid;

    /** true if represents dynamic proxy class */
    private boolean isProxy;
    /** true if represented class implements Serializable */
    private boolean serializable;
    /** true if represented class implements Externalizable */
    private boolean externalizable;
    /** true if desc has data written by class-defined writeObject method */
    private boolean hasWriteObjectData;
    /** 
     * true if desc has externalizable data written in block data format; this
     * must be true by default to accomodate ObjectInputStream subclasses which
     * override readClassDescriptor() to return class descriptors obtained from
     * ObjectStreamClass.lookup() (see 4461737)
     */
    private boolean hasBlockExternalData = true;

    /** exception (if any) thrown while attempting to resolve class */
    private ClassNotFoundException resolveEx;
    /** exception (if any) to be thrown if deserialization attempted */
    private InvalidClassException deserializeEx;
    /** exception (if any) to be thrown if default serialization attempted */
    private InvalidClassException defaultSerializeEx;

    /** serializable fields */
    private ObjectStreamField[] fields;
    /** aggregate marshalled size of primitive fields */
    private int primDataSize;
    /** number of non-primitive fields */
    private int numObjFields;
    /** reflector for setting/getting serializable field values */
    private FieldReflector fieldRefl;
    /** data layout of serialized objects described by this class desc */
    private volatile ClassDataSlot[] dataLayout;

    /** serialization-appropriate constructor, or null if none */
    // private Constructor cons; // - Back-ported from JDK 1.4 

    /** class-defined writeObject method, or null if none */
    private Method writeObjectMethod;
    /** class-defined readObject method, or null if none */
    private Method readObjectMethod;
    /** class-defined readObjectNoData method, or null if none */
    private Method readObjectNoDataMethod;
    /** class-defined writeReplace method, or null if none */
    private Method writeReplaceMethod;
    /** class-defined readResolve method, or null if none */
    private Method readResolveMethod;

    /** local class descriptor for represented class (may point to self) */
    private ObjectStreamClass localDesc;
    /** superclass descriptor appearing in stream */
    private ObjectStreamClass superDesc;

    /** Class to be initialized -- for back-port to J2ME Foundation */
    private Class initClass;  // - Back-ported from JDK 1.4 

    /**
     * Initializes native code.
     */
    private static native void initNative();
    static {
	initNative();
    }

    /*
     * Get the field IDs associated with the given fields.  The field IDs are
     * later passed as arguments to the various ObjectInputStream and
     * ObjectOutputStream native methods for setting and getting field values.
     */
    private static native void getFieldIDs(ObjectStreamField[] fields,
	    long[] primFieldIDs, long[] objFieldIDs);

    /** 
     * Find the descriptor for a class that can be serialized. 
     * Creates an ObjectStreamClass instance if one does not exist 
     * yet for class. Null is returned if the specified class does not 
     * implement java.io.Serializable or java.io.Externalizable.
     *
     * @param cl class for which to get the descriptor
     * @return the class descriptor for the specified class
     */
    public static ObjectStreamClass lookup(Class cl) {
	return lookup(cl, false);
    }
    
    /**
     * The name of the class described by this descriptor.
     *
     * @return a <code>String</code> representing the fully qualified name of
     * the class
     */
    public String getName() {
	return name;
    }

    /**
     * Return the serialVersionUID for this class.
     * The serialVersionUID defines a set of classes all with the same name
     * that have evolved from a common root class and agree to be serialized
     * and deserialized using a common format.
     * NonSerializable classes have a serialVersionUID of 0L.
     *
     * @return the SUID of the class described by this descriptor
     */
    public long getSerialVersionUID() {
	// TODO: synchronize instead of relying on volatile?
	if (suid == null) {
	    suid = (Long) AccessController.doPrivileged(
		new PrivilegedAction() {
		    public Object run() {
			return new Long(computeDefaultSUID(cl));
		    }
		}
	    );
	}
	return suid.longValue();
    }

    /**
     * Return the class in the local VM that this version is mapped to.
     * Null is returned if there is no corresponding local class.
     *
     * @return the <code>Class</code> instance that this descriptor represents
     */
    public Class forClass() {
	return cl;
    }
    
    /**
     * Return an array of the fields of this serializable class.
     *
     * @return an array containing an element for each persistent
     * field of this class. Returns an array of length zero if
     * there are no fields.
     * @since 1.2
     */
    public ObjectStreamField[] getFields() {
	return getFields(true);
    }

    /**
     * Get the field of this class by name.
     *
     * @param name the name of the data field to look for
     * @return The ObjectStreamField object of the named field or null if there
     * is no such named field.
     */
    public ObjectStreamField getField(String name) {
	return getField(name, null);
    }

    /**
     * Return a string describing this ObjectStreamClass.
     */
    public String toString() {
	return name + ": static final long serialVersionUID = " + 
	    getSerialVersionUID() + "L;";
    }
    
    /**
     * Looks up and returns class descriptor for given class, or null if class
     * is non-serializable and "all" is set to false.
     * 
     * @param	cl class to look up
     * @param	all if true, return descriptors for all classes; if false, only
     * 		return descriptors for serializable classes
     */
    static ObjectStreamClass lookup(Class cl, boolean all) {
	if (!(all || Serializable.class.isAssignableFrom(cl))) {
	    return null;
	}
	/*
	 * Note: using the class directly as the key for storing entries does
	 * not pin the class indefinitely, since SoftCache removes strong refs
	 * to keys when the corresponding values are gc'ed.
	 */
	Object entry;
	EntryFuture future = null;
	synchronized (localDescs) {
	    if ((entry = localDescs.get(cl)) == null) {
		localDescs.put(cl, future = new EntryFuture());
	    }
	}
	
	if (entry instanceof ObjectStreamClass) {  // check common case first
	    return (ObjectStreamClass) entry;
	} else if (entry instanceof EntryFuture) {
	    entry = ((EntryFuture) entry).get();
	} else if (entry == null) {
	    try {
		entry = new ObjectStreamClass(cl);
	    } catch (Throwable th) {
		entry = th;
	    }
	    future.set(entry);
	    synchronized (localDescs) {
		localDescs.put(cl, entry);
	    }
	}
	
	if (entry instanceof ObjectStreamClass) {
	    return (ObjectStreamClass) entry;
	} else if (entry instanceof RuntimeException) {
	    throw (RuntimeException) entry;
	} else if (entry instanceof Error) {
	    throw (Error) entry;
	} else {
	    throw new InternalError("unexpected entry: " + entry);
	}
    }

    /**
     * Placeholder used in class descriptor and field reflector lookup tables
     * for an entry in the process of being initialized.  (Internal) callers
     * which receive an EntryFuture as the result of a lookup should call the
     * get() method of the EntryFuture; this will return the actual entry once
     * it is ready for use and has been set().  To conserve objects,
     * EntryFutures synchronize on themselves.
     */
    private static class EntryFuture {
	
	private static final Object unset = new Object();
	private Object entry = unset;

	synchronized void set(Object entry) {
	    if (this.entry != unset) {
		throw new IllegalStateException();
	    }
	    this.entry = entry;
	    notifyAll();
	}
	
	synchronized Object get() {
	    boolean interrupted = false;
	    while (entry == unset) {
		try { 
		    wait(); 
		} catch (InterruptedException ex) {
		    interrupted = true;
		}
	    }
	    if (interrupted) {
		AccessController.doPrivileged(
		    new PrivilegedAction() {
			public Object run() {
			    Thread.currentThread().interrupt();
			    return null;
			}
		    }
		);
	    }
	    return entry;
	}
    }

    /**
     * Creates local class descriptor representing given class.
     */
    private ObjectStreamClass(final Class cl) {
	this.cl = cl;
	name = cl.getName();
	isProxy = Proxy.isProxyClass(cl);
	serializable = Serializable.class.isAssignableFrom(cl);
	externalizable = Externalizable.class.isAssignableFrom(cl);

	Class superCl = cl.getSuperclass();
	superDesc = (superCl != null) ? lookup(superCl, false) : null;
	localDesc = this;

	if (serializable) {
	    AccessController.doPrivileged(new PrivilegedAction() {
		public Object run() {
		    suid = getDeclaredSUID(cl);
		    fields = getSerialFields(cl);
		    computeFieldOffsets();
		    
		    if (externalizable) {
                      // Back-ported from JDK 1.4
		      // cons = getExternalizableConstructor(cl);
		      initClass = cl;
		    } else {
                        // Back-ported from JDK 1.4
		        // cons = getSerializableConstructor(cl);
		        initClass = getSerializableInitClass(cl);

			writeObjectMethod = getPrivateMethod(cl, "writeObject", 
			    new Class[] { ObjectOutputStream.class }, 
			    Void.TYPE);
			readObjectMethod = getPrivateMethod(cl, "readObject", 
			    new Class[] { ObjectInputStream.class }, 
			    Void.TYPE);
			readObjectNoDataMethod = getPrivateMethod(
			    cl, "readObjectNoData", 
			    new Class[0], Void.TYPE);
			hasWriteObjectData = (writeObjectMethod != null);
		    }
		    writeReplaceMethod = getInheritableMethod(
			cl, "writeReplace", new Class[0], Object.class);
		    readResolveMethod = getInheritableMethod(
			cl, "readResolve", new Class[0], Object.class);
		    return null;
		}
	    });
	} else {
	    suid = new Long(0);
	    fields = NO_FIELDS;
	}

	try {
	    fieldRefl = getReflector(fields, this);
	} catch (InvalidClassException ex) {