FileDocCategorySizeDatePackage
ObjectOutputStream.javaAPI DocJava SE 5 API70928Fri Aug 26 14:57:00 BST 2005java.io

ObjectOutputStream

public class ObjectOutputStream extends OutputStream implements ObjectStreamConstants, ObjectOutput
An ObjectOutputStream writes primitive data types and graphs of Java objects to an OutputStream. The objects can be read (reconstituted) using an ObjectInputStream. Persistent storage of objects can be accomplished by using a file for the stream. If the stream is a network socket stream, the objects can be reconstituted on another host or in another process.

Only objects that support the java.io.Serializable interface can be written to streams. The class of each serializable object is encoded including the class name and signature of the class, the values of the object's fields and arrays, and the closure of any other objects referenced from the initial objects.

The method writeObject is used to write an object to the stream. Any object, including Strings and arrays, is written with writeObject. Multiple objects or primitives can be written to the stream. The objects must be read back from the corresponding ObjectInputstream with the same types and in the same order as they were written.

Primitive data types can also be written to the stream using the appropriate methods from DataOutput. Strings can also be written using the writeUTF method.

The default serialization mechanism for an object writes the class of the object, the class signature, and the values of all non-transient and non-static fields. References to other objects (except in transient or static fields) cause those objects to be written also. Multiple references to a single object are encoded using a reference sharing mechanism so that graphs of objects can be restored to the same shape as when the original was written.

For example to write an object that can be read by the example in ObjectInputStream:

FileOutputStream fos = new FileOutputStream("t.tmp");
ObjectOutputStream oos = new ObjectOutputStream(fos);

oos.writeInt(12345);
oos.writeObject("Today");
oos.writeObject(new Date());

oos.close();

Classes that require special handling during the serialization and deserialization process must implement special methods with these exact signatures:

private void readObject(java.io.ObjectInputStream stream)
throws IOException, ClassNotFoundException;
private void writeObject(java.io.ObjectOutputStream stream)
throws IOException

The writeObject method is responsible for writing the state of the object for its particular class so that the corresponding readObject method can restore it. The method does not need to concern itself with the state belonging to the object's superclasses or subclasses. State is saved by writing the individual fields to the ObjectOutputStream using the writeObject method or by using the methods for primitive data types supported by DataOutput.

Serialization does not write out the fields of any object that does not implement the java.io.Serializable interface. Subclasses of Objects that are not serializable can be serializable. In this case the non-serializable class must have a no-arg constructor to allow its fields to be initialized. In this case it is the responsibility of the subclass to save and restore the state of the non-serializable class. It is frequently the case that the fields of that class are accessible (public, package, or protected) or that there are get and set methods that can be used to restore the state.

Serialization of an object can be prevented by implementing writeObject and readObject methods that throw the NotSerializableException. The exception will be caught by the ObjectOutputStream and abort the serialization process.

Implementing the Externalizable interface allows the object to assume complete control over the contents and format of the object's serialized form. The methods of the Externalizable interface, writeExternal and readExternal, are called to save and restore the objects state. When implemented by a class they can write and read their own state using all of the methods of ObjectOutput and ObjectInput. It is the responsibility of the objects to handle any versioning that occurs.

Enum constants are serialized differently than ordinary serializable or externalizable objects. The serialized form of an enum constant consists solely of its name; field values of the constant are not transmitted. To serialize an enum constant, ObjectOutputStream writes the string returned by the constant's name method. Like other serializable or externalizable objects, enum constants can function as the targets of back references appearing subsequently in the serialization stream. The process by which enum constants are serialized cannot be customized; any class-specific writeObject and writeReplace methods defined by enum types are ignored during serialization. Similarly, any serialPersistentFields or serialVersionUID field declarations are also ignored--all enum types have a fixed serialVersionUID of 0L.

Primitive data, excluding serializable fields and externalizable data, is written to the ObjectOutputStream in block-data records. A block data record is composed of a header and data. The block data header consists of a marker and the number of bytes to follow the header. Consecutive primitive data writes are merged into one block-data record. The blocking factor used for a block-data record will be 1024 bytes. Each block-data record will be filled up to 1024 bytes, or be written whenever there is a termination of block-data mode. Calls to the ObjectOutputStream methods writeObject, defaultWriteObject and writeFields initially terminate any existing block-data record.

author
Mike Warres
author
Roger Riggs
version
1.145, 04/05/28
see
java.io.DataOutput
see
java.io.ObjectInputStream
see
java.io.Serializable
see
java.io.Externalizable
see
Object Serialization Specification, Section 2, Object Output Classes
since
JDK1.1

Fields Summary
private static final sun.misc.SoftCache
subclassAudits
cache of subclass security audit results
private final BlockDataOutputStream
bout
filter stream for handling block data conversion
private final HandleTable
handles
obj -> wire handle map
private final ReplaceTable
subs
obj -> replacement obj map
private int
protocol
stream protocol version
private int
depth
recursion depth
private byte[]
primVals
buffer for writing primitive field values
private final boolean
enableOverride
if true, invoke writeObjectOverride() instead of writeObject()
private boolean
enableReplace
if true, invoke replaceObject()
private Object
curObj
object currently being serialized
private ObjectStreamClass
curDesc
descriptor for current class (null if in writeExternal())
private PutFieldImpl
curPut
current PutField object
Constructors Summary
public ObjectOutputStream(OutputStream out)
Creates an ObjectOutputStream that writes to the specified OutputStream. This constructor writes the serialization stream header to the underlying stream; callers may wish to flush the stream immediately to ensure that constructors for receiving ObjectInputStreams will not block when reading the header.

If a security manager is installed, this constructor will check for the "enableSubclassImplementation" SerializablePermission when invoked directly or indirectly by the constructor of a subclass which overrides the ObjectOutputStream.putFields or ObjectOutputStream.writeUnshared methods.

param
out output stream to write to
throws
IOException if an I/O error occurs while writing stream header
throws
SecurityException if untrusted subclass illegally overrides security-sensitive methods
throws
NullPointerException if out is null
see
ObjectOutputStream#ObjectOutputStream()
see
ObjectOutputStream#putFields()
see
ObjectInputStream#ObjectInputStream(InputStream)


                                                                               	      	          	      		  	     	 	 	     
         
	verifySubclass();
	bout = new BlockDataOutputStream(out);
	handles = new HandleTable(10, (float) 3.00);
	subs = new ReplaceTable(10, (float) 3.00);
	enableOverride = false;
	writeStreamHeader();
	bout.setBlockDataMode(true);
    
protected ObjectOutputStream()
Provide a way for subclasses that are completely reimplementing ObjectOutputStream to not have to allocate private data just used by this implementation of ObjectOutputStream.

If there is a security manager installed, this method first calls the security manager's checkPermission method with a SerializablePermission("enableSubclassImplementation") permission to ensure it's ok to enable subclassing.

throws
SecurityException if a security manager exists and its checkPermission method denies enabling subclassing.
see
SecurityManager#checkPermission
see
java.io.SerializablePermission

	SecurityManager sm = System.getSecurityManager();
	if (sm != null) {
	    sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
	}
	bout = null;
	handles = null;
	subs = null;
	enableOverride = true;
    
Methods Summary
protected voidannotateClass(java.lang.Class cl)
Subclasses may implement this method to allow class data to be stored in the stream. By default this method does nothing. The corresponding method in ObjectInputStream is resolveClass. This method is called exactly once for each unique class in the stream. The class name and signature will have already been written to the stream. This method may make free use of the ObjectOutputStream to save any representation of the class it deems suitable (for example, the bytes of the class file). The resolveClass method in the corresponding subclass of ObjectInputStream must read and use any data or objects written by annotateClass.

param
cl the class to annotate custom data for
throws
IOException Any exception thrown by the underlying OutputStream.

    
protected voidannotateProxyClass(java.lang.Class cl)
Subclasses may implement this method to store custom data in the stream along with descriptors for dynamic proxy classes.

This method is called exactly once for each unique proxy class descriptor in the stream. The default implementation of this method in ObjectOutputStream does nothing.

The corresponding method in ObjectInputStream is resolveProxyClass. For a given subclass of ObjectOutputStream that overrides this method, the resolveProxyClass method in the corresponding subclass of ObjectInputStream must read any data or objects written by annotateProxyClass.

param
cl the proxy class to annotate custom data for
throws
IOException any exception thrown by the underlying OutputStream
see
ObjectInputStream#resolveProxyClass(String[])
since
1.3

    
private static booleanauditSubclass(java.lang.Class subcl)
Performs reflective checks on given subclass to verify that it doesn't override security-sensitive non-final methods. Returns true if subclass is "safe", false otherwise.

	Boolean result = (Boolean) AccessController.doPrivileged(
	    new PrivilegedAction() {
		public Object run() {
		    for (Class cl = subcl;
			 cl != ObjectOutputStream.class;
			 cl = cl.getSuperclass())
		    {
			try {
			    cl.getDeclaredMethod(
				"writeUnshared", new Class[] { Object.class });
			    return Boolean.FALSE;
			} catch (NoSuchMethodException ex) {
			}
			try {
			    cl.getDeclaredMethod("putFields", new Class[0]);
			    return Boolean.FALSE;
			} catch (NoSuchMethodException ex) {
			}
		    }
		    return Boolean.TRUE;
		}
	    }
	);
	return result.booleanValue();
    
private voidclear()
Clears internal data structures.

	subs.clear();
	handles.clear();
    
public voidclose()
Closes the stream. This method must be called to release any resources associated with the stream.

throws
IOException If an I/O error has occurred.

	flush();
	clear();
	bout.close();
    
private voiddefaultWriteFields(java.lang.Object obj, java.io.ObjectStreamClass desc)
Fetches and writes values of serializable fields of given object to stream. The given class descriptor specifies which field values to write, and in which order they should be written.

	// REMIND: perform conservative isInstance check here?
	desc.checkDefaultSerialize();

	int primDataSize = desc.getPrimDataSize();
	if (primVals == null || primVals.length < primDataSize) {
	    primVals = new byte[primDataSize];
	}
	desc.getPrimFieldValues(obj, primVals);
	bout.write(primVals, 0, primDataSize, false);
	
	ObjectStreamField[] fields = desc.getFields(false);
	Object[] objVals = new Object[desc.getNumObjFields()];
	int numPrimFields = fields.length - objVals.length;
	desc.getObjFieldValues(obj, objVals);
	for (int i = 0; i < objVals.length; i++) {
	    writeObject0(objVals[i], fields[numPrimFields + i].isUnshared());
	}
    
public voiddefaultWriteObject()
Write the non-static and non-transient fields of the current class to this stream. This may only be called from the writeObject method of the class being serialized. It will throw the NotActiveException if it is called otherwise.

throws
IOException if I/O errors occur while writing to the underlying OutputStream

	if (curObj == null || curDesc == null) {
	    throw new NotActiveException("not in call to writeObject");
	}
	bout.setBlockDataMode(false);
	defaultWriteFields(curObj, curDesc);
	bout.setBlockDataMode(true);
    
private static native voiddoublesToBytes(double[] src, int srcpos, byte[] dst, int dstpos, int ndoubles)
Converts specified span of double values into byte values.

protected voiddrain()
Drain any buffered data in ObjectOutputStream. Similar to flush but does not propagate the flush to the underlying stream.

throws
IOException if I/O errors occur while writing to the underlying stream

	bout.drain();
    
protected booleanenableReplaceObject(boolean enable)
Enable the stream to do replacement of objects in the stream. When enabled, the replaceObject method is called for every object being serialized.

If enable is true, and there is a security manager installed, this method first calls the security manager's checkPermission method with a SerializablePermission("enableSubstitution") permission to ensure it's ok to enable the stream to do replacement of objects in the stream.

param
enable boolean parameter to enable replacement of objects
return
the previous setting before this method was invoked
throws
SecurityException if a security manager exists and its checkPermission method denies enabling the stream to do replacement of objects in the stream.
see
SecurityManager#checkPermission
see
java.io.SerializablePermission

	if (enable == enableReplace) {
	    return enable;
	}
	if (enable) {
	    SecurityManager sm = System.getSecurityManager();
	    if (sm != null) {
		sm.checkPermission(SUBSTITUTION_PERMISSION);
	    }
	}
	enableReplace = enable;
	return !enableReplace;
    
private static native voidfloatsToBytes(float[] src, int srcpos, byte[] dst, int dstpos, int nfloats)
Converts specified span of float values into byte values.

public voidflush()
Flushes the stream. This will write any buffered output bytes and flush through to the underlying stream.

throws
IOException If an I/O error has occurred.

	bout.flush();
    
intgetProtocolVersion()
Returns protocol version in use.

	return protocol;
    
public java.io.ObjectOutputStream$PutFieldputFields()
Retrieve the object used to buffer persistent fields to be written to the stream. The fields will be written to the stream when writeFields method is called.

return
an instance of the class Putfield that holds the serializable fields
throws
IOException if I/O errors occur
since
1.2

	if (curPut == null) {
	    if (curObj == null || curDesc == null) {
		throw new NotActiveException("not in call to writeObject");
	    }
	    curPut = new PutFieldImpl(curDesc);
	}
	return curPut;
    
protected java.lang.ObjectreplaceObject(java.lang.Object obj)
This method will allow trusted subclasses of ObjectOutputStream to substitute one object for another during serialization. Replacing objects is disabled until enableReplaceObject is called. The enableReplaceObject method checks that the stream requesting to do replacement can be trusted. The first occurrence of each object written into the serialization stream is passed to replaceObject. Subsequent references to the object are replaced by the object returned by the original call to replaceObject. To ensure that the private state of objects is not unintentionally exposed, only trusted streams may use replaceObject.

The ObjectOutputStream.writeObject method takes a parameter of type Object (as opposed to type Serializable) to allow for cases where non-serializable objects are replaced by serializable ones.

When a subclass is replacing objects it must insure that either a complementary substitution must be made during deserialization or that the substituted object is compatible with every field where the reference will be stored. Objects whose type is not a subclass of the type of the field or array element abort the serialization by raising an exception and the object is not be stored.

This method is called only once when each object is first encountered. All subsequent references to the object will be redirected to the new object. This method should return the object to be substituted or the original object.

Null can be returned as the object to be substituted, but may cause NullReferenceException in classes that contain references to the original object since they may be expecting an object instead of null.

param
obj the object to be replaced
return
the alternate object that replaced the specified one
throws
IOException Any exception thrown by the underlying OutputStream.

	return obj;
    
public voidreset()
Reset will disregard the state of any objects already written to the stream. The state is reset to be the same as a new ObjectOutputStream. The current point in the stream is marked as reset so the corresponding ObjectInputStream will be reset at the same point. Objects previously written to the stream will not be refered to as already being in the stream. They will be written to the stream again.

throws
IOException if reset() is invoked while serializing an object.

	if (depth != 0) {
	    throw new IOException("stream active");
	}
	bout.setBlockDataMode(false);
	bout.writeByte(TC_RESET);
	clear();
	bout.setBlockDataMode(true);
    
public voiduseProtocolVersion(int version)
Specify stream protocol version to use when writing the stream.

This routine provides a hook to enable the current version of Serialization to write in a format that is backwards compatible to a previous version of the stream format.

Every effort will be made to avoid introducing additional backwards incompatibilities; however, sometimes there is no other alternative.

param
version use ProtocolVersion from java.io.ObjectStreamConstants.
throws
IllegalStateException if called after any objects have been serialized.
throws
IllegalArgumentException if invalid version is passed in.
throws
IOException if I/O errors occur
see
java.io.ObjectStreamConstants#PROTOCOL_VERSION_1
see
java.io.ObjectStreamConstants#PROTOCOL_VERSION_2
since
1.2

	if (handles.size() != 0) {
	    // REMIND: implement better check for pristine stream?
	    throw new IllegalStateException("stream non-empty");
	}
	switch (version) {
	    case PROTOCOL_VERSION_1:
	    case PROTOCOL_VERSION_2:
		protocol = version;
		break;
		
	    default:
		throw new IllegalArgumentException(
		    "unknown version: " + version);
	}
    
private voidverifySubclass()
Verifies that this (possibly subclass) instance can be constructed without violating security constraints: the subclass must not override security-sensitive non-final methods, or else the "enableSubclassImplementation" SerializablePermission is checked.

	Class cl = getClass();
	synchronized (subclassAudits) {
	    Boolean result = (Boolean) subclassAudits.get(cl);
	    if (result == null) {
		/*
		 * Note: only new Boolean instances (i.e., not Boolean.TRUE or
		 * Boolean.FALSE) must be used as cache values, otherwise cache
		 * entry will pin associated class.
		 */
		result = new Boolean(auditSubclass(cl));
		subclassAudits.put(cl, result);
	    }
	    if (result.booleanValue()) {
		return;
	    }
	}
	SecurityManager sm = System.getSecurityManager();
	if (sm != null) {
	    sm.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
	}
    
public voidwrite(int val)
Writes a byte. This method will block until the byte is actually written.

param
val the byte to be written to the stream
throws
IOException If an I/O error has occurred.

	bout.write(val);
    
public voidwrite(byte[] buf)
Writes an array of bytes. This method will block until the bytes are actually written.

param
buf the data to be written
throws
IOException If an I/O error has occurred.

	bout.write(buf, 0, buf.length, false);
    
public voidwrite(byte[] buf, int off, int len)
Writes a sub array of bytes.

param
buf the data to be written
param
off the start offset in the data
param
len the number of bytes that are written
throws
IOException If an I/O error has occurred.

	if (buf == null) {
	    throw new NullPointerException();
	}
	int endoff = off + len;
	if (off < 0 || len < 0 || endoff > buf.length || endoff < 0) {
	    throw new IndexOutOfBoundsException();
	}
	bout.write(buf, off, len, false);
    
private voidwriteArray(java.lang.Object array, java.io.ObjectStreamClass desc, boolean unshared)
Writes given array object to stream.

	bout.writeByte(TC_ARRAY);
	writeClassDesc(desc, false);
	handles.assign(unshared ? null : array);
	
	Class ccl = desc.forClass().getComponentType();
	if (ccl.isPrimitive()) {
	    if (ccl == Integer.TYPE) {
		int[] ia = (int[]) array;
		bout.writeInt(ia.length);
		bout.writeInts(ia, 0, ia.length);
	    } else if (ccl == Byte.TYPE) {
		byte[] ba = (byte[]) array;
		bout.writeInt(ba.length);
		bout.write(ba, 0, ba.length, true);
	    } else if (ccl == Long.TYPE) {
		long[] ja = (long[]) array;
		bout.writeInt(ja.length);
		bout.writeLongs(ja, 0, ja.length);
	    } else if (ccl == Float.TYPE) {
		float[] fa = (float[]) array;
		bout.writeInt(fa.length);
		bout.writeFloats(fa, 0, fa.length);
	    } else if (ccl == Double.TYPE) {
		double[] da = (double[]) array;
		bout.writeInt(da.length);
		bout.writeDoubles(da, 0, da.length);
	    } else if (ccl == Short.TYPE) {
		short[] sa = (short[]) array;
		bout.writeInt(sa.length);
		bout.writeShorts(sa, 0, sa.length);
	    } else if (ccl == Character.TYPE) {
		char[] ca = (char[]) array;
		bout.writeInt(ca.length);
		bout.writeChars(ca, 0, ca.length);
	    } else if (ccl == Boolean.TYPE) {
		boolean[] za = (boolean[]) array;
		bout.writeInt(za.length);
		bout.writeBooleans(za, 0, za.length);
	    } else {
		throw new InternalError();
	    }
	} else {
	    Object[] objs = (Object[]) array;
	    int len = objs.length;
	    bout.writeInt(len);
	    for (int i = 0; i < len; i++) {
		writeObject0(objs[i], false);
	    }
	}
    
public voidwriteBoolean(boolean val)
Writes a boolean.

param
val the boolean to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeBoolean(val);
    
public voidwriteByte(int val)
Writes an 8 bit byte.

param
val the byte value to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeByte(val);
    
public voidwriteBytes(java.lang.String str)
Writes a String as a sequence of bytes.

param
str the String of bytes to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeBytes(str);
    
public voidwriteChar(int val)
Writes a 16 bit char.

param
val the char value to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeChar(val);
    
public voidwriteChars(java.lang.String str)
Writes a String as a sequence of chars.

param
str the String of chars to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeChars(str);
    
private voidwriteClass(java.lang.Class cl, boolean unshared)
Writes representation of given class to stream.

	bout.writeByte(TC_CLASS);
	writeClassDesc(ObjectStreamClass.lookup(cl, true), false);
	handles.assign(unshared ? null : cl);
    
private voidwriteClassDesc(java.io.ObjectStreamClass desc, boolean unshared)
Writes representation of given class descriptor to stream.

	int handle;
	if (desc == null) {
	    writeNull();
	} else if (!unshared && (handle = handles.lookup(desc)) != -1) {
	    writeHandle(handle);
	} else if (desc.isProxy()) {
	    writeProxyDesc(desc, unshared);
	} else {
	    writeNonProxyDesc(desc, unshared);
	}
    
protected voidwriteClassDescriptor(java.io.ObjectStreamClass desc)
Write the specified class descriptor to the ObjectOutputStream. Class descriptors are used to identify the classes of objects written to the stream. Subclasses of ObjectOutputStream may override this method to customize the way in which class descriptors are written to the serialization stream. The corresponding method in ObjectInputStream, readClassDescriptor, should then be overridden to reconstitute the class descriptor from its custom stream representation. By default, this method writes class descriptors according to the format defined in the Object Serialization specification.

Note that this method will only be called if the ObjectOutputStream is not using the old serialization stream format (set by calling ObjectOutputStream's useProtocolVersion method). If this serialization stream is using the old format (PROTOCOL_VERSION_1), the class descriptor will be written internally in a manner that cannot be overridden or customized.

param
desc class descriptor to write to the stream
throws
IOException If an I/O error has occurred.
see
java.io.ObjectInputStream#readClassDescriptor()
see
#useProtocolVersion(int)
see
java.io.ObjectStreamConstants#PROTOCOL_VERSION_1
since
1.3

	desc.writeNonProxy(this);
    
public voidwriteDouble(double val)
Writes a 64 bit double.

param
val the double value to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeDouble(val);
    
private voidwriteEnum(java.lang.Enum en, java.io.ObjectStreamClass desc, boolean unshared)
Writes given enum constant to stream.

	bout.writeByte(TC_ENUM);
	ObjectStreamClass sdesc = desc.getSuperDesc();
	writeClassDesc((sdesc.forClass() == Enum.class) ? desc : sdesc, false);
	handles.assign(unshared ? null : en);
	writeString(en.name(), false);
    
private voidwriteExternalData(java.io.Externalizable obj)
Writes externalizable data of given object by invoking its writeExternal() method.

	Object oldObj = curObj;
	ObjectStreamClass oldDesc = curDesc;
	PutFieldImpl oldPut = curPut;
	curObj = obj;
	curDesc = null;
	curPut = null;
	
	if (protocol == PROTOCOL_VERSION_1) {
	    obj.writeExternal(this);
	} else {
	    bout.setBlockDataMode(true);
	    obj.writeExternal(this);
	    bout.setBlockDataMode(false);
	    bout.writeByte(TC_ENDBLOCKDATA);
	}

	curObj = oldObj;
	curDesc = oldDesc;
	curPut = oldPut;
    
private voidwriteFatalException(java.io.IOException ex)
Attempts to write to stream fatal IOException that has caused serialization to abort.

	/*
	 * Note: the serialization specification states that if a second
	 * IOException occurs while attempting to serialize the original fatal
	 * exception to the stream, then a StreamCorruptedException should be
	 * thrown (section 2.1).  However, due to a bug in previous
	 * implementations of serialization, StreamCorruptedExceptions were
	 * rarely (if ever) actually thrown--the "root" exceptions from
	 * underlying streams were thrown instead.  This historical behavior is
	 * followed here for consistency.
	 */
	clear();
	boolean oldMode = bout.setBlockDataMode(false);
	try {
	    bout.writeByte(TC_EXCEPTION);
	    writeObject0(ex, false);
	    clear();
	} finally {
	    bout.setBlockDataMode(oldMode);
	}
    
public voidwriteFields()
Write the buffered fields to the stream.

throws
IOException if I/O errors occur while writing to the underlying stream
throws
NotActiveException Called when a classes writeObject method was not called to write the state of the object.
since
1.2

	if (curPut == null) {
	    throw new NotActiveException("no current PutField object");
	}
	bout.setBlockDataMode(false);
	curPut.writeFields();
	bout.setBlockDataMode(true);
    
public voidwriteFloat(float val)
Writes a 32 bit float.

param
val the float value to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeFloat(val);
    
private voidwriteHandle(int handle)
Writes given object handle to stream.

	bout.writeByte(TC_REFERENCE);
	bout.writeInt(baseWireHandle + handle);
    
public voidwriteInt(int val)
Writes a 32 bit int.

param
val the integer value to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeInt(val);
    
public voidwriteLong(long val)
Writes a 64 bit long.

param
val the long value to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeLong(val);
    
private voidwriteNonProxyDesc(java.io.ObjectStreamClass desc, boolean unshared)
Writes class descriptor representing a standard (i.e., not a dynamic proxy) class to stream.

	bout.writeByte(TC_CLASSDESC);
	handles.assign(unshared ? null : desc);
	
	if (protocol == PROTOCOL_VERSION_1) {
	    // do not invoke class descriptor write hook with old protocol
	    desc.writeNonProxy(this);
	} else {
	    writeClassDescriptor(desc);
	}
	
	Class cl = desc.forClass();
	bout.setBlockDataMode(true);
	annotateClass(cl);
	bout.setBlockDataMode(false);
	bout.writeByte(TC_ENDBLOCKDATA);
	
	writeClassDesc(desc.getSuperDesc(), false);
    
private voidwriteNull()
Writes null code to stream.

	bout.writeByte(TC_NULL);
    
public final voidwriteObject(java.lang.Object obj)
Write the specified object to the ObjectOutputStream. The class of the object, the signature of the class, and the values of the non-transient and non-static fields of the class and all of its supertypes are written. Default serialization for a class can be overridden using the writeObject and the readObject methods. Objects referenced by this object are written transitively so that a complete equivalent graph of objects can be reconstructed by an ObjectInputStream.

Exceptions are thrown for problems with the OutputStream and for classes that should not be serialized. All exceptions are fatal to the OutputStream, which is left in an indeterminate state, and it is up to the caller to ignore or recover the stream state.

throws
InvalidClassException Something is wrong with a class used by serialization.
throws
NotSerializableException Some object to be serialized does not implement the java.io.Serializable interface.
throws
IOException Any exception thrown by the underlying OutputStream.

	if (enableOverride) {
	    writeObjectOverride(obj);
	    return;
	}
	try {
	    writeObject0(obj, false);
	} catch (IOException ex) {
	    if (depth == 0) {
		writeFatalException(ex);
	    }
	    throw ex;
	}
    
private voidwriteObject0(java.lang.Object obj, boolean unshared)
Underlying writeObject/writeUnshared implementation.

	boolean oldMode = bout.setBlockDataMode(false);
	depth++;
	try {
	    // handle previously written and non-replaceable objects
	    int h;
	    if ((obj = subs.lookup(obj)) == null) {
		writeNull();
		return;
	    } else if (!unshared && (h = handles.lookup(obj)) != -1) {
		writeHandle(h);
		return;
	    } else if (obj instanceof Class) {
		writeClass((Class) obj, unshared);
		return;
	    } else if (obj instanceof ObjectStreamClass) {
		writeClassDesc((ObjectStreamClass) obj, unshared);
		return;
	    }
	    
	    // check for replacement object
	    Object orig = obj;
	    Class cl = obj.getClass();
	    ObjectStreamClass desc;
	    for (;;) {
		// REMIND: skip this check for strings/arrays?
		Class repCl;
		desc = ObjectStreamClass.lookup(cl, true);
		if (!desc.hasWriteReplaceMethod() ||
		    (obj = desc.invokeWriteReplace(obj)) == null ||
		    (repCl = obj.getClass()) == cl)
		{
		    break;
		}
		cl = repCl;
	    }
	    if (enableReplace) {
		Object rep = replaceObject(obj);
		if (rep != obj && rep != null) {
		    cl = rep.getClass();
		    desc = ObjectStreamClass.lookup(cl, true);
		}
		obj = rep;
	    }

	    // if object replaced, run through original checks a second time
	    if (obj != orig) {
		subs.assign(orig, obj);
		if (obj == null) {
		    writeNull();
		    return;
		} else if (!unshared && (h = handles.lookup(obj)) != -1) {
		    writeHandle(h);
		    return;
		} else if (obj instanceof Class) {
		    writeClass((Class) obj, unshared);
		    return;
		} else if (obj instanceof ObjectStreamClass) {
		    writeClassDesc((ObjectStreamClass) obj, unshared);
		    return;
		}
	    }
	    
	    // remaining cases
	    if (obj instanceof String) {
		writeString((String) obj, unshared);
	    } else if (cl.isArray()) {
		writeArray(obj, desc, unshared);
	    } else if (obj instanceof Enum) {
		writeEnum((Enum) obj, desc, unshared);
	    } else if (obj instanceof Serializable) {
		writeOrdinaryObject(obj, desc, unshared);
	    } else {
		throw new NotSerializableException(cl.getName());
	    }
	} finally {
	    depth--;
	    bout.setBlockDataMode(oldMode);
	}
    
protected voidwriteObjectOverride(java.lang.Object obj)
Method used by subclasses to override the default writeObject method. This method is called by trusted subclasses of ObjectInputStream that constructed ObjectInputStream using the protected no-arg constructor. The subclass is expected to provide an override method with the modifier "final".

param
obj object to be written to the underlying stream
throws
IOException if there are I/O errors while writing to the underlying stream
see
#ObjectOutputStream()
see
#writeObject(Object)
since
1.2

    
private voidwriteOrdinaryObject(java.lang.Object obj, java.io.ObjectStreamClass desc, boolean unshared)
Writes representation of a "ordinary" (i.e., not a String, Class, ObjectStreamClass, array, or enum constant) serializable object to the stream.

	desc.checkSerialize();

	bout.writeByte(TC_OBJECT);
	writeClassDesc(desc, false);
	handles.assign(unshared ? null : obj);

	if (desc.isExternalizable() && !desc.isProxy()) {
	    writeExternalData((Externalizable) obj);
	} else {
	    writeSerialData(obj, desc);
	}
    
private voidwriteProxyDesc(java.io.ObjectStreamClass desc, boolean unshared)
Writes class descriptor representing a dynamic proxy class to stream.

	bout.writeByte(TC_PROXYCLASSDESC);
	handles.assign(unshared ? null : desc);

	Class cl = desc.forClass();
	Class[] ifaces = cl.getInterfaces();
	bout.writeInt(ifaces.length);
	for (int i = 0; i < ifaces.length; i++) {
	    bout.writeUTF(ifaces[i].getName());
	}
	
	bout.setBlockDataMode(true);
	annotateProxyClass(cl);
	bout.setBlockDataMode(false);
	bout.writeByte(TC_ENDBLOCKDATA);
	
	writeClassDesc(desc.getSuperDesc(), false);
    
private voidwriteSerialData(java.lang.Object obj, java.io.ObjectStreamClass desc)
Writes instance data for each serializable class of given object, from superclass to subclass.

	ObjectStreamClass.ClassDataSlot[] slots = desc.getClassDataLayout();
	for (int i = 0; i < slots.length; i++) {
	    ObjectStreamClass slotDesc = slots[i].desc;
	    if (slotDesc.hasWriteObjectMethod()) {
		Object oldObj = curObj;
		ObjectStreamClass oldDesc = curDesc;
		PutFieldImpl oldPut = curPut;
		curObj = obj;
		curDesc = slotDesc;
		curPut = null;

		bout.setBlockDataMode(true);
		slotDesc.invokeWriteObject(obj, this);
		bout.setBlockDataMode(false);
		bout.writeByte(TC_ENDBLOCKDATA);

		curObj = oldObj;
		curDesc = oldDesc;
		curPut = oldPut;
	    } else {
		defaultWriteFields(obj, slotDesc);
	    }
	}
    
public voidwriteShort(int val)
Writes a 16 bit short.

param
val the short value to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeShort(val);
    
protected voidwriteStreamHeader()
The writeStreamHeader method is provided so subclasses can append or prepend their own header to the stream. It writes the magic number and version to the stream.

throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeShort(STREAM_MAGIC);
	bout.writeShort(STREAM_VERSION);
    
private voidwriteString(java.lang.String str, boolean unshared)
Writes given string to stream, using standard or long UTF format depending on string length.

	handles.assign(unshared ? null : str);
	long utflen = bout.getUTFLength(str);
	if (utflen <= 0xFFFF) {
	    bout.writeByte(TC_STRING);
	    bout.writeUTF(str, utflen);
	} else {
	    bout.writeByte(TC_LONGSTRING);
	    bout.writeLongUTF(str, utflen);
	}
    
voidwriteTypeString(java.lang.String str)
Writes string without allowing it to be replaced in stream. Used by ObjectStreamClass to write class descriptor type strings.

	int handle;
	if (str == null) {
	    writeNull();
	} else if ((handle = handles.lookup(str)) != -1) {
	    writeHandle(handle);
	} else {
	    writeString(str, false);
	}
    
public voidwriteUTF(java.lang.String str)
Primitive data write of this String in modified UTF-8 format. Note that there is a significant difference between writing a String into the stream as primitive data or as an Object. A String instance written by writeObject is written into the stream as a String initially. Future writeObject() calls write references to the string into the stream.

param
str the String to be written
throws
IOException if I/O errors occur while writing to the underlying stream

	bout.writeUTF(str);
    
public voidwriteUnshared(java.lang.Object obj)
Writes an "unshared" object to the ObjectOutputStream. This method is identical to writeObject, except that it always writes the given object as a new, unique object in the stream (as opposed to a back-reference pointing to a previously serialized instance). Specifically:
  • An object written via writeUnshared is always serialized in the same manner as a newly appearing object (an object that has not been written to the stream yet), regardless of whether or not the object has been written previously.
  • If writeObject is used to write an object that has been previously written with writeUnshared, the previous writeUnshared operation is treated as if it were a write of a separate object. In other words, ObjectOutputStream will never generate back-references to object data written by calls to writeUnshared.
While writing an object via writeUnshared does not in itself guarantee a unique reference to the object when it is deserialized, it allows a single object to be defined multiple times in a stream, so that multiple calls to readUnshared by the receiver will not conflict. Note that the rules described above only apply to the base-level object written with writeUnshared, and not to any transitively referenced sub-objects in the object graph to be serialized.

ObjectOutputStream subclasses which override this method can only be constructed in security contexts possessing the "enableSubclassImplementation" SerializablePermission; any attempt to instantiate such a subclass without this permission will cause a SecurityException to be thrown.

param
obj object to write to stream
throws
NotSerializableException if an object in the graph to be serialized does not implement the Serializable interface
throws
InvalidClassException if a problem exists with the class of an object to be serialized
throws
IOException if an I/O error occurs during serialization

	try {
	    writeObject0(obj, true);
	} catch (IOException ex) {
	    if (depth == 0) {
		writeFatalException(ex);
	    }
	    throw ex;
	}