The ObjectStreamField.java Java example source code
/*
* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code 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 in the LICENSE file that
* accompanied this code).
*
* 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* questions.
*/
package java.io;
import java.lang.reflect.Field;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;
import sun.reflect.misc.ReflectUtil;
/**
* A description of a Serializable field from a Serializable class. An array
* of ObjectStreamFields is used to declare the Serializable fields of a class.
*
* @author Mike Warres
* @author Roger Riggs
* @see ObjectStreamClass
* @since 1.2
*/
public class ObjectStreamField
implements Comparable<Object>
{
/** field name */
private final String name;
/** canonical JVM signature of field type */
private final String signature;
/** field type (Object.class if unknown non-primitive type) */
private final Class<?> type;
/** whether or not to (de)serialize field values as unshared */
private final boolean unshared;
/** corresponding reflective field object, if any */
private final Field field;
/** offset of field value in enclosing field group */
private int offset = 0;
/**
* Create a Serializable field with the specified type. This field should
* be documented with a <code>serialField tag.
*
* @param name the name of the serializable field
* @param type the <code>Class object of the serializable field
*/
public ObjectStreamField(String name, Class<?> type) {
this(name, type, false);
}
/**
* Creates an ObjectStreamField representing a serializable field with the
* given name and type. If unshared is false, values of the represented
* field are serialized and deserialized in the default manner--if the
* field is non-primitive, object values are serialized and deserialized as
* if they had been written and read by calls to writeObject and
* readObject. If unshared is true, values of the represented field are
* serialized and deserialized as if they had been written and read by
* calls to writeUnshared and readUnshared.
*
* @param name field name
* @param type field type
* @param unshared if false, write/read field values in the same manner
* as writeObject/readObject; if true, write/read in the same
* manner as writeUnshared/readUnshared
* @since 1.4
*/
public ObjectStreamField(String name, Class<?> type, boolean unshared) {
if (name == null) {
throw new NullPointerException();
}
this.name = name;
this.type = type;
this.unshared = unshared;
signature = getClassSignature(type).intern();
field = null;
}
/**
* Creates an ObjectStreamField representing a field with the given name,
* signature and unshared setting.
*/
ObjectStreamField(String name, String signature, boolean unshared) {
if (name == null) {
throw new NullPointerException();
}
this.name = name;
this.signature = signature.intern();
this.unshared = unshared;
field = null;
switch (signature.charAt(0)) {
case 'Z': type = Boolean.TYPE; break;
case 'B': type = Byte.TYPE; break;
case 'C': type = Character.TYPE; break;
case 'S': type = Short.TYPE; break;
case 'I': type = Integer.TYPE; break;
case 'J': type = Long.TYPE; break;
case 'F': type = Float.TYPE; break;
case 'D': type = Double.TYPE; break;
case 'L':
case '[': type = Object.class; break;
default: throw new IllegalArgumentException("illegal signature");
}
}
/**
* Creates an ObjectStreamField representing the given field with the
* specified unshared setting. For compatibility with the behavior of
* earlier serialization implementations, a "showType" parameter is
* necessary to govern whether or not a getType() call on this
* ObjectStreamField (if non-primitive) will return Object.class (as
* opposed to a more specific reference type).
*/
ObjectStreamField(Field field, boolean unshared, boolean showType) {
this.field = field;
this.unshared = unshared;
name = field.getName();
Class<?> ftype = field.getType();
type = (showType || ftype.isPrimitive()) ? ftype : Object.class;
signature = getClassSignature(ftype).intern();
}
/**
* Get the name of this field.
*
* @return a <code>String representing the name of the serializable
* field
*/
public String getName() {
return name;
}
/**
* Get the type of the field. If the type is non-primitive and this
* <code>ObjectStreamField was obtained from a deserialized {@link
* ObjectStreamClass} instance, then <code>Object.class is returned.
* Otherwise, the <code>Class object for the type of the field is
* returned.
*
* @return a <code>Class object representing the type of the
* serializable field
*/
@CallerSensitive
public Class<?> getType() {
if (System.getSecurityManager() != null) {
Class<?> caller = Reflection.getCallerClass();
if (ReflectUtil.needsPackageAccessCheck(caller.getClassLoader(), type.getClassLoader())) {
ReflectUtil.checkPackageAccess(type);
}
}
return type;
}
/**
* Returns character encoding of field type. The encoding is as follows:
* <blockquote> * B byte
* C char
* D double
* F float
* I int
* J long
* L class or interface
* S short
* Z boolean
* [ array
* </pre>
*
* @return the typecode of the serializable field
*/
// REMIND: deprecate?
public char getTypeCode() {
return signature.charAt(0);
}
/**
* Return the JVM type signature.
*
* @return null if this field has a primitive type.
*/
// REMIND: deprecate?
public String getTypeString() {
return isPrimitive() ? null : signature;
}
/**
* Offset of field within instance data.
*
* @return the offset of this field
* @see #setOffset
*/
// REMIND: deprecate?
public int getOffset() {
return offset;
}
/**
* Offset within instance data.
*
* @param offset the offset of the field
* @see #getOffset
*/
// REMIND: deprecate?
protected void setOffset(int offset) {
this.offset = offset;
}
/**
* Return true if this field has a primitive type.
*
* @return true if and only if this field corresponds to a primitive type
*/
// REMIND: deprecate?
public boolean isPrimitive() {
char tcode = signature.charAt(0);
return ((tcode != 'L') && (tcode != '['));
}
/**
* Returns boolean value indicating whether or not the serializable field
* represented by this ObjectStreamField instance is unshared.
*
* @return {@code true} if this field is unshared
*
* @since 1.4
*/
public boolean isUnshared() {
return unshared;
}
/**
* Compare this field with another <code>ObjectStreamField. Return
* -1 if this is smaller, 0 if equal, 1 if greater. Types that are
* primitives are "smaller" than object types. If equal, the field names
* are compared.
*/
// REMIND: deprecate?
public int compareTo(Object obj) {
ObjectStreamField other = (ObjectStreamField) obj;
boolean isPrim = isPrimitive();
if (isPrim != other.isPrimitive()) {
return isPrim ? -1 : 1;
}
return name.compareTo(other.name);
}
/**
* Return a string that describes this field.
*/
public String toString() {
return signature + ' ' + name;
}
/**
* Returns field represented by this ObjectStreamField, or null if
* ObjectStreamField is not associated with an actual field.
*/
Field getField() {
return field;
}
/**
* Returns JVM type signature of field (similar to getTypeString, except
* that signature strings are returned for primitive fields as well).
*/
String getSignature() {
return signature;
}
/**
* Returns JVM type signature for given class.
*/
private static String getClassSignature(Class<?> cl) {
StringBuilder sbuf = new StringBuilder();
while (cl.isArray()) {
sbuf.append('[');
cl = cl.getComponentType();
}
if (cl.isPrimitive()) {
if (cl == Integer.TYPE) {
sbuf.append('I');
} else if (cl == Byte.TYPE) {
sbuf.append('B');
} else if (cl == Long.TYPE) {
sbuf.append('J');
} else if (cl == Float.TYPE) {
sbuf.append('F');
} else if (cl == Double.TYPE) {
sbuf.append('D');
} else if (cl == Short.TYPE) {
sbuf.append('S');
} else if (cl == Character.TYPE) {
sbuf.append('C');
} else if (cl == Boolean.TYPE) {
sbuf.append('Z');
} else if (cl == Void.TYPE) {
sbuf.append('V');
} else {
throw new InternalError();
}
} else {
sbuf.append('L' + cl.getName().replace('.', '/') + ';');
}
return sbuf.toString();
}
}
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