1 /*
2 * Copyright (c) 1996, 2022, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.io;
27
28 import java.lang.reflect.Field;
29 import jdk.internal.reflect.CallerSensitive;
30 import jdk.internal.reflect.Reflection;
31 import sun.reflect.misc.ReflectUtil;
32
33 /**
34 * A description of a Serializable field from a Serializable class. An array
35 * of ObjectStreamFields is used to declare the Serializable fields of a class.
36 *
37 * @author Mike Warres
38 * @author Roger Riggs
39 * @see ObjectStreamClass
40 * @since 1.2
41 */
42 public class ObjectStreamField
43 implements Comparable<Object>
44 {
45
46 /** field name */
47 private final String name;
48 /** canonical JVM signature of field type, if given */
49 private final String signature;
50 /** field type (Object.class if unknown non-primitive type) */
51 private final Class<?> type;
52 /** lazily constructed signature for the type, if no explicit signature */
53 private String typeSignature;
54 /** whether or not to (de)serialize field values as unshared */
55 private final boolean unshared;
56 /** corresponding reflective field object, if any */
57 private final Field field;
58 /** offset of field value in enclosing field group */
59 private int offset;
60
61 /**
62 * Create a Serializable field with the specified type. This field should
63 * be documented with a {@code serialField} tag.
64 *
65 * @param name the name of the serializable field
66 * @param type the {@code Class} object of the serializable field
67 */
68 public ObjectStreamField(String name, Class<?> type) {
69 this(name, type, false);
70 }
71
72 /**
73 * Creates an ObjectStreamField representing a serializable field with the
74 * given name and type. If unshared is false, values of the represented
75 * field are serialized and deserialized in the default manner--if the
76 * field is non-primitive, object values are serialized and deserialized as
77 * if they had been written and read by calls to writeObject and
78 * readObject. If unshared is true, values of the represented field are
79 * serialized and deserialized as if they had been written and read by
80 * calls to writeUnshared and readUnshared.
81 *
82 * @param name field name
83 * @param type field type
84 * @param unshared if false, write/read field values in the same manner
85 * as writeObject/readObject; if true, write/read in the same
86 * manner as writeUnshared/readUnshared
87 * @since 1.4
88 */
89 public ObjectStreamField(String name, Class<?> type, boolean unshared) {
90 if (name == null) {
91 throw new NullPointerException();
92 }
93 this.name = name;
94 this.type = type;
95 this.unshared = unshared;
96 this.field = null;
97 this.signature = null;
98 }
99
100 /**
101 * Creates an ObjectStreamField representing a field with the given name,
102 * signature and unshared setting.
103 */
104 ObjectStreamField(String name, String signature, boolean unshared) {
105 if (name == null) {
106 throw new NullPointerException();
107 }
108 this.name = name;
109 this.signature = signature.intern();
110 this.unshared = unshared;
111 this.field = null;
112
113 type = switch (signature.charAt(0)) {
114 case 'Z' -> Boolean.TYPE;
115 case 'B' -> Byte.TYPE;
116 case 'C' -> Character.TYPE;
117 case 'S' -> Short.TYPE;
118 case 'I' -> Integer.TYPE;
119 case 'J' -> Long.TYPE;
120 case 'F' -> Float.TYPE;
121 case 'D' -> Double.TYPE;
122 case 'L', '[' -> Object.class;
123 default -> throw new IllegalArgumentException("illegal signature");
124 };
125 }
126
127 /**
128 * Creates an ObjectStreamField representing the given field with the
129 * specified unshared setting. For compatibility with the behavior of
130 * earlier serialization implementations, a "showType" parameter is
131 * necessary to govern whether or not a getType() call on this
132 * ObjectStreamField (if non-primitive) will return Object.class (as
133 * opposed to a more specific reference type).
134 */
135 ObjectStreamField(Field field, boolean unshared, boolean showType) {
136 this.field = field;
137 this.unshared = unshared;
138 name = field.getName();
139 Class<?> ftype = field.getType();
140 type = (showType || ftype.isPrimitive()) ? ftype : Object.class;
141 signature = ftype.descriptorString().intern();
142 }
143
144 /**
145 * Get the name of this field.
146 *
147 * @return a {@code String} representing the name of the serializable
148 * field
149 */
150 public String getName() {
151 return name;
152 }
153
154 /**
155 * Get the type of the field. If the type is non-primitive and this
156 * {@code ObjectStreamField} was obtained from a deserialized {@link
157 * ObjectStreamClass} instance, then {@code Object.class} is returned.
158 * Otherwise, the {@code Class} object for the type of the field is
159 * returned.
160 *
161 * @return a {@code Class} object representing the type of the
162 * serializable field
163 */
164 @SuppressWarnings("removal")
165 @CallerSensitive
166 public Class<?> getType() {
167 if (System.getSecurityManager() != null) {
168 Class<?> caller = Reflection.getCallerClass();
169 if (ReflectUtil.needsPackageAccessCheck(caller.getClassLoader(), type.getClassLoader())) {
170 ReflectUtil.checkPackageAccess(type);
171 }
172 }
173 return type;
174 }
175
176 /**
177 * Returns character encoding of field type. The encoding is as follows:
178 * <blockquote><pre>
179 * B byte
180 * C char
181 * D double
182 * F float
183 * I int
184 * J long
185 * L class or interface
186 * S short
187 * Z boolean
188 * [ array
189 * </pre></blockquote>
190 *
191 * @return the typecode of the serializable field
192 */
193 // REMIND: deprecate?
194 public char getTypeCode() {
195 return getSignature().charAt(0);
196 }
197
198 /**
199 * Return the JVM type signature.
200 *
201 * @return null if this field has a primitive type.
202 */
203 // REMIND: deprecate?
204 public String getTypeString() {
205 return isPrimitive() ? null : getSignature();
206 }
207
208 /**
209 * Offset of field within instance data.
210 *
211 * @return the offset of this field
212 * @see #setOffset
213 */
214 // REMIND: deprecate?
215 public int getOffset() {
216 return offset;
217 }
218
219 /**
220 * Offset within instance data.
221 *
222 * @param offset the offset of the field
223 * @see #getOffset
224 */
225 // REMIND: deprecate?
226 protected void setOffset(int offset) {
227 this.offset = offset;
228 }
229
230 /**
231 * Return true if this field has a primitive type.
232 *
233 * @return true if and only if this field corresponds to a primitive type
234 */
235 // REMIND: deprecate?
236 public boolean isPrimitive() {
237 char tcode = getTypeCode();
238 return ((tcode != 'L') && (tcode != '['));
239 }
240
241 /**
242 * Returns boolean value indicating whether or not the serializable field
243 * represented by this ObjectStreamField instance is unshared.
244 *
245 * @return {@code true} if this field is unshared
246 *
247 * @since 1.4
248 */
249 public boolean isUnshared() {
250 return unshared;
251 }
252
253 /**
254 * Compare this field with another {@code ObjectStreamField}. Return
255 * -1 if this is smaller, 0 if equal, 1 if greater. Types that are
256 * primitives are "smaller" than object types. If equal, the field names
257 * are compared.
258 */
259 // REMIND: deprecate?
260 public int compareTo(Object obj) {
261 ObjectStreamField other = (ObjectStreamField) obj;
262 boolean isPrim = isPrimitive();
263 if (isPrim != other.isPrimitive()) {
264 return isPrim ? -1 : 1;
265 }
266 return name.compareTo(other.name);
267 }
268
269 /**
270 * Return a string that describes this field.
271 */
272 public String toString() {
273 return getSignature() + ' ' + name;
274 }
275
276 /**
277 * Returns field represented by this ObjectStreamField, or null if
278 * ObjectStreamField is not associated with an actual field.
279 */
280 Field getField() {
281 return field;
282 }
283
284 /**
285 * Returns JVM type signature of field (similar to getTypeString, except
286 * that signature strings are returned for primitive fields as well).
287 */
288 String getSignature() {
289 if (signature != null) {
290 return signature;
291 }
292
293 String sig = typeSignature;
294 // This lazy calculation is safe since signature can be null iff one
295 // of the public constructors are used, in which case type is always
296 // initialized to the exact type we want the signature to represent.
297 if (sig == null) {
298 typeSignature = sig = type.descriptorString().intern();
299 }
300 return sig;
301 }
302 }