1 /* 2 * Copyright (C) 2007 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.database.sqlite; 18 19 import android.compat.annotation.UnsupportedAppUsage; 20 21 import java.io.Closeable; 22 23 /** 24 * An object created from a SQLiteDatabase that can be closed. 25 * 26 * This class implements a primitive reference counting scheme for database objects. 27 */ 28 @android.ravenwood.annotation.RavenwoodKeepWholeClass 29 public abstract class SQLiteClosable implements Closeable { 30 @UnsupportedAppUsage 31 private int mReferenceCount = 1; 32 33 /** 34 * True if the instance should record when it was closed. Tracking closure can be expensive, 35 * so it is best reserved for subclasses that have long lifetimes. 36 * @hide 37 */ 38 protected boolean mTrackClosure = false; 39 40 /** 41 * The caller that finally released this instance. If this is not null, it is supplied as the 42 * cause to the IllegalStateException that is thrown when the object is reopened. Subclasses 43 * are responsible for populating this field, if they wish to use it. 44 */ 45 private Throwable mClosedBy = null; 46 47 /** 48 * Called when the last reference to the object was released by 49 * a call to {@link #releaseReference()} or {@link #close()}. 50 */ onAllReferencesReleased()51 protected abstract void onAllReferencesReleased(); 52 53 /** 54 * Called when the last reference to the object was released by 55 * a call to {@link #releaseReferenceFromContainer()}. 56 * 57 * @deprecated Do not use. 58 */ 59 @Deprecated onAllReferencesReleasedFromContainer()60 protected void onAllReferencesReleasedFromContainer() { 61 onAllReferencesReleased(); 62 } 63 64 /** 65 * Acquires a reference to the object. 66 * 67 * @throws IllegalStateException if the last reference to the object has already 68 * been released. 69 */ acquireReference()70 public void acquireReference() { 71 synchronized(this) { 72 if (mReferenceCount <= 0) { 73 throw new IllegalStateException( 74 "attempt to re-open an already-closed object: " + this, mClosedBy); 75 } 76 mReferenceCount++; 77 } 78 } 79 80 /** 81 * Releases a reference to the object, closing the object if the last reference 82 * was released. 83 * 84 * @see #onAllReferencesReleased() 85 */ releaseReference()86 public void releaseReference() { 87 boolean refCountIsZero = false; 88 synchronized(this) { 89 refCountIsZero = --mReferenceCount == 0; 90 } 91 if (refCountIsZero) { 92 onAllReferencesReleased(); 93 } 94 } 95 96 /** 97 * Releases a reference to the object that was owned by the container of the object, 98 * closing the object if the last reference was released. 99 * 100 * @see #onAllReferencesReleasedFromContainer() 101 * @deprecated Do not use. 102 */ 103 @Deprecated releaseReferenceFromContainer()104 public void releaseReferenceFromContainer() { 105 boolean refCountIsZero = false; 106 synchronized(this) { 107 refCountIsZero = --mReferenceCount == 0; 108 } 109 if (refCountIsZero) { 110 onAllReferencesReleasedFromContainer(); 111 } 112 } 113 114 /** 115 * Releases a reference to the object, closing the object if the last reference 116 * was released. 117 * 118 * Calling this method is equivalent to calling {@link #releaseReference}. 119 * 120 * @see #releaseReference() 121 * @see #onAllReferencesReleased() 122 */ close()123 public void close() { 124 releaseReference(); 125 synchronized (this) { 126 if (mTrackClosure && (mClosedBy == null)) { 127 String name = getClass().getName(); 128 mClosedBy = new Exception("closed by " + name + ".close()").fillInStackTrace(); 129 } 130 } 131 } 132 } 133