[10824] | 1 | // License: GPL. For details, see LICENSE file.
|
---|
| 2 | package org.openstreetmap.josm.tools;
|
---|
| 3 |
|
---|
| 4 | import java.lang.ref.WeakReference;
|
---|
| 5 | import java.text.MessageFormat;
|
---|
| 6 | import java.util.HashMap;
|
---|
| 7 | import java.util.Iterator;
|
---|
| 8 | import java.util.Objects;
|
---|
| 9 | import java.util.concurrent.CopyOnWriteArrayList;
|
---|
| 10 | import java.util.stream.Stream;
|
---|
| 11 |
|
---|
| 12 | import org.openstreetmap.josm.Main;
|
---|
| 13 |
|
---|
| 14 | /**
|
---|
| 15 | * This is a list of listeners. It does error checking and allows you to fire all listeners.
|
---|
| 16 | *
|
---|
| 17 | * @author Michael Zangl
|
---|
| 18 | * @param <T> The type of listener contained in this list.
|
---|
| 19 | * @since 10824
|
---|
| 20 | */
|
---|
| 21 | public class ListenerList<T> {
|
---|
| 22 | /**
|
---|
| 23 | * This is a function that can be invoked for every listener.
|
---|
| 24 | * @param <T> the listener type.
|
---|
| 25 | */
|
---|
| 26 | @FunctionalInterface
|
---|
| 27 | public interface EventFirerer<T> {
|
---|
| 28 | /**
|
---|
| 29 | * Should fire the event for the given listener.
|
---|
| 30 | * @param listener The listener to fire the event for.
|
---|
| 31 | */
|
---|
| 32 | void fire(T listener);
|
---|
| 33 | }
|
---|
| 34 |
|
---|
| 35 | private static final class WeakListener<T> {
|
---|
| 36 |
|
---|
[10939] | 37 | private final WeakReference<T> listener;
|
---|
[10824] | 38 |
|
---|
| 39 | WeakListener(T listener) {
|
---|
| 40 | this.listener = new WeakReference<>(listener);
|
---|
| 41 | }
|
---|
| 42 |
|
---|
| 43 | @Override
|
---|
| 44 | public boolean equals(Object obj) {
|
---|
| 45 | if (obj != null && obj.getClass() == WeakListener.class) {
|
---|
| 46 | return Objects.equals(listener.get(), ((WeakListener<?>) obj).listener.get());
|
---|
| 47 | } else {
|
---|
| 48 | return false;
|
---|
| 49 | }
|
---|
| 50 | }
|
---|
| 51 |
|
---|
| 52 | @Override
|
---|
| 53 | public int hashCode() {
|
---|
| 54 | T l = listener.get();
|
---|
| 55 | if (l == null) {
|
---|
| 56 | return 0;
|
---|
| 57 | } else {
|
---|
| 58 | return l.hashCode();
|
---|
| 59 | }
|
---|
| 60 | }
|
---|
| 61 |
|
---|
| 62 | @Override
|
---|
| 63 | public String toString() {
|
---|
[10939] | 64 | return "WeakListener [listener=" + listener + ']';
|
---|
[10824] | 65 | }
|
---|
| 66 | }
|
---|
| 67 |
|
---|
| 68 | private final CopyOnWriteArrayList<T> listeners = new CopyOnWriteArrayList<>();
|
---|
| 69 | private final CopyOnWriteArrayList<WeakListener<T>> weakListeners = new CopyOnWriteArrayList<>();
|
---|
| 70 |
|
---|
| 71 | protected ListenerList() {
|
---|
| 72 | // hide
|
---|
| 73 | }
|
---|
| 74 |
|
---|
| 75 | /**
|
---|
| 76 | * Adds a listener. The listener will not prevent the object from being garbage collected.
|
---|
| 77 | *
|
---|
| 78 | * This should be used with care. It is better to add good cleanup code.
|
---|
| 79 | * @param listener The listener.
|
---|
| 80 | */
|
---|
| 81 | public synchronized void addWeakListener(T listener) {
|
---|
| 82 | ensureNotInList(listener);
|
---|
| 83 | // clean the weak listeners, just to be sure...
|
---|
| 84 | while (weakListeners.remove(new WeakListener<T>(null))) {
|
---|
| 85 | // continue
|
---|
| 86 | }
|
---|
| 87 | weakListeners.add(new WeakListener<>(listener));
|
---|
| 88 | }
|
---|
| 89 |
|
---|
| 90 | /**
|
---|
| 91 | * Adds a listener.
|
---|
| 92 | * @param listener The listener to add.
|
---|
| 93 | */
|
---|
| 94 | public synchronized void addListener(T listener) {
|
---|
| 95 | ensureNotInList(listener);
|
---|
| 96 | listeners.add(listener);
|
---|
| 97 | }
|
---|
| 98 |
|
---|
| 99 | private void ensureNotInList(T listener) {
|
---|
| 100 | CheckParameterUtil.ensureParameterNotNull(listener, "listener");
|
---|
| 101 | if (containsListener(listener)) {
|
---|
| 102 | failAdd(listener);
|
---|
| 103 | }
|
---|
| 104 | }
|
---|
| 105 |
|
---|
| 106 | protected void failAdd(T listener) {
|
---|
| 107 | throw new IllegalArgumentException(
|
---|
[10936] | 108 | MessageFormat.format("Listener {0} (instance of {1}) was already registered.", listener,
|
---|
[10824] | 109 | listener.getClass().getName()));
|
---|
| 110 | }
|
---|
| 111 |
|
---|
| 112 | private boolean containsListener(T listener) {
|
---|
| 113 | return listeners.contains(listener) || weakListeners.contains(new WeakListener<>(listener));
|
---|
| 114 | }
|
---|
| 115 |
|
---|
| 116 | /**
|
---|
| 117 | * Removes a listener.
|
---|
| 118 | * @param listener The listener to remove.
|
---|
| 119 | * @throws IllegalArgumentException if the listener was not registered before
|
---|
| 120 | */
|
---|
| 121 | public synchronized void removeListener(T listener) {
|
---|
| 122 | if (!listeners.remove(listener) && !weakListeners.remove(new WeakListener<>(listener))) {
|
---|
| 123 | failRemove(listener);
|
---|
| 124 | }
|
---|
| 125 | }
|
---|
| 126 |
|
---|
| 127 | protected void failRemove(T listener) {
|
---|
| 128 | throw new IllegalArgumentException(
|
---|
| 129 | MessageFormat.format("Listener {0} (instance of {1}) was not registered before or already removed.",
|
---|
[10936] | 130 | listener, listener.getClass().getName()));
|
---|
[10824] | 131 | }
|
---|
| 132 |
|
---|
| 133 | /**
|
---|
| 134 | * Check if any listeners are registered.
|
---|
| 135 | * @return <code>true</code> if any are registered.
|
---|
| 136 | */
|
---|
| 137 | public boolean hasListeners() {
|
---|
| 138 | return !listeners.isEmpty();
|
---|
| 139 | }
|
---|
| 140 |
|
---|
| 141 | /**
|
---|
| 142 | * Fires an event to every listener.
|
---|
| 143 | * @param eventFirerer The firerer to invoke the event method of the listener.
|
---|
| 144 | */
|
---|
| 145 | public void fireEvent(EventFirerer<T> eventFirerer) {
|
---|
| 146 | for (T l : listeners) {
|
---|
| 147 | eventFirerer.fire(l);
|
---|
| 148 | }
|
---|
| 149 | for (Iterator<WeakListener<T>> iterator = weakListeners.iterator(); iterator.hasNext();) {
|
---|
| 150 | WeakListener<T> weakLink = iterator.next();
|
---|
| 151 | T l = weakLink.listener.get();
|
---|
[10894] | 152 | if (l != null) {
|
---|
| 153 | // cleanup during add() should be enough to not cause memory leaks
|
---|
| 154 | // therefore, we ignore null listeners.
|
---|
[10824] | 155 | eventFirerer.fire(l);
|
---|
| 156 | }
|
---|
| 157 | }
|
---|
| 158 | }
|
---|
| 159 |
|
---|
| 160 | /**
|
---|
| 161 | * This is a special {@link ListenerList} that traces calls to the add/remove methods. This may cause memory leaks.
|
---|
| 162 | * @author Michael Zangl
|
---|
| 163 | *
|
---|
| 164 | * @param <T> The type of listener contained in this list
|
---|
| 165 | */
|
---|
| 166 | public static class TracingListenerList<T> extends ListenerList<T> {
|
---|
[10939] | 167 | private final HashMap<T, StackTraceElement[]> listenersAdded = new HashMap<>();
|
---|
| 168 | private final HashMap<T, StackTraceElement[]> listenersRemoved = new HashMap<>();
|
---|
[10824] | 169 |
|
---|
| 170 | protected TracingListenerList() {
|
---|
| 171 | // hidden
|
---|
| 172 | }
|
---|
| 173 |
|
---|
| 174 | @Override
|
---|
| 175 | public synchronized void addListener(T listener) {
|
---|
| 176 | super.addListener(listener);
|
---|
| 177 | listenersRemoved.remove(listener);
|
---|
| 178 | listenersAdded.put(listener, Thread.currentThread().getStackTrace());
|
---|
| 179 | }
|
---|
| 180 |
|
---|
| 181 | @Override
|
---|
| 182 | public synchronized void addWeakListener(T listener) {
|
---|
| 183 | super.addWeakListener(listener);
|
---|
| 184 | listenersRemoved.remove(listener);
|
---|
| 185 | listenersAdded.put(listener, Thread.currentThread().getStackTrace());
|
---|
| 186 | }
|
---|
| 187 |
|
---|
| 188 | @Override
|
---|
| 189 | public synchronized void removeListener(T listener) {
|
---|
| 190 | super.removeListener(listener);
|
---|
| 191 | listenersAdded.remove(listener);
|
---|
| 192 | listenersRemoved.put(listener, Thread.currentThread().getStackTrace());
|
---|
| 193 | }
|
---|
| 194 |
|
---|
| 195 | @Override
|
---|
| 196 | protected void failAdd(T listener) {
|
---|
| 197 | Main.trace("Previous addition of the listener");
|
---|
| 198 | dumpStack(listenersAdded.get(listener));
|
---|
| 199 | super.failAdd(listener);
|
---|
| 200 | }
|
---|
| 201 |
|
---|
| 202 | @Override
|
---|
| 203 | protected void failRemove(T listener) {
|
---|
| 204 | Main.trace("Previous removal of the listener");
|
---|
| 205 | dumpStack(listenersRemoved.get(listener));
|
---|
| 206 | super.failRemove(listener);
|
---|
| 207 | }
|
---|
| 208 |
|
---|
[11018] | 209 | private static void dumpStack(StackTraceElement ... stackTraceElements) {
|
---|
[10824] | 210 | if (stackTraceElements == null) {
|
---|
| 211 | Main.trace(" - (no trace recorded)");
|
---|
| 212 | } else {
|
---|
| 213 | Stream.of(stackTraceElements).limit(20).forEach(
|
---|
| 214 | e -> Main.trace(e.getClassName() + "." + e.getMethodName() + " line " + e.getLineNumber()));
|
---|
| 215 | }
|
---|
| 216 | }
|
---|
| 217 | }
|
---|
| 218 |
|
---|
| 219 | /**
|
---|
| 220 | * Create a new listener list
|
---|
| 221 | * @param <T> The listener type the list should hold.
|
---|
| 222 | * @return A new list. A tracing list is created if trace is enabled.
|
---|
| 223 | */
|
---|
| 224 | public static <T> ListenerList<T> create() {
|
---|
| 225 | if (Main.isTraceEnabled()) {
|
---|
| 226 | return new TracingListenerList<>();
|
---|
| 227 | } else {
|
---|
| 228 | return new ListenerList<>();
|
---|
| 229 | }
|
---|
| 230 | }
|
---|
| 231 | }
|
---|