1 | import javax.management.*; |
2 | import java.lang.management.*; |
3 | |
4 | /** |
5 | * from: https://www.javaspecialists.eu/archive/Issue092.html |
6 | * This memory warning system will call the listener when we |
7 | * exceed the percentage of available memory specified. There |
8 | * should only be one instance of this object created, since the |
9 | * usage threshold can only be set to one number. |
10 | */ |
11 | sclass MemoryWarningSystem {
|
12 | new L<Listener> listeners; |
13 | |
14 | public interface Listener {
|
15 | public void memoryUsageLow(long usedMemory, long maxMemory); |
16 | } |
17 | |
18 | public MemoryWarningSystem() {
|
19 | MemoryMXBean mbean = ManagementFactory.getMemoryMXBean(); |
20 | NotificationEmitter emitter = (NotificationEmitter) mbean; |
21 | emitter.addNotificationListener(new NotificationListener() {
|
22 | public void handleNotification(Notification n, Object hb) {
|
23 | if (n.getType().equals( |
24 | MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {
|
25 | long maxMemory = tenuredGenPool.getUsage().getMax(); |
26 | long usedMemory = tenuredGenPool.getUsage().getUsed(); |
27 | for (Listener listener : listeners) {
|
28 | listener.memoryUsageLow(usedMemory, maxMemory); |
29 | } |
30 | } |
31 | } |
32 | }, null, null); |
33 | } |
34 | |
35 | public boolean addListener(Listener listener) {
|
36 | return listeners.add(listener); |
37 | } |
38 | |
39 | public boolean removeListener(Listener listener) {
|
40 | return listeners.remove(listener); |
41 | } |
42 | |
43 | private static final MemoryPoolMXBean tenuredGenPool = |
44 | findTenuredGenPool(); |
45 | |
46 | public static void setPercentageUsageThreshold(double percentage) {
|
47 | if (percentage <= 0.0 || percentage > 1.0) {
|
48 | throw new IllegalArgumentException("Percentage not in range");
|
49 | } |
50 | long maxMemory = tenuredGenPool.getUsage().getMax(); |
51 | long warningThreshold = (long) (maxMemory * percentage); |
52 | tenuredGenPool.setUsageThreshold(warningThreshold); |
53 | } |
54 | |
55 | /** |
56 | * Tenured Space Pool can be determined by it being of type |
57 | * HEAP and by it being possible to set the usage threshold. |
58 | */ |
59 | private static MemoryPoolMXBean findTenuredGenPool() {
|
60 | for (MemoryPoolMXBean pool : |
61 | ManagementFactory.getMemoryPoolMXBeans()) {
|
62 | // I don't know whether this approach is better, or whether |
63 | // we should rather check for the pool name "Tenured Gen"? |
64 | if (pool.getType() == MemoryType.HEAP && |
65 | pool.isUsageThresholdSupported()) {
|
66 | return pool; |
67 | } |
68 | } |
69 | throw new AssertionError("Could not find tenured space");
|
70 | } |
71 | } |
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| Snippet ID: | #1018951 |
| Snippet name: | MemoryWarningSystem |
| Eternal ID of this version: | #1018951/2 |
| Text MD5: | b36c52234a19a554c7bb74878841c110 |
| Author: | stefan |
| Category: | javax |
| Type: | JavaX fragment (include) |
| Public (visible to everyone): | Yes |
| Archived (hidden from active list): | No |
| Created/modified: | 2018-10-18 13:31:59 |
| Source code size: | 2526 bytes / 71 lines |
| Pitched / IR pitched: | No / No |
| Views / Downloads: | 383 / 894 |
| Version history: | 1 change(s) |
| Referenced in: | [show references] |