rdonkin 2004/11/11 14:31:05
Modified: logging/optional/src/java/org/apache/commons/logging/impl
WeakHashtable.java
logging/optional/src/test/org/apache/commons/logging/impl
WeakHashtableTest.java
Log:
Added code to purge entries who references have been collected. Test
contributed by Brian Stansberry.
Revision Changes Path
1.3 +63 -0
jakarta-commons/logging/optional/src/java/org/apache/commons/logging/impl/WeakHashtable.java
Index: WeakHashtable.java
===================================================================
RCS file:
/home/cvs/jakarta-commons/logging/optional/src/java/org/apache/commons/logging/impl/WeakHashtable.java,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- WeakHashtable.java 11 Nov 2004 21:43:43 -0000 1.2
+++ WeakHashtable.java 11 Nov 2004 22:31:05 -0000 1.3
@@ -25,6 +25,11 @@
* to hold it's keys thus allowing them to be reclaimed by the garbage
collector.
* This class follows the symantics of <code>Hashtable</code> as closely as
possible.
* It therefore does not accept null values or keys.
+ * <p>
+ * This implementation is also tuned towards a particular purpose: for use
as a replacement
+ * for <code>Hashtable</code> in <code>LogFactory</code>. This application
requires
+ * good liveliness for <code>get</code> and <code>put</code>. Various
tradeoffs
+ * have been made with this in mind.
* </p>
* <p>
* <strong>Usage:</strong> typical use case is as a drop-in replacement
@@ -35,6 +40,8 @@
*/
public final class WeakHashtable extends Hashtable {
+ /** Empty array of <code>Entry</code>'s */
+ private static final Entry[] EMPTY_ENTRY_ARRAY = {};
public WeakHashtable() {}
@@ -42,6 +49,7 @@
[EMAIL PROTECTED] Hashtable
*/
public boolean contains(Object value) {
+ // purge should not be required
if (value instanceof Referenced) {
return super.contains(value);
}
@@ -53,6 +61,7 @@
[EMAIL PROTECTED] Hashtable
*/
public boolean containsKey(Object key) {
+ // purge should not be required
Referenced referenced = new Referenced(key);
return super.containsKey(referenced);
}
@@ -61,6 +70,7 @@
[EMAIL PROTECTED] Hashtable
*/
public boolean containsValue(Object value) {
+ // purge should not be required
if (value instanceof Referenced) {
return super.contains(value);
}
@@ -72,6 +82,7 @@
[EMAIL PROTECTED] Hashtable
*/
public Enumeration elements() {
+ purge();
final Enumeration enum = super.elements();
return new Enumeration() {
public boolean hasMoreElements() {
@@ -88,6 +99,7 @@
[EMAIL PROTECTED] Hashtable
*/
public Set entrySet() {
+ purge();
Set referencedEntries = super.entrySet();
Set unreferencedEntries = new HashSet();
for (Iterator it=referencedEntries.iterator(); it.hasNext();) {
@@ -108,6 +120,7 @@
[EMAIL PROTECTED] Hashtable
*/
public Object get(Object key) {
+ // for performance reasons, no purge
Object result = null;
Referenced referenceKey = new Referenced(key);
Referenced referencedValue = (Referenced) super.get(referenceKey);
@@ -121,6 +134,7 @@
[EMAIL PROTECTED] Hashtable
*/
public Enumeration keys() {
+ purge();
final Enumeration enum = super.keys();
return new Enumeration() {
public boolean hasMoreElements() {
@@ -138,6 +152,7 @@
[EMAIL PROTECTED] Hashtable
*/
public Set keySet() {
+ purge();
Set referencedKeys = super.keySet();
Set unreferencedKeys = new HashSet();
for (Iterator it=referencedKeys.iterator(); it.hasNext();) {
@@ -154,6 +169,7 @@
[EMAIL PROTECTED] Hashtable
*/
public Object put(Object key, Object value) {
+ // for performance reasons, no purge
// check for nulls, ensuring symantics match superclass
if (key == null) {
throw new NullPointerException("Null keys are not allowed");
@@ -187,6 +203,7 @@
[EMAIL PROTECTED] Hashtable
*/
public Collection values() {
+ purge();
Collection referencedValues = super.values();
ArrayList unreferencedValues = new ArrayList();
for (Iterator it = referencedValues.iterator(); it.hasNext();) {
@@ -206,6 +223,52 @@
return super.remove(new Referenced(key));
}
+ /**
+ [EMAIL PROTECTED] Hashtable
+ */
+ public boolean isEmpty() {
+ purge();
+ return super.isEmpty();
+ }
+
+ /**
+ [EMAIL PROTECTED] Hashtable
+ */
+ public int size() {
+ purge();
+ return super.size();
+ }
+
+ /**
+ [EMAIL PROTECTED] Hashtable
+ */
+ public String toString() {
+ purge();
+ return super.toString();
+ }
+
+ /**
+ * Purges all entries whose wrapped keys or values
+ * have been garbage collected.
+ */
+ private synchronized void purge() {
+ Set entrySet = super.entrySet();
+ for (Iterator it=entrySet.iterator(); it.hasNext();) {
+ Map.Entry entry = (Map.Entry) it.next();
+ Referenced referencedKey = (Referenced) entry.getKey();
+ Referenced referencedValue = (Referenced) entry.getValue();
+
+ // test whether either referant has been collected
+ if (referencedKey.getValue() == null ||
referencedValue.getValue() == null) {
+ // if so, purge this entry
+ it.remove();
+ }
+ }
+ }
+
+
+
+ /** Entry implementation */
private final static class Entry implements Map.Entry {
private Object key;
1.3 +3 -0
jakarta-commons/logging/optional/src/test/org/apache/commons/logging/impl/WeakHashtableTest.java
Index: WeakHashtableTest.java
===================================================================
RCS file:
/home/cvs/jakarta-commons/logging/optional/src/test/org/apache/commons/logging/impl/WeakHashtableTest.java,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- WeakHashtableTest.java 11 Nov 2004 21:43:43 -0000 1.2
+++ WeakHashtableTest.java 11 Nov 2004 22:31:05 -0000 1.3
@@ -232,5 +232,8 @@
bytz = bytz * 2;
}
}
+
+ // Test that the released objects are not taking space in the table
+ assertEquals("underlying table not emptied", 0,
weakHashtable.size());
}
}
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