改进PreparedStatementCache

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@915 b9813039-fb51-4c41-a8b9-e21c2acb5095

src/main/java/com/alibaba/druid/pool/ConnectionHolder.java

@@ -53,7 +53,7 @@ public final class ConnectionHolder {
         this.lastActiveTimeMillis = connecttimeMillis;
 
         if (this.poolPreparedStatements) {
-            statementPool = new PreparedStatementPool();
+            statementPool = new PreparedStatementPool(dataSource.getMaxPoolPreparedStatementPerConnectionSize());
         } else {
             statementPool = null;
         }

src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java

@@ -118,7 +118,7 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
     private boolean                                                                          testOnReturn                              = DEFAULT_TEST_ON_RETURN;
     private boolean                                                                          testWhileIdle                             = DEFAULT_WHILE_IDLE;
     protected boolean                                                                        poolPreparedStatements                    = false;
-    protected int                                                                            maxPoolPreparedStatementPerConnectionSize = -1;
+    protected int                                                                            maxPoolPreparedStatementPerConnectionSize = 10;
 
     protected boolean                                                                        inited                                    = false;
 
@@ -192,11 +192,11 @@ public abstract class DruidAbstractDataSource extends WrapperAdapter implements
     public Histogram getTransactionHistogram() {
         return transactionHistogram;
     }
-    
+
     public void incrementPreparedStatementCount() {
         reusePreparedStatement.incrementAndGet();
     }
-    
+
     public long getReusePreparedStatement() {
         return reusePreparedStatement.get();
     }

src/main/java/com/alibaba/druid/pool/PreparedStatementPool.java

@@ -16,16 +16,20 @@
 package com.alibaba.druid.pool;
 
 import java.sql.PreparedStatement;
-import java.util.HashMap;
 
 import com.alibaba.druid.pool.PoolablePreparedStatement.PreparedStatementKey;
+import com.alibaba.druid.util.LRUCache;
 
 /**
  * @author wenshao<szujobs@hotmail.com>
  */
 public class PreparedStatementPool {
 
-    private HashMap<PreparedStatementKey, PreparedStatement> map = new HashMap<PreparedStatementKey, PreparedStatement>();
+    private final LRUCache<PreparedStatementKey, PreparedStatement> map;
+
+    public PreparedStatementPool(int maxSize){
+        map = new LRUCache<PreparedStatementKey, PreparedStatement>(maxSize);
+    }
 
     public static enum MethodType {
         M1, M2, M3, M4, M5, M6, Precall_1, Precall_2, Precall_3
@@ -40,7 +44,7 @@ public class PreparedStatementPool {
         map.put(key, poolableStatement.getRawPreparedStatement());
     }
 
-    public HashMap<PreparedStatementKey, PreparedStatement> getMap() {
+    public LRUCache<PreparedStatementKey, PreparedStatement> getMap() {
         return map;
     }
 

src/main/java/com/alibaba/druid/util/LRUCache.java

@@ -0,0 +1,19 @@
+package com.alibaba.druid.util;
+
+import java.util.LinkedHashMap;
+import java.util.Map.Entry;
+
+public class LRUCache<K, V> extends LinkedHashMap<K, V> {
+
+    private static final long serialVersionUID = 1L;
+    protected int             maxElements;
+
+    public LRUCache(int maxSize){
+        super(maxSize);
+        this.maxElements = maxSize;
+    }
+
+    protected boolean removeEldestEntry(Entry<K, V> eldest) {
+        return (size() > this.maxElements);
+    }
+}