From 38fcc483f6e58b8b9c17dff6ce4ac52984b3362a Mon Sep 17 00:00:00 2001
From: wenshao <szujobs@hotmail.com>
Date: Wed, 28 Sep 2011 23:45:54 +0000
Subject: [PATCH] =?UTF-8?q?=E6=94=B9=E8=BF=9BPreparedStatementCache?=
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git-svn-id: http://code.alibabatech.com/svn/druid/trunk@915 b9813039-fb51-4c41-a8b9-e21c2acb5095
---
 .../alibaba/druid/pool/ConnectionHolder.java  |  2 +-
 .../druid/pool/DruidAbstractDataSource.java   |  6 +++---
 .../druid/pool/PreparedStatementPool.java     | 10 +++++++---
 .../java/com/alibaba/druid/util/LRUCache.java | 19 +++++++++++++++++++
 4 files changed, 30 insertions(+), 7 deletions(-)
 create mode 100644 src/main/java/com/alibaba/druid/util/LRUCache.java

diff --git a/src/main/java/com/alibaba/druid/pool/ConnectionHolder.java b/src/main/java/com/alibaba/druid/pool/ConnectionHolder.java
index d884b05fcb..ce6f288124 100644
--- a/src/main/java/com/alibaba/druid/pool/ConnectionHolder.java
+++ b/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;
         }
diff --git a/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java b/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java
index a08e83449c..03bdea2f11 100644
--- a/src/main/java/com/alibaba/druid/pool/DruidAbstractDataSource.java
+++ b/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();
     }
diff --git a/src/main/java/com/alibaba/druid/pool/PreparedStatementPool.java b/src/main/java/com/alibaba/druid/pool/PreparedStatementPool.java
index 1e3878a22a..724814d0fe 100644
--- a/src/main/java/com/alibaba/druid/pool/PreparedStatementPool.java
+++ b/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;
     }
 
diff --git a/src/main/java/com/alibaba/druid/util/LRUCache.java b/src/main/java/com/alibaba/druid/util/LRUCache.java
new file mode 100644
index 0000000000..936898f571
--- /dev/null
+++ b/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);
+    }
+}