IN PROGRESS - issue DRUID-82: 当sql没有参数化时，sql数量过多会导致OOM

http://code.alibabatech.com/jira/browse/DRUID-82

src/main/java/com/alibaba/druid/filter/stat/StatFilter.java

@@ -67,6 +67,8 @@ public class StatFilter extends FilterEventAdapter implements StatFilterMBean {
 
     protected final AtomicLong         resetCount                 = new AtomicLong();
 
+    protected int                      maxSqlStatCount            = 1000 * 10;
+
     public boolean isConnectionStackTraceEnable() {
         return connectionStackTraceEnable;
     }
@@ -81,10 +83,10 @@ public class StatFilter extends FilterEventAdapter implements StatFilterMBean {
 
     public void reset() {
         dataSourceStat.reset();
-        
+
         resetCount.incrementAndGet();
     }
-    
+
     public long getResetCount() {
         return resetCount.get();
     }
@@ -670,6 +672,10 @@ public class StatFilter extends FilterEventAdapter implements StatFilterMBean {
         final ConcurrentMap<String, JdbcSqlStat> sqlStatMap = dataSourceStat.getSqlStatMap();
         JdbcSqlStat sqlStat = sqlStatMap.get(sql);
         if (sqlStat == null) {
+            if (dataSourceStat.getSqlStatMap().size() >= maxSqlStatCount) {
+                return null;
+            }
+            
             JdbcSqlStat newSqlStat = new JdbcSqlStat(sql);
             if (dataSourceStat.getSqlStatMap().putIfAbsent(sql, newSqlStat) == null) {
                 newSqlStat.setId(JdbcStatManager.getInstance().generateSqlId());

src/test/java/com/alibaba/druid/bvt/pool/TestPoolPreparedStatement2.java

@@ -0,0 +1,58 @@
+package com.alibaba.druid.bvt.pool;
+
+import java.sql.Connection;
+import java.sql.PreparedStatement;
+
+import junit.framework.Assert;
+import junit.framework.TestCase;
+
+import com.alibaba.druid.mock.MockDriver;
+import com.alibaba.druid.mock.MockPreparedStatement;
+import com.alibaba.druid.pool.DruidDataSource;
+import com.alibaba.druid.stat.DruidDataSourceStatManager;
+
+public class TestPoolPreparedStatement2 extends TestCase {
+
+    private MockDriver      driver;
+    private DruidDataSource dataSource;
+
+    protected void setUp() throws Exception {
+        Assert.assertEquals(0, DruidDataSourceStatManager.getInstance().getDataSourceList().size());
+        
+        driver = new MockDriver();
+
+        dataSource = new DruidDataSource();
+        dataSource.setUrl("jdbc:mock:xxx");
+        dataSource.setDriver(driver);
+        dataSource.setInitialSize(1);
+        dataSource.setMaxActive(2);
+        dataSource.setMaxIdle(2);
+        dataSource.setMinIdle(1);
+        dataSource.setMinEvictableIdleTimeMillis(300 * 1000); // 300 / 10
+        dataSource.setTimeBetweenEvictionRunsMillis(10); // 180 / 10
+        dataSource.setTestWhileIdle(true);
+        dataSource.setTestOnBorrow(false);
+        dataSource.setValidationQuery("SELECT 1");
+        dataSource.setFilters("stat");
+        dataSource.setPoolPreparedStatements(true);
+        dataSource.setMaxPoolPreparedStatementPerConnectionSize(20);
+    }
+
+    protected void tearDown() throws Exception {
+        dataSource.close();
+        Assert.assertEquals(0, DruidDataSourceStatManager.getInstance().getDataSourceList().size());
+    }
+
+    public void test_stmtCache() throws Exception {
+
+        for (int i = 0; i < 1000 * 1000 * 10; ++i){
+            Connection conn = dataSource.getConnection();
+            PreparedStatement stmt = conn.prepareStatement("SELECT " + i);
+            stmt.close();
+            conn.close();
+        }
+
+        Assert.assertEquals(0, dataSource.getActiveCount());
+        Assert.assertEquals(1, dataSource.getPoolingCount());
+    }
+}