improved oracle pscache error handle.

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

@@ -60,7 +60,7 @@ public final class DruidConnectionHolder {
 
     private PreparedStatementPool               statementPool;
 
-    private final List<Statement>               statementTrace           = new ArrayList<Statement>(2);
+    protected final List<Statement>             statementTrace           = new ArrayList<Statement>(2);
 
     private final boolean                       defaultReadOnly;
     private final int                           defaultHoldability;

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

@@ -22,6 +22,7 @@ import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.sql.Connection;
 import java.sql.SQLException;
+import java.sql.Statement;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.ConcurrentModificationException;
@@ -438,6 +439,17 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                 this.setConnectionProperties(property);
             }
         }
+        {
+            String property = properties.getProperty("druid.maxPoolPreparedStatementPerConnectionSize");
+            if (property != null && property.length() > 0) {
+                try {
+                    int value = Integer.parseInt(property);
+                    this.setMaxPoolPreparedStatementPerConnectionSize(value);
+                } catch (NumberFormatException e) {
+                    LOG.error("illegal property 'druid.maxPoolPreparedStatementPerConnectionSize'", e);
+                }
+            }
+        }
     }
 
     public boolean isKillWhenSocketReadTimeout() {
@@ -1443,6 +1455,12 @@ public class DruidDataSource extends DruidAbstractDataSource implements DruidDat
                 }
 
                 if (requireDiscard) {
+                    if (holder.statementTrace != null) {
+                        for (Statement stmt : holder.statementTrace) {
+                            JdbcUtils.close(stmt);
+                        }
+                    }
+
                     this.discardConnection(holder.getConnection());
                     holder.setDiscard(true);
                 }

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

@@ -167,14 +167,15 @@ public class DruidPooledConnection extends PoolableWrapper implements javax.sql.
             }
         }
 
-        stmt.getPreparedStatementHolder().decrementInUseCount();
+        PreparedStatementHolder stmtHolder = stmt.getPreparedStatementHolder();
+        stmtHolder.decrementInUseCount();
         if (stmt.isPooled() && holder.isPoolPreparedStatements() && stmt.exceptionCount == 0) {
-            holder.getStatementPool().put(stmt.getPreparedStatementHolder());
+            holder.getStatementPool().put(stmtHolder);
 
             stmt.clearResultSet();
             holder.removeTrace(stmt);
 
-            stmt.getPreparedStatementHolder().setFetchRowPeak(stmt.getFetchRowPeak());
+            stmtHolder.setFetchRowPeak(stmt.getFetchRowPeak());
 
             stmt.setClosed(true); // soft set close
         } else if (stmt.isPooled() && holder.isPoolPreparedStatements()) {
@@ -182,7 +183,8 @@ public class DruidPooledConnection extends PoolableWrapper implements javax.sql.
             stmt.clearResultSet();
             holder.removeTrace(stmt);
 
-            holder.getStatementPool().remove(stmt.getPreparedStatementHolder());
+            holder.getStatementPool()
+                    .remove(stmtHolder);
         } else {
             try {
                 //Connection behind the statement may be in invalid state, which will throw a SQLException.