apply modified suggstion from https://issues.apache.org/activemq/browse/AMQ-1191 - executeQuery conditional on statement metadata which works when statement does not return a result set like with derby which is used in the unit tests

git-svn-id: https://svn.apache.org/repos/asf/activemq/trunk@787990 13f79535-47bb-0310-9956-ffa450edef68

activemq-core/src/main/java/org/apache/activemq/store/jdbc/DefaultDatabaseLocker.java

@@ -19,6 +19,8 @@ package org.apache.activemq.store.jdbc;
 import java.io.IOException;
 import java.sql.Connection;
 import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
 import java.sql.SQLException;
 
 import javax.sql.DataSource;
@@ -64,7 +66,13 @@ public class DefaultDatabaseLocker implements DatabaseLocker {
                 connection.setAutoCommit(false);
                 String sql = statements.getLockCreateStatement();
                 statement = connection.prepareStatement(sql);
+                if (statement.getMetaData() != null) {
+                    ResultSet rs = statement.executeQuery();
+                    // if not already locked the statement below blocks until lock acquired
+                    rs.next();
+                } else {
                     statement.execute();
+                }
                 break;
             } catch (Exception e) {
                 if (stopping) {

activemq-core/src/main/java/org/apache/activemq/store/jdbc/adapter/DefaultJDBCAdapter.java

@@ -291,7 +291,7 @@ public class DefaultJDBCAdapter implements JDBCAdapter {
                 throw new SQLException("Failed to remove message");
             }
         } finally {
-            if (!this.batchStatments) {
+            if (!this.batchStatments && s != null) {
                 s.close();
             }
         }