Make sure that the DB drivers are loaded before initiating connections

framework/db/src/com/cloud/utils/db/DriverLoader.java

@@ -0,0 +1,69 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// the License.  You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+package com.cloud.utils.db;
+
+import com.cloud.utils.exception.CloudRuntimeException;
+import org.apache.log4j.Logger;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class DriverLoader {
+
+    private static final Logger LOGGER = Logger.getLogger(DriverLoader.class.getName());
+    private static final List<String> LOADED_DRIVERS;
+    private static final Map<String, String> DRIVERS;
+
+    static {
+        DRIVERS = new HashMap<String, String>();
+        DRIVERS.put("jdbc:mysql", "com.mysql.jdbc.Driver");
+        DRIVERS.put("jdbc:postgresql", "org.postgresql.Driver");
+        DRIVERS.put("jdbc:h2", "org.h2.Driver");
+
+        LOADED_DRIVERS = new ArrayList<String>();
+    }
+
+
+    public static void loadDriver(String dbDriver) {
+        String driverClass = DRIVERS.get(dbDriver);
+        if (driverClass == null) {
+            LOGGER.error("DB driver type " + dbDriver + " is not supported!");
+            throw new CloudRuntimeException("DB driver type " + dbDriver + " is not supported!");
+        }
+
+        if (LOADED_DRIVERS.contains(dbDriver)) {
+            if (LOGGER.isDebugEnabled()) {
+                LOGGER.debug("DB driver " + driverClass + " was already loaded.");
+            }
+            return;
+        }
+
+        try {
+            Class.forName(driverClass).newInstance();
+            LOADED_DRIVERS.add(dbDriver);
+            if (LOGGER.isDebugEnabled()) {
+                LOGGER.debug("Successfully loaded DB driver " + driverClass);
+            }
+        } catch (ClassNotFoundException | InstantiationException | IllegalAccessException e) {
+            LOGGER.error("Failed to load DB driver " + driverClass);
+            throw new CloudRuntimeException("Failed to load DB driver " + driverClass, e);
+        }
+    }
+
+}

framework/db/src/com/cloud/utils/db/TransactionLegacy.java

@@ -20,8 +20,6 @@ import java.io.Closeable;
 import java.io.File;
 import java.io.IOException;
 import java.sql.Connection;
-import java.sql.Driver;
-import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
@@ -1078,7 +1076,7 @@ public class TransactionLegacy implements Closeable {
             final String cloudConnectionUri = cloudDriver + "://" + cloudHost + (s_dbHAEnabled ? "," + cloudSlaves : "") + ":" + cloudPort + "/" + cloudDbName +
                     "?autoReconnect=" + cloudAutoReconnect + (url != null ? "&" + url : "") + (useSSL ? "&useSSL=true" : "") +
                     (s_dbHAEnabled ? "&" + cloudDbHAParams : "") + (s_dbHAEnabled ? "&loadBalanceStrategy=" + loadBalanceStrategy : "");
-            loadDbDriver(cloudConnectionUri);
+            DriverLoader.loadDriver(cloudDriver);
 
             final ConnectionFactory cloudConnectionFactory = new DriverManagerConnectionFactory(cloudConnectionUri, cloudUsername, cloudPassword);
 
@@ -1109,7 +1107,7 @@ public class TransactionLegacy implements Closeable {
             final String usageConnectionUri = usageDriver + "://" + usageHost + (s_dbHAEnabled ? "," + dbProps.getProperty("db.cloud.slaves") : "") + ":" + usagePort +
                     "/" + usageDbName + "?autoReconnect=" + usageAutoReconnect + (usageUrl != null ? "&" + usageUrl : "") +
                     (s_dbHAEnabled ? "&" + getDBHAParams("usage", dbProps) : "") + (s_dbHAEnabled ? "&loadBalanceStrategy=" + loadBalanceStrategy : "");
-            loadDbDriver(usageConnectionUri);
+            DriverLoader.loadDriver(usageDriver);
 
             final ConnectionFactory usageConnectionFactory = new DriverManagerConnectionFactory(usageConnectionUri, usageUsername, usagePassword);
 
@@ -1137,7 +1135,7 @@ public class TransactionLegacy implements Closeable {
 
                 final String simulatorConnectionUri = simulatorDriver + "://" + simulatorHost + ":" + simulatorPort + "/" + simulatorDbName + "?autoReconnect=" +
                         simulatorAutoReconnect;
-                loadDbDriver(simulatorConnectionUri);
+                DriverLoader.loadDriver(simulatorDriver);
 
                 final ConnectionFactory simulatorConnectionFactory = new DriverManagerConnectionFactory(simulatorConnectionUri, simulatorUsername, simulatorPassword);
 
@@ -1157,16 +1155,6 @@ public class TransactionLegacy implements Closeable {
         }
     }
 
-    private static void loadDbDriver(String dbConnectionUri) {
-        try {
-            Driver driver = DriverManager.getDriver(dbConnectionUri);
-            s_logger.debug("Successfully loaded DB driver " + driver.getClass().getName() + " for connection " + dbConnectionUri);
-        } catch (SQLException e) {
-            s_logger.error("Failed to load DB driver for connection " + dbConnectionUri, e);
-            throw new CloudRuntimeException("Failed to load DB driver for connection " + dbConnectionUri, e);
-        }
-    }
-
     private static String getDBHAParams(String dbName, Properties dbProps) {
         StringBuilder sb = new StringBuilder();
         sb.append("failOverReadOnly=" + dbProps.getProperty("db." + dbName + ".failOverReadOnly"));