Modify the createDbClient() method

lib/src/ConfigLoader.cc

@@ -231,9 +231,9 @@ static void loadApp(const Json::Value &app)
 }
 static void loadDbClients(const Json::Value &dbClients)
 {
-#if USE_ORM
     if (!dbClients)
         return;
+#if USE_ORM   
     for (auto &client : dbClients)
     {
         auto type = client.get("rdbms", "postgresql").asString();
@@ -252,6 +252,9 @@ static void loadDbClients(const Json::Value &dbClients)
         auto filename = client.get("filename", "").asString();
         drogon::app().createDbClient(type, host, (u_short)port, dbname, user, password, connNum, filename, name);
     }
+#else
+    std::cout << "No database is supported by drogon, please install the database development library first." << std::endl;
+    exit(1);
 #endif
 }
 static void loadListeners(const Json::Value &listeners)

lib/src/HttpAppFrameworkImpl.cc

@@ -1277,6 +1277,9 @@ void HttpAppFrameworkImpl::createDbClient(const std::string &dbType,
 #if USE_POSTGRESQL
         auto client = drogon::orm::DbClient::newPgClient(connStr, connectionNum);
         _dbClientsMap[name] = client;
+#else
+        std::cout << "The PostgreSQL is not supported by drogon, please install the development library first." << std::endl;
+        exit(1);
 #endif
     }
     else if (type == "mysql")
@@ -1284,6 +1287,9 @@ void HttpAppFrameworkImpl::createDbClient(const std::string &dbType,
 #if USE_MYSQL
         auto client = drogon::orm::DbClient::newMysqlClient(connStr, connectionNum);
         _dbClientsMap[name] = client;
+#else
+        std::cout << "The Mysql is not supported by drogon, please install the development library first." << std::endl;
+        exit(1);
 #endif
     }
     else if (type == "sqlite3")
@@ -1292,6 +1298,9 @@ void HttpAppFrameworkImpl::createDbClient(const std::string &dbType,
         std::string sqlite3ConnStr = "filename=" + filename;
         auto client = drogon::orm::DbClient::newSqlite3Client(sqlite3ConnStr, connectionNum);
         _dbClientsMap[name] = client;
+#else
+        std::cout << "The Sqlite3 is not supported by drogon, please install the development library first." << std::endl;
+        exit(1);
 #endif
     }
 }