JDBC: Tipos de Drivers
Posted by wpjr2 em maio 12, 2008
JDBC driver types
JDBC drivers are divided into four types or levels. Each type defines a JDBC driver implementation with increasingly higher levels of platform independence, performance, and deployment administration. The four types are:
- Type 1: JDBC-ODBC Bridge
- Type 2: Native-API/partly Java driver
- Type 3: Net-protocol/all-Java driver
- Type 4: Native-protocol/all-Java driver
Type 1: JDBC-ODBC Bridge
The type 1 driver, JDBC-ODBC Bridge, translates all JDBC calls into ODBC (Open DataBase Connectivity) calls and sends them to the ODBC driver. As such, the ODBC driver, as well as, in many cases, the client database code, must be present on the client machine. Figure 1 shows a typical JDBC-ODBC Bridge environment.
Figure 1. Type 1: JDBC-ODBC Bridge
The JDBC-ODBC Bridge allows access to almost any database, since the database’s ODBC drivers are already available. Type 1 drivers may be useful for those companies that have an ODBC driver already installed on client machines.
- The performance is degraded since the JDBC call goes through the bridge to the ODBC driver, then to the native database connectivity interface. The result comes back through the reverse process. Considering the performance issue, type 1 drivers may not be suitable for large-scale applications.
- The ODBC driver and native connectivity interface must already be installed on the client machine. Thus any advantage of using Java applets in an intranet environment is lost, since the deployment problems of traditional applications remain.
Type 2: Native-API/partly Java driver
JDBC driver type 2 — the native-API/partly Java driver — converts JDBC calls into database-specific calls for databases such as SQL Server, Informix, Oracle, or Sybase. The type 2 driver communicates directly with the database server; therefore it requires that some binary code be present on the client machine.
Figure 2. Type 2: Native-API/partly Java driver
Type 2 drivers typically offer significantly better performance than the JDBC-ODBC Bridge.
The vendor database library needs to be loaded on each client machine. Consequently, type 2 drivers cannot be used for the Internet. Type 2 drivers show lower performance than type 3 and type 4 drivers.
Type 3: Net-protocol/all-Java driver
JDBC driver type 3 — the net-protocol/all-Java driver — follows a three-tiered approach whereby the JDBC database requests are passed through the network to the middle-tier server. The middle-tier server then translates the request (directly or indirectly) to the database-specific native-connectivity interface to further the request to the database server. If the middle-tier server is written in Java, it can use a type 1 or type 2 JDBC driver to do this.
Figure 3. Type 3: Net-protocol/all-Java driver
The net-protocol/all-Java driver is server-based, so there is no need for any vendor database library to be present on client machines. Further, there are many opportunities to optimize portability, performance, and scalability. Moreover, the net protocol can be designed to make the client JDBC driver very small and fast to load. Additionally, a type 3 driver typically provides support for features such as caching (connections, query results, and so on), load balancing, and advanced system administration such as logging and auditing.
Type 3 drivers require database-specific coding to be done in the middle tier. Additionally, traversing the recordset may take longer, since the data comes through the backend server.
Type 4: Native-protocol/all-Java driver
The native-protocol/all-Java driver (JDBC driver type 4) converts JDBC calls into the vendor-specific database management system (DBMS) protocol so that client applications can communicate directly with the database server. Level 4 drivers are completely implemented in Java to achieve platform independence and eliminate deployment administration issues.
Figure 4. Type 4: Native-protocol/all-Java driver
Since type 4 JDBC drivers don’t have to translate database requests to ODBC or a native connectivity interface or to pass the request on to another server, performance is typically quite good. Moreover, the native-protocol/all-Java driver boasts better performance than types 1 and 2. Also, there’s no need to install special software on the client or server. Further, these drivers can be downloaded dynamically.
With type 4 drivers, the user needs a different driver for each database.