Wednesday, 29 March 2017

JDBC Drivers

JDBC Drivers

A JDBC driver is a software component which enables a Java application to interact with a database. To connect with individual databases, JDBC requires drivers for each database. The JDBC driver felicitates connection to the database and implements the mechanism for transferring the query and result between client and database.

There are 4 (four) types of JDBC drivers.

1.    JDBC-ODBC bridge 
2.    Native-API driver 
3.    Network-Protocol driver (Middleware driver) 
4.    Database-Protocol driver (Pure Java driver) or thin driver.

Type 1 driver – JDBC-ODBC bridge

The JDBC type 1 driver, also known as the JDBC-ODBC bridge, is a database driver implementation that uses the ODBC driver to connect to the database. The driver converts JDBC method calls into ODBC function calls.

Type 1 driver is platform-dependent as it makes use of ODBC which in turn depends on native libraries of the underlying operating system the JVM is running on. ODBC must be installed on the computer having the driver and the database must support an ODBC driver. The use of this driver is discouraged. Any application using a type 1 driver is non-portable.
Sun (now Oracle) provided a JDBC-ODBC Bridge driver: sun.jdbc.odbc.JdbcOdbcDriver. This driver is native code and not Java, and is closed source.

Advantages
·         Any database for which an ODBC driver is installed can be accessed, and data can be retrieved.
Disadvantages 
·         Performance overhead since the calls have to go through the JDBC bridge to the ODBC driver, then to the native database connectivity interface. 
·         The ODBC driver needs to be installed on the client machine.
·         Not suitable for applets, because the ODBC driver needs to be installed on the client.
·         Specific ODBC drivers are not always available on all platforms; hence, portability of this driver is limited.
·         No support from JDK 1.8 (Java 8) onwards.

Type 2 driver – Native-API drive

The JDBC type 2 driver, also known as the Native-API driver, is a database driver implementation that uses the client-side libraries of the database. The driver converts JDBC method calls into native calls of the database API.
Advantages
·         As there is no implementation of JDBC-ODBC bridge, it may be considerably faster than a Type 1 driver.
Disadvantages
·         The vendor client library needs to be installed on the client machine.
·         Not all databases have a client-side library.
·         This driver is platform dependent.
·         This driver supports all Java applications except applets.

Type 3 driver – Network-Protocol driver (middleware driver)

The JDBC type 3 driver, also known as the Pure Java driver for database middleware, is a database driver implementation which makes use of a middle tier between the calling program and the database.
The middle-tier (application server) converts JDBC calls directly or indirectly into a vendor-specific database protocol. The type 3 driver is written entirely in Java. The same client-side JDBC driver may be used for multiple databases.
It depends on the number of databases the middleware has been configured to support. The type 3 driver is platform-independent as the platform-related differences are taken care of by the middleware.  Also, making use of the middleware provides additional advantages of security and firewall access.
Advantages
·  Since the communication between client and the middleware server is database independent,  there is no need for the database vendor library on the client. The client need not be changed for a new database.
·  The middleware server can provide typical middleware services like caching (of connections, query results, etc.),  load balancing, logging, and auditing.
·         A single driver can handle any database, provided the middleware supports it.

Disadvantages
·         Requires database-specific coding to be done in the middle tier.
·        The middleware layer added may result in additional latency, but is typically overcome by using better middleware services.

Type 4 driver – Database-Protocol driver (Pure Java driver)

The JDBC type 4 driver, also known as the Direct to Database Pure Java Driver, is a database driver implementation that converts JDBC calls directly into a vendor-specific database protocol. Type 4 drivers are platform independent as they are written in Java. They install inside the Java Virtual Machine of the client. This provides better performance as it does not have the overhead of conversion of calls into ODBC or database API calls.
As the database protocol is vendor specific, the JDBC client requires separate drivers, usually vendor supplied, to connect to different types of databases.
Advantages
·         Completely implemented in Java to achieve platform independence.
·        These drivers don't translate the requests into an intermediary format.
·  The client application connects directly to the database server. No translation or middleware layers are used, improving performance.
·   The JVM can manage all aspects of the application-to-database connection; this can facilitate debugging.
Disadvantages
·         Drivers are database specific, as different database vendors use widely different network protocols.

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