A JDBC driver uses the JDBC™ (Java Database Connectivity) API developed by Sun Microsystems, now part of Oracle, that provides a standard way to access data using the Java™ programming language. Using JDBC, an application can access a variety of databases and run on any platform with a Java Virtual Machine. It isn't necessary to write separate applications to access different database systems (Oracle and Salesforce, for example). Using JDBC allows you to write one application that can send SQL statements to different data sources. SQL is the standard language for accessing relational databases.
The JDBC API defines a set of Java interfaces that encapsulate major database functionality, such as running queries, processing results, and determining configuration information. Because JDBC applications are written in Java, applications work on any platform.
Types of JDBC Driver
JDBC Driver is a software component that enables java application to interact with the database. There are 4 types of JDBC drivers:
JDBC-ODBC bridge driver
Native-API driver (partially java driver)
Network Protocol driver (fully java driver)
Thin driver (fully java driver)
1) JDBC-ODBC bridge driver
The JDBC-ODBC bridge driver uses ODBC driver to connect to the database. The JDBC-ODBC bridge driver converts JDBC method calls into the ODBC function calls. This is now discouraged because of thin driver.
In Java 8, the JDBC-ODBC Bridge has been removed.
Oracle does not support the JDBC-ODBC Bridge from Java 8. Oracle recommends that you use JDBC drivers provided by the vendor of your database instead of the JDBC-ODBC Bridge.
Advantages:
easy to use.
can be easily connected to any database.
Disadvantages:
Performance degraded because JDBC method call is converted into the ODBC function calls.
The ODBC driver needs to be installed on the client machine.
2) Native-API driver
The Native API driver uses the client-side libraries of the database. The driver converts JDBC method calls into native calls of the database API. It is not written entirely in java.
Advantage:
performance upgraded than JDBC-ODBC bridge driver.
Disadvantage:
The Native driver needs to be installed on the each client machine.
The Vendor client library needs to be installed on client machine.
3) Network Protocol driver
The Network Protocol driver uses middleware (application server) that converts JDBC calls directly or indirectly into the vendor-specific database protocol. It is fully written in java.
Advantage:
No client side library is required because of application server that can perform many tasks like auditing, load balancing, logging etc.
Disadvantages:
Network support is required on client machine.
Requires database-specific coding to be done in the middle tier.
Maintenance of Network Protocol driver becomes costly because it requires database-specific coding to be done in the middle tier.
4) Thin driver
The thin driver converts JDBC calls directly into the vendor-specific database protocol. That is why it is known as thin driver. It is fully written in Java language.
Advantage:
Better performance than all other drivers.
No software is required at client side or server side.
Disadvantage:
Drivers depend on the Database.
How Does JDBC Work?
JDBC makes it possible to do establish a connection with a data source, send queries and update statements, and process the results.
Simply, JDBC makes it possible to do the following things within a Java application:
Establish a connection with a data source
Send queries and update statements to the data source
Process the results
The following figure shows the components of the JDBC model.
The Java application calls JDBC classes and interfaces to submit SQL statements and retrieve results. The JDBC API is implemented through the JDBC driver. The JDBC Driver is a set of classes that implement the JDBC interfaces to process JDBC calls and return result sets to a Java application. The database (or data store) stores the data retrieved by the application using the JDBC Driver. The main objects of the JDBC API include:
A DataSource object is used to establish connections. Although the Driver Manager can also be used to establish a connection, connecting through a DataSource object is the preferred method.
A Connection object controls the connection to the database. An application can alter the behavior of a connection by invoking the methods associated with this object. An application uses the connection object to create statements.
Statement, PreparedStatement, and CallableStatement objects are used for executing SQL statements. A PreparedStatement object is used when an application plans to reuse a statement multiple times. The application prepares the SQL it plans to use. Once prepared, the application can specify values for parameters in the prepared SQL statement. The statement can be executed multiple times with different parameter values specified for each execution. A CallableStatement is used to call stored procedures that return values. The CallableStatement has methods for retrieving the return values of the stored procedure.
A ResultSet object contains the results of a query. A ResultSet is returned to an application when a SQL query is executed by a statement object. The ResultSet object provides methods for iterating through the results of the query.
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