JDBC API

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This JDBC tutorial covers all the topics of JDBC with the simple examples. JDBC is a Java API that is used to connect and execute query to the database. JDBC API uses jdbc drivers to connects to the database.

JDBC API

Why use JDBC?

Before JDBC, ODBC API was used to connect and execute query to the database. But ODBC API uses ODBC driver that is written in C language which is plateform dependent and unsecured. That is why Sun Microsystem has defined its own API (JDBC API) that uses JDBC driver written in Java language.

 

What is API?

API (Application programming interface) is a document that contains description of all the features of a product or software. It represents classes and interfaces that software programs can follow to communicate with each other. An API can be created for applications, libraries, operating systems, etc

 

JDBC Driver is a software component that enables java application to interact with the database.There are 4 types of JDBC drivers:

  1. JDBC-ODBC bridge driver
  2. Native-API driver (partially java driver)
  3. Network Protocol driver (fully java driver)
  4. 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.

JDBC-ODBC bridge driver


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.

 Native-API driver


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.

 Network Protocol driver


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.

Thin driver

Step by Step connect database in java

connect any java application with the database in java using JDBC. They are as follows:

  • Register the driver class
  • Creating connection
  • Creating statement
  • Executing queries
  • Closing connection

1) Register the driver class

The forName() method of Class class is used to register the driver class. This method is used to dynamically load the driver class.

Syntax of forName() method


 

Example to register the OracleDriver class


 


2) Create the connection object

The getConnection() method of DriverManager class is used to establish connection with the database.

Syntax of getConnection() method


 

Example to establish connection with the Oracle database


 


3) Create the Statement object

The createStatement() method of Connection interface is used to create statement. The object of statement is responsible to execute queries with the database.

Syntax of createStatement() method


 

Example to create the statement object


 

 


4) Execute the query

The executeQuery() method of Statement interface is used to execute queries to the database. This method returns the object of ResultSet that can be used to get all the records of a table.

Syntax of executeQuery() method


 

Example to execute query


 


5) Close the connection object

By closing connection object statement and ResultSet will be closed automatically. The close() method of Connection interface is used to close the connection.

Syntax of close() method


 

Example to close connection


 

connect to the mysql database Example

In this example we are using MySql as the database. So we need to know following informations for the mysql database:

  1. Driver class: The driver class for the mysql database is com.mysql.jdbc.Driver.
  2. Connection URL: The connection URL for the mysql database is jdbc:mysql://localhost:3306/sonoo where jdbc is the API, mysql is the database, localhost is the server name on which mysql is running, we may also use IP address, 3306 is the port number and sonoo is the database name. We may use any database, in such case, you need to replace the sonoo with your database name.
  3. Username: The default username for the mysql database is root.
  4. Password: Password is given by the user at the time of installing the mysql database. In this example, we are going to use root as the password.

Let’s first create a table in the mysql database, but before creating table, we need to create database first.

  1. create database sonoo;
  2. use sonoo;
  3. create table emp(id int(10),name varchar(40),age int(3));

Example to Connect Java Application with mysql database

In this example, sonoo is the database name, root is the username and password.


 

The above example will fetch all the records of emp table.


To connect java application with the mysql database mysqlconnector.jar file is required to be loaded.

Two ways to load the jar file:

  1. paste the mysqlconnector.jar file in jre/lib/ext folder
  2. set classpath

1) paste the mysqlconnector.jar file in JRE/lib/ext folder:

Download the mysqlconnector.jar file. Go to jre/lib/ext folder and paste the jar file here.

2) set classpath:

There are two ways to set the classpath:

  • temporary
  • permament

How to set the temporary classpath

open comman prompt and write:

 

How to set the permanent classpath

Go to environment variable then click on new tab. In variable name write classpath and in variable value paste the path to the mysqlconnector.jar file by appending mysqlconnector.jar;.; as C:\folder\mysql-connector-java-5.0.8-bin.jar;.;

 

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