JDBC stands for Java Database Connectivity. JDBC is a Java API to connect and execute the query with the database. It is a part of JavaSE (Java Standard Edition). JDBC API uses JDBC drivers to connect with the database. There are four types of JDBC drivers:
• JDBC-ODBC Bridge Driver,
• Native Driver,
• Network Protocol Driver, and
• Thin Driver
We have discussed the above four drivers in the next chapter.
We can use JDBC API to access tabular data stored in any relational database. By the help of JDBC API, we can save, update, delete and fetch data from the database. It is like Open Database Connectivity (ODBC) provided by Microsoft.

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The current version of JDBC is 4.3. It is the stable release since 21st September, 2017. It is based on the X/Open SQL Call Level Interface. The java.sql package contains classes and interfaces for JDBC API. A list of popular interfaces of JDBC API are given below:
• Driver interface
• Connection interface
• Statement interface
• PreparedStatement interface
• CallableStatement interface
• ResultSet interface
• ResultSetMetaData interface
• DatabaseMetaData interface
• RowSet interface
A list of popular classes of JDBC API are given below:
• DriverManager class
• Blob class
• Clob class
• Types class

Table of Contents

Why Should We Use JDBC

Before JDBC, ODBC API was the database API to connect and execute the query with the database. But, ODBC API uses ODBC driver which is written in C language (i.e. platform dependent and unsecured). That is why Java has defined its own API (JDBC API) that uses JDBC drivers (written in Java language).
We can use JDBC API to handle database using Java program and can perform the following activities:
1. Connect to the database
2. Execute queries and update statements to the database
3. Retrieve the result received from the database.

JDBC Driver

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.

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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.

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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.

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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.

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Advantage:

• Better performance than all other drivers.
• No software is required at client side or server side.

Disadvantage:

• Drivers depend on the Database.
Java Database Connectivity with 5 Steps
There are 5 steps to connect any java application with the database using JDBC. These steps are as follows:
• Register the Driver class
• Create connection
• Create statement
• Execute queries
• Close connection

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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

1. public static void forName(String className)throws ClassNotFoundException
Note: Since JDBC 4.0, explicitly registering the driver is optional. We just need to put vender’s Jar in the classpath, and then JDBC driver manager can detect and load the driver automatically.

Example to register the OracleDriver class

Here, Java program is loading oracle driver to esteblish database connection.
1. Class.forName(“oracle.jdbc.driver.OracleDriver”);

2) Create the connection object

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

Syntax of getConnection() method

1. 1) public static Connection getConnection(String url)throws SQLException
2. 2) public static Connection getConnection(String url,String name,String password)
3. throws SQLException

Example to establish connection with the Oracle database

1. Connection con=DriverManager.getConnection(
2. “jdbc:oracle:thin:@localhost:1521:xe”,”system”,”password”);

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

1. public Statement createStatement()throws SQLException

Example to create the statement object

1. Statement stmt=con.createStatement();

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

1. public ResultSet executeQuery(String sql)throws SQLException
Example to execute query
1. ResultSet rs=stmt.executeQuery(“select * from emp”);
2.
3. while(rs.next()){
4. System.out.println(rs.getInt(1)+” “+rs.getString(2));
5. }

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

1. public void close()throws SQLException

Example to close connection

1. con.close();
Note: Since Java 7, JDBC has ability to use try-with-resources statement to automatically close resources of type Connection, ResultSet, and Statement.
It avoids explicit connection closing step.

Java Database Connectivity with Oracle

To connect java application with the oracle database, we need to follow 5 following steps. In this example, we are using Oracle 10g as the database. So we need to know following information for the oracle database:
1. Driver class: The driver class for the oracle database is oracle.jdbc.driver.OracleDriver.
2. Connection URL: The connection URL for the oracle10G database is jdbc:oracle:thin:@localhost:1521:xe where jdbc is the API, oracle is the database, thin is the driver, localhost is the server name on which oracle is running, we may also use IP address, 1521 is the port number and XE is the Oracle service name. You may get all these information from the tnsnames.ora file.
3. Username: The default username for the oracle database is system.
4. Password: It is the password given by the user at the time of installing the oracle database.

Create a Table

Before establishing connection, let’s first create a table in oracle database. Following is the SQL query to create a table.
1. create table emp(id number(10),name varchar2(40),age number(3));

Example to Connect Java Application with Oracle database

In this example, we are connecting to an Oracle database and getting data from emp table. Here, system and oracle are the username and password of the Oracle database.

1. import java.sql.*; 
2. class OracleCon{ 
3. public static void main(String args[]){ 
4. try{ 
5. //step1 load the driver class 
6. Class.forName("oracle.jdbc.driver.OracleDriver"); 
7. 
8. //step2 create the connection object 
9. Connection con=DriverManager.getConnection( 
10. "jdbc:oracle:thin:@localhost:1521:xe","system","oracle"); 
11. 
12. //step3 create the statement object 
13. Statement stmt=con.createStatement(); 
14. 
15. //step4 execute query 
16. ResultSet rs=stmt.executeQuery("select * from emp"); 
17. while(rs.next()) 
18. System.out.println(rs.getInt(1)+" "+rs.getString(2)+" "+rs.getString(3)); 
19. 
20. //step5 close the connection object 
21. con.close(); 
22. 
23. }catch(Exception e){ System.out.println(e);} 
24. 
25. } 
26. }

download this example
The above example will fetch all the records of emp table.
To connect java application with the Oracle database ojdbc14.jar file is required to be loaded.
download the jar file ojdbc14.jar

Two ways to load the jar file:

1. paste the ojdbc14.jar file in jre/lib/ext folder
2. set classpath

1) paste the ojdbc14.jar file in JRE/lib/ext folder:

Firstly, search the ojdbc14.jar file then go to JRE/lib/ext folder and paste the jar file here.

2) set classpath:

There are two ways to set the classpath:
• temporary
• permanent

How to set the temporary classpath:

Firstly, search the ojdbc14.jar file then open command prompt and write:
1. C:>set classpath=c:\folder\ojdbc14.jar;.;

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 ojdbc14.jar by appending ojdbc14.jar;.; as C:\oraclexe\app\oracle\product\10.2.0\server\jdbc\lib\ojdbc14.jar;.;
To see the slides of seting parmanent path click here

Java Database Connectivity with MySQL

To connect Java application with the MySQL database, we need to follow 5 following steps.
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, we need to replace the sonoo with our database name.
3. Username: The default username for the mysql database is root.
4. Password: It is the password 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 both.

1. import java.sql.*; 
2. class MysqlCon{ 
3. public static void main(String args[]){ 
4. try{ 
5. Class.forName("com.mysql.jdbc.Driver"); 
6. Connection con=DriverManager.getConnection( 
7. "jdbc:mysql://localhost:3306/sonoo","root","root"); 
8. //here sonoo is database name, root is username and password 
9. Statement stmt=con.createStatement(); 
10. ResultSet rs=stmt.executeQuery("select * from emp"); 
11. while(rs.next()) 
12. System.out.println(rs.getInt(1)+" "+rs.getString(2)+" "+rs.getString(3)); 
13. con.close(); 
14. }catch(Exception e){ System.out.println(e);} 
15. } 
16. }

download this example
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.
download the jar file mysql-connector.jar

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
• permanent

How to set the temporary classpath

open command prompt and write:
1. C:>set classpath=c:\folder\mysql-connector-java-5.0.8-bin.jar;.;
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;.;

Jdbc New Features

The latest version of JDBC is 4.0 currently. Java has updated jdbc api to ease and simplify the coding to database interactivity.
Here, we are going to see the features included in Jdbc 3.0 and Jdbc 4.0.

Jdbc 3.0 Features

The important features of JDBC API 3.0 are as follows:
• Jdbc RowSet We have done the great discussion on JdbcRowSet in the previous page.
• Savepoint in transaction management Now you are able to create, rollback and release the savepoint by Connection.setSavepoint(), Connection.rollback(Savepoint svpt) and Connection.releaseSavepoint(Savepoint svpt) methods.
• Statement and ResultSet Caching for Connection Pooling Now you are able to reuse the statement and result set because jdbc 3 provides you the facility of statement caching and result set caching.
• Switching between Global and Local Transactions
• Retrieval of auto generated keys Now you are able to get the auto generated keys by the method getGeneratedKeys().

Jdbc 4.0 Features

The important features of JDBC API 4.0 are given below:
• Automatic Loading of Driver class You don’t need to write Class.forName() now because it is loaded bydefault since jdbc4.
• Subclasses of SQLException Jdbc 4 provides new subclasses of SQLException class for better readability and handling.
• New methods There are many new methods introduced in Connection, PreparedStatement, CallableStatement, ResultSet etc.
• Improved DataSource Now data source implementation is improved.
• Event Handling support in Statement for Connection Pooling Now Connection Pooling can listen statement error and statement closing events.

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