- 5 Steps to connect to the database in java Register the driver class Create the connection object Create the Statement object Execute the query Close the connection object
- Register the driver class
- Create the connection object
- Create the Statement object
- Execute the query
- Close the connection object
| There are 5 steps to connect any java application with the database using JDBC. These steps are as follows:Register the Driver classCreate connectionCreate statementExecute queriesClose connection |
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- Register the Driver class
- Create connection
- Create statement
- Execute queries
- Close connection
1) Register the driver class
| TheforName()method of Class class is used to register the driver class. This method is used to dynamically load the driver class. |
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Syntax of forName method
Example
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
In this instance, a Java program is importing the Oracle driver to establish a connection with a database.
Example
Class.forName("oracle.jdbc.driver.OracleDriver");
2) Create the connection object
| ThegetConnection()method of DriverManager class is used to establish connection with the database. |
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Syntax of getConnection method
Example
1) public static Connection getConnection(String url)throws SQLException
2) public static Connection getConnection(String url,String name,String password)
throws SQLException
Example to establish connection with the Oracle database
Example
Connection con=DriverManager.getConnection(
"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. |
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Syntax of createStatement method
Example
public Statement createStatement()throws SQLException
Example to create the statement object
Example
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. |
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Syntax of executeQuery method
Example
public ResultSet executeQuery(String sql)throws SQLException
Example to execute query
Example
ResultSet rs=stmt.executeQuery("select * from emp");
while(rs.next()){
System.out.println(rs.getInt(1)+" "+rs.getString(2));
}
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. |
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Syntax of close method
Example
public void close()throws SQLException
Example to close connection
Example
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 MCQ
- What is the first step to connect to a database in Java?
- Load the JDBC driver
- Create a connection
- Execute a query
- Close the connection
Explanation: The first step to connect to a database in Java is to load the JDBC driver, which establishes the communication between Java application and the database.
- Which method is used to establish a connection to the database?
- DriverManager.getConnection
- DriverManager.createConnection
- Connection.getConnection
- Connection.create
Explanation: The DriverManager.getConnection method is used to establish a connection to the database by providing the database URL, username, and password.
- What must be done after executing a query to avoid memory leaks?
- Close the Statement object
- Close the ResultSet object
- Close the Connection object
- All of the above
Explanation: After executing a query, you should close the Statement, ResultSet, and Connection objects to avoid memory leaks and free up database resources.
- Which interface provides the methods to execute SQL queries?
- Connection
- Statement
- DriverManager
- ResultSet
Explanation: The Statement interface provides methods to execute SQL queries such as executeQuery, executeUpdate, and execute.
- How do you handle SQL exceptions in JDBC?
- Using try-catch blocks
- Using if-else statements
- Using a switch statement
- Using for loops
In JDBC, SQL exceptions are managed by enclosing the code inside try-catch blocks to capture SQLExceptions and manage the issue accordingly.