Core jdbc basics

1. Core JDBC Basics
Sourabrata Mukherjee

2. Topics:
1. What is JDBC
2. Why Use JDBC and not ODBC?
3. JDBC Architecture
4. Steps to connect to the database using java
5. JDBC Driver and it’s Types
6. JDBC Connection
7. JDBC Statements

3. JDBC and It’s Architecture
● The JDBC (Java Database Connectivity) API defines interfaces and classes
for writing database applications in Java by making database connections.
Using JDBC you can send SQL, PL/SQL statements to almost any relational
database. JDBC is a Java API for executing SQL statements and supports
basic SQL functionality. It provides RDBMS access by allowing you to embed
SQL inside Java code.

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● JDBC standardizes how to connect to a database, how to execute queries
against it, how to navigate the result of such a query, and how to execute
updates in the database.
● Although JDBC was designed specifically to provide a Java interface to
relational databases, you may find that you need to write Java code to access
non-relational databases as well.

5. Why use JDBC and not ODBC?
Before JDBC, ODBC API was the database API to connect and execute 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).
* 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.

6. JDBC Architecture
In general, JDBC Architecture consists of two layers − JDBC API: This provides the
application-to-JDBC Manager connection. JDBC Driver API: This supports the
JDBC Manager-to-Driver Connection. The JDBC API uses a driver manager and
database-specific drivers to provide transparent connectivity to heterogeneous
databases.

7. Steps to connect to the database using java
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.
Class.forName("com.mysql.jdbc.Driver");

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Create the connection object The getConnection() method of DriverManager
class is used to establish connection with the database. Syntax of
getConnection() method:
public static Connection getConnection(String url)throws SQLException
public static Connection getConnection(String url,String name,String password) throws
SQLException
Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/SOURODB","root","souro");

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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.
Statement stmt=con.createStatement();

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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.
ResultSet rs=stmt.executeQuery("SELECT EmpID,LastName,FirstName,Address,City FROM
EMPLOYEE");

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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.
con.close();

12. JDBC Driver and It’s Types
A JDBC driver is a collection of Java classes that enables you to connect to a certain
database. For instance, MySQL will have its own JDBC driver. A JDBC driver implements a
lot of the JDBC API interfaces. When your code uses a given JDBC driver, it actually just
uses the standard JDBC interfaces. The concrete JDBC driver used is hidden behind the
JDBC interfaces.
There are 4 types of JDBC drivers:
● JDBC-ODBC bridge driver
● Native-API driver
● Network Protocol driver
● Thin driver

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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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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.

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Native-API driver - JDBC API calls are converted into native C/C++ API calls, which are
unique to the database. These drivers are typically provided by the database vendors and
used in the same manner as the JDBC-ODBC Bridge.

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Advantage:
Performance upgrade 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.

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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.

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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 depends on the Database.

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Which Driver should be used when?
If you are accessing one type of database, such as Oracle, Sybase, or IBM, the
preferred driver type is 4.
If your Java application is accessing multiple types of databases at the same
time, type 3 is the preferred driver.
Type 2 drivers are useful in situations, where a type 3 or type 4 driver is not
available yet for your database.
The type 1 driver is not considered a deployment-level driver, and is typically
used for development and testing purposes only.

22. JDBC Connection
Once a JDBC driver is loaded and initialized, you need to connect to the database. You
do so by obtaining a Connection to the database via the JDBC API and the loaded
driver. All communication with the database happens via a connection. An application
can have more than one connection open to a database at a time. This is actually very
common.
A Connection is the session between java application and database. The Connection
interface is a factory of Statement, PreparedStatement, and DatabaseMetaData i.e.
object of Connection can be used to get the object of Statement and
DatabaseMetaData. The Connection interface provide many methods for transaction
management like commit(),rollback() etc.

23. JDBC Statements
A Statement is what you use to execute queries against the database. There are a
few different types of statements you can use. Each statement corresponds to a
single query.
Once a connection is obtained we can interact with the database. The JDBC
Statement, CallableStatement, and PreparedStatement interfaces define the
methods and properties that enable you to send SQL or PL/SQL commands

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Each interface's purpose -
Interface Recommended Use
Statement Use for general-purpose access to your database. Useful when you
are using static SQL statements at runtime. The Statement interface
cannot accept parameters.
PreparedStatement Use when you plan to use the SQL statements many times. The
PreparedStatement interface accepts input parameters at runtime.
CallableStatement Use when you want to access the database stored procedures. The
CallableStatement interface can also accept runtime input
parameters.

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The important methods of Statement interface are as follows:
public ResultSet executeQuery(String sql): is used to execute SELECT query. It
returns the object of ResultSet.
public int executeUpdate(String sql): is used to execute specified query, it may
be create, drop, insert, update, delete etc.
public boolean execute(String sql): is used to execute queries that may return
multiple results.
public int[] executeBatch(): is used to execute batch of commands.

26. JDBC Result Sets
When you perform a query against the database you get back a ResultSet. You can
then traverse this ResultSet to read the result of the query.
The object of ResultSet maintains a cursor pointing to a particular row of data.
Initially, cursor points to before the first row.
But we can make this object to move forward and backward direction by passing
either TYPE_SCROLL_INSENSITIVE or TYPE_SCROLL_SENSITIVE in
createStatement(int,int) method

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Commonly used methods of ResultSet interface -
public boolean next(): is used to move the cursor to the one row next from the
current position.
public boolean previous(): is used to move the cursor to the one row previous
from the current position.
public boolean first(): is used to move the cursor to the first row in result set
object.
public boolean last(): is used to move the cursor to the last row in result set
object.

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public boolean relative(int row): is used to move the cursor to the relative row
number in the ResultSet object, it may be positive or negative.
public int getInt(int columnIndex): is used to return the data of specified
column index of the current row as int.
public int getInt(String columnName): is used to return the data of specified
column name of the current row as int.
public String getString(int columnIndex): is used to return the data of specified
column index of the current row as String.
public String getString(String columnName): is used to return the data of

29. JDBC Transaction
Transaction represents a single unit of work. The ACID properties describes the
transaction management well. ACID stands for Atomicity, Consistency, isolation
and durability.
Atomicity means either all successful or none.
Consistency ensures bringing the database from one consistent state to
another consistent state.
Isolation ensures that transaction is isolated from other transaction.
Durability means once a transaction has been committed, it will remain so, even
in the event of errors, power loss etc.

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If your JDBC Connection is in autocommit mode, which it is by default, then every
SQL statement is committed to the database upon its completion.
Transactions enable you to control if, and when, changes are applied to the
database.
To enable manual- transaction support instead of the auto-commit mode that the
JDBC driver uses by default, use the Connection object's setAutoCommit()
method. If you pass a boolean false to setAutoCommit( ), you turn off auto-
commit. You can pass a boolean true to turn it back on again.

31. Conclusion

32. Thank You