JDBC(JAVA DATABASE CONNECTIVITY)
•JDBC
stands for Java Database Connectivity.
•Which
is a standard Java API for database-independent
connectivity between the Java programming language and a
wide range of databases.
•The
JDBC library includes APIs for each of the tasks associated
with database usage
WHAT DOES JDBC DO?
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Simply , JDBC makes it possible to do three things:
1. Establish a connection with a database
2. Send SQL/MYSQL statements (Creating SQL or MySQL
statement and executing queries)
3. Process the results (Viewing & Modifying the resulting
records)
JDBC ARCHITECTURE
Java code calls JDBC library (API)
 JDBC loads a driver
 Driver talks to a particular database
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Java
Application
JDBC API
JDBC
Driver
DBMS/RDB
MS
JDBC ARCHITECTURE
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JDBC Architecture consists of two layers:
JDBC API: This provides the application-to-JDBC Manager
connection.
The JDBC API uses a driver manager and database-specific drivers to
provide transparent connectivity to heterogeneous databases.
JDBC Driver API: This supports the JDBC Manager-to-Driver
Connection.
The JDBC driver manager ensures that the correct driver is used
to access each data source. The driver manager is capable of
supporting multiple concurrent drivers connected to multiple
heterogeneous databases.
Following is the architectural diagram, which shows the location of the
driver manager with respect to the JDBC drivers and the Java application:
TYPE 1: JDBC-TO-ODBC BRIDGE
Microsoft created ODBC (Open Database Connection),
which is the basis from which Sun created JDBC. Both
have similar driver specifications and an API.
 The JDBC-to-ODBC driver, also called the JDBC/ODBC
Bridge, is used to translate DBMS calls between the
JDBC specification and the ODBC specification.
 MS Access and SQL Server contains ODBC driver
written in C language using pointers, but java does not
support the mechanism to handle pointers.
 So JDBC-ODBC Driver is created as a bridge between
the two so that JDBC-ODBC bridge driver translates the
JDBC API to the ODBC API.
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Type-1 ODBC Driver for MS Access and SQL
Server
Drawbacks of Type-1 Driver:
ODBC drivers must be loaded on each client.
 Translation overhead between JDBC and ODBC.
 It doesn’t support all features of Java.
 it is slow compare with other types.
 Type-1 driver isn’t written in java, that’s why it isn’t a
portable driver.
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TYPE 2: NATIVE-API DRIVER
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This driver converts JDBC method calls into native calls
of the database API. In order to interact with different
database, this driver needs their local API.
The Java/Native Code driver uses Java classes to
generate platform- specific code that is code only
understood by a specific DBMS.
Ex: Driver for DB2, Informix, Oracle Driver,
WebLogic drivers
Drawbacks of Type-II Driver:
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The driver directly communicates with database
servers and therefore driver needs to be installed
separately in individual client machines
Type-2 driver isn’t written in java, that’s why it isn’t a
portable driver
TYPE 3: NET-PROTOCOL DRIVER OR
MIDDLEWARE DRIVER
Based on intermediate (middleware) database servers.
 Connect to various database servers via an intermediate
server that acts like a gateway for multiple database
servers.
 The Network Protocol driver uses middleware (application
server) that converts JDBC calls directly or indirectly into
the vendor-specific database protocol.
 Here all the database connectivity drivers are present in a
single server, hence no need of individual client-side
installation.
 Type-3 drivers are fully written in Java, hence they are
portable drivers.
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Ex: Symantec DB
Drawbacks:
 Network support is required on client machine.
 Maintenance of Network Protocol driver becomes
costly because it requires database-specific
coding to be done in the middle tier.
 It does not support all network protocols.
 If the middleware server is failed entire system
will be failed.
TYPE 4: DATABASE-PROTOCOL DRIVER OR PURE
JAVA DRIVER
Type-4 driver is also called native protocol driver. This
driver interact directly with database.
 It does not require any native database library, that is
why it is also known as Thin Driver.
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Only disadvantage: need to download a new
driver for each database engine
Which Driver to use When?
 If you are accessing one type of database, such as
Oracle, Sybase, or IBM, the preferred driver type is
type-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 deploymentlevel driver, and is typically used for development
and testing purposes only.
Components of JDBC
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DriverManager : It loads database drivers and
manages the connection between the application and
the driver
Driver : It translates API calls into operation for a
specific data source.
Connection :It is a session between application
and a database.
Statement : It is an sql statement to perform a
query or update operation
MetaData : It gives information about returned
data, the database
Resultset : logical set of columns and rows of
data returned by executing a statement.
E
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BASIC JDBC DATA TYPES
Char, varchar and longvarchar
The role of the char is to represent a
small, fixed length character string. Varchar
represents a small , variable-length character
string, and Lonvarchar represent a large
variable length character string.
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As a java string, each can be expressed.
Binary, VarBinary and Longbinary.
The role of the BINARY is to represent a
small, fixed-length binary value. Varbinary
represents a small, variable-length binary
value. Longvarbinary represents a large,
variable-length binary value.
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For retrieving BINARY and VARBINARY
values, the method recommended is
ResultSet.getBytes.
BIT
 A single bit value is represented by the JDBC
type BIT that can be zero or one.
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For the JDBC BIT type, the recommended
Java mapping is as Java boolean.
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TinyInt
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An 8-bit integer value, between 0 and
255. Java short will always be able to hold all
TINYINT values.
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SMALLINT
 A 16-bit signed integer alue between -32768 and
32767. Java mapping is as Java short.
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INTEGER:
 A 32-bit signed integer value -21473648 and
2147483647. Java mapping is Java int.
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BIGINT
 A 64-bit signed integer value. Java mapping is as
Java long.
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REAL
 A “ single precision” floating point number.
Java mapping as Java float.
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DOUBLE
A “ double precision” floating point number is
represented as Java double.
DECIMAL AND numeric
DECIMAL and NUMERIC which are JDBC types.
They both represent fixed-precision decimal values.
Java mapping is java.math.BigDecimal.
DATE , TIME and TIMESTAMP
Jdbc DATE type represents a date consisting of day,
month and year. Corresponding java.util. Date
The second type is known as JDBC time that
represents a time which is consitin of hours, minutes
and second. Corresponding java type is
java.util.Time.
The third type is JDBC TIMESTAMP represents
DATE plus TIME plus a nanosecond. Corresponding
java type is java.util.Timestamp.
ADVANCED JDBC DATA TYPES
BLOB datatype
Binary Large Object File. Video
 CLOB data type
Character Large Object file. Text files, Stories.
 User defined types:
 Structured type: User-defined type; for example:
CREATE TYPE PLANE_POINT AS (X FLOAT,
Y FLOAT)
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DISTINCT type: User-defined type based on a builtin type; for example: (typedef in C or C++)
CREATE TYPE MONEY AS NUMERIC(10,2)
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REF(structured-type): Pointer that
persistently denotes an instance of a
structured type that resides in the database
Mapping Advanced Data Types
 The JDBC API provides default mappings for
advanced data types specified . The following list
gives the data types and the interfaces or classes
to which they are mapped:
 BLOB: Blob interface
 CLOB: Clob interface
 ARRAY: Array interface
 Structured types: Struct interface
 REF(structured type): Ref interface
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Common JDBC Components:
The JDBC API provides the following interfaces and
classes:
DriverManager: This class manages a list of database
drivers. Matches connection requests from the java
application with the proper database driver using
communication subprotocol.
Driver: This interface handles the communications
with the database server.
Connection : This interface with all methods for
contacting a database. All communication with
database is through connection object only.
Statement : We use objects created from this
interface to submit the SQL statements to the database.
Some derived interfaces accept parameters in addition to
executing stored procedures.
ResultSet: These objects hold data retrieved from a
database after you execute an SQL query using Statement
objects
SQLException: This class handles any errors that occur
in a database application.
http://www.slideshare.net/java2all/jdbc-architecture-anddriver-types
JDBC PACKAGES
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JDBC API is mainly divided into two package
1. java.sql
2. javax.sql
java.sql package
This package include classes and interface to
perform almost all JDBC operation such as
creating and executing SQL Queries.
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Important classes and interface of java.sql package
classes/interface
java.sql.BLOB
java.sql.Connection
Description
Provide support for BLOB(Binary Large
Object) SQL type.
creates a connection with specific database
java.sql.CallableStatement
Execute stored procedures
java.sql.CLOB
Provide support for CLOB(Character Large
Object) SQL type.
java.sql.Date
Provide support for Date SQL type.
java.sql.Driver
create an instance of a driver with the
DriverManager.
This class manages database drivers.
java.sql.DriverManager
java.sql.PreparedStatement
java.sql.ResultSet
Used to create and execute parameterized
query.
It is an interface that provide methods to
access the result row-by-row.
java.sql.Savepoint
Specify savepoint in transaction.
java.sql.SQLException
Encapsulate all JDBC related exception.
java.sql.Statement
This interface is used to execute SQL
statements.
JAVAX.SQL PACKAGE
THIS PACKAGE IS ALSO KNOWN AS JDBC EXTENSION API.
IT PROVIDES CLASSES AND INTERFACE TO ACCESS SERVER-SIDE DATA.
Important classes and interface of javax.sql package
classes/interface
Description
javax.sql.ConnectionEvent
Provide information about occurence
of event.
javax.sql.ConnectionEventListener
Used to register event generated
by PooledConnectionobject.
javax.sql.DataSource
Represent the DataSource interface
used in an application.
javax.sql.PooledConnection
provide object to manage connection
pools.
JDBC - EXCEPTIONS HANDLING
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JDBC Exception handling is very similar to the
Java Exception handling but for JDBC, the most
common exception you'll deal with
is java.sql.SQLException.
SQLException Methods
 An SQLException can occur both in the driver
and the database. When such an exception
occurs, an object of type SQLException will be
passed to the catch clause.
 The passed SQLException object has the
following methods available for retrieving
additional information about the exception
JDBC - EXCEPTIONS HANDLING
Method
getErrorCode( )
getMessage( )
Description
Gets the error number associated with the
exception.
Gets the JDBC driver's error message for an
error, handled by the driver or gets the Oracle
error number and message for a database error.
getSQLState( )
Gets the XOPEN SQLstate string. For a JDBC
driver error, no useful information is returned
from this method. For a database error, the
five-digit XOPEN SQLstate code is returned.
This method can return null.
getNextException( )
Gets the next Exception object in the exception
chain.
Prints the current exception, or throwable, and
it's backtrace to a standard error stream.
printStackTrace( )
printStackTrace(PrintStream s)
Prints this throwable and its backtrace to the
print stream you specify.
printStackTrace(PrintWriter w)
Prints this throwable and it's backtrace to the
print writer you specify.
JDBC - EXCEPTIONS HANDLING
Exception Handling Approach
try{
// all statements including commit
}catch(SQLException e)
{
// rollback or commit if rollback for a given
savepoint
}
Finally{
// close connection or statements or resultsets
}