Jdbc

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JDBC

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JDBC is an alternative to ODBC and ADO that provides
database access to programs written in Java.

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JDBC drivers are available for most DBMS
products:
http://java.sun.com/products/jdbc

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JDBC

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Java API for connecting programs written in Java to the
data in relational databases
The standard defined by Sun Microsystems, allowing
individual providers to implement and extend the
standard with their own JDBC drivers.
Tasks of JDBC:
1) establishes a connection with a database
2) sends SQL statements
3) processes the results

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JDBC

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The JDBC API supports both two-tier and three-tier
models for database access.
Two-tier model - a Java applet or application interacts
directly with the database.
Three-tier model - introduces a middle-level server for
execution of business logic:
The middle tier to maintain control over data access.
The user can employ an easy-to-use higher-level API
which is translated by the middle tier into the
appropriate low-level calls.

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JDBC provides API or Protocol to interact
with different databases.
With the help of JDBC driver we can
connect with different types of
databases.
Driver is must needed for connection
establishment with any database.
A driver works as an interface between
the
client and a database server.

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JDBC have so many classes and
interfaces that allow a Java application to
send request made by user to any
specific DBMS(Data Base Management
System).
JDBC supports a wide level of portability.
JDBC provides interfaces that are
compatible with java application

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Establish a connection
Begin transaction
Create a statement object
Associate SQL with the statement object
Provide values for statement parameters
Execute the statement object
Process the results
End transaction
Release resources

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Load the driver:
• The driver class libraries need to be in the

CLASSPATH for the Java compiler and for the
Java virtual machine.
• The most reliable way to load the driver into
the program is:
Class.forName(string).newInstance();

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Establish a connection to the database:
• A connection URL string includes the
literal jdbc:, followed by the name of
the driver and a URL to the database
String url =
"jdbc:oracle:thin:@localhost:1521:csodb";
jdbc “subprotocol”“subname” host

port

database

• Create a Connection object:
Connection con = DriverManager.getConnection(url,
dbUser,dbPassword);

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Begin the transaction

con.setTransactionIsolation(
Connection.TRANSACTION_SERIALIZABLE );
con.setAutoCommit( false );

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Create a statement object

Statement stmt = conn.createStatement();

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Associate SQL with the statement object
String queryString = "create table students "
+ "(name varchar(30), id int, phone char(9))";

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Process the statement:
Example statements:

ResultSet rs = stmt.executeQuery(querystring);
Int result = stmt.executeUpdate(updatestring);
ResultSetMetaData rsMeta = rs.getMetaData();

•

Compiled queries can be processed via a
PreparedStatement object

•

Stored procedures can be processed via a
CallableStatement object

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End transaction
con.commit();
con.rollback();

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Release resources
con.close();

Driver
Manager

Creates Connection Creates

Statement Creates

ResultSet

SQL
Establish
Link to DB

Driver
Result
(tuples)

Database

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Java Application talks
directly to the
database
Accomplished
through the JDBC
driver which sends
commands directly to
the database
Results sent back
directly to the
application

Application Space

Java Application

JDBC Driver

SQL
Command

Result
Set

Database

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JDBC driver sends
commands to a
middle tier, which
in turn sends
commands to
database.
Results are sent
back to the middle
tier, which
communicates
them back to the
application

Application Space
Java Application
JDBC Driver
SQL
Command

Result
Set

Application Server
(middle-tier)

Proprietary
Protocol
Database

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The JDBC type 1 driver which is also
known as a JDBC-ODBC Bridge is a
convert JDBC methods into ODBC
function calls.
Sun provides a JDBC-ODBC Bridge driver
by "sun.jdbc.odbc.JdbcOdbcDriver".

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The driver is a platform dependent
because it uses ODBC which is depends
on native libraries of the operating
system and also the driver needs other
installation for example, ODBC must be
installed on the computer and the
database must support ODBC Driver

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Type 1 is the simplest compare to all
other driver but it's a platform specific
i.e. only on Microsoft platform.
The JDBC-ODBC Bridge is use only when
there is no PURE-JAVA driver available
for a particular database.

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Process:
Java Application -> JDBC APIs JDBC
Driver Manager —» Type 1 Driver —» ODBC
Driver —> Database library APIs —> Database

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Advantage:
(1) Connect to almost any database on any
system, for which ODBC driver is installed.
(2) It's an easy for installation as well as
easy(simplest) to use as compare the all other
driver.

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Disadvantage:
(1) The ODBC Driver needs to be installed on
the client machine.
(2) It's a not a purely platform independent
because its use ODBC which is depends on
native libraries of the operating system on
client machine.
(3) Not suitable for applets because the ODBC
driver needs to be installed on the client
machine.

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JDBC:ODBC ( mainly for Desktop
Applications)
Use bridging technology
Requires installation/configuration on
client machines
Not good for Web

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The JDBC type 2 driver is uses the
libraries of the database which is
available at client side and this driver
converts the JDBC method calls into
native calls of the database so this driver
is also known as a
Native-API driver.

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Process:
Java Application -> JDBC APIs JDBC
Driver Manager —» Type 2 Driver —» Vendor
Client Database library APIs —> Database

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Advantage:
(1) There is no implantation of JDBCODBC Bridge so it's faster than a type 1
driver; hence the performance is better as
compare the type 1 driver
(JDBC-ODBC Bridge).

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Disadvantage

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(1) On the client machine require the extra
installation because this driver uses the vendor
client libraries.
(2) The Client side software needed so cannot
use such type of driver in the web-based
application.
(3) Not all databases have the client side
library.
(4) This driver supports all JAVA applications
eXCept applets.

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Native API Drivers (Vendor Specific
drivers)
Requires installation/configuration on
client machines
Used to leverage existing CLI libraries
Usually not thread-safe
Mostly obsolete now

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The JDBC type 3 driver uses the middle
tier(application server) between the
calling program and the database and
this middle tier converts JDBC method
calls into the vendor specific database
protocol and the same driver can be
used for multiple
databases also so it's also known as a
Network-Protocol driver as well as a JAVA
driver for database middleware.

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Process
Java Application —> JDBC APIs -> JDBC
Driver Manager —> Type 3 Driver —> Middleware
(Server)—> any Database

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Advantage:
(1) There is no need for the vendor database
library on the client machine because the
middleware is database independent and it
communicates with
client.

(2) Type 3 driver can be used in any web
application as well as on internet also because
there is no anv software require at client side.
(3) A single driver can handle any database at
client side so there is no need a Separate
driver for each database.
(4) The middleware server can also provide the
typical services such as connections, auditing,
load balancing, logging etc.

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Disadvantage:
(1) An Extra layer added, may be time
consuming.
(2) At the middleware develop the database
specific coding, may be increase complexity.

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Network API
Calls middleware server, usually on
database host
Very flexible & allows access to multiple
databases using one driver
Only need to download one driver
But it's another server application to
install and maintain.

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The JDBC type 4 driver converts JDBC
method calls directly into the vendor
specific database protocol and in
between do not need to be converted
any other formatted system so this is the
fastest way to communicate quires to
DBMS and it is completely written in
JAVA because of that this is also known as
the "direct to database Pure JAVA driver".

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Disadvantage:
(1) There is a separate driver needed for
each database at the client side.
(2) Drivers are Database dependent, as
different database vendors use different
network protocols.

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Network Protocol Driver (used for
Network based Applications)
Pure Java Drivers
Use Java networking libraries to talk
directly to database engines
need to
download a new driver for each database
engine.

Type I
“Bridge”

JDBC

Type II
“Native”

Type III
“Middleware”

ODBC

ODBC
Driver

CLI (.lib)

Middleware
Server

Type IV
“Pure”
Alex Chaffee

DriverManager
Driver
Connection
Statement

ResultSet
Copyright © 1997 Alex Chaffee

jdbc:subprotocol:source
 each driver has its own subprotocol
 each subprotocol has its own syntax for
the source
jdbc:odbc:DataSource
• e.g. jdbc:odbc:Northwind

jdbc:msql://host[:port]/database
• e.g. jdbc:msql://foo.nowhere.com:4333/accounting


Loads database drivers, and manages the
connection between the application and
the driver
Connection getConnection
(String url, String user,
String password)
 Connects to given JDBC URL with given
user name and password
 Throws java.sql.SQLException
 returns a Connection object

Translates API calls into operations for a
specific data source


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A Connection represents a session with a specific
database or a session between an application and
a database
Within the context of a Connection, SQL
statements are executed and results are returned.
Can have multiple connections to a database
Also provides “metadata” -- information about the
database, tables, and fields
Also methods to deal with transactions

String url
= "jdbc:odbc:Northwind";
try {
Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver");
Connection con = DriverManager.getConnection(url);
}
catch (ClassNotFoundException e)
{ e.printStackTrace(); }
catch (SQLException e)
{ e.printStackTrace(); }


Statement createStatement()
• returns a new Statement object

PreparedStatement prepareStatement(String
sql)
• returns a new PreparedStatement object

CallableStatement prepareCall(String sql)
• returns a new CallableStatement object

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Why all these different kinds of statements?
Optimization.


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A Statement object is used for executing
a static SQL statement and obtaining the
results produced by it.
An SQL Statement to perform a query or
update operation.


ResultSet executeQuery(String)
• Execute a SQL statement that returns a single

ResultSet.

int executeUpdate(String)
• Execute a SQL INSERT, UPDATE or DELETE

statement. Returns the number of rows changed.

boolean execute(String)
• Execute a SQL statement that may return multiple

results.

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Why all these different kinds of queries?
Optimization.

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A ResultSet provides access to a table of data
generated by executing a Statement.
Logical set of columns and rows returned by
executing an SQL statement
Only one ResultSet per Statement can be open
at once.
The table rows are retrieved in sequence.
A ResultSet maintains a cursor pointing to its
current row of data.
The 'next' method moves the cursor to the next
row.
• you can’t rewind

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boolean next()
• activates the next row
• the first call to next() activates the first row
• returns false if there are no more rows

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void close()
• disposes of the ResultSet
• allows you to re-use the Statement that

created it
• automatically called by most Statement
methods

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Type getType(int columnIndex)
• returns the given field as the given type
• fields indexed starting at 1 (not 0)

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Type getType(String columnName)
• same, but uses name of field
• less efficient

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int findColumn(String columnName)
• looks up column index given column name


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String getString(int columnIndex)
boolean getBoolean(int columnIndex)
byte getByte(int columnIndex)
short getShort(int columnIndex)
int getInt(int columnIndex)
long getLong(int columnIndex)
float getFloat(int columnIndex)
double getDouble(int columnIndex)
Date getDate(int columnIndex)
Time getTime(int columnIndex)
Timestamp getTimestamp(int columnIndex)

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String getString(String columnName)
boolean getBoolean(String columnName)
byte getByte(String columnName)
short getShort(String columnName)
int getInt(String columnName)
long getLong(String columnName)
float getFloat(String columnName)
double getDouble(String columnName)
Date getDate(String columnName)
Time getTime(String columnName)
Timestamp getTimestamp(String columnName)

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In SQL, NULL means the field is empty
Not the same as 0 or “”
In JDBC, you must explicitly ask if a field
is null by calling ResultSet.isNull(column)


Employee ID
1
2
3
4
5

Last Name
Davolio
Fuller
Leverling
Peacock
Buchanan

First Name
Nancy
Andrew
Janet
Margaret
Steven


Connection con =
DriverManager.getConnection(url, "alex",
"8675309");
Statement st = con.createStatement();
ResultSet results = st.executeQuery("SELECT
EmployeeID, LastName, FirstName FROM
Employees");


while (results.next()) {
int id = results.getInt(1);
String last = results.getString(2);
String first = results.getString(3);
System.out.println("" + id + ": " + first
+ " " + last);
}
st.close();
con.close();


SQL type

Java Type

CHAR, VARCHAR, LONGVARCHAR
NUMERIC, DECIMAL
BIT
TINYINT
SMALLINT
INTEGER
BIGINT
REAL
FLOAT, DOUBLE
BINARY, VARBINARY, LONGVARBINARY
DATE
TIME
TIMESTAMP

String
java.math.BigDecimal
boolean
byte
short
int
long
float
double
byte[]
java.sql.Date
java.sql.Time
java.sql.Timestamp


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Times in SQL are notoriously unstandard
Java defines three classes to help
java.sql.Date
• year, month, day

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java.sql.Time

• hours, minutes, seconds

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java.sql.Timestamp

• year, month, day, hours, minutes, seconds,

nanoseconds
• usually use this one

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use executeUpdate if the SQL contains
“INSERT” or “UPDATE”
Why isn’t it smart enough to parse the
SQL? Optimization.
executeUpdate returns the number of
rows modified
executeUpdate also used for “CREATE
TABLE” etc. (DDL)

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Transactions are not explicitly opened
and closed
Instead, the connection has a state called
AutoCommit mode
if AutoCommit is true, then every
statement is automatically committed
default case: true


Connection.setAutoCommit(boolean)
 if AutoCommit is false, then every
statement is added to an ongoing
transaction
 you must explicitly commit or rollback
the transaction using
Connection.commit() and
Connection.rollback()

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Hint: for a large threaded database server, create a
Connection Manager object
It is responsible for maintaining a certain number of
open connections to the database
When your applications need a connection, they ask for
one from the CM’s pool
Why? Because opening and closing connections takes
a long time
Warning: the CM should always setAutoCommit(false)
when a connection is returned


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Prepared Statements
• SQL calls you make again and again
• allows driver to optimize (compile) queries
• created with Connection.prepareStatement()

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Stored Procedures
• written in DB-specific language
• stored inside database
• accesed with Connection.prepareCall()


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Connection:
• DatabaseMetaData getMetaData()

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ResultSet:
• ResultSetMetaData getMetaData()


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What's the number of columns in the
ResultSet?
What's a column's name?
What's a column's SQL type?
What's the column's normal max width in
chars?
What's the suggested column title for use
in printouts and displays?
What's a column's number of decimal
digits?

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Does a column's case matter?
Is the column a cash value?
Will a write on the column definitely
succeed?
Can you put a NULL in this column?
Is a column definitely not writable?
Can the column be used in a where
clause?
Is the column a signed number?
Is it possible for a write on the column to
succeed?
and so on... Copyright © 1997 Alex Chaffee

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What tables are available?
What's our user name as known to the
database?
Is the database in read-only mode?
If table correlation names are supported,
are they restricted to be different from
the names of the tables?
and so on…

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Scrollable result set
Batch updates
Advanced data types
• Blobs, objects, structured types

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Rowsets

• Persistent JavaBeans

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JNDI
Connection Pooling
Distributed transactions via JTS

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In JDBC1.0, result sets could be
navigated in only one direction (forward)
and starting at only one point (first row)
Since JDBC 2.0, the cursor can be
manipulated as if it were a array index
Methods exist for reading both forward
and backward, for starting from any row,
and for testing the current cursor
location.

boolean next ( )
Advances the cursor to the next row.
boolean previous ( ) Moves the cursor back one row.
boolean first ( )
Moves the cursor to the first row.
boolean last ( )
Moves the cursor to the last row.
void beforeFirst ( ) Moves the cursor before the first
row, usually in anticipation of
calling next ( )
void afterLast ( )
Moves the cursor after the last row,
usually in anticipation of
calling previous ( )
boolean
Moves the cursor to the specified
absolute (int row) row. Specifying a negative number
moves the cursor relative to the
end of the result set;

boolean
Moves the cursor forward or
relative (int row) backward the number of rows
specified.
boolean
isBeforeFirst ( )

True if the cursor is before the
first row.

boolean
isAfterLast ( )

True if the cursor is after the
last row.

boolean isFirst ( ) True if the cursor is positioned on
the first row.
boolean isLast ( ) True if the cursor is positioned on
the last row.

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Statement object created with parameters to
indicate specific capabilities
Connection.createStatement() method can have
up to three parameters:
• resultSetType – type of scrolling to be used
• resultSetConcurrency – indicates whether the result

set can be updated
• resultSetHoldability – specifies whether to close
cursors when a commit is done

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Example

• stmt = con.createStatement(

ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);

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Cursor Related Constants
• TYPE_FORWARD_ONLY

 JDBC 1.0-style navigation in which the cursor
starts at the first row and can only move forward.
• TYPE_SCROLL_INSENSITIVE
 All cursor positioning methods are enabled; the
result set doesn’t reflect changes made by others
in the underlying table.
• TYPE_SCROLL_SENSITIVE
 All cursor positioning methods are enabled the
result set reflects changes made by others in the
underlying table.

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Updating Record Sets
• CONCUR_READ_ONLY

 The results set won’t be updatable
• CONCUR_UPDATABLE
 Rows can be added and deleted, and columns
can be updated.
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Closing Cursors
• HOLD_CURSORS_OVER_COMMIT

 Do not close cursors after a commit is done.
• CLOSE_COURSORS_AT_COMMIT
 Close cursors when a commit is done.

Jdbc

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