Download Data - Garuda Trainings

JDBC
 Java online Training By Garudatrainings
Register for a Free DEMO
www.garudatrainings.com
[email protected]
 Phone: +1 508-841-6144
JDBC
 JDBC
 JDBC is an alternative to ODBC and ADO that provides database
access to programs written in Java.
 JDBC drivers are available for most DBMS products:
http://java.sun.com/products/jdbc
JDBC
 JDBC
 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
JDBC
 JDBC
 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.
JDBC
 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.
JDBC
 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
JDBC Components
Database Programming Steps
 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
Using JDBC (Continued)
 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();
Using JDBC (Continued)
 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
database
 Create a Connection object:
Connection con =
DriverManager.getConnection(url,
dbUser,dbPassword);
port
Using JDBC (Continued)
 Begin the transaction
con.setTransactionIsolation(
Connection.TRANSACTION_SERIALIZABLE );
con.setAutoCommit( false );
 Create
a statement object
Statement stmt = conn.createStatement();
 Associate SQL with the statement object
String queryString = "create table students "
+ "(name varchar(30), id int, phone
char(9))";
Using JDBC (Continued)
 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
Using JDBC (Continued)
 End transaction
con.commit();
con.rollback();
 Release
resources
con.close();
JDBC Component Interaction
Driver
Manager
Creates
Connection Creates
Statement Creates
ResultSet
SQL
Establish
Link to DB
Driver
Result
(tuples)
Database
Two-Tier Database Access Model
 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
Three-Tier Database Access Model
 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
Type 1 Driver: JDBC-ODBC Bridge
 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".
Type 1 Driver: JDBC-ODBC Bridge
 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
Type 1 Driver: JDBC-ODBC Bridge
 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 PUREJAVA driver available for a particular database.
Architecture Diagram
Type 1 Driver: JDBC-ODBC Bridge
 Process:
Java Application -> JDBC APIs JDBC
Driver Manager —» Type 1 Driver —» ODBC Driver
—> Database library APIs —> Database
 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.
Type 1 Driver: JDBC-ODBC Bridge
 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.
Type 1 Driver: JDBC-ODBC Bridge
 JDBC:ODBC ( mainly for Desktop Applications)
Use bridging technology
Requires installation/configuration on client machines
Not good for Web
Type 2 Driver: Native-API Driver
(Partly Java driver)
 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.
Architecture Diagram
Type 2 Driver: Native-API Driver
(Partly Java driver)
 Process:
Java Application -> JDBC APIs JDBC
Driver Manager —» Type 2 Driver —» Vendor
Client Database library APIs —> Database
 Advantage:
(1) There is no implantation of JDBC-ODBC Bridge so it's faster
than a type 1 driver; hence the performance is better as compare
the type 1 driver
(JDBC-ODBC Bridge).
Type 2 Driver: Native-API Driver
(Partly Java driver)
 Disadvantage
(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.
Type 2 Driver: Native-API Driver
(Partly Java driver)
 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
Type 3 Driver: Network-Protocol Driver (Pure
Java driver for database Middleware)
 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.
Architecture Diagram
Type 3 Driver: Network-Protocol Driver
(Pure Java driver for database Middleware)
 Process
Java Application —> JDBC APIs -> JDBC
Driver Manager —> Type 3 Driver —> Middleware
(Server)—> any Database
 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.
Type 3 Driver: Network-Protocol Driver
(Pure
Java driver for database Middleware)
(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.
Type 3 Driver: Network-Protocol Driver
Java driver for database Middleware)
 Disadvantage:
(1) An Extra layer added, may be time
consuming.
(2) At the middleware develop the database
specific coding, may be increase complexity.
(Pure
Type 3 Driver: Network-Protocol Driver
(Pure
Java driver for database Middleware)
 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.
Type 4 Driver: Native-Protocol Driver
(Pure Java driver directly connected to database)
 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".
Architecture Diagram
Type 4 Driver: Native-Protocol Driver
(Pure Java driver directly connected to database)
 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.
Type 4 Driver: Native-Protocol Driver
(Pure Java driver directly connected to database)
 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.
All JDBC Types Diagram
Type I
“Bridge”
JDBC
Type II
“Native”
Type III
“Middleware”
ODBC
ODBC
Driver
CLI (.lib)
Middleware
Server
Type IV
“Pure”
Alex Chaffee
JDBC Steps
DriverManager
Driver
Connection
Statement
ResultSet
Garudatrainings.com +1 508-841-6144
JDBC URLs
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
Garudatrainings.com +1 508-841-6144
DriverManager
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
Garudatrainings.com +1 508-841-6144
Driver
Translates API calls into operations for a specific data source
Garudatrainings.com +1 508-841-6144
Connection
 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
Obtaining a Connection
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(); }
Garudatrainings.com +1 508-841-6144
Connection Methods
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
 Why all these different kinds of statements?
Optimization.
Garudatrainings.com +1 508-841-6144
Statement
 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.
Garudatrainings.com +1 508-841-6144
Statement Methods
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.
 Why all these different kinds of queries? Optimization.
Garudatrainings.com +1 508-841-6144
ResultSet
 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
ResultSet Methods
 boolean next()
 activates the next row
 the first call to next() activates the first row
 returns false if there are no more rows
 void close()
 disposes of the ResultSet
 allows you to re-use the Statement that created it
 automatically called by most Statement methods
Garudatrainings.com +1 508-841-6144
ResultSet Methods
 Type getType(int columnIndex)
 returns the given field as the given type
 fields indexed starting at 1 (not 0)
 Type getType(String columnName)
 same, but uses name of field
 less efficient
 int findColumn(String columnName)
 looks up column index given column name
Garudatrainings.com +1 508-841-6144
ResultSet Methods











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)
Garudatrainings.com +1 508-841-6144
ResultSet Methods











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)
Garudatrainings.com +1 508-841-6144
isNull
 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)
Garudatrainings.com +1 508-841-6144
Sample Database
Employee ID
Last Name
First Name
1
2
3
4
Davolio
Fuller
Leverling
Peacock
Nancy
Andrew
Janet
Margaret
5
Buchanan
Steven
Garudatrainings.com +1 508-841-6144
SELECT Example
Connection con =
DriverManager.getConnection(url, "alex",
"8675309");
Statement st = con.createStatement();
ResultSet results =
st.executeQuery("SELECT EmployeeID,
LastName, FirstName FROM Employees");
Garudatrainings.com +1 508-841-6144
SELECT Example (Cont.)
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();
Garudatrainings.com +1 508-841-6144
Mapping Java Types to SQL Types
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
Garudatrainings.com +1 508-841-6144
Database Time
 Times in SQL are notoriously unstandard
 Java defines three classes to help
 java.sql.Date
 year, month, day
 java.sql.Time
 hours, minutes, seconds
 java.sql.Timestamp
 year, month, day, hours, minutes, seconds, nanoseconds
 usually use this one
Garudatrainings.com +1 508-841-6144
Modifying the Database
 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)
Garudatrainings.com +1 508-841-6144
Transaction Management
 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
Garudatrainings.com +1 508-841-6144
setAutoCommit
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()
Garudatrainings.com +1 508-841-6144
Connection Managers
 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
Garudatrainings.com +1 508-841-6144
Optimized Statements
 Prepared Statements
 SQL calls you make again and again
 allows driver to optimize (compile) queries
 created with Connection.prepareStatement()
 Stored Procedures
 written in DB-specific language
 stored inside database
 accesed with Connection.prepareCall()
Garudatrainings.com +1 508-841-6144
JDBC Class Diagram

Examples
Check Connection
Print ResultSet
Update Records
Execute Example
Metadata
 Connection:
 DatabaseMetaData getMetaData()
 ResultSet:
 ResultSetMetaData getMetaData()
Garudatrainings.com +1 508-841-6144
ResultSetMetaData
 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?
Garudatrainings.com +1 508-841-6144
ResultSetMetaData









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...
Garudatrainings.com +1 508-841-6144
DatabaseMetaData
 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…
Garudatrainings.com +1 508-841-6144
JDBC 2.0
 Scrollable result set
 Batch updates
 Advanced data types
 Blobs, objects, structured types
 Rowsets
 Persistent JavaBeans
 JNDI
 Connection Pooling
 Distributed transactions via JTS
Scrollable Result Sets
 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.
JDBC 2.0 Navigation Methods for
Scrollable Result Sets
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;
JDBC 2.0 Navigation Methods for
Scrollable Result Sets (contd.)
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.
Creating Scrollable Result Sets
 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
 Example
 stmt = con.createStatement(
ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);
Constants in Result Sets
 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.
Constants in Result Sets (contd.)
 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.
 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.