241-301 Lab: JDBC 1

Computer Engineering Lab Computer Engineering Lab IIIIII

ObjectiveObjective– to give some background on JDBC to help wito give some background on JDBC to help wi

th the lab exercises th the lab exercises

241-301, Semester 1, 2009-2010

Introduction to Java Database Connectivity (JDBC)

241-301 Lab: JDBC 2

OverviewOverview

1. 1. What is JDBC?What is JDBC?

2. 2. The JDBC-ODBC BridgeThe JDBC-ODBC Bridge

3.3. Four Kinds of JDBC DriversFour Kinds of JDBC Drivers

4.4. JDBC PseudocodeJDBC Pseudocode

5.5. SimpleJDBCSimpleJDBC.java.java

Continued

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6.6. Meta DataMeta Data

7.7. Books.Books.accdbaccdb as an ODBC as an ODBC Data SourceData Source

8.8. TableTabless in in Books.Books.accaccdbdb

9.9. More InformationMore Information

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1. What is JDBC?1. What is JDBC?

JDBC is an interface which allows Java codJDBC is an interface which allows Java code to execute SQL statements inside relationae to execute SQL statements inside relational databasesl databases– the databases must follow the ANSI SQL-2 stanthe databases must follow the ANSI SQL-2 stan

darddard

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JDBC in UseJDBC in Use

Java program

connectivity

data processingutilities

JDBCdriver

for Oracle

driverfor Sybase

jdbc-odbcbridge

odbcdriver

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2. The JDBC-ODBC Bridge2. The JDBC-ODBC Bridge

ODBC (Open Database Connectivity) is a ODBC (Open Database Connectivity) is a Microsoft standard from the mid 1990’s.Microsoft standard from the mid 1990’s.

It is an API that allows C/C++ programs to It is an API that allows C/C++ programs to execute SQL inside databasesexecute SQL inside databases

ODBC is supported by many products.ODBC is supported by many products.

Continued

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The JDBC-ODBC bridge allows Java code tThe JDBC-ODBC bridge allows Java code to use the C/C++ interface of ODBCo use the C/C++ interface of ODBC– it means that JDBC can access many different dit means that JDBC can access many different d

atabase productsatabase products

The layers of translation (Java --> C --> SQThe layers of translation (Java --> C --> SQL) can slow down execution.L) can slow down execution.

Continued

241-301 Lab: JDBC 8

The JDBC-ODBC bridge comes The JDBC-ODBC bridge comes freefree with t with the JDK:he JDK:– called called sun.jdbc.odbc.JdbcOdbcDriversun.jdbc.odbc.JdbcOdbcDriver

The ODBC driver for Microsoft Access coThe ODBC driver for Microsoft Access comes with MS Officemes with MS Office– so it is easy to connect Java and Accessso it is easy to connect Java and Access

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3. Four Kinds of JDBC Driver3. Four Kinds of JDBC Driver

1. JDBC-ODBC Bridge1. JDBC-ODBC Bridge– translate Java to the ODBC APItranslate Java to the ODBC API

2. Native API2. Native API– translate Java to the database’s own APItranslate Java to the database’s own API

Continued

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3. Native Protocol3. Native Protocol– use Java to access the database more directly ususe Java to access the database more directly us

ing its low level protocolsing its low level protocols

4. Net Protocol4. Net Protocol– use Java to access the database via networking use Java to access the database via networking

middleware (usually TCP/IP)middleware (usually TCP/IP)– required for networked applicationsrequired for networked applications

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JDBC DriversJDBC Drivers

A searchable list of drivers (freeware, shareA searchable list of drivers (freeware, shareware, and commercial) can be found at:ware, and commercial) can be found at:

http://developers.sun.com/product/jdbc/drivershttp://developers.sun.com/product/jdbc/drivers

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4. JDBC PseudoCode4. JDBC PseudoCode

All JDBC programs do the following:All JDBC programs do the following:– 1) load the JDBC driver1) load the JDBC driver

– 2) Specify the name and location of the databas2) Specify the name and location of the database being usede being used

– 3) Connect to the database with a 3) Connect to the database with a ConnectionConnection objectobject

Continued

241-301 Lab: JDBC 13

– 4) Execute a SQL query using a 4) Execute a SQL query using a StatementStatement ob objectject

– 5) Get the results in a 5) Get the results in a ResultSetResultSet object object

– 6) Finish by closing the 6) Finish by closing the ResultSetResultSet, , StatemenStatemen

tt and and ConnectionConnection objects objects

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4.1. Pseudocode as a Diagram4.1. Pseudocode as a Diagram

DriveManager Connection Statement ResultSetcreates creates creates

Driver

SQL

SQL

data

data

make linkto driver

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4.2. DriveManager4.2. DriveManager

It is responsible for establishing the connectiIt is responsible for establishing the connection to the database through the driver.on to the database through the driver.

e.g.e.g.Class.forName(

"sun.jdbc.odbc.JdbcOdbcDriver");Connection conn = DriveManager.getConnection(url);

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4.3. Name the Database 4.3. Name the Database

The name and location of the database is giThe name and location of the database is given as a URLven as a URL– the details of the URL vary depending on the tythe details of the URL vary depending on the ty

pe of database that is being usedpe of database that is being used

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ODBC Database URLODBC Database URL

jdbc:odbc: //host.domain.com: 2048 /data/filejdbc:odbc: //host.domain.com: 2048 /data/file

The commsprotocol

The machineholding the database.

The portused for the connection.

The path tothe databaseon the machine

e.g. jdbc:odbc:Books

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4.4. Statement Object4.4. Statement Object

The The StatementStatement object provides a ‘workspace’ object provides a ‘workspace’ where SQL queries can be created, executed, anwhere SQL queries can be created, executed, and results collected.d results collected.

e.g.e.g.Statement st = Statement st =

conn.createStatement():conn.createStatement():ResultSet rs = st.executeQuery(ResultSet rs = st.executeQuery(

“ select * from Authors” );“ select * from Authors” );::

st.close();st.close();

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4.5. ResultSet Object4.5. ResultSet Object

Stores the results of a SQL query.Stores the results of a SQL query.

A A ResultSetResultSet object is similar to a ‘table object is similar to a ‘table’ of answers, which can be examined by ’ of answers, which can be examined by moving a ‘pointer’ (cursor).moving a ‘pointer’ (cursor).

Continued

241-301 Lab: JDBC 20

Cursor operations:Cursor operations:– first()first(),, last() last(), , next()next(), , previous()previous(), etc., etc.

Typical code:Typical code:while( rs.next() ) {while( rs.next() ) { // process the row; // process the row;}}

23

5

17

98

John

Mark

Paul

Peter

cursor

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5. 5. SimpleJDBCSimpleJDBC.java.java// SimpleJDBC.java// Displays the firstnames and lastnames// of the Authors table in the Books db.

import java.sql.*;

public class SimpleJDBC {

public static void main(String[] args) { // The URL for the Books database.

// ’Protected' by a login and password. String url = "jdbc:odbc:Books"; String username = "anonymous"; String password = "guest";

:

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try { // load the JDBC-ODBC Bridge driver

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

// connect to db using DriverManager Connection conn =

DriverManager.getConnection( url, username, password );

// Create a statement object Statement statement = conn.createStatement();

// Execute the SQL query

ResultSet rs = statement.executeQuery( "SELECT lastName, firstName FROM Authors" );

:

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// Print the result set while( rs.next() )

System.out.println(

rs.getString("lastName") + ", " + rs.getString("firstName") );

// Close down statement.close(); conn.close(); }

:

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catch ( ClassNotFoundException cnfex ) { System.err.println( "Failed to load JDBC/ODBC driver." ); cnfex.printStackTrace(); System.exit( 1 ); // terminate program }

catch ( SQLException sqlex ) { System.err.println( sqlex ); sqlex.printStackTrace(); }

} // end of main()

} // end of SimpleJDBC class

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Section 7not done.

Section 7now done.

OutputOutput

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5.1. Username & Password5.1. Username & Password

The database’s link to the outside (e.g. its OThe database’s link to the outside (e.g. its ODBC interface) must be configured to have DBC interface) must be configured to have a login and passworda login and password– details for ODBC are given laterdetails for ODBC are given later

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5.2. Accessing a ResultSet5.2. Accessing a ResultSet

The The ResultSetResultSet class contains many metho class contains many methods for accessing the value of a column of thds for accessing the value of a column of the current rowe current row– can use the column name or positioncan use the column name or position– e.g. get the value in the lastName column:e.g. get the value in the lastName column:

rs.getString("lastName")

Continued

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The ‘tricky’ aspect is that the values are SQThe ‘tricky’ aspect is that the values are SQL data, and so must be converted to Java tyL data, and so must be converted to Java types/objects.pes/objects.

There are many methods for accessing/convThere are many methods for accessing/converting the data, e.g.erting the data, e.g.– getString(), getDate(), getInt(), getgetString(), getDate(), getInt(), getFloat(), getObject()Float(), getObject()

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6. Meta Data6. Meta Data

Meta data is the information Meta data is the information aboutabout the datab the database:ase:– e.g. the number of columns, the types of the cole.g. the number of columns, the types of the col

umnsumns– meta data is the meta data is the schemaschema information information

ID Name Course Mark

007 James Bond Shooting 99

008 Aj. Andrew Kung Fu 1

meta data

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6.1. Accessing Meta Data6.1. Accessing Meta Data

The The getMetaData()getMetaData() method can be used o method can be used on a n a ResultSetResultSet object to create its meta dat object to create its meta data object.a object.

e.g.e.g.ResultSetMetaData md = ResultSetMetaData md =

rs.getMetaData();rs.getMetaData();

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6.2. Using Meta Data6.2. Using Meta Data

int numCols = int numCols = md.md.getColumnCount();getColumnCount();

for (int i = 0; i <= numCols; i++) {for (int i = 0; i <= numCols; i++) { if (md.getColumnType(i) == if (md.getColumnType(i) ==

Types.CHAR)Types.CHAR) System.out.println( System.out.println(

md.getColumnName(i) )md.getColumnName(i) )}}

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6.3. More Meta Data Methods6.3. More Meta Data Methods

getTableName()getTableName() getPrecision()getPrecision()

– number of decimal digits in the columnnumber of decimal digits in the column isSigned()isSigned()

– returns true if column has signed numbersreturns true if column has signed numbers isCurrency()isCurrency() etc.etc.

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7. Books.7. Books.accaccdb as an ODBC Data Sourcedb as an ODBC Data Source

1. Click on1. Click on“Data“Data Sources Sources ((ODBCODBC)”)” in in “Administrative “Administrative Tools” folder in Tools” folder in tthe Controlhe ControlPanel.Panel.

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2. Press “Add’ to 2. Press “Add’ to add a data source add a data source and select and select Microsoft Access Microsoft Access Driver (*.mdbDriver (*.mdb,,*.accdb*.accdb). ). Press “Finish”.Press “Finish”.

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3. Type in a 3. Type in a source name, descriptiosource name, description, n, and press “Select” and press “Select” to browse to set to browse to set the path to the the path to the Books.Books.accaccdb db oror Books.mdb Books.mdb file.file.

Now click onNow click on“Advanced”.“Advanced”.

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4. Type in a username 4. Type in a username and password (guest).and password (guest).Click “Ok”Click “Ok”

241-301 Lab: JDBC 37

Two Access Database TypesTwo Access Database Types

In Access 2007, the standard database file In Access 2007, the standard database file format is ".accdb"format is ".accdb"– use use Books.accdbBooks.accdb if you have Access 2007 on your if you have Access 2007 on your

machinemachine

In earlier versions of Access (e.g. Access In earlier versions of Access (e.g. Access 2003), the file format was ".mdb"2003), the file format was ".mdb"– use use Books.mdbBooks.mdb if you have an earlier version of if you have an earlier version of

Access on your machineAccess on your machine

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8. Table8. Tabless in Books. in Books.accaccdbdb(and Books.mdb)

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9. More Information9. More Information

Ivor Horton’s Beginning Java 2, JDK 5 Edition, Ivor Horton’s Beginning Java 2, JDK 5 Edition, Wiley Publishing, 2005Wiley Publishing, 2005Chapters Chapters 24 24 and and 25 (starts on p.1306)25 (starts on p.1306)

Advanced Java 2 Platform: How to Program Advanced Java 2 Platform: How to Program Deitel & Deitel, Prentice-Hall, Deitel & Deitel, Prentice-Hall, 20012001Chapter Chapter 88

http://java.coe.psu.ac.th/ForMember/

Continued

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Current Information:Current Information:http://java.sun.com/javase/technologies/database/index.jsp

The Java Documentation and tutorialThe Java Documentation and tutorial– http://java.sun.com/docs/books/tutorial/

– the the JDBC Database Access JDBC Database Access ‘trail’ is very good‘trail’ is very good