M12 - JDBC

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Module 12Core Java API: JDBC

Java Course

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Module Objectives

At the end of this module, participants will beable to:

Use JDBC technology and describe its features.

Use Database drivers and describe their

features.

Establish a connection to a database using theConnectionobject.

Create and execute SQL statements in Java and

manipulate data resulting from executed SQL

statements.

Define the concept of Database Access Objects.

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Database Drivers

Database Drivers or JDBCDrivers are required to connect

to different databases. The

JDBC requires different drivers

for each database.

JDBC drivers provide theconnection to the database and

implement the protocol

necessary for sending queries

and retrieving results.

Application

JDBC API

JDBC Driver

Database

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Database Drivers (cont.)

Type 1 JDBC-ODBC Bridge + ODBC Driver Type 2 Native API / Partly Java technology-enabled driver

Type 3 Pure Java Driver for Database Middleware

Type 4 Direct to Database Pure Java Driver

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Retrieving a Connection Object

A Connectionobject defines a connection or session with aspecific database.

It is where SQL statements are executed and results are

returned.

Before a Connectionobject can be used, the

java.sql.Connectionclass has to be imported first.

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Retrieving a Connection Object (cont.)

A database driver can be loaded by using theClass.forName()method.

Syntax : Class.forName(JDBCDriver_Name);

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

A Connectionobject has three (3) important parts:

The URL or location of the data source

The username

The password

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Retrieving a Connection Object (cont.)

A connection can be established by using thegetConnection()method.

Creating a connection by using the URL, username and

password as parameters.

Connection myConnection = DriverManager.getConnection ( URL, username, password );

Creating a connection by using the URL; In this case, the URL

already includes the username and password.

Connection myConnection = DriverManager.getConnection ( URL );

** Refer to the ConnectionSample.java sample code

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Creating Query Statements (cont.)

A Statementis created by using the following syntax:

Syntax : Statement = .createStatement();

Sample : Connection myConn = DriverManager.getConnection();

Statement myStatement = myConn.createStatement();

A Statementneeds to use a Connectionobject to identify

which connection the statement will be associated with.

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Creating Query Statements (cont.)

A Statementcan be executed by using either theexecute(), executeQuery()and executeUpdate()

methods.

Syntax : .executeQuery(SQL Statement goes here);

Sample : Connection myConn = DriverManager.getConnection();

Statement myStatement = myConn.createStatement();

myStatement.executeQuery(Select * from aTable);

** Refer to the StatementSample.java sample code

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Basic SELECT Statement (cont.)

To retrieve data from two or more tables, the column nameshould be appended by the table name.

Syntax:.

Example:

SELECT patients.name, meds.name FROM patients, meds WHERE patients.med_id= meds.med_id;

Aliasing is used to shorten the statement.

Syntax:

.

Example:SELECT a.name, b.name FROM patients a, meds b WHERE a.med_id = b.med_id;

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Basic INSERT Statement

Use the INSERT statement to add data to a specific table:

INSERT INTO

[ ( ) ]

VALUES ()

table- the name of the table where data is to be inserted.

column- the names of the columns in the table to be populated.

value - the corresponding values to be inserted for each column

specified. Note: column is optional. Optional is represented by [ ]

INSERT INTO userVALUES (Luis, Chua)

INSERT INTO user(firstname, lastname) VALUES (Luis, Chua)

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Basic DELETE Statement

Use the DELETE statement to delete rows in a specific table:

DELETE FROM

[WHERE ] ;

table - the name of the table.

condition - identifies the rows to be deleted, which contains

expressions, constraints, sub-queries, and comparison

operators.

DELETE FROM user WHERE firstname = Manny;

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Creating Query Statements

After a Statementhas been executed, it returns different kindsof data depending on the type of execute used.

execute()returns a booleanvalue and is used to execute

SQL statements written as a Stringobject.

executeUpdate()returns an intvalue pertaining to the

number of rows affected and is used to execute DDL SQLstatements.

executeQuery()returns a ResultSetobject and is used to

execute SELECT SQL statements.

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Transactions

Transaction management is vital for operations that modify orupdate the records in the database.

Transaction management allows the application to confirm the

execution of a group of SQL statements by committing the

changes.

Should an exception occur, the transaction can be rolled-backto undo the changes that were made.

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Transactions (cont.)

Setting the Connection.autocommit() field of the Connectionobject to false will prevent the statements from being committed

until an explicit Connection.commit() is executed by the

application.

The Connection.rollback() method can be executed should an

event occur requiring the changes made so far to be undone.

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Using PreparedStatement

PreparedStatementis a Java object, which represents aprecompiled SQL statement.

PreparedStatementis usually used for SQL statements that

take parameters, although it can also execute SQL statements

that have no parameters.

Before a Statement object can be used, thejava.sql.PreparedStatementclass has to be imported

first.

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Using PreparedStatement (cont.)

A PreparedStatementis useful when an SQL statement hasto be executed multiple times.

A PreparedStatementis precompiled, hence it is immediately

executed by the DBMS, unlike Statement,which has to be

compiled first.

Syntax :

PreparedStatement = .prepareStatement(");

Example :Connection myConn = DriverManager.getConnection();

PreparedStatement pStmt = myConn.prepareStatement(Select * from Dogs Where

breed = ?);

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The question mark (?) serves as a wildcard or parameter andcan be replaced with a value.

The wildcard can be replaced by using the appropriate methodsfor a particular data type, including but not limited to:

setString() setInt()

setDouble()

setDate()

** Refer to the PreparedStatementSample.java sample code

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The PreparedStatementobject also has the differentexecution commands as the Statementobject, yielding similar

results.

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Questions and Comments

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Setting up the Database

1. MySQL 5.0 is an Accenture approved OSS. Please read the License

Agreement located in the Appendix section of this module.

2. Install MySQL 5. Refer to MySQL 5 Installation and Configuration

Guide.doc. It will ask you create the root password. Type abcd1234.

3. Install MySQL GUI Tools. Refer to MySQL GUI Tools Installation

Guide.doc.

4. Once installed, open Program Files -> MySQL -> MySQL Administrator.

This will launch the MySQL Authentication UI as shown below.

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Setting up the Database (cont.)

5. Type in the root password entered during installation as the password then

click OK. Once verified, the MySQL Administrator UI will be displayed.

6. In the left pane of the UI, click the Restore option. This will display the

Restore page.

7. Click the Open Backup File button found at the lower right portion of the UI.

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8. In the open file window, browse to the directory where the Eclipse SEF

Workspace archive is extracted.

9. Select the sql file to restore:

\SEF\src\sef\module13\activity\SEF Activity.sql

10. Click Open. This will close the open file window.

11. Once in the Restore page, click Start Restore at the lower right portion of

the UI.

12. A dialog box displaying the progress bar will appear. Click Close once done.

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13. At this point, the activity database containing all the tables and dataneeded in this activity has been successfully created.

14. Closethe MySQL Administrator UI. Click the File Menu and then Close.

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Questions and Comments

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Activity

1) Open Eclipse and navigate to

sef.module13.activity.

2) Take a note of AccountDAO and its

implementing class AccountDAOImpl.

Complete the implementation of

AccountDAOImpl.

3) Run The AccountDAOTest Unit test toverify your results.

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Appendix

MySQL Version : 5.0

License : http://www.opensource.org/licenses/gpl-license.php
http://www.opensource.org/licenses/gpl-license.phphttp://www.opensource.org/licenses/gpl-license.phphttp://www.opensource.org/licenses/gpl-license.phphttp://www.opensource.org/licenses/gpl-license.php

M12 - JDBC

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