Jdbc session02

JDBC
Objectives

In this session, you will learn to:
Create applications using the PreparedStatement object
Manage database transactions
Perform batch updates
Create and call stored procedures in JDBC
Use metadata in JDBC

Ver. 1.0 Session 2 Slide 1 of 39

JDBC
Create Applications Using the PreparedStatement Object

The PreparedStatement interface is derived from the
Statement interface and is available in the java.sql
package.
The PreparedStatement object:
Allows you to pass runtime parameters to the SQL statements
to query and modify the data in a table.
Is compiled and prepared only once by JDBC. The future
invocation of the PreparedStatement object does not
recompile the SQL statements.
Helps in reducing the load on the database server and thus
improving the performance of the application.


JDBC
Methods of the PreparedStatement Interface

• The PreparedStatement interface inherits the following
methods to execute SQL statements from the Statement
interface:
– ResultSet executeQuery(): Executes a SELECT
statement and returns the result in a ResultSet object.
– int executeUpdate(): Executes an SQL statement,
INSERT, UPDATE, or DELETE and returns the count of the
rows affected.
– boolean execute(): Executes an SQL statement and
returns a boolean value.


JDBC
Methods of the PreparedStatement Interface (Contd.)

• The prepareStatement() method of the Connection
object is used to submit parameterized query to a database.
• The SQL statement can contain ‘?’ symbol as placeholders
that can be replaced by input parameters at runtime. For
example:
stat=con.prepareStatement("SELECT * FROM
Authors WHERE au_id = ?");


JDBC
Methods of the PreparedStatement Interface (Contd.)

The value of each ‘?’ parameter is set by calling an
appropriate setXXX() method, where xxx is the data type of
the parameter. For example:
stat.setString(1,“a001");
ResultSet result=stat.executeQuery();


JDBC
Retrieving Rows

• The code snippet to retrieve books written by an author
from the books table using the PreparedStatement
object is:
String str = "SELECT * FROM books WHERE
au_id = ?";
PreparedStatement ps=
con.prepareStatement(str);
ps.setString(1, “a001");
ResultSet rs=ps.executeQuery();


JDBC
Inserting Rows

The code snippet to create a PreparedStatement object
that inserts a row into authors table by passing authors data
at run time is:
String str = "INSERT INTO Authors(au_id,
au_name) VALUES (?, ?)";
PreparedStatement ps =
ps.setString(1, “a001");
ps.setString(2, "Abraham White");
int rt=ps.executeUpdate();


JDBC
Updating and Deleting Rows

The code snippet to modify the state to CA where city is
Oakland in the Authors table using the
PreparedStatement object is:
String str = "UPDATE Authors SET state= ?
WHERE city= ? ";
ps.setString(1, "CA");
ps.setString(2, "Oakland");


JDBC
Updating and Deleting Rows (Contd.)

• The code snippet to delete a row from the Authors table
where author’s name is Abraham White using the
PreparedStatement object is:
String str = "DELETE FROM Authors WHERE
au_name= ? ";
ps.setString(1, "Abraham White");


JDBC
Just a minute

Name the three methods of the PreparedStatement
Interface.

Answer:
The three methods of the PreparedStatement Interface are:
1. ResultSet executeQuery()
2. int executeUpdate()
3. Boolean execute()


JDBC
Demonstration

Problem Statement:
The management of the City Library has decided to
computerize the book inventory. You have been asked to
create the Publisher Information application that has an
interactive user interface. The application should allow the user
to add the details of the new publishers to the publishers table.


JDBC
Demonstration (Contd.)

A sample of the user interface is shown in the following fugure.


JDBC

To insert information about a new publisher in the publishers
table:
1. Specify the id for a publisher in the ID textbox and publishers
details, such as name, phone, address, city, state, and zip in the
respective text boxes.
2. Click the Insert button to insert information.
3. To exit from the application, click the Exit button.


JDBC

Solution:
To solve the problem, you need to perform the following tasks:
1. Code the application.
2. Compile and execute the application.


JDBC
Managing Database Transactions

A transaction:
Is a set of one or more SQL statements that are executed as a
single unit.
Is complete only when all the SQL statements in a transaction
execute successfully.
Maintains consistency of data in a database.


JDBC
Managing Database Transactions (Contd.)

JDBC API provides support for transaction management.
The database transactions can be committed in two ways in
the JDBC applications:
– Implicit: The Connection object uses the auto-commit mode
to execute the SQL statements implicitly.
– Explicit: The auto-commit mode is set to false to commit the
transaction statement explicitly. The method call to set the
auto-commit mode to false is:
con.setAutoCommit(false);


JDBC
Committing a Transaction

• The commit() method is used to reflect the changes made
by the transactions in a database.
• The rollback() method is used to undo the changes
made in the database after the last commit operation.
• You need to explicitly invoke commit() and rollback()
methods.


JDBC
Just a minute

How can you commit a transaction explicitly?

Answer:
You can commit a transaction explicitly by setting auto-commit
mode to false.


JDBC
Implementing Batch Updates in JDBC

A batch:
Is a group of update statements that are sent to a database to
be executed as a single unit.
Reduces network calls between the application and the
database.
Is a more efficient way as compared to the processing of a
single SQL statement.


JDBC
Implementing Batch Updates in JDBC (Contd.)

• The Statement or PreparedStatement interface
provides the following methods to create and execute a
batch of SQL statements:
– void addBatch(): Adds an SQL statement to a batch.
– int executeBatch(): Sends a batch of SQL statements to
a database for processing and returns the total number of the
rows updated.
– void clearBatch(): Removes the SQL statements from
the batch.


JDBC
Implementing Batch Updates in JDBC (Contd.)

The code snippet to create a batch of SQL statements is:
con.setAutoCommit(false);
Statement stmt=con.createStatement();
stmt.addBatch("INSERT INTO Publishers
(pub_id, pub_name) VALUES (‘p001’,‘Tate
Publishing')");
stmt.addBatch("INSERT INTO Publishers
(pub_id, pub_name) VALUES (‘p002’, ‘Publish
America')");
The SQL statements in a batch are processed in the order
in which the statements appear in a batch.
The method call to execute a batch of SQL statements is:
int[] updcount=stmt.executeBatch();


JDBC
Exception Handling in Batch Updates

The batch update operations can throw two types of
exceptions:
SQLException
BatchUpdateException
– The BatchUpdateException class is derived from the
SQLException class.


JDBC
Exception Handling in Batch Updates (Contd.)

• The SQLException is thrown by the JDBC API methods,
addBatch() or executeBatch(), when problem occurs
while accessing a database.
• The BatchUpdateException exception is thrown when
the SQL statements in the batch cannot be executed due to:
Presence of illegal arguments in the SQL statement.
Absence of the database table from which you need to retrieve
data.
• The BatchUpdateException uses an array of the update
count to identify the SQL statement that throws the
exception.


JDBC
Creating and Calling Stored Procedures in JDBC

• The java.sql package provides the
CallableStatement interface that contains various
methods to enable you to call the stored procedures from a
database.
• The CallableStatement interface is derived from the
PreparedStatement interface.


JDBC
Creating Stored Procedures

• Can be created using the CREATE PROCEDURE SQL
statement in JDBC applications.
• Are of two types:
Parameterized
Non-parameterized


JDBC
Creating Stored Procedures (Contd.)

A parameterized stored procedure can accept one or
multiple parameters.
A parameter of a stored procedure can take any of these
forms:
– IN: Refers to the argument that you pass to a stored
procedure.
– OUT: Refers to the return value of a stored procedure.
– INOUT: Combines the functionality of the IN and OUT
parameters. The INOUT parameter enables you to pass an
argument to a stored procedure. The same parameter can also
be used to store a return value of a stored procedure.


JDBC
Calling a Stored Procedure Without Parameters

• The Connection interface provides the prepareCall()
method that is used to create the CallableStatement
object to call a stored procedure.
• The prepareCall() has the following three forms:
CallableStatement prepareCall(String str)
CallableStatement prepareCall(String str, int
resSetType, int resSetConcurrency)
CallableStatement prepareCall(String str, int
resSetType, int resSetConcurrency, int
resSetHoldability)
The syntax to call a stored procedure without parameters is:
{ call <procedure_name> };


JDBC
Calling a Stored Procedure with Parameters

The SQL escape syntax is a standard way to call a stored
procedure from a Relational Database Management System
(RDBMS) and is independent of the RDBMS.
There are two forms of the SQL escape syntax, one that
contains result parameter and one that does not.
The syntax of the SQL escape syntax is:
{[? =] call <procedure_name>
[<parameter1>,<parameter2>, ...,
<parameterN>]}


JDBC
Calling a Stored Procedure with Parameters (Contd.)

• The placeholders are used to represent the IN, OUT, and
INOUT parameters of a stored procedure in the procedure
call.
• The syntax to call a stored procedure with parameters is:
{ call <procedure_name>(?) };
• You need to set the value of the IN parameters using the
set methods before the CallableStatement object is
executed.
• The syntax to set the value of the IN parameter is:
<CallableStatement_object>.setInt(<value>);


JDBC
Calling a Stored Procedure with Parameters (Contd.)

• If the stored procedure contains OUT and INOUT
parameters, these parameters should be registered with the
corresponding JDBC types.
• The registerOut() method is used to register the
parameters.
• The prototypes of the registerOut() method are:
registerOut(int index, int stype)
registerOut(int index, int stype, int scale)


JDBC
Using Metadata in JDBC

Metadata is the information about data, such as structure
and properties of table.
The metadata of the employee table includes following
information:
Names of the columns.
Data type of each column.
Constraints to enter data values in the table columns.
JDBC API provides the following two metadata interfaces to
retrieve the information about the database and result set:
– DatabaseMetaData interface
– ResultSetMetaData interface


JDBC
Using the DatabaseMetadata Interface

• The DatabaseMetaData interface provides the methods that
enable you to determine the properties of a database or
RDBMS.
• An object of DatabaseMetaData is created using the
getMetaData() method of the Connection interface.
• The method call to create an object of the
DatabaseMetaData interface is:
DatabaseMetaData dm=con.getMetaData();


JDBC
Using the ResultMetadata Interface

The ReultSetMetaData Interface contains various
methods that enable you to retrieve information about the
data in a result set.
The ResultSet interface provides the getMetaData()
method to create an object of the ResultSetMetaData
interface.
The method call to create an object of the
ResultSetMetaData interface:
ResultSetMetaData rm=rs.getMetaData();


JDBC
Just a minute

What are the metadata interfaces used to retrieve
information about the database and result set?

Answer:
The metadata interfaces used to retrieve information about the
database and result set are:
1. DatabaseMetaData interface
2. ResultSetMetaData interface


JDBC
Demonstration

Problem Statement:
The Manager of New Publishers publishing company,
sometimes require the information about the tables of the
database used by the company. He is not familiar with the SQL
statements, therefore, he has asked you to create an
application to determine the total number of columns and the
data types of the columns of a given table. The table name has
to be specified at the run time.


JDBC

Solution:
To solve the Preceding problem, perform the following tasks:
1. Code the application.
2. Pass the command line argument.
3. Compile and execute the application.


JDBC
Summary

In this session, you learned that:
– The PreparedStatement object allows you to pass runtime
parameters to the SQL statements using the placeholders.
– There can be multiple placeholders in a single SQL statement.
An index value is associated with each placeholder depending
upon the position of the placeholder in the SQL statement.
– The placeholder stores the value assigned to it until the value
is explicitly changed.
– A transaction is a set of one or more SQL statements that are
executed as a single unit. A transaction is complete only when
all the SQL statements in a transaction are successfully
executed.
– If the setAutoCommit() method is set to true the database
operations performed by the SQL statements are automatically
committed in the database.


JDBC
Summary (Contd.)

The commit() method reflects the changes made by the SQL
statements permanently in the database.
The rollback() method is used to undo the effect of all the
SQL operations performed after the last commit operation.
A batch is a group of update statements that are sent to a
database to be executed as a single unit. You send the batch
to a database as a single request using the same
Connection object.
Batch update operations can throw two types of exceptions,
SQLException and BatchUpdateException.
The SQLException is thrown when the database access
problem occurs. The SQLException is also thrown when a
SELECT statement that returns a ResultSet object is executed
in a batch.


JDBC
Summary (Contd.)

The BatchUpdateException is thrown when the SQL
statement in the batch cannot be executed due to the problem
in accessing the specified table or presence of illegal
arguments in the SQL statement.
The CallableStatement interface contains various methods
that enable you to call the stored procedures from a database.
Metadata is the information about data, such as structure and
properties of table
JDBC API provides two metadata interfaces to retrieve the
information about the database and result set,
DatabaseMetaData and ResultSetMetaData


Jdbc session02

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