JDBC_Session02

8/8/2019 JDBC_Session02

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Slide 1 of 39Session 2Ver. 1.0

JDBC

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

Objectives


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JDBC

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 statementsto query and modify the data in a table.

Is compiled and prepared only once by JDBC. The futureinvocation 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.

Create Applications Using the PreparedStatement Object


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JDBC

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, orDELETE and returns the count of the

rows affected.

boolean execute(): Executes an SQL statement and

returns a boolean value.

Methods of the PreparedStatement Interface


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JDBC

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 = ?");

Methods of the PreparedStatement Interface (Contd.)


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JDBC

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();

Methods of the PreparedStatement Interface (Contd.)


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JDBC

The code snippet to retrieve books written by an author fromthe 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();

Retrieving Rows


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JDBC

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 =

con.prepareStatement(str);

ps.setString(1, a001");

ps.setString(2, "Abraham White");

int rt=ps.executeUpdate();

Inserting Rows


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JDBC

The code snippet to modify the state to CA where city is

Oakland in the Authors table using thePreparedStatement object is:

String str = "UPDATE Authors SET state= ?

WHERE city= ? ";PreparedStatement ps =


ps.setString(1, "CA");

ps.setString(2, "Oakland");


Updating and Deleting Rows


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JDBC

The code snippet to delete a row from the Authors table

where authors name is Abraham White using thePreparedStatement object is:

String str = "DELETE FROM Authors WHERE

au_name= ? ";PreparedStatement ps =


ps.setString(1, "Abraham White");


Updating and Deleting Rows (Contd.)


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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()


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JDBC

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.

Demonstration


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JDBC

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

Demonstration (Contd.)


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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.



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JDBC

Solution:

To solve the problem, you need to perform the following tasks:

1. Code the application.

2. Compile and execute the application.



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JDBC

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.

ManagingDatabase Transactions


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JDBC

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);

ManagingDatabase Transactions (Contd.)


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JDBC

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.

Committing a Transaction


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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.

Implementing Batch Updates in JDBC


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JDBC

The Statement orPreparedStatement 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 toa database for processing and returns the total number of the

rows updated.

void clearBatch(): Removes the SQL statements from

the batch.

Implementing Batch Updates in JDBC (Contd.)


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JDBC

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,TatePublishing')");

stmt.addBatch("INSERT INTO Publishers

(pub_id, pub_name) VALUES (p002, Publish

America')");

The SQL statements in a batch are processed in the order inwhich the statements appear in a batch.

The method call to execute a batch of SQL statements is:

int[] updcount=stmt.executeBatch();

Implementing Batch Updates in JDBC (Contd.)


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JDBC

The batch update operations can throw two types of

exceptions:

SQLException

BatchUpdateException

The BatchUpdateException class is derived from theSQLException class.

Exception Handling in Batch Updates


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JDBC

The SQLException is thrown by the JDBC API methods,

addBatch() orexecuteBatch(), 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 theexception.

Exception Handling in Batch Updates (Contd.)


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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 thePreparedStatement interface.

Creating and Calling Stored Procedures in JDBC


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JDBC

Can be created using the CREATE PROCEDURE SQL

statement in JDBC applications.

Are of two types:

Parameterized

Non-parameterized

Creating Stored Procedures


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JDBC

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 storedprocedure.

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.

Creating Stored Procedures (Contd.)


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JDBC

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 };

Calling a Stored Procedure Without Parameters


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JDBC

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 (?) };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:

.setInt();

Calling a Stored Procedure with Parameters (Contd.)


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JDBC

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)

Calling a Stored Procedure with Parameters (Contd.)


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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 interfaceResultSetMetaData interface

Using Metadata in JDBC


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JDBC

The DatabaseMetaData interface provides the methods that

enable you to determine the properties of a database or

RDBMS.

An object ofDatabaseMetaData is created using the

getMetaData() method of the Connection interface.The method call to create an object of theDatabaseMetaData interface is:

DatabaseMetaData dm=con.getMetaData();

Using the DatabaseMetadata Interface


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JDBC

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 ResultSetMetaDatainterface.

The method call to create an object of theResultSetMetaData interface:

ResultSetMetaData rm=rs.getMetaData();

Using the ResultMetadata Interface


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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


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JDBC

Problem Statement:

The Manager ofNew 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.

Demonstration


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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.



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JDBC

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 successfullyexecuted.

If the setAutoCommit() method is set to true the database

operations performed by the SQL statements are automatically

committed in the database.

Summary


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JDBC

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 sameConnection object.

Batch update operations can throw two types of exceptions,

SQLException and BatchUpdateException.

The SQLException is thrown when the database accessproblem occurs. The SQLException is also thrown when a

SELECT statement that returns a ResultSet object is executed

in a batch.

Summary (Contd.)


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JDBC

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

Summary (Contd.)

JDBC_Session02

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