Slides DBAccess

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22-Jul-12 1Database Prorgaming with Java

Database Programming with Java

JDBC Basics Basic steps in using JDBC Statement

ResultSet

PreparedStatement


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JDBCBasics

JDBC (Java DataBase Connectivity)provides a standard library for

accessing relational databases

JDBC consists of two parts:

o JDBC API, a purely Java-based APIo JDBC Driver Manager,which

communicates with vendor-specific

drivers that perform the real

communication with the database. JDBC classes are in the java.sql

package

Current JDBC version: 3.0


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22-Jul-12 3DatabaseProrgamingwithJava

AdvantagesofJDBC

Continued usage of existing data Vendor independent

Platform independent

Ease of use


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4 types:

Type 1

Type 2

Type 3

Type 4


JDBCDrivertypes


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Type 1: JDBC-ODBC Bridge plus ODBC Driver

This combination provides JDBC access via ODBCdrivers. ODBC binary code -- and in many cases,database client code -- must be loaded on eachclient machine that uses a JDBC-ODBC Bridge.

Example: Sun ODBC


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AdvantagesThe JDBC-ODBC Bridge allows access to almost anydatabase, since the database's ODBC drivers are

already available.

Disadvantages

Since the Bridge driver is not written fully in Java,type 1 drivers are not portable.

A performance issue is. They are the slowest of alldriver types.

The client system requires the ODBC Installation to

use the driver.


Type 1: JDBC-ODBC Bridge plus ODBC Driver


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This type of driver converts JDBC calls into callson the client API for Oracle, Sybase, Informix,

DB2, or other DBMS. Note that, like the bridge

driver, this style of driver requires that some

binary code be loaded on each client machine.


Type 2: A native API partly Java technology


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Advantages

The distinctive characteristic of type 2 jdbc drivers are

that they are typically offer better performance than

the JDBC-ODBC Bridge.

Disadvantages

Native API must be installed in the Client System and

hence type 2 drivers cannot be used for the Internet.

Its not written in Java Language which forms aportability issue.

If we change the Database we have to change the

native api as it is specific to a database


Type 2: A native API partly Java technology


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Type 3 database requests are passed throughthe network to the middle-tier server. The

middle-tier then translates the request to the

database


Type 3: All Java/Net-protocol driver


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Advantages This driver is server-based, so there is no need for

any vendor database library to be present on client

machines.

This driver is fully written in Java and hence

Portable. It is suitable for the web.

There are many opportunities to optimize

portability, performance, and scalability. The net protocol can be designed to make the client

JDBC driver very small and fast to load.




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The type 3 driver typically provides support for

features such as caching (connections, query results,

and so on), load balancing, and advanced system

administration such as logging and auditing. This driver is very flexible allows access to multiple

databases using one driver.

They are the most efficient amongst all driver types.




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Disadvantages

It requires another server application to install and

maintain.

Traversing the recordset may take longer, since the

data comes through the backend server.




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This type of driver converts JDBC calls into the

network protocol used directly by DBMSs,

allowing a direct call from the client machine

to the DBMS server and providing a practicalsolution for intranet access.


Type 4: Direct-to-Database Pure Java Driver


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Advantages Type 4 jdbc drivers are completely written in Java to

achieve platform independence and eliminate

deployment administration issues. It is most suitable

for the web. Type 4 JDBC drivers don't have to translate database

requests to ODBC performance is typically quite

good.

Dont need to install special software on the client

or server.




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DisadvantagesWith type 4 drivers, the user needs a different driver

for each database.




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JDBCDrivertypes(Sumary)


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Basic Steps in using JDBC

1. Load the driver2. Define the connection URL and establish the

connection

3. Create a Statement object

4. Executing the Statement5. Getting data from executing result

6. Process the results.

7. Close the connection


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Loading JDBC drivers

Class.forName("DriverXYZ");o Use Class.forName() to load the Driver classo No need to register with DriverManager.

Some examples.

o Class.forName("oracle.jdbc.driver.OracleDriver");o Class.forName("org.gjt.mm.mysql.Driver");

o Class.forName(com.mysql.jdbc.Driver");

o Class.forName(com.ibm.db2j.jdbc.DB2jDriver");

o Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");o Class.forName(com.microsoft.sqlserver.jdbc.SQLServer

Driver);



Establish the DB connection

Need to know which database to connect too In JDBC you need to specify the URL

o Need username, password

Get a java.sql.Connection object

o Connection con = DriverManager.getConnection(url,user, password);

Examples:o jdbc:oracle:thin:@localhost:1521:orcl

o jdbc:mysql://127.0.0.1:3306/bookso jdbc:sqlserver://localhost:1433;database = schoolManagement;user=sa;password=1234567";



JDBC Statement Object

A Statement object is what sends your SQLstatement to the DBMS

Create a Statement object and then execute it,

supplying appropriate method with the SQL

statement you want to send.o Statement stmt = con.createStatement();

For a SELECT statement, the method to use is

executeQuery.o stmt.executeQuery( SELECT * FROM XXX"); For statements that create or modify tables, the

method to use is executeUpdate.

o stmt.executeUpdate( "INSERT INTO XXX );



ResultSet object

A ResultSet object is a table of data representing adatabase result set, which is usually generated by

executing a statement that queries the database.

You access the data in a ResultSet object through acursor. This cursor is a pointer that points to one

row of data in the ResultSet. Initially, the cursor is

positioned before the first row.



ResultSet type

TYPE_FORWARD_ONLY:The result set cannot be scrolled; its cursor moves forward only, frobefore the first row to after the last row.

TYPE_SCROLL_INSENSITIVE:The result can be scrolled; its cursor can move both forward andbackward relative to the current position, and it can move to anabsolute position.

TYPE_SCROLL_SENSITIVE:The result can be scrolledThe result set reflects changes made to theunderlying data source while the result set remains open.

The default ResultSet type is TYPE_FORWARD_ONLY.



ResultSet Concurrency

The concurrency of a ResultSet object determineswhat level of update functionality is supported.

There are two concurrency levels:

CONCUR_READ_ONLY: The ResultSet object cannot beupdated using the ResultSet interface.

CONCUR_UPDATABLE: The ResultSet object can beupdated using the ResultSet interface.

The default ResultSet concurrency isCONCUR_READ_ONLY.


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ResultSet navigation

Method Descriptionnext() Moves the cursor froward one row from its current position.

previous() Moves the cursor to the previous row in this ResultSet object.

first() Moves the cursor to the first row in this ResultSet object.

last() Moves the cursor to the last row in this ResultSet object.

beforeFirst() Moves the cursor to the front of this ResultSet object, just

before the first row. This method has no effect if the result set

contains no rows.

afterLast() Moves the cursor to the end of this ResultSet object, just after

the last row. This method has no effect if the result set contains

no rows.

getRow() Retrieves the current row number. The first row is number 1, the

second number 2, and so on.


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ResultSet navigation (cont)Method Description

absolute(int row) Moves the cursor to the given row number in this ResultSet object.

Row number is positive, the cursor moves to the given row

number with respect to the beginning of the result set. The first

row is row 1, the second is row 2, and so on.

row number is negative, the cursor moves to an absolute row

position with respect to the end of the result set. For example,

calling the method absolute(-1) positions the cursor on the last

row; calling the method absolute(-2) moves the cursor to the next-

to-last row, and so on.

relative(int rows) Moves the cursor a relative number of rows, either positive

(forward) or negative (backward).

Note: Calling the method relative(1) is identical to calling the

method next() and calling the method relative(-1) is identical to

calling the method previous(). Calling relative(0) is valid, but does

not change the cursor position.


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Methods of returning Scrollable ResultSet

public StatementreateStatement(int resultSetType,int resultSetConcurrency) throws SQLException

public PreparedStatement

prepareStatement(Stringsql, int resultSetType,int resultSetConcurrency) throws SQLException

public CallableStatementprepareCall(Stringsql,

int resultSetType, int resultSetConcurrency) throwsSQLException
http://localhost/var/Program%20Files/Java/docs/api/java/sql/Statement.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/SQLException.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/PreparedStatement.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/lang/String.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/SQLException.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/CallableStatement.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/lang/String.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/SQLException.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/SQLException.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/lang/String.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/CallableStatement.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/SQLException.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/lang/String.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/PreparedStatement.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/SQLException.htmlhttp://localhost/var/Program%20Files/Java/docs/api/java/sql/Statement.html


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Retrieving Column Values from Rows

The ResultSet declares methods (example:getBoolean, getLong, ) for retrieving columnvalues from the current row.

Retrieve values using either the index numberorthe aliasor name of the column.

Columns are numbered from 1.

For maximum portability, result set columns within

each row should be read in left-to-right order


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Updating Rows in ResultSet Objects

With CONCUR_UPDATABLE ResultSet, you canupdate values using updateXXX() method.

Must call the method ResultSet.updateRow toupdate the database.


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Inserting a row

Step 1: Positioning the CursorStatement st =

cn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,

ResultSet.CONCUR_UPDATABLE)

ResultSet rs = st.executeQuery(SELECT NAME, EMPLOEE_

FROM EMPLOYEES);

rs.first();

Step 2: Updating the columns: rs.update

Step 3: inserting a row :rs.insertRow();


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Example: Inserting Rowstry {

stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,

ResultSet.CONCUR_UPDATABLE);

ResultSet uprs = stmt.executeQuery(

"SELECT * FROM " + dbName + ".COFFEES");

uprs.moveToInsertRow();

uprs.updateString("COF_NAME", coffeeName);

uprs.updateInt("SUP_ID", supplierID);

uprs.updateFloat("PRICE", price);

uprs.updateInt("SALES", sales);

uprs.updateInt("TOTAL", total);

uprs.insertRow();uprs.beforeFirst();

} catch (SQLException e ) {


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Deleting a row

Step 1: Positioning the cursor// Move the cursor to the last row of the result set

rs.last();

Step 2: Deleting the row// Deleting the row from the result set

rs.deleteRow();


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Connecting & Querying sample Database

DisplayAuthorso Retrieves the entire authorstable

o Displays the data in a JTextArea


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DisplayAuthors.java

1 // DisplayAuthors.java

2 // Displaying the contents of the authors table.3 importjava.awt.*;5 importjava.sql.*;6 importjava.util.*;7 importjavax.swing.*;89publicclassDisplayAuthors extendsJFrame {1011 // JDBC driver name and database URL12 staticString JDBC_DRIVER = "oracle.jdbc.driver.OracleDriver";13 String DATABASE_URL = "jdbc:oracle:thin:@localhost:1521:orcl";1415 // declare Connection and Statement for accessing16 // and querying database17privateConnection connection;

18privateStatement statement;1920 // constructor connects to database, queries database, processes21 // results and displays results in window22publicDisplayAuthors()23 {24 super( "Authors Table of Books Database");

25


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DisplayAuthors.java26 // connect to database books and query database

27 try{28293032 // load database driver class33 Class.forName( JDBC_DRIVER);34

35 // establish connection to database36 connection = DriverManager.getConnection( DATABASE_URL);3738 // create Statement for querying database39 statement = connection.createStatement();4041 // query database

42 ResultSet resultSet =43 statement.executeQuery( "SELECT * FROM authors");4445 // process query results46 StringBuffer results = newStringBuffer();47 ResultSetMetaData metaData = resultSet.getMetaData();48 intnumberOfColumns = metaData.getColumnCount();

49


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DisplayAuthors.java50 for( inti = 1; i


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DisplayAuthors.java74 // detect problems interacting with the database

75 catch( SQLException sqlException ) {76 JOptionPane.showMessageDialog( null, sqlException.getMessage(),77 "Database Error", JOptionPane.ERROR_MESSAGE );7879 System.exit( 1);80 }8182 // detect problems loading database driver

83 catch( ClassNotFoundException classNotFound ) {84 JOptionPane.showMessageDialog( null, classNotFound.getMessage(),85 "Driver Not Found", JOptionPane.ERROR_MESSAGE);8687 System.exit( 1);88 }89

90 // ensure statement and connection are closed properly91 finally{9293 try{94 statement.close();95 connection.close();96 }97


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DisplayAuthors.java

98 // handle exceptions closing statement and connection

99 catch( SQLException sqlException ) {100 JOptionPane.showMessageDialog( null,101 sqlException.getMessage(), "Database Error",102 JOptionPane.ERROR_MESSAGE );103104 System.exit( 1);105 }106 }

107108 } // end DisplayAuthors constructor109110 // launch the application111publicstaticvoidmain( String args[] )112 {113 DisplayAuthors window = newDisplayAuthors();114window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE);

115 }116117 } // end class DisplayAuthors


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PreparedStatement Object

An object that represents a precompiledSQLstatement.

PreparedStatement object is given an SQL

statement when it is created

When the PreparedStatement is executed, theDBMS can just run the PreparedStatement 's

SQL statement without having to compile it first.

PreparedStatement objects are used more forSQL statements that take parameters.


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PreparedStatement Example

PreparedStatement pstmt = con.prepareStatement("UPDATE authorsSET lastName = ?WHERE authorID = ?");

pstmt.setString(1, John);pstmt.setInt(2, 3);

pstmt.executeUpdate();

Set value John to the first placeholder. Set value 3to the second placeholder.


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