ec-unit 1b enterprise foundations

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Unit 1

Enterprise Foundations

Part BBalasubba Raman Guruswamy

11 January 2011 1Enterprise ComputingEnterprise Foundations


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Goal to represent business concepts to

Applications within the business

An XML interface for vendors or clients

Web interface for customers

Requirements

Must have minimal proprietary components Platform independent, database independent

Able to integrate new technologies

Must be capable of personlised experience

Internationalisation, Localsation, Accessibilty, Customisation

Must be authoritative, shared source for businessconcepts

Transparent to the user


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Multi-tier typical application


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Stand-alone client


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Web-centric application


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Business-to-business


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JDBC JavaMail

Java API for XML Parsing (JAXP)

Web services APIs


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JDBCTM technology is an API that lets you

access virtually any tabular data source fromthe JavaTM programming language.

Cross-DBMS connectivity to a wide range of SQLdatabases

Access to other tabular data sources, such asspreadsheets or flat files.

http://java.sun.com/products/jdbc/index.html
http://java.sun.com/products/jdbc/index.htmlhttp://java.sun.com/products/jdbc/index.html


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JVM

Application

JDBC API

JDBC Driver

Database

Server

Database

Java Application

Java Core

APIs


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Level 1 - AJDBC-ODBC bridge provides JDBC APIaccess via one or more ODBC drivers.

Level 2 - A native-API partly Java technology-enableddriverconverts JDBC calls into calls on the clientAPI for Oracle, Sybase, Informix, DB2, or otherDBMS.

Level 3 - A net-protocol fully Java technology-enableddrivertranslates JDBC API calls into a DBMS-independent net protocol which is then translatedto a DBMS protocol by a server.

Level 4 - A native-protocol fully Java technology-enabled driverconverts JDBC technology calls intothe network protocol used by DBMSs directly.

http://java.sun.com/products/jdbc/driverdesc.html
http://java.sun.com/products/jdbc/driverdesc.htmlhttp://java.sun.com/products/jdbc/driverdesc.html


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Type 1:

ODBC

Bridge

Java

App

JDBC

API

JDBC

Bridge

Driver

MS

ODBC

Database

Server

Database

Type 2:

NativeDB API

Java

App

JDBC

API

JDBC

Driver

Native API

Library

Native

APIDatabase


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Type 3:

Pure

Java

Java

App

JDBC

API

JDBC

DriverDatabase

Translator

Database

Server

Database

Type 4:

Pure

JavaDirect

Java

App

JDBC

API

JDBC

Driver

Database

Server

Database


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Basic sequence of operations for a program that will

use JDBC to interact with a database:

Load the correct JDBC driver (using the classname)

Open a Connection to the database (using a URL)

Create statements (using the Connection) Execute statements and process results

Close the Connection


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JDBC always refers to databases by URLs.

General structure of a JDBC URL is:

jdbc::[params]

Some common examples:jdbc:odbc:aMSAccessDBjdbc:odbc:oDatabase2;UID=jeffsix;PWD=simplePW

jdbc:mysql://dbserver/myDB?user=jeff&password=easy

jdbc:postgresql://psServer.mycorp.com:1878/myDB

jdbc:sequelink://host5/someDB;uid=bob;password=pop


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There are many methods a program can call

on its valid Connection object. createStatement() method will create a Statement

object that can be used to assemble and run SQLcommands.

preparedStatement() creates an object that isassociated with a predefined SQL command (theStatement object can be used for arbitrary statements and can be reused for other SQL commands)

getMetaData() method will return metadata

associated with the database, including descriptions ofall of the tables in the DB.

prepareCall() method is used to call storedprocedures in the SQL database.


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There are many methods a program can

call on its valid Statement object. executeQuery() method executes a SQL query

statement and returns the results (as a ResultSet)

executeUpdate() method executes a SQL update

(such as UPDATE, INSERT, or DELETE) execute() method executes other, more generic,

SQL statements.

setMaxRows() method allows the program to setthe maximum number of data elements (rows)that can be returned from a query statement.

There are MANY more methods for boththe Connection and Statement classes.


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Performing a query and interacting with

the ResultSet ResultSet queryResults;

theQueryResults = theStatement.executeQuery(

"select distinct dept from instructors");

while(theQueryResults.next()){

System.out.println(Dept:" +

queryResults.getInt(1));

}

theQueryResults.close(); ResultSet objects keep track of their

position internally, starting before the firstrow. You can use next() and other

navigation methods to move through them


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There are multiple methods of extracting datafrom the current row in a ResultSet.

getString() method returns the value of a particularcolumn in the current row as a String.

getInt() method returns the value of a particular column in

the current row as an int. getBoolean() method returns the value of a particularcolumn in the current row as an boolean.

getDouble() method returns the value of a particularcolumn in the current row as an double.

getObject()method returns the value of a particular

column in the current row as an Object.

Two versions of both of these methodsonetakes the column as an integer index, one takesthe columns name as a String.


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There are three types of statement objects

in JDBC programming: Statement - allows the execution of arbitrary

statements on the database.

PreparedStatement - allows the program toexecute the same SQL command repeatedly,while allowing substitutions for particular words orvalues (to make it more useful).

CallableStatement - allows the program toexecute SQL stored procedures, with substitutions

for arguments. A stored procedure is a functionthat is part of, and stored inside, a SQL database(hence the name).


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import java.sql.*;

public class IDQuery {

static String url = "jdbc:mysql://localhost/instructors";

public static void main(String [] args) {

try {

Class.forName("org.gjt.mm.mysql.Driver").newInstance();

Connection theConnection;

PreparedStatement prep_statement;

ResultSet theQueryResults;

theConnection = DriverManager.getConnection(url,jeffsix,arrrr!);

prep_statement =

theConn.prepareStatement("SELECT name,dept FROM instructors WHEREID=?");

for(int i = 0; i < args.length; rs.close(), i++) {

prep_statement.setString(1, args[i]);

theQueryResults = prep_statement.executeQuery();

if (theQueryResults.next())System.out.println(theQueryResults.getString(1) + ","

+ theQueryResults.getString(2));

else System.out.println(Query + i + not found!);

}

prep_Statement.close(); theConnection.close();

} catch (Exception exp) { System.err.println("Execption! - " + exp); }

}}


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CallableStatement calls a SQL stored procedure insidethe DB. The stored procedure is specified upon objectcreation (using the Connections prepareCall()method).

Syntax of this call is

? = call procedurename(?,?) }

for a procedure that takes 2 arguments; returns a value { call procedurename(?,?,?,?) }

for a procedure that takes 4 arguments; does not return avalue

The syntax is

CallableStatement callable;callable = conn.prepareCall("{ call replace(?,?) }");callable.setString(1, oldString);callable.setString(2, newString);int rows_modified = callable.executeUpdate();


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Your program can create a Batch of statements (anyof the three types) and execute that batch on thedatabase all at once

The addBatch() method adds a statement to the currentbatch

The executeBatch() method runs all of the statements in the

batch on the database The clearBatch() method clears the statements from the

batch without running them


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As SQL defines its own datatypes, it is important

to understand the mapping between SQL and Javadatatypes

SQL Java SQL Java--------------------- ------------ -------------BIT boolean NUMERIC BigDecimal

BIGINT long REAL floatBINARY byte[] SMALLINT shortCHAR String TIME TimeDATE Date TIMESTAMPTimestampDOUBLE double TINYINT byteFLOAT float VARBINARYbyte[]

INTEGER int VARCHAR char[]

BLOB Blob REF Ref CLOB Clob STRUCT Struct


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SQLs offer two ways to support storage and

retrieval of binary data in database tables: Binary columns: BINARY/ VARBINARY

- these kinds of columns are suitable for small arrays ofbytes (they are not very memory efficient).

Binary large object columns: BLOB / LONGBLOB

- these kinds of columns are suitable for large arrays ofbytes, but are not supported in all database systems (theyare much more memory efficient).

BLOBs are useful in many databases:

used to store image, audio, signal, or video data

used to store serialized Java objects

suitable for storing entire documents inside databases (asdocuments are really just binary data)


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Storing binary data into the database

Using the SQL INSERT verb, the binary column is set usingeither the setObject() method and passing it a byte arrayor using the setBinaryStream() method and passing it anInputStream (which the JDBC driver will then use to fill inthe columns data field)

Retrieve binary data from the database

Use a normal query, and either getObject() to return a bytearray, getBlob() to return a Blob object, orgetBinaryStream() to get an InputStream which can be

used to read from this data field


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JDBC is a core Java technology that supports access torelational databases and database servers.

JDBC uses the standard Structured Query Language(SQL) for all database interaction.

In order to use JDBC with a particular database, you

must install a driver for the database server you areusing and load that driver in your programs.

Almost all JDBC functionality is accomplished throughthe use of SQL statements, of three kinds Statement,

PreparedStatement, and CallableStatement.


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1. What are the goals and objectives of True EnterpriseSystem ?

2. What is JDBC?

3. Give basic sequence of operations for a program usingJDBC to interact with a database.

4. What is ResultSet in JDC?

5. How does JDBC refer to a database in a program code?Give the syntax.

6. What are the three types of JDBC statement objects?

11 January 2011Enterprise ComputingEnterprise Foundations 28


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1. Give details of different types of JDBC drivers.

2. Give brief note on JDBC Connection Class and JDBCStatement Class.

3. Describe the four methods of extracting data fromcurrent row n a ResultSet.

4. Give s brief note on JDBCs support for binary data in

dstabase tables.

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ec-unit 1b enterprise foundations

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