JDBC

by Jon Pearce

DBase Concepts

Table

Row*

1

Field

*1

1

*

1*

DBMSDataBase

*

1

*

1* 1* 1

< manages

Terms

• Table

• Row/Entity

• Column/Field/Attribute

• Key/Primary Key/Foreign Key

Entity-Relation Diagram

Person

OID

FIRST

LAST

ADDRESS

PHONE

Phone

OID

AREA

NUMBER

Address

OID

STREET

CITY

STATE

1

*

*

1

Person Table

OID FIRST LAST ADDRESS PHONE

500 Bill Ding 282 150

501 Carl LaFong 283 151

Address Table

OID STREET CITY STATE

282123 Sesame

NYC NY

28377 Sunset

LA CA

Phone Table

OIDAREA CODE

NUMBER

150 212 555-4321

151 213 333-5245

SQL

• SELECT-FROM-WHERE

• INSERT INTO

• UPDATE

• DELETE-FROM

Select

SELECT field1, field2, field3 ... FROM table1, table2, table3 ... WHERE condition

Projection

SELECT first, last FROM Person

Selection

SELECT * FROM Person WHERE last LIKE 'D%'

Join

SELECT * FROM Person, Address WHERE Person.Address = Address.OID

Insert

INSERT INTO table (field, field, ...) VALUES (value, value, ...)

Update

UPDATE table SET field = value, ... WHERE condition

Delete

DELETE FROM table WHERE condition

Cloudview

java.sql

Connection

createStatement()commit()rollback()

<<Interface>>

java.xml

DriverManager

getDriver()Driver

<<Interface>>

connect()

<<creates>>

<<creates>>

Statement<<Interface>>

executeQuery()

<<creates>>

ResultSet<<Interface>>

<<creates>>

JDBC Driver Types

• JDBC-to-ODBC Bridge

• Native API partly Java drivers

• JDBC-Net pure Java drivers

• Native-protocol pure Java drivers

JDBC Driver Types II

Driver<<Interface>>

VendorAPI

PureJava JNI

NetBased Bridge

ODBCDriver

Informix Cloudscape

CSServerCSClient <<RMI>>

Web Appframeworks\RmiJdbc

An SQL Browser

Console

controlLoop()help()about()handle()execute()

Connection<<Interface>>

Statement<<Interface>>

<<creates>>

SQLBrowser

execute()

ResultSet<<Interface>>

<<creates>>

Reusable CUI Class

SQL Browser Declaration

public class SQLBrowser extends Console { protected String driverName; protected String dbaseName; protected Connection connection; protected Statement statement; protected ResultSet result; public SQLBrowser(String db) throws SQLException, ClassNotFoundException {...} public void finalize() throws SQLException {...} private String toString (ResultSet rs) throws SQLException {...} public String execute(String sql) throws AppError {...}}

Connecting

public SQLBrowser(String db) throws SQLException, ClassNotFoundException { Class.forName(driverName); dbaseName = "jdbc:cloudscape:rmi:" + db; connection = DriverManager.getConnection(dbaseName); statement = connection.createStatement(); meta = connection.getMetaData();}

Executing a Query

public String execute(String sql) throws AppError { String answer = "???"; try { result = statement.executeQuery(sql); answer = toString(result); } catch (SQLException e) { } return answer;}

Processing a Result Set

private String toString (ResultSet rs) throws SQLException { StringBuffer results = new StringBuffer(); ResultSetMetaData metaData = rs.getMetaData(); int numCols = metaData.getColumnCount(); for(int i = 1; i <= numCols; i++) { // get column names results.append(metaData.getColumnName(i) + "\t"); } results.append("\n"); while(rs.next()) { // get next row for(int i = 1; i <= numCols; i++) { results.append(rs.getObject(i) + "\t"); } results.append("\n"); } return results.toString();}

Closing the Connection

public void finalize() throws SQLException { statement.close(); connection.close();}

DBase DAO

public class DBaseDAO { protected String driver; protected String url; // "protocol:subprotocol:dbase" protected Connection connection; public DBaseDAO(String d, String u) throws DAOException {...} protected void connect() throws Exception {...} public void close() throws DAOException {...} protected void finalize() {...}}

Connecting

protected void connect() throws Exception { Class.forName( driver ); connection = DriverManager.getConnection( url ); connection.setAutoCommit( false );}

DAO Pattern

PersonDAO<<Interface>>

insert()delete()find()update()

DAOFactory<<Interface>>

makeDAOFactory()makePersonDAO()

CloudscapeDAOFactgory

makePersonDAO()

<<creates>>

DBasePersonDAO

<<creates>>

uses JDBC

DBasePersonDAO

PersonDAO<<Interface>>

insert()delete()update()find()

Driver<<Interface>>

DBaseDAO

connect()

Statement<<Interface>>

Connection<<Interface>>

<<creates>>

<<creates>> DBasePersonDAO

PreparedStatement<<Interface>>

**