Copyright Oracle Corporation, 1998. All rights reserved. 2 Java and Databases: An Overview

Copyright Oracle Corporation, 1998. All rights reserved.

22

Java and Databases: An Overview

Java and Databases: An Overview

Copyright Oracle Corporation, 1998. All rights reserved. 2-2-22

ObjectivesObjectives

After completing this lesson, you should be able to do the following:

• Describe how to use JDBC to access a database from Java

• Describe how to use JBCL data components to access a database

• Describe how to use SQLJ to access a database

After completing this lesson, you should be able to do the following:

• Describe how to use JDBC to access a database from Java

• Describe how to use JBCL data components to access a database

• Describe how to use SQLJ to access a database


OverviewOverview

This lesson introduces the technologies involved in accessing databases from a Java program

This lesson introduces the technologies involved in accessing databases from a Java program

DatabaseDatabaseApplet or Applet or applicationapplication

JDBCJDBC


Accessing Databases in the Non-Java World

Accessing Databases in the Non-Java World

• Database vendors provide APIs that programs can call to access a database

– Known as a Call Level Interface (CLI)

– For example, Oracle Call Interface (OCI)

• Vendor provides a driver to receive CLI calls and forward to database

• Database vendors provide APIs that programs can call to access a database

– Known as a Call Level Interface (CLI)

– For example, Oracle Call Interface (OCI)

• Vendor provides a driver to receive CLI calls and forward to database

Oracle OCI driver

OracleOracleserverserver

ProgramCalls OCI functions


Dealing with Different Databases Dealing with Different Databases

Different databases have their own CLI to access different databases

• Need to use different CLIs

• Need a driver for each CLI

Different databases have their own CLI to access different databases

• Need to use different CLIs

• Need a driver for each CLI

Oracle OCI driver Other driver

OracleOracle Other dbOther db

Program 1, calls OCI functions

Program 2, calls other CLI functions


ODBC: A Standard CLIODBC: A Standard CLI

ODBC provides a standard interface to any databaseODBC provides a standard interface to any database

ODBC driver for Oracle ODBC driver for other db


ODBC Driver Manager

Program 1, calls ODBC functions

Program 2, calls ODBC functions


From ODBC to JDBCFrom ODBC to JDBC

• JDBC plays a similar role in Java

• JDBC defines standard interfaces and classes that you can call from Java

• JDBC plays a similar role in Java

• JDBC defines standard interfaces and classes that you can call from Java

JDBC driver for Oracle JDBC driver for other db


JDBC Driver Manager

Java Program 1, uses JDBC classes/interfaces

Java Program 2, uses JDBC classes/interfaces


What Is JDBC?What Is JDBC?

JDBC defines standard interfaces

• Import java.sql package in a Java app

• Interfaces implemented by JDBC drivers

JDBC defines standard interfaces

• Import java.sql package in a Java app

• Interfaces implemented by JDBC drivers

interface Driver{…}

interface Connection{…}

interface Statement{…}

interface ResultSet{…}

class AAA implements Driver{…}

class BBB implements Connection{…}

etc…

Example JDBC interfacesExample JDBC interfaces JDBC driver, such as OracleJDBC driver, such as Oracle


Using JDBCUsing JDBC

A simplified example:

A simplified example:

import java.sql.*;

public class MyClass {

public void MyMethod() {

Connection con = DriverManager.getConnection(…);

Statement st = con.createStatement();

ResultSet res;

res = st.executeQuery("select * from emp");

// … Loop through result set, one row at a time


Oracle JDBC DriversOracle JDBC Drivers

• Oracle provides two different types of JDBC driver

– “JDBC Thin” driver

– “JDBC OCI” driver

• Use one or the other, depending on which type of Java program you are building

• Oracle provides two different types of JDBC driver

– “JDBC Thin” driver

– “JDBC OCI” driver

• Use one or the other, depending on which type of Java program you are building


Oracle JDBC Thin DriverOracle JDBC Thin Driver

• The Oracle JDBC Thin driver is written in 100% pure Java

• Can be downloaded over the network, with a Java applet

• Use this driver for Java applets or applications

• The Oracle JDBC Thin driver is written in 100% pure Java

• Can be downloaded over the network, with a Java applet

• Use this driver for Java applets or applications

Oracle JDBC Thin driverOracleOracle

Java applet or application


Oracle JDBC OCI DriverOracle JDBC OCI Driver

• The Oracle JDBC OCI driver makes OCI calls to a preinstalled “native” driver on the client

• Use for Java applications only

• The Oracle JDBC OCI driver makes OCI calls to a preinstalled “native” driver on the client

• Use for Java applications only

oci803jdbc.dll

Java application

Oracle JDBC OCI driver

OracleOracle


AppBuilder Support for JDBCAppBuilder Support for JDBC

• AppBuilder for Java includes:

– JDBC classes / interfaces in java.sql

– Sun JDBC-ODBC Bridge driver

• The installation also provides:

– Oracle Thin drivers for Oracle7 and Oracle8

– Oracle JDBC-OCI drivers for Oracle7 and Oracle8

• AppBuilder for Java includes:

– JDBC classes / interfaces in java.sql

– Sun JDBC-ODBC Bridge driver

• The installation also provides:

– Oracle Thin drivers for Oracle7 and Oracle8

– Oracle JDBC-OCI drivers for Oracle7 and Oracle8


AppBuilder Data ComponentsAppBuilder Data Components

• The JavaBeans Component Library (JBCL) provides many data components

– Some are visual “data-aware” controls

– Some are nonvisual “worker” controls

• Allows a Java program to manipulate a database with the minimum of code

– Hides much of the complexity

• The JavaBeans Component Library (JBCL) provides many data components

– Some are visual “data-aware” controls

– Some are nonvisual “worker” controls

• Allows a Java program to manipulate a database with the minimum of code

– Hides much of the complexity


JBCL Data Components Example

JBCL Data Components Example

This applet connects to an Oracle8 database, and performs a simple query

• Results of query are displayed in a grid

• No code neededin this example

This applet connects to an Oracle8 database, and performs a simple query

• Results of query are displayed in a grid

• No code neededin this example


Dynamic SQL in JavaDynamic SQL in Java

• The JBCL data components use JDBC to achieve database connectivity

• The JDBC calls use “dynamic SQL”

– SQL strings are parsed at run time

– Not precompiled

• The JBCL data components use JDBC to achieve database connectivity

• The JDBC calls use “dynamic SQL”

– SQL strings are parsed at run time

– Not precompiled

Statement stmt;

stmt = conn.execute("select * from EMP " +

"where SAL > 1000 " +

"order by HIREDATE");


Static SQL in JavaStatic SQL in Java

• Oracle also provides the capability to provide “static SQL” in a Java program

– SQL statements are precompiled, and converted to equivalent Java code

– Allows SQL statements to be verified against database at compile time

– Fewer run time errors

• This ability is provided by “SQLJ”

• Oracle also provides the capability to provide “static SQL” in a Java program

– SQL statements are precompiled, and converted to equivalent Java code

– Allows SQL statements to be verified against database at compile time

– Fewer run time errors

• This ability is provided by “SQLJ”


SQL

What Is SQLJ?What Is SQLJ?

• SQLJ is a way to embed static SQL in Java programs

• Looks like standard Java, with a small number of localized extensions

• Translates embedded SQL into calls to JDBC

• SQLJ is a way to embed static SQL in Java programs

• Looks like standard Java, with a small number of localized extensions

• Translates embedded SQL into calls to JDBC


SQLJ ExampleSQLJ Example

A simplified example of how to use SQLJ

• Inserts a new row into emp table:

A simplified example of how to use SQLJ

• Inserts a new row into emp table:

import java.sql.*;

import sqlj.runtime.ref.*;

#sql { insert into EMP values('Thomas' , 1200) };

afile.sqlj


Precompiling SQLJ CodePrecompiling SQLJ Code

SQLJ code must be precompiled to Java, using the SQLJ translator

• Checks the SQL code at compile time

• Converts afile.sqlj into afile.java

• Translates embedded SQL into appropriate calls to JDBC

SQLJ code must be precompiled to Java, using the SQLJ translator

• Checks the SQL code at compile time

• Converts afile.sqlj into afile.java

• Translates embedded SQL into appropriate calls to JDBC

SQLJ translatorSQLJ translator

JDBC callsJDBC calls

afile.sqlj afile.java


SummarySummary

• JDBC defines a standard database interface for Java programs

• Two primary types of Oracle JDBC driver: JDBC Thin, and JDBC OCI

• AppBuilder for Java provides many data-aware components

• SQLJ can be used to embed static SQL code in Java programs

• JDBC defines a standard database interface for Java programs

• Two primary types of Oracle JDBC driver: JDBC Thin, and JDBC OCI

• AppBuilder for Java provides many data-aware components

• SQLJ can be used to embed static SQL code in Java programs

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Copyright Oracle Corporation, 1998. All rights reserved. 2 Java and Databases: An Overview