1. JDBC API

2. Introduction
JDBC is a set of programming APIs that allows easy connection to a wide range of databases
JDBC is a database-independent API for accessing a relational database
You pass SQL to Java methods in the JDBC classes (the packages java.sql and javax.sql) and get back JDBC objects
JDBC is designed so simply that most database programmers need learn only a few methods to accomplish most of what they need to do

3. Types of Drivers There are 4 types of JDBC Drivers
Type 1 - JDBC-ODBC Bridge
Type 2 - JDBC-Native Bridge
Type 3 - JDBC-Net Bridge
Type 4 - Direct JDBC Driver
Type 1 only runs on platforms where ODBC is available
ODBC must be configured separately
Type 2 Drivers map between a proprietary Database API and the JDBC API
Type 3 Drivers are used with middleware products
Type 4 Drivers are written in Java
In most cases, type 4 drivers are preferred

4. Introduction
java.sql provides the API for accessing and processing data stored in a data source (usually a relational database) using the Java programming language
this package provides classes and interfaces to get both database and result set metadata from the database server
javax.sql provides the API for server-side data source access
This package supplements the java.sql package and, as of the version 1.4 release, is included in the JDK

5. Architecture
The DriverManager loads JDBC drivers in memory, and can also be used to create java.sql.Connection objects to data sources
You can have more than one driver and therefore more than one database

6. JDBC Class Usage DriverManager Driver Connection Statement ResultSet
Copyright © 1997 Alex Chaffee

7. Architecture
DriverManager: It is a “factory” class and can also be used to create java.sql.Connection objects to data sources (such as Oracle, MySQL, etc.).
Connection: This interface represents a connection with a data source. The Connection object is used for creating Statement, PreparedStatement, and CallableStatement objects.
DatabaseMetaData: This interface provides detailed information about the database as a whole. The Connection object is used for creating DatabaseMetaData objects.
Statement: This interface represents a static SQL statement. It can be used to retrieve ResultSet objects.
PreparedStatement: This interface extends Statement and represents a precompiled SQL statement. It can be used to retrieve ResultSet objects.

8. Architecture
CallableStatement: This interface represents a database stored procedure. It can execute stored procedures in a database server.
ResultSet: This interface represents a database result set generated by using SQL’s SELECT statement.
ResultSetMetaData: This interface provides information about the types and properties of the columns in a ResultSet object.
SQLException: This class is an exception class that provides information on a database access error or other errors.

9. JDBC Class Diagram Whoa! Copyright © 1997 Alex Chaffee

10. Data Types

11. Steps JDBC programming can be explained in the following simple steps:
Importing required packages
Registering the JDBC drivers
Opening a connection to a database
Creating a Statement/PreparedStatement/CallableStatement object
Executing a SQL query and returning a ResultSet object
Processing the ResultSet object
Closing the ResultSet and Statement objects
Closing the connection

12. Step 1: Import the Required Packages
Before you can use the JDBC driver to get and use a database connection, you must import the following packages: java.sql and javax.sql.
import java.sql.*;
import javax.sql.*;

13. Step 2: Register the JDBC Drivers
A JDBC driver is a set of database-specific implementations for the interfaces defined by JDBC
Oracle: First, the main driver class must be loaded into the Java virtual machine (VM):
Class.forName("oracle.jdbc.driver.OracleDriver");
The specified driver (i.e., the oracle.jdbc.driver.OracleDriver class) must implement the java.sql.Driver interface
A class initializer (a static code block) within the oracle.jdbc.driver.OracleDriver class registers the driver with the java.sql.DriverManager

14. Step 2: Register the JDBC Drivers
MySQL:
Class.forName("com.mysql.jdbc.Driver");
A class initializer (a static code block) within the com.mysql.jdbc.Driver class registers the driver with the java.sql.DriverManager
Note that when loading a JDBC driver, you must make sure that the database-specific driver API (usually a JAR file) is in your CLASSPATH environment variable

15. Step 3: Opening a Connection to a Database
Next, we need to obtain a connection to the database
To get a connection object to a database, you need at least three pieces of information: the database URL, the database username, and the database user’s password
import java.sql.Connection;
import java.sql. DriverManager; …
String dbURL =
String dbUsername = "scott";
String dbPassword = "tiger";
Connection conn = DriverManager.getConnection(dbURL, dbUsername, dbPassword);

16. Step 3: Opening a Connection to a Database
There is an alternate method for creating a database connection: first get a JDBC driver, then use that driver to get a connection
import java.sql.Connection;
import java.sql. Driver;
import java.sql. DriverManager;
import java.util.Properties; …
String dbURL =
String dbUsername = "scott";
String dbPassword = "tiger";
Properties dbProps = new Properties();
String driverName = "oracle.jdbc.driver.OracleDriver";
Driver jdbcDriver = (Driver) Class.forName(driverName).newInstance();
dbProps.put("user", dbUsername);
dbProps.put("password", dbPassword);
Connection conn = jdbcDriver.connect(databaseURL, dbProps);

17. Step 3: Opening a Connection to a Database
Once you have a valid java.sql.Connection object, you can create statement objects (such as Statement, PreparedStatement, and CallableStatement)
Connection conn = <get-a-valid-Connection-object>;
Statement stmt = conn.createStatement();

18. Step 3: Opening a Connection to a Database
Example Database
create table MyEmployees (
id INT PRIMARY KEY,
firstName VARCHAR(20),
lastName VARCHAR(20),
title VARCHAR(20),
salary INT );
insert into MyEmployees(id, firstName, lastName, title, salary) values(60, 'Bill', 'Russel', 'CTO', );
insert into MyEmployees(id, firstName, lastName, title, salary)
values(70, 'Alex', 'Baldwin', 'Software Engineer', 88000);

19. Step 5: Executing a Query and Returning a ResultSet Object
Invoking the execute() method of the statement object will execute the database-specific code necessary to issue a SQL statement against the database and retrieve the results (as a table)
String query = "SELECT id, lastName FROM MyEmployees";
ResultSet result = stmt.executeQuery(query);
The result is a table (as a ResultSet object) returned by executing the SELECT statement
By iterating the result, we can get all of the selected records

20. Step 6: Processing the ResultSet Object
ResultSet.next() returns a boolean: true if there is a next row or record and false if not (meaning the end of the data or set has been reached)
Conceptually, a pointer or cursor is positioned just before the first row when the ResultSet is obtained
Invoking the next() method moves to the first row, then the second, and so on

21. Step 6: Processing the ResultSet Object
Once positioned at a row, the application can get the data on a column-by- column basis using the appropriate ResultSet.getXXX() method
if (rs.next()) {
String firstName = rs.getString(1);
String lastName = rs.getString(2);
String title = rs.getString(3);
int salary = rs.getInt(4); }
or we may use the column names (instead of column positions):
String firstName = rs.getString("firstName");
String lastName = rs.getString("lastName");
String title = rs.getString("title");
int salary = rs.getInt("salary");

22. Step 7: Closing JDBC Objects
Releasing or closing JDBC resources (such as ResultSet, Statement, PreparedStatement, and Connection objects) immediately instead of waiting for it to happen on its own can improve the overall performance
From a good software engineering point of view, you should put close() statements in a finally clause

23. Step 7: Closing JDBC Objects
ResultSet has a close() method that releases the ResultSet object’s database and JDBC resources
Another major reason to close the ResultSet objects immediately after they are done is that we increase concurrency; as long as the ResultSet object is open, the DBMS internally holds a lock

24. Step 7: Closing JDBC Objects
public static void close(java.sql.ResultSet rs) { if (rs == null) { return; } try { rs.close(); // result set is closed now catch(Exception ignore) { // ignore the exception // could not close the result set // cannot do much here

25. Step 7: Closing JDBC Objects
public static void close(java.sql.Statement stmt) { if (stmt == null) { return; } try { stmt.close(); // result set is closed now catch(Exception ignore) { // ignore the exception // could not close the statement // can not do much here

26. Step 7: Closing JDBC Objects
public static void close(java.sql.Connection conn) { if (conn == null) { return; } try { if (!conn.isClosed()) { // close the connection-object conn.close(); // connection object is closed now catch(Exception ignore) { // ignore the exception // could not close the connection-object // can not do much here

27. JDBC Errors/Exceptions
In JDBC, errors and exceptions are identified by the java.sql.SQLException class (which extends the java.lang.Exception class)
SQLException is a checked exception
Checked exceptions have to be caught (and handled properly) or appear in a method that specifies in its signature that it throws that kind of exception
When a JDBC object (such as Connection, Statement, or ResultSet) encounters a serious error, it throws a SQLException

28. JDBC Errors/Exceptions
JDBC give access to such information by providing several levels of error conditions:
SQLException: SQLException is an exception that provides information on a database access error or other errors.
SQLWarning: SQLWarnings are subclasses of SQLException, but they represent nonfatal errors or unexpected conditions, and as such, can be ignored.
BatchUpdateException: BatchUpdateException is an exception thrown when an error occurs during a batch update operation.
DataTruncation: DataTruncation is an exception that reports a DataTruncation warning (on reads) or throws a DataTruncation exception (on writes) when JDBC unexpectedly truncates a data value

29. Metadata
DatabaseMetaData: Provides information about the database as a whole.
ResultSetMetaData: Used to identify the types and properties of the columns in a ResultSet object.
RowSetMetaData: An object that contains information about the columns in a RowSet object.
ParameterMetaData: An object that can be used to get information about the types and properties of the parameters in a PreparedStatement object.
DriverPropertyInfo: Driver properties for making a connection.

30. Example

31. More Details
The important methods of Statement interface are as follows:
1) public ResultSet executeQuery(String sql): is used to execute SELECT query. It returns the object of ResultSet.
2) public int executeUpdate(String sql): is used to execute specified query, it may be create, drop, insert, update, delete etc.
3) public boolean execute(String sql): is used to execute queries that may return multiple results.
4) public int[] executeBatch(): is used to execute batch of commands.

32. More Details Example import java.sql.*; class FetchRecord{
public static void main(String args[])throws Exception{  
Class.forName("oracle.jdbc.driver.OracleDriver");  
:1521:xe","system","oracle");  
Statement stmt=con.createStatement();     
//stmt.executeUpdate("insert into emp765 values(33,'Irfan',50000)");  
//int result=stmt.executeUpdate("update emp765 set name='Vimal',salary=10 000 where id=33");  
int result=stmt.executeUpdate("delete from emp765 where id=33");  
System.out.println(result+" records affected");   con.close();   }
}  

33. More Details
ResultSet

34. More Details
The PreparedStatement interface is a sub-interface of Statement. It is used to execute parameterized query.
The important methods of PreparedStatement interface are given below:

35. More Details
Example
PreparedStatement stmt=con.prepareStatement("insert into  Emp values(?,?)");  
stmt.setInt(1,101);
//1 specifies the first parameter in the query  
stmt.setString(2,"Ratan");    
int i=stmt.executeUpdate();  
System.out.println(i+" records inserted"); 

36. More Details
Example
PreparedStatement stmt=con.prepareStatement("update emp  set name=? where id=?");  
stmt.setString(1,"Sonoo");
//1 specifies the first parameter in the query i.e. name  
stmt.setInt(2,101);     
int i=stmt.executeUpdate();  
System.out.println(i+" records updated");  

37. More Details
Example
PreparedStatement stmt=con.prepareStatement("delete from  emp where id=?");  
stmt.setInt(1,101);     
int i=stmt.executeUpdate();  
System.out.println(i+" records deleted");  

38. More Details
CallableStatement interface is used to call the stored procedures and functions
The differences between stored procedures and functions are given below:

39. CallableStatement stmt=con.prepareCall("{call myprocedur e(?,?)}");
More Details
Syntax
CallableStatement stmt=con.prepareCall("{call myprocedur e(?,?)}");  

40. More Details
Example
CallableStatement stmt=con.prepareCall("{call insertR(?,?)}");  
stmt.setInt(1,1011);  
stmt.setString(2,"Amit");  
stmt.execute();  
create or replace procedure "INSERTR"  
(id IN NUMBER,  name IN VARCHAR2)  
is  
begin  
insert into user420 values(id,name);  
end;  
/   

41. More Details
Example
CallableStatement stmt=con.prepareCall("{?= call sum4(?,?)}");  
stmt.setInt(2,10);  
stmt.setInt(3,43);  
stmt.registerOutParameter(1,Types.INTEGER);  
stmt.execute(); 
create or replace function sum4  
(n1 in number,n2 in number)  
return number is temp number(8);  
begin  
temp :=n1+n2;  
return temp;  
end;   / 

42. More Details
Instead of executing a single query, we can execute a batch (group) of queries.
It makes the performance fast.
The java.sql.Statement and java.sql.PreparedStatement interfaces provide methods for batch processing.
The required methods for batch processing are given below:

43. More Details Example Statement stmt=con.createStatement();
stmt.addBatch("insert into user420 values(190,'abhi',40000)");  
stmt.addBatch("insert into user420 values(191,'umesh',50000)");     
stmt.executeBatch();
//executing the batch    
con.commit();

44. More Details
Example
PreparedStatement ps=con.prepareStatement("insert into user420 values(?,?,?)");    
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));  
while(true){    
System.out.println("enter id");   String s1=br.readLine();  
int id=Integer.parseInt(s1);    
System.out.println("enter name");   String name=br.readLine();    
System.out.println("enter salary");  String s3=br.readLine();  
int salary=Integer.parseInt(s3);    
ps.setInt(1,id);  ps.setString(2,name);  ps.setInt(3,salary);    
ps.addBatch();  
System.out.println("Want to add more records y/n");   String ans=br.readLine();  
if(ans.equals("n")){  break;  }    
}  
ps.executeBatch();

45. Thank You! Questions?