Jdbc day-1

JDBC: What & Why?
As we all know, Java is platform independent,
there must be some means to have some ready-to-
hand way, specifically some API to handle
Database activities that can interface between
your Java Code and an RDBMS and perform the
desired SQL. This is known as Java DataBase
Connectivity (JDBC). JDBC-version 2.x defines 2
packages, java.sql and javax.sql that provide the
basement of a JDBC API
Monday, October 13, 2014sohamsengupta@yahoo.com 1

JDBC Drivers & Types
• As JDBC plays the role to interface between the
RDBMS and Java Code, from the Database’s part,
there must be some vendor specific utilities that
will cooperate with JDBC. These are known as
JDBC Drivers, having 4 Types, Type-1 to Type-4.
We, however, must avoid theoretical discussion
about them but shall deal with Type-1, also known
as JDBC-ODBC Bridge, and Type-4, also known
as Pure Java Driver. So, on to the next slide…

Primary Steps to code JDBC with
ODBC Bridge Driver
• STEP-1: Load the Driver Class, coded as
• Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
• This statement loads the said class in memory,
thus allowing your code to succeed.
• STEP-2: Obtain a Database Connection
represented by java.sql.Connection interface, to
be obtained through code as
• Connection
conn=DriverManager.getConnection(“jdbc:odbc:ibm”);
• Here “jdbc:odbc:ibm” is the connection
String, where ibm is set up through
Control Panel as follows…

STEP-1: Ctrl Panel>Admin
Tools>Data Sources (ODBC)

STEP-2: Go to System DSN tab
and then click on Add Button

STEP-3: Select the Driver and Click
Finish Button
• Select the required Driver that you need

STEP-4: Type the Data Source
Name (DSN)
• and browse the Database (here IBM.mdb)
and click OK

Final Step: Now click OK,
• and ibm will appear under System DSN
TAB

Creating A Table in an MS-Access (.mdb)
Database: First import java.sql.* to access
the JDBC API
• static void createTable(String strTableName) throws Exception{
• Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
• Connection
conn=DriverManager.getConnection("jdbc:odbc:ibm");
• Statement st=conn.createStatement();
• st.executeUpdate("create table "+strTableName+"(name
varchar(30),id varchar(20),marks INTEGER)");
• st.close();
• conn.close();
• System.out.println("Table "+strTableName+" created
successfully!");
• }

How to insert a Row
• static void insertRow(String strId,String strName,int marks) throws
Exception{
• Connection conn=DriverManager.getConnection("jdbc:odbc:ibm");
• PreparedStatement ps=conn.prepareStatement("insert into
StudentTable (id,name,marks) values(?,?,?)");
• ps.setString(1,strId);
• ps.setString(2,strName);
• ps.setInt(3,marks);
• ps.executeUpdate();
• System.out.println(ps.getResultSet());
• ps.close();
• conn.close();
• System.out.println("Row inserted successfully!");
• }

How to fetch All Rows of a Table
static void selectAllRowsOtherMethod() throws Exception{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
Connection
Statement st=conn.createStatement();
ResultSet rs=st.executeQuery("select * from StudentTable");
while(rs.next()){
System.out.println(rs.getString("id")+"t"+rs.getString("name")
+"t"+rs.getInt("marks"));
}
st.close();
conn.close();
}

Another Approach
• static void selectAllRows() throws Exception{
• Connection
• Statement st=conn.createStatement();
• st.execute("select * from StudentTable");
• ResultSet rs=st.getResultSet();
• while(rs.next()){
• System.out.println(rs.getString("id")
+"t"+rs.getString("name")+"t"+rs.getInt("marks"));
• }
• st.close();
• conn.close();
• }

How to fetch a single row
• static void selectAStudent(String strId) throws Exception{
• Connection
• PreparedStatement ps=conn.prepareStatement("select * from
StudentTable where id=?");
• ResultSet rs=ps.executeQuery();
• if(rs.next()){
System.out.println(rs.getString("name")+"t"+rs.getString("id")
+"t"+rs.getInt("marks"));
• }else{ System.out.println(strId+" Not found!");
• }
• ps.close();
• conn.close();
• }

Update Rows
• static void updateAStudent(String strId,int intNewMarks)
throws Exception{
• Connection
• PreparedStatement ps=conn.prepareStatement("update
StudentTable set marks=? where id=?");
• ps.setInt(1,intNewMarks);
• int intStatus=ps.executeUpdate();
• System.out.println(intStatus+" Row(s) updated");
• ps.close();
• conn.close();
• }

Update Rows : Another Approach
• static void updateARowOtherMethod(int intNewMarks,String
strNewName) throws Exception{
• Connection
• Statement
st=conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITI
VE,ResultSet.CONCUR_UPDATABLE);
• ResultSet rs=st.executeQuery("select marks,name from
StudentTable order by id");
• rs.absolute(2);
• rs.updateInt(1,intNewMarks);
• rs.updateString(2,strNewName);
• rs.updateRow();
• st.close();
• conn.close();
• System.out.println("Updated successfully");
• }

Finally Calling these methods
• public static void main(String[]args) throws Exception{
• createTable("StudentTable");
insertRow("it/00/57","Soham Sengupta",940);
• insertRow("it/00/01","Manas Ghosh",620);
• insertRow("it/00/2","Tanay Das",657);
• insertRow("it/00/63","Abhisek Biswas",721);
• selectAllRowsOtherMethod();
• selectAStudent("it/00/02");
• updateAStudent("it/00/1",755);
• updateARowOtherMethod(102,"Tanoy Dash");
• }

Some important features
• After establishing a Connection, we have to create
a Statement or PreparedStatement object that
would execute the desired SQL.
• There are 3 methods: execute(), executeUpdate()
and executeQuery(). The first 2 return int indicating
the number of rows updated/ otherwise, whereas
the last one returns a java.sql.ResultSet that holds
the data. At first it points to the BOC so we have to
call next() method that returns false when no data
is available else true. Also, next() causes the cursor
to advance one step. Some special ResultSets may
fetch data in either direction.

Executing SQL through JDBC
• SQL, though may differ from an RDBMS to
another, always involves 4 basic operations
known as CRUD (Create, Read, Update,
Delete).
• Basically there are 2 categories of options; first,
Write operation involving create, insert, update,
delete etc… and second, READ operation. We
perform these through Statement and/or
PreparedStatement.
• The next slide depicts how basic SQL can be
executed through these objects.

A Simple Insert Command
• Assuming a table, StudentTable comprising 3 fields: id
varchar(30), name varchar(40) and marks INTEGER, we
may insert the data set (‘it/00/57’, ‘Soham’, 940) with the
command:
• Insert into StudentTable (id,name,marks) values(‘it/00/57’, ‘Soham’,
940);
• If we represent the above by a Java String object and the column values
being termed by variables strName, strId and intMarks, then, the SQL
becomes, in code,
• String strSQL=“insert into StudentTable (id,name,marks) values(‘”+
strId+”’,’”+strName+”’,”+intMarks+”)”;
• Here, + operator concatenates the SQL with column values replaced
by corresponding variables. We, however, must be aware to close an
open parenthesis and/or a single-quote( ‘ ). This is to be executed with
a java.sql.Statement object.
• But this is a nasty coding, and should be avoided with
PreparedStatement decsribed in the next slide

How PreparedStatement Betters
Clumsiness in code
• After loading the driver class, and obtaining the
Connection object (say, conn), we should code
as :
• PreparedStatement ps=conn.prepareStatement(“insert into
StudentTable (id,name,marks) values(?,?,?)”);
• ps.setString(2,strName);
• ps.setInt(3,intMarks);
• ps.executeUpdate();
• What we should keep in mind is, index the setters correctly, for
example, ps.setString(1,strId) as I’m inserting the column id at
1, name at 2 and marks at 3.
• Thus, PreparedStatement can be used for other SQL
commands, too, like select commands et al.

Transaction Failure Management
(TFM)
• The Software market extensively uses RDBMS and
it’s quite obvious those built on Java Technology
would involve JDBC. Also, what goes without saying
is, these Software packages involve highly delicate
Transactions like Banking etc. and hence must
conform to the maximum level of TFM, else the
entire ACID paradigms would be violated causing
much a chaos. JDBC API provides with built-in TFM
at coding level. You must be aware that if any thing
goes wrong in a JDBC transaction, checked
Exception like java.sql.SQLException and others are
thrown. So, we put the entire ATOMIC Transaction
code under a try-catch Exception handling scanner.

TFM Coding Style
Connection conn;
try{
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
conn=DriverManager.getConnection(“jdbc:odbc:dsn”);
conn.setAutoCommit(false); // don’t coomit until entire done
…
…
conn.commit(); // now, no Exception, thank God, now commit it
}catch(Throwable t){
conn.rollback(); // This makes the system to roll back on
//Exception
}

Jdbc day-1

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