Calling a oracle stored procedure in a servlet - multithreading

Question

We know the servlet instance is created once and based on multiple user requests to the servlet , container creates threads to address each of the user request.
What if I have stored procedure in the servlet which is multithreaded. The stored procedure takes the parameters from the user request and generates output for that user alone.
What if ,i have multiple users request coming at same time. Does procedure results generated by user1 will be overwritten by another user request as each thread have its own execution flow. please help to understand.
I have given simple example end to end which I'm trying. here i didn't use synchronization
public class Demo {
public static void main(String[] args) {
DBThread db = new DBThread();
//Only one instance and multiple threads
Thread request1= new Thread(db, "request1");
Thread request2= new Thread(db, "request2");
request1.start();
request2.start();
}
}
DBThread.java
import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class DBThread implements Runnable {
public void getData(){
Connection con=null;
Statement statement = null;
CallableStatement callProcedure = null;
ResultSet rs = null;
try {
con = getDBConnection();
if(con==null)
System.out.println("Unable to get connection for " + Thread.currentThread().getName());
else
{
callProcedure = con.prepareCall("{call PROCEDURE1(?)}");
callProcedure.setString(1,Thread.currentThread().getName());
callProcedure.execute();
statement = con.createStatement();
rs = statement.executeQuery("select id,inputname from temp1");
while(rs.next()){
System.out.println("Thread "+Thread.currentThread().getName() +":"+ rs.getString(1) +":" + rs.getString(2));
}
}
} catch (SQLException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
finally{
try{
if(callProcedure!=null){
callProcedure.close();
}
if(rs!=null)
rs.close();
if(con!=null){
con.close();
System.out.println("Connection close for " + Thread.currentThread().getName());
}
}catch(Exception e){
System.out.println("print therea" + Thread.currentThread().getName());
}
}
}
public void run() {
this.getData();
}
public Connection getDBConnection() throws SQLException, Exception{
String user = null;
String pwd = null;
String dbURL = null;
String driverClassName = null;
Connection con = null;
if(con == null || con.isClosed() == true){
user = "readonly";
pwd = "XXXX"
dbURL = "jdbc:oracle:thin:#host:port:SID;
driverClassName = "oracle.jdbc.driver.OracleDriver";
Class.forName(driverClassName);
con = DriverManager.getConnection(dbURL, user, pwd);
}
System.out.println("Connection got for " + Thread.currentThread().getName()+ "Connection "+ con);
return con;
}
}
Oracle procedure :
create or replace
PROCEDURE PROCEDURE1(id varchar2) AS
BEGIN
DELETE from temp1;
FOR i IN 1..5 LOOP
INSERT INTO temp1 VALUES (i,id);
END LOOP;
COMMIT;
END PROCEDURE1;

Answer 1

Since you're using the same connection which is closed at the end of the function (finally block) then in case of parallel execution you will very likely get some SQLException inside the second thread after the first one completed.