Cancel - Aster Client

For detailed documentation on the cancel() method, see the Java documentation on this web site:

http://docs.oracle.com/javase/7/docs/api/java/sql/Statement.html#cancel%28%29

The following is a code example that uses the cancel() method:

// This demonstrates how to run a query in one thread and cancel it in
// a different thread.
//
// You will need to customize the IP address of the queen in the variable
// "DB_URL" later in this code.
// You'll also need to add a table named "demo1", or modify the SQL statement
// to use a table that you already have.
import java.sql.*;
// This class allows us to run a query in a separate thread from the main
// thread (the main thread will cancel this query).
class MyThread extends Thread {
Statement myStatement;
// The SQL statement that we want to execute.
String mySql = "";
MyThread(Statement myStmt, String pSql) {
myStatement = myStmt;
mySql = pSql;
}
public void run(){
try {
System.out.println("Running query in different thread");
myStatement.executeQuery(mySql);
}
catch(Exception e) {
e.printStackTrace();
}
}
}
public class CancelQuery {
static final String JDBC_DRIVER = "com.asterdata.ncluster.Driver";
// Customize this URL to access your own server!
static final String DB_URL = "jdbc:ncluster://10.80.169.10:2406/beehive";
public static void main(String[] args) throws Exception
{
Connection conn = null;
Statement stmt = null;
try{
// Register JDBC driver
Class.forName(JDBC_DRIVER);
// Open a connection to the database server.
System.out.println("Connecting to database...");
// Customize the database user and password if you wish.
conn = DriverManager.getConnection(DB_URL,"beehive","beehive");
// Execute a query
System.out.println("Creating statement...");
stmt = conn.createStatement();
// If the table "demo1" is a large table, this statement might run long
// enough that it will be practical to cancel it.
String sql = "SELECT COUNT(*) FROM demo1;";
ResultSet rs = null;
// Run the query in a separate thread.
MyThread thread = new MyThread(stmt, sql);
thread.start();
Thread.sleep(5000);   // 5,000 milliseconds, in this case
System.out.println("Invoking cancel");
stmt.cancel();
// Wait until the thread running the query finishes.
thread.join();
// Clean up.
stmt.close();
conn.close();
} catch(SQLException se) {
//Handle errors for JDBC
se.printStackTrace();
} catch(Exception e){
//Handle errors for Class.forName
e.printStackTrace();
} finally{
//finally block used to close resources
try{
if (stmt!=null)
stmt.close();
} catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
} catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}
}