JDBC中Scrollable ResultSet(滚动结果集)(四)

1.Scrollable ResultSet

Normal ResultSet allows fetching elements in forward only direction. However, Scrollable ResultSet allows us to easily move in forward/backward direction.

To create scrollable ResultSet, we must use a Statement/PreparedStatement object and provide scroll type to createStatement/prepareStatement method.

2.Syntax :

1.PreparedStatement pstmt = conn.prepareStatement(sql,Scroll type constant,Concurrency constant);

Statement stmt = conn.createStatement(Scroll type constant,Concurrency constant);

3.Scroll type constant

There are 3 scroll type constants can be used with ResultSets.

ResultSet.TYPE_FORWARD_ONLY

Default type.. only allows forward only fetching

ResultSet.TYPE_SCROLL_INSENSITIVE

Allows both forward and backward movement. Not sensitive to ResultSet updates.

ResultSet.TYPE_SCROLL_SENSITIVE

Allows both forward and backward movement. Not sensitive to ResultSet updates.

4.Concurrency constant

We can use following Concurrency constants for the ResultSets.

ResultSet.CONCUR_READ_ONLY

Default value .. ResultSet can not be updated.

ResultSet.CONCUR_UPDATABLE

Signifies an updatable ResultSet.

1.Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_UPDATABLE);

2.PreparedStatement pstmt = conn.prepareStatement(sql,ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);

5.Demo Code

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStat
4000
ement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class ScrollableResultsetDemo {

public static void main(String[] args) throws SQLException {
String url ="jdbc:mysql://localhost:3306/TestDB";

String user = "userid";
String password = "password";

Connection conn = DriverManager.getConnection(url, user, password);
System.out.println("Successfully connected");
getEmployeeData(conn);
}

private static void getEmployeeData(Connection conn) throws SQLException{
String sql = "select id,name,age from employee";

try(PreparedStatement pstmt = conn.prepareStatement(sql,ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_READ_ONLY);){
ResultSet rs = pstmt.executeQuery();

//First Record
rs.first();
System.out.println("Emp Id : " + rs.getInt("id") + ", Name : " + rs.getString("name") + ", Age : " + rs.getInt("age"));

//Last Record
rs.last();
System.out.println("Emp Id : " + rs.getInt("id") + ", Name : " + rs.getString("name") + ", Age : " + rs.getInt("age"));

//Previous Record
rs.previous();
System.out.println("Emp Id : " + rs.getInt("id") + ", Name : " + rs.getString("name") + ", Age : " + rs.getInt("age"));

//Next Record
rs.next();
System.out.println("Emp Id : " + rs.getInt("id") + ", Name : " + rs.getString("name") + ", Age : " + rs.getInt("age"));

}
}
}