How to get the size of a column of a table using JDBC?

You can get the size of a column of a table using the getPrecision() method of the ResultSetMetaData class.

//Retrieving the ResultSetMetaData object
ResultSetMetaData rsmd = rs.getMetaData();

//getting the column type
int size_name = rsmd. getPrecision(3);

Assume we have a table named employee_data in the database with description as shown below:

+----------+--------------+------+-----+---------+-------+
| Field    | Type         | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| id       | int(11)      | YES  |     | NULL    |       |
| Name     | varchar(255) | YES  |     | NULL    |       |
| Dob      | date         | YES  |     | NULL    |       |
| Location | varchar(255) | YES  |     | NULL    |       |
+----------+--------------+------+-----+---------+-------+

Following JDBC program establishes connection with the database, retrieves the ResultSetMetaData object of the employee_data table, and prints the size of the third column.

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
public class SizeOfColumn {
   public static void main(String args[])throws Exception {
      //Registering the Driver
      DriverManager.registerDriver(new com.mysql.jdbc.Driver());
      //Getting the connection
      String mysqlUrl = "jdbc:mysql://localhost/mydatabase";
      Connection con = DriverManager.getConnection(mysqlUrl, "root", "password");
      System.out.println("Connection established......");

      //Creating a Statement object
      Statement stmt = con.createStatement();
      ResultSet rs = stmt.executeQuery("select * from employee_data");

      //Retrieving the ResultSetMetaData object
      ResultSetMetaData rsmd = rs.getMetaData();

      //getting the column type
      int column_size = rsmd.getPrecision(3);
      System.out.println("Size of the 3rd column : "+column_size);
   }
}

Output

Connection established......
Size of the 3rd column : 11