Why does executeUpdate() function not work? Give steps to solve in a normal project rather than a maven based project

Question

CODE:

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package aaa;
import static aaa.DB.geom;
import static aaa.DB.getConnection;
import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class JDBCExample {

  public static void main(String[] argv) throws SQLException {



    try {

      Class.forName("org.postgresql.Driver");
      // Class.forName("com.mysql.jdbc.Driver");

    } catch (ClassNotFoundException e) {

      System.out.println("Where is your PostgreSQL JDBC Driver? " +
        "Include in your library path!");
      e.printStackTrace();
      return;

    }

    System.out.println("PostgreSQL JDBC Driver Registered!");

    Connection connection = null;

    try {

      connection = DriverManager.getConnection(
        "jdbc:postgresql://localhost:5432/postgres", "postgres",
        "abc");

    } catch (SQLException e) {

      System.out.println("Connection Failed! Check output console");
      e.printStackTrace();
      return;

    }

    if (connection != null) {
      System.out.println("You made it, take control your database now!");

      //Connection conn = getConnection();


      connection.setAutoCommit(false);
      Statement s = null;
      try {
        s = connection.createStatement();
      } catch (Exception e) {
        System.out.println("statmnt connection not works");
      }
      PreparedStatement ss = connection.prepareStatement("SELECT * FROM nodes_road_geoms");
      try {
        ss.executeUpdate();
      } catch (Exception e) {
        System.out.println("statmnt excute update connection not works: ");
        e.printStackTrace();
      }
      String query = "CREATE TABLE COMPANY(ID INT );";

      ResultSet r = s.executeQuery(query);
      connection.commit();
    } else {
      System.out.println("Failed to make connection!");
    }
  }

}

RUN:

-------- PostgreSQL JDBC Connection Testing ------------

PostgreSQL JDBC Driver Registered!

You made it, take control your database now!

Exception in thread "main" java.lang.NoSuchMethodError: 

org.postgresql.core.BaseConnection.getPreferQueryMode()Lorg/postgresql/jdbc/PreferQueryMode;
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:151)
    at org.postgresql.jdbc.PgPreparedStatement.executeUpdate(PgPreparedStatement.java:132)
    at aaa.JDBCExample.main(JDBCExample.java:69)
C:\Users\Dell\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 0 seconds)

QUESTION:Give me steps to solve it since database is connected already! What is the core of the problem? The problem is that if database postgresql connected then why not insert into database. The tables are also available and seen from netbeans. There needs to be a way to solve this run time exception issue when there is a query execution... So I needed step by step details to make it correct.

Answer 1

A SELECT statements has to be executed using executeQuery(). executeUpdate() is for DML statements like UPDATE, INSERT, or DELETE that don't normally return a ResultSet. Also, a DDL statement like CREATE TABLE can not be executed using executeQuery() you need execute() or executeUpdate() for that.

So your code should be:

PreparedStatement ss = connection.prepareStatement("SELECT * FROM nodes_road_geoms");
try {
   ResultSet rs = ss.executeQuery();
   while (rs.next() {
      // do something
   }
   rs.close();
} catch (Exception e) {
  System.out.println("statmnt excute update connection not works: ");
  e.printStackTrace();
}

And:

String query = "CREATE TABLE COMPANY(ID INT );";
s.execute(query);
connection.commit();

Answer 2

You have connection.setAutoCommit(false); and you didnt commit after performing update. You have to commit your transaction in order for changes to apply. You can also setAutoCommit(true);