SampleManager.java

package com.godoro.em;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

public class SampleManager {

  public boolean delete(long sampleId) throws Exception {

    Connection connection = DatabaseUtilities.getConnection();
    String sql = "delete from Sample where sampleId=?";
    PreparedStatement statement = connection.prepareStatement(sql);
    statement.setLong(1, sampleId);
    int affected = statement.executeUpdate();
    connection.close();
   return affected > 0;
  }

  public Sample find(long sampleId) throws Exception {
    Sample sample = null;
    Connection connection = DatabaseUtilities.getConnection();
    String sql = "select * from Sample where sampleId=?";
    PreparedStatement statement = connection.prepareStatement(sql);
    statement.setLong(1, sampleId);
    ResultSet resultSet = statement.executeQuery();
    if (resultSet.next()) {
      String sampleName = resultSet.getString("sampleName");
      double sampleValue = resultSet.getDouble("sampleValue");
      sample = new Sample(sampleId, sampleName, sampleValue);
    }
    connection.close();
    return sample;
  }

  public boolean insert(Sample sample) throws Exception {
    Connection connection = DatabaseUtilities.getConnection();

    String sql = "insert into Sample(sampleName,sampleValue) values(?,?)";
    PreparedStatement statement = connection.prepareStatement(sql);
    statement.setString(1, sample.getSampleName());
    statement.setDouble(2, sample.getSampleValue());
    int affected = statement.executeUpdate();

    connection.close();
    return affected > 0;
  }

  public boolean update(Sample sample) throws Exception {
    Connection connection = DatabaseUtilities.getConnection();

    String sql = "update Sample set sampleName=?,sampleValue=? where sampleId=?";
    PreparedStatement statement = connection.prepareStatement(sql);
    statement.setString(1, sample.getSampleName());
    statement.setDouble(2, sample.getSampleValue());
    statement.setLong(3, sample.getSampleId());
    int affected = statement.executeUpdate();

    connection.close();
    return affected > 0;
  }

  public List<Sample> list() throws Exception {
    List<Sample> sampleList = new ArrayList<Sample>();
    Connection connection = DatabaseUtilities.getConnection();

    String sql = "select * from Sample";
    PreparedStatement statement = connection.prepareStatement(sql);
    ResultSet resultSet = statement.executeQuery();
    while (resultSet.next()) {
      long sampleId = resultSet.getLong("sampleId");
      String sampleName = resultSet.getString("sampleName");
      double sampleValue = resultSet.getDouble("sampleValue");
      Sample sample = new Sample(sampleId, sampleName, sampleValue);
      sampleList.add(sample);
    }
    connection.close();
    return sampleList;
  }
}