Bugs.java

package userdb;

import com.mchange.v2.c3p0.ComboPooledDataSource;
import org.junit.Test;

import java.beans.PropertyVetoException;
import java.sql.*;

import static org.junit.Assert.assertEquals;

public class Bugs {

    public static final String SELECT_1 = "SELECT 1 AS value";

    // This test succeeds because there is no statement pooling
    @Test
    public void withoutStatementPooling() throws PropertyVetoException, SQLException {
        ComboPooledDataSource db = new ComboPooledDataSource();

        db.setDriverClass("org.postgresql.Driver");
        db.setJdbcUrl("jdbc:postgresql://localhost/testdb");

        try (Connection connection = db.getConnection()) {
            assertEquals(1, getOne(connection));
            assertEquals("value", getName(connection));
        }
    }

    // This test fails because it re-uses the same PreparedStatement
    @Test
    public void withStatementPooling() throws PropertyVetoException, SQLException {
        ComboPooledDataSource db = new ComboPooledDataSource();

        db.setDriverClass("org.postgresql.Driver");
        db.setMaxStatementsPerConnection(100); // THIS LINE IS CRITICAL
        db.setJdbcUrl("jdbc:postgresql://localhost/testdb");

        try (Connection connection = db.getConnection()) {
            assertEquals(1, getOne(connection));
            assertEquals("value", getName(connection));
        }
    }

    private int getOne(Connection connection) throws SQLException {
        PreparedStatement statement = connection.prepareStatement(SELECT_1);
        ResultSet resultSet = statement.executeQuery();
        resultSet.next();
        int value = resultSet.getInt(1);
        statement.close();

        return value;
    }

    private String getName(Connection connection) throws SQLException {
        PreparedStatement statement = connection.prepareStatement(SELECT_1);
        ResultSetMetaData metaData = statement.getMetaData();
        String name = metaData.getColumnName(1);
        statement.close();

        return name;
    }
}