TestTooManyCursors.java

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jdbi.v3.core;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.jdbi.v3.core.rule.H2DatabaseRule;
import org.jdbi.v3.core.statement.DefaultStatementBuilder;
import org.junit.Rule;
import org.junit.Test;

/**
 * Oracle was getting angry about too many open cursors because of the large number
 * of prepared statements being created and cached indefinitely.
 */
public class TestTooManyCursors
{
    @Rule
    public H2DatabaseRule dbRule = new H2DatabaseRule();

    @Test
    public void testFoo() throws Exception
    {
        ConnectionFactory cf = dbRule.getConnectionFactory();
        ConnectionFactory errorCf = new ErrorProducingConnectionFactory(cf, 99);
        Jdbi db = Jdbi.create(errorCf);

        db.useHandle(handle -> {
            handle.setStatementBuilder(new DefaultStatementBuilder());
            for (int idx = 0; idx < 100; idx++) {
                handle.createQuery("SELECT " + idx + " FROM something").mapTo(int.class).findFirst();
            }
        });
    }

    private static class ErrorProducingConnectionFactory implements ConnectionFactory
    {
        private final ConnectionFactory target;
        private final int connCount;

        ErrorProducingConnectionFactory(ConnectionFactory target, int i)
        {
            this.target = target;
            connCount = i;
        }

        @Override
        public Connection openConnection() throws SQLException
        {
            return ConnectionInvocationHandler.newInstance(target.openConnection(), connCount);
        }
    }


    private static class ConnectionInvocationHandler implements InvocationHandler
    {
        private final Connection connection;
        private final int numSuccessfulStatements;
        private int numStatements = 0;

        public static Connection newInstance(Connection connection, int numSuccessfulStatements)
        {
            return (Connection) Proxy.newProxyInstance(connection.getClass().getClassLoader(),
                                                       new Class[]{Connection.class},
                                                       new ConnectionInvocationHandler(connection, numSuccessfulStatements));
        }

        public ConnectionInvocationHandler(Connection connection, int numSuccessfulStatements)
        {
            this.connection = connection;
            this.numSuccessfulStatements = numSuccessfulStatements;
        }

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
        {
            try {
                if ("createStatement".equals(method.getName()) ||
                    "prepareCall".equals(method.getName()) ||
                    "prepareStatement".equals(method.getName())) {
                    if (++numStatements > numSuccessfulStatements) {
                        throw new SQLException("Fake 'maximum open cursors exceeded' error");
                    }
                    return StatementInvocationHandler.newInstance((Statement) method.invoke(connection, args), this);
                }
                else {
                    return method.invoke(connection, args);
                }
            }
            catch (InvocationTargetException ex) {
                throw ex.getTargetException();
            }
        }

        public void registerCloseStatement()
        {
            numStatements--;
        }
    }

    private static class StatementInvocationHandler implements InvocationHandler
    {
        private final Statement stmt;
        private final ConnectionInvocationHandler connectionHandler;

        public static Statement newInstance(Statement stmt, ConnectionInvocationHandler connectionHandler)
        {

            Class<?> o = stmt.getClass();
            List<Class<?>> interfaces = new ArrayList<>();
            while (!o.equals(Object.class)) {
                interfaces.addAll(Arrays.asList(o.getInterfaces()));
                o = o.getSuperclass();
            }

            return (Statement) Proxy.newProxyInstance(stmt.getClass().getClassLoader(),
                                                      interfaces.toArray(new Class[interfaces.size()]),
                                                      new StatementInvocationHandler(stmt, connectionHandler));
        }

        public StatementInvocationHandler(Statement stmt, ConnectionInvocationHandler connectionHandler)
        {
            this.stmt = stmt;
            this.connectionHandler = connectionHandler;
        }

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
        {
            if ("close".equals(method.getName())) {
                connectionHandler.registerCloseStatement();
            }
            try {
                return method.invoke(stmt, args);
            }
            catch (InvocationTargetException ex) {
                throw ex.getTargetException();
            }
        }
    }
}