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SchemaCrawler is an open-source Java API that makes working with database metadata as easy as working with plain old Java objects. SchemaCrawler is also a database schema discovery and comprehension, and schema documentation tool. You can search for database schema objects using regular expressions, and output the schema and data in a readable text format. The output is designed to be diff-ed against other database schemas.

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/*
========================================================================
SchemaCrawler
http://www.schemacrawler.com
Copyright (c) 2000-2024, Sualeh Fatehi .
All rights reserved.
------------------------------------------------------------------------

SchemaCrawler is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SchemaCrawler and the accompanying materials are made available under
the terms of the Eclipse Public License v1.0, GNU General Public License
v3 or GNU Lesser General Public License v3.

You may elect to redistribute this code under any of these licenses.

The Eclipse Public License is available at:
http://www.eclipse.org/legal/epl-v10.html

The GNU General Public License v3 and the GNU Lesser General Public
License v3 are available at:
http://www.gnu.org/licenses/

========================================================================
*/

package us.fatehi.utility.datasource;

import static java.lang.reflect.Proxy.newProxyInstance;
import static java.util.Objects.requireNonNull;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Arrays;

public class PooledConnectionUtility {

  private static class PooledConnectionInvocationHandler implements InvocationHandler {

    private final Connection connection;
    private final DatabaseConnectionSource databaseConnectionSource;
    private boolean isClosed;

    PooledConnectionInvocationHandler(
        final Connection connection, final DatabaseConnectionSource databaseConnectionSource) {
      requireNonNull(connection, "No database connnection provided");
      if (connection instanceof DatabaseConnectionSourceConnection) {
        try {
          this.connection = connection.unwrap(Connection.class);
        } catch (final SQLException e) {
          throw new RuntimeException("Could not unwrap proxy connection");
        }
      } else {
        this.connection = connection;
      }
      this.databaseConnectionSource =
          requireNonNull(databaseConnectionSource, "No database connection source provided");
      isClosed = false;
    }

    @Override
    public Object invoke(final Object proxy, final Method method, final Object[] args)
        throws Exception {
      final String methodName = method.getName();
      if (!Arrays.asList("isClosed", "unwrap").contains(methodName) && isClosed) {
        throw new SQLException(
            String.format("Cannot call <%s> since connection is closed", method));
      }
      switch (methodName) {
        case "close":
          databaseConnectionSource.releaseConnection(connection);
          isClosed = true;
          return null;
        case "isClosed":
          return isClosed;
        case "isWrapperFor":
          final Class clazz = (Class) args[0];
          return clazz.isAssignableFrom(connection.getClass());
        case "unwrap":
          return connection;
        case "toString":
          return String.format(
              "Pooled connection <%s@%d> for <%s>",
              proxy.getClass().getName(), proxy.hashCode(), connection);
        default:
          try {
            return method.invoke(connection, args);
          } catch (IllegalAccessException
              | IllegalArgumentException
              | InvocationTargetException e) {
            final Throwable cause = e.getCause();
            if (cause instanceof Exception) {
              throw (Exception) cause;
            }
            throw new SQLException(String.format("Could not delegate method <%s>", method), e);
          }
      }
    }
  }

  public static Connection newPooledConnection(
      final Connection connection, final DatabaseConnectionSource databaseConnectionSource) {

    return (Connection)
        newProxyInstance(
            PooledConnectionUtility.class.getClassLoader(),
            new Class[] {Connection.class, DatabaseConnectionSourceConnection.class},
            new PooledConnectionInvocationHandler(connection, databaseConnectionSource));
  }

  private PooledConnectionUtility() {
    // Prevent instantiation
  }
}




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