Mercurial > hg > LightPIT / file revision

 /*

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

  *

  * Copyright 2018 Mike Becker. All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions are met:

  *

  *   1. Redistributions of source code must retain the above copyright

  *      notice, this list of conditions and the following disclaimer.

  *

  *   2. Redistributions in binary form must reproduce the above copyright

  *      notice, this list of conditions and the following disclaimer in the

  *      documentation and/or other materials provided with the distribution.

  *

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE

  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

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  *

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 package de.uapcore.lightpit;

 import de.uapcore.lightpit.dao.DataAccessObjects;

 import de.uapcore.lightpit.dao.postgres.PGDataAccessObjects;

 import org.slf4j.Logger;

 import org.slf4j.LoggerFactory;

 import javax.naming.Context;

 import javax.naming.InitialContext;

 import javax.naming.NamingException;

 import javax.servlet.ServletContext;

 import javax.servlet.ServletContextEvent;

 import javax.servlet.ServletContextListener;

 import javax.servlet.annotation.WebListener;

 import javax.sql.DataSource;

 import java.sql.Connection;

 import java.sql.DatabaseMetaData;

 import java.sql.SQLException;

 import java.util.Optional;

 /**

  * Provides access to different privilege layers within the database.

  */

 @WebListener

 public final class DatabaseFacade implements ServletContextListener {

     private static final Logger LOG = LoggerFactory.getLogger(DatabaseFacade.class);

     /**

      * Timeout in seconds for the validation test.

      */

     private static final int DB_TEST_TIMEOUT = 10;

     /**

      * Specifies the database dialect.

      */

     public enum Dialect {

         Postgres

     }

     /**

      * The database dialect to use.

      * <p>

      * May be overridden by context parameter.

      *

      * @see Constants#CTX_ATTR_DB_DIALECT

      */

     private Dialect dialect = Dialect.Postgres;

     /**

      * The default schema to test against when validating the connection.

      * <p>

      * May be overridden by context parameter.

      *

      * @see Constants#CTX_ATTR_DB_SCHEMA

      */

     private static final String DB_DEFAULT_SCHEMA = "lightpit";

     /**

      * The attribute name in the Servlet context under which an instance of this class can be found.

      */

     public static final String SC_ATTR_NAME = DatabaseFacade.class.getName();

     private static final String DS_JNDI_NAME = "jdbc/lightpit/app";

     private DataSource dataSource;

     private DataAccessObjects dataAccessObjects;

     /**

      * Returns the data source.

      * <p>

      * The Optional returned should never be empty. However, if something goes

      * wrong during initialization, the data source might be absent.

      * Hence, users of this data source are forced to check the existence.

      *

      * @return a data source

      */

     public Optional<DataSource> getDataSource() {

         // TODO: this should not be an optional, if an empty optional is actually an exception

         return Optional.ofNullable(dataSource);

     }

     /**

      * Returns the data access objects.

      *

      * @return an interface to obtain the data access objects

      */

     public DataAccessObjects getDataAccessObjects() {

         return dataAccessObjects;

     }

     public Dialect getSQLDialect() {

         return dialect;

     }

     private static void checkConnection(DataSource ds, String testSchema) {

         try (Connection conn = ds.getConnection()) {

             if (!conn.isValid(DB_TEST_TIMEOUT)) {

                 throw new SQLException("Validation check failed.");

             }

             if (conn.isReadOnly()) {

                 throw new SQLException("Connection is read-only and thus unusable.");

             }

             if (!conn.getSchema().equals(testSchema)) {

                 throw new SQLException(String.format("Connection is not configured to use the schema %s.", testSchema));

             }

             DatabaseMetaData metaData = conn.getMetaData();

             LOG.info("Connections as {} to {}/{} ready to go.", metaData.getUserName(), metaData.getURL(), conn.getSchema());

         } catch (SQLException ex) {

             LOG.error("Checking database connection failed", ex);

         }

     }

     private static DataSource retrieveDataSource(Context ctx) {

         DataSource ret = null;

         try {

             ret = (DataSource) ctx.lookup(DS_JNDI_NAME);

             LOG.info("Data source retrieved.");

         } catch (NamingException ex) {

             LOG.error("Data source {} not available.", DS_JNDI_NAME);

             LOG.error("Reason for the missing data source: ", ex);

         }

         return ret;

     }

     @Override

     public void contextInitialized(ServletContextEvent sce) {

         ServletContext sc = sce.getServletContext();

         dataSource = null;

         final String contextName = Optional

                 .ofNullable(sc.getInitParameter(Constants.CTX_ATTR_JNDI_CONTEXT))

                 .orElse("java:comp/env");

         final String dbSchema = Optional

                 .ofNullable(sc.getInitParameter(Constants.CTX_ATTR_DB_SCHEMA))

                 .orElse(DB_DEFAULT_SCHEMA);

         final String dbDialect = sc.getInitParameter(Constants.CTX_ATTR_DB_DIALECT);

         if (dbDialect != null) {

             try {

                 dialect = Dialect.valueOf(dbDialect);

             } catch (IllegalArgumentException ex) {

                 LOG.error("Unknown or unsupported database dialect {}. Defaulting to {}.", dbDialect, dialect);

             }

         }

         dataAccessObjects = createDataAccessObjects(dialect);

         try {

             LOG.debug("Trying to access JNDI context {}...", contextName);

             Context initialCtx = new InitialContext();

             Context ctx = (Context) initialCtx.lookup(contextName);

             dataSource = retrieveDataSource(ctx);

             if (dataSource != null) {

                 checkConnection(dataSource, dbSchema);

             }

         } catch (NamingException | ClassCastException ex) {

             LOG.error("Cannot access JNDI resources.", ex);

         }

         sc.setAttribute(SC_ATTR_NAME, this);

         LOG.info("Database facade injected into ServletContext.");

     }

     private static DataAccessObjects createDataAccessObjects(Dialect dialect) {

         switch (dialect) {

             case Postgres:

                 return new PGDataAccessObjects();

             default:

                 throw new AssertionError("Non-exhaustive switch - this is a bug.");

         }

     }

     @Override

     public void contextDestroyed(ServletContextEvent sce) {

         dataSource = null;

     }

 }