LightPIT: src/main/java/de/uapcore/lightpit/DatabaseFacade.java@824d4042c857 (annotated)

src/main/java/de/uapcore/lightpit/DatabaseFacade.java@824d4042c857 (annotated)

src/main/java/de/uapcore/lightpit/DatabaseFacade.java

Sat, 09 May 2020 17:01:29 +0200

author: Mike Becker <universe@uap-core.de>
date: Sat, 09 May 2020 17:01:29 +0200
changeset 34: 824d4042c857
parent 33: fd8c40ff78c3
child 38: cf85ef18f231
permissions: -rw-r--r--

cleanup and simplification of database access layer

 /*
  * 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
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  *
  */
 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;
     }
 }

Mercurial > hg > LightPIT / annotate

src/main/java/de/uapcore/lightpit/DatabaseFacade.java@824d4042c857 (annotated)

src/main/java/de/uapcore/lightpit/DatabaseFacade.java