1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/main/java/de/uapcore/lightpit/DatabaseFacade.java Sat May 09 14:26:31 2020 +0200
1.3 @@ -0,0 +1,178 @@
1.4 +/*
1.5 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
1.6 + *
1.7 + * Copyright 2018 Mike Becker. All rights reserved.
1.8 + *
1.9 + * Redistribution and use in source and binary forms, with or without
1.10 + * modification, are permitted provided that the following conditions are met:
1.11 + *
1.12 + * 1. Redistributions of source code must retain the above copyright
1.13 + * notice, this list of conditions and the following disclaimer.
1.14 + *
1.15 + * 2. Redistributions in binary form must reproduce the above copyright
1.16 + * notice, this list of conditions and the following disclaimer in the
1.17 + * documentation and/or other materials provided with the distribution.
1.18 + *
1.19 + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
1.20 + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
1.21 + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
1.22 + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
1.23 + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
1.24 + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
1.25 + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
1.26 + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
1.27 + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
1.28 + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
1.29 + * POSSIBILITY OF SUCH DAMAGE.
1.30 + *
1.31 + */
1.32 +package de.uapcore.lightpit;
1.33 +
1.34 +import java.sql.Connection;
1.35 +import java.sql.DatabaseMetaData;
1.36 +import java.sql.SQLException;
1.37 +import java.util.Optional;
1.38 +import javax.naming.Context;
1.39 +import javax.naming.InitialContext;
1.40 +import javax.naming.NamingException;
1.41 +import javax.servlet.ServletContext;
1.42 +import javax.servlet.ServletContextEvent;
1.43 +import javax.servlet.ServletContextListener;
1.44 +import javax.servlet.annotation.WebListener;
1.45 +import javax.sql.DataSource;
1.46 +import org.slf4j.Logger;
1.47 +import org.slf4j.LoggerFactory;
1.48 +
1.49 +/**
1.50 + * Provides access to different privilege layers within the database.
1.51 + */
1.52 +@WebListener
1.53 +public final class DatabaseFacade implements ServletContextListener {
1.54 +
1.55 + private static final Logger LOG = LoggerFactory.getLogger(DatabaseFacade.class);
1.56 +
1.57 + /**
1.58 + * Timeout in seconds for the validation test.
1.59 + */
1.60 + private static final int DB_TEST_TIMEOUT = 10;
1.61 +
1.62 + public static enum Dialect {
1.63 + Postgres;
1.64 + }
1.65 +
1.66 + /**
1.67 + * The database dialect to use.
1.68 + *
1.69 + * May be override by context parameter.
1.70 + *
1.71 + * @see Constants#CTX_ATTR_DB_DIALECT
1.72 + */
1.73 + private Dialect dialect = Dialect.Postgres;
1.74 +
1.75 + /**
1.76 + * The default schema to test against when validating the connection.
1.77 + *
1.78 + * May be overridden by context parameter.
1.79 + *
1.80 + * @see Constants#CTX_ATTR_DB_SCHEMA
1.81 + */
1.82 + private static final String DB_DEFAULT_SCHEMA = "lightpit";
1.83 +
1.84 + /**
1.85 + * The attribute name in the Servlet context under which an instance of this class can be found.
1.86 + */
1.87 + public static final String SC_ATTR_NAME = DatabaseFacade.class.getName();
1.88 + private ServletContext sc;
1.89 +
1.90 + private static final String DS_JNDI_NAME = "jdbc/lightpit/app";
1.91 + private Optional<DataSource> dataSource;
1.92 +
1.93 + /**
1.94 + * Returns the data source.
1.95 + *
1.96 + * The Optional returned should never be empty. However, if something goes
1.97 + * wrong during initialization, the data source might be absent.
1.98 + * Hence, users of this data source are forced to check the existence.
1.99 + *
1.100 + * @return a data source
1.101 + */
1.102 + public Optional<DataSource> getDataSource() {
1.103 + return dataSource;
1.104 + }
1.105 +
1.106 + public Dialect getSQLDialect() {
1.107 + return dialect;
1.108 + }
1.109 +
1.110 + private static void checkConnection(DataSource ds, String testSchema, String errMsg) {
1.111 + try (Connection conn = ds.getConnection()) {
1.112 + if (!conn.isValid(DB_TEST_TIMEOUT)) {
1.113 + throw new SQLException("Validation check failed.");
1.114 + }
1.115 + if (conn.isReadOnly()) {
1.116 + throw new SQLException("Connection is read-only and thus unusable.");
1.117 + }
1.118 + if (!conn.getSchema().equals(testSchema)) {
1.119 + throw new SQLException(String.format("Connection is not configured to use the schema %s.", testSchema));
1.120 + }
1.121 + DatabaseMetaData metaData = conn.getMetaData();
1.122 + LOG.info("Connections as {} to {}/{} ready to go.", metaData.getUserName(), metaData.getURL(), conn.getSchema());
1.123 + } catch (SQLException ex) {
1.124 + LOG.error(errMsg, ex);
1.125 + }
1.126 + }
1.127 +
1.128 + private static Optional<DataSource> retrieveDataSource(Context ctx) {
1.129 + DataSource ret = null;
1.130 + try {
1.131 + ret = (DataSource)ctx.lookup(DS_JNDI_NAME);
1.132 + LOG.info("Data source retrieved.");
1.133 + } catch (NamingException ex) {
1.134 + LOG.error("Data source {} not available.", DS_JNDI_NAME);
1.135 + LOG.error("Reason for the missing data source: ", ex);
1.136 + }
1.137 + return Optional.ofNullable(ret);
1.138 + }
1.139 +
1.140 + @Override
1.141 + public void contextInitialized(ServletContextEvent sce) {
1.142 + sc = sce.getServletContext();
1.143 +
1.144 + dataSource = null;
1.145 +
1.146 + final String contextName = Optional
1.147 + .ofNullable(sc.getInitParameter(Constants.CTX_ATTR_JNDI_CONTEXT))
1.148 + .orElse("java:comp/env");
1.149 + final String dbSchema = Optional
1.150 + .ofNullable(sc.getInitParameter(Constants.CTX_ATTR_DB_SCHEMA))
1.151 + .orElse(DB_DEFAULT_SCHEMA);
1.152 + final String dbDialect = sc.getInitParameter(Constants.CTX_ATTR_DB_DIALECT);
1.153 + if (dbDialect != null) {
1.154 + try {
1.155 + dialect = Dialect.valueOf(dbDialect);
1.156 + } catch (IllegalArgumentException ex) {
1.157 + LOG.error("Unknown or unsupported database dialect {}. Defaulting to {}.", dbDialect, dialect);
1.158 + }
1.159 + }
1.160 +
1.161 + try {
1.162 + LOG.debug("Trying to access JNDI context {}...", contextName);
1.163 + Context initialCtx = new InitialContext();
1.164 + Context ctx = (Context) initialCtx.lookup(contextName);
1.165 +
1.166 + dataSource = retrieveDataSource(ctx);
1.167 +
1.168 + dataSource.ifPresent((ds) -> checkConnection(ds, dbSchema, "Checking database connection failed"));
1.169 + } catch (NamingException | ClassCastException ex) {
1.170 + LOG.error("Cannot access JNDI resources.", ex);
1.171 + }
1.172 +
1.173 + sc.setAttribute(SC_ATTR_NAME, this);
1.174 + LOG.info("Database facade injected into ServletContext.");
1.175 + }
1.176 +
1.177 + @Override
1.178 + public void contextDestroyed(ServletContextEvent sce) {
1.179 + dataSource = null;
1.180 + }
1.181 +}
