public MongoDbProvider build()

in log4j-mongodb3/src/main/java/org/apache/logging/log4j/mongodb3/MongoDbProvider.java [130:223]
85 lines of code
16 McCabe index (conditional complexity)

        public MongoDbProvider build() {
            MongoDatabase database;
            String description;
            MongoClient mongoClient = null;

            if (Strings.isNotEmpty(factoryClassName) && Strings.isNotEmpty(factoryMethodName)) {
                try {
                    final Class<?> factoryClass = LoaderUtil.loadClass(factoryClassName);
                    final Method method = factoryClass.getMethod(factoryMethodName);
                    final Object object = method.invoke(null);

                    if (object instanceof MongoDatabase) {
                        database = (MongoDatabase) object;
                    } else if (object instanceof MongoClient) {
                        if (Strings.isNotEmpty(databaseName)) {
                            database = ((MongoClient) object).getDatabase(databaseName);
                        } else {
                            LOGGER.error("The factory method [{}.{}()] returned a MongoClient so the database name is "
                                    + "required.", factoryClassName, factoryMethodName);
                            return null;
                        }
                    } else {
                        if (object == null) {
                            LOGGER.error("The factory method [{}.{}()] returned null.", factoryClassName,
                                    factoryMethodName);
                        } else {
                            LOGGER.error("The factory method [{}.{}()] returned an unsupported type [{}].",
                                    factoryClassName, factoryMethodName, object.getClass().getName());
                        }
                        return null;
                    }

                    final String databaseName = database.getName();
                    description = "database=" + databaseName;
                } catch (final ClassNotFoundException e) {
                    LOGGER.error("The factory class [{}] could not be loaded.", factoryClassName, e);
                    return null;
                } catch (final NoSuchMethodException e) {
                    LOGGER.error("The factory class [{}] does not have a no-arg method named [{}].", factoryClassName,
                            factoryMethodName, e);
                    return null;
                } catch (final Exception e) {
                    LOGGER.error("The factory method [{}.{}()] could not be invoked.", factoryClassName,
                            factoryMethodName, e);
                    return null;
                }
            } else if (Strings.isNotEmpty(databaseName)) {
                MongoCredential mongoCredential = null;
                description = "database=" + databaseName;
                if (Strings.isNotEmpty(userName) && Strings.isNotEmpty(password)) {
                    description += ", username=" + userName;
                    mongoCredential = MongoCredential.createCredential(userName, databaseName, password.toCharArray());
                }
                try {
                    final int portInt = TypeConverters.convert(port, int.class, DEFAULT_PORT);
                    description += ", server=" + server + ", port=" + portInt;
                    final WriteConcern writeConcern = toWriteConcern(writeConcernConstant, writeConcernConstantClassName);
                    // @formatter:off
                    final MongoClientOptions options = MongoClientOptions.builder()
                            .codecRegistry(CODEC_REGISTRIES)
                            .writeConcern(writeConcern)
                            .build();
                    // @formatter:on
                    final ServerAddress serverAddress = new ServerAddress(server, portInt);
                    mongoClient = mongoCredential == null ?
                    // @formatter:off
                            new MongoClient(serverAddress, options) :
                            new MongoClient(serverAddress, mongoCredential, options);
                    // @formatter:on
                    database = mongoClient.getDatabase(databaseName);
                } catch (final Exception e) {
                    LOGGER.error("Failed to obtain a database instance from the MongoClient at server [{}] and "
                            + "port [{}].", server, port);
                    close(mongoClient);
                    return null;
                }
            } else {
                LOGGER.error("No factory method was provided so the database name is required.");
                close(mongoClient);
                return null;
            }

            try {
                database.listCollectionNames().first(); // Check if the database actually requires authentication
            } catch (final Exception e) {
                LOGGER.error(
                        "The database is not up, or you are not authenticated, try supplying a username and password to the MongoDB provider.",
                        e);
                close(mongoClient);
                return null;
            }

            return new MongoDbProvider(mongoClient, database, collectionName, capped, collectionSize, description);
        }