LogBuilder.java

package org.wahlzeit.services;

import org.wahlzeit.model.Client;
import org.wahlzeit.model.UserManager;
import org.wahlzeit.model.UserSession;

import java.io.PrintWriter;
import java.io.StringWriter;

/**
 * Builder class for log messages, that ensures that log messages are all formatted equally.
 *
 * Google App Engine as a PaaS has certain restrictions depending their services, hence a default Java logging
 * <code>Formatter</code> could not be used
 *
 * (see https://stackoverflow.com/questions/30345665/how-to-customize-logging-for-google-app-engine-java).
 * 
 * @review
 */
public class LogBuilder {

	protected static final String LEVEL = "level";
	protected static final String USER_LEVEL = "ul";
	protected static final String SYSTEM_LEVEL = "sl";
	protected static final String SESSION = "session";
	protected static final String CLIENT = "client";
	protected static final String MESSAGE = "message";
	protected static final String ACTION = "action";
	protected static final String NAME_VALUE_SEPARATOR = "=";
	protected static final String INFO_SEPARATOR = ", ";
	protected static final String EXCEPTION_REASON = "exception reason";
	protected static final String STACKTRACE = "stacktrace";

	protected StringBuilder logMessage;


	protected LogBuilder() {
		logMessage = new StringBuilder();
	}


	// create-methods --------------------------------------------------------------------------------------------------

	/**
	 * @methodtype factory
	 *
	 * Creates a LogBuilder Object and adds the Level (user level), the current <code>HttpSession</code>, and the
	 * clients name.
	 */
	public static LogBuilder createUserMessage() {
		return doCreateMessage(USER_LEVEL);
	}

	/**
	 * @methodtype factory
	 *
	 * Primitive Method that creates a LogBuilder Object and adds the Level, the current <code>HttpSession</code>, and
	 * the clients name.
	 */
	protected static LogBuilder doCreateMessage(String level) {
		LogBuilder result = new LogBuilder();
		Session session = SessionManager.getThreadLocalSession();
		String sessionName;
		String clientName;
		if (session != null) {
			sessionName = session.getName();
			Client client = UserManager.getInstance().getClientById(session.getClientId());
			if (client != null) {
				clientName = client.getNickName();
			} else {
				clientName = UserSession.ANONYMOUS_CLIENT;
			}
		} else {
			sessionName = Session.NO_SESSION;
			clientName = UserSession.ANONYMOUS_CLIENT;
		}

		result.add(LEVEL + NAME_VALUE_SEPARATOR + level);
		result.add(SESSION + NAME_VALUE_SEPARATOR + sessionName);
		result.add(CLIENT + NAME_VALUE_SEPARATOR + clientName);

		return result;
	}

	/**
	 * @methodtype set
	 */
	protected void add(String logMessagePart) {

		assert logMessage != null;

		if (logMessage.length() == 0) {
			logMessage.append(logMessagePart);
		} else {
			logMessage.append(INFO_SEPARATOR);
			logMessage.append(logMessagePart);
		}
	}


	// add-methods -----------------------------------------------------------------------------------------------------

	/**
	 * @methodtype factory
	 *
	 * Creates a LogBuilder Object and adds the Level (system level), the current <code>HttpSession</code>, and the
	 * clients name.
	 */
	public static LogBuilder createSystemMessage() {
		return doCreateMessage(SYSTEM_LEVEL);
	}

	/**
	 * @methodtype mutate
	 *
	 * Adds the following to the LogMessage: ", <name>=<value>".
	 */
	public LogBuilder addParameter(String name, int value) {
		add(name + NAME_VALUE_SEPARATOR + String.valueOf(value));
		return this;
	}

	/**
	 * @methodtype mutate
	 *
	 * Adds the following to the LogMessage: ", <name>=<value>".
	 */
	public LogBuilder addParameter(String name, boolean value) {
		add(name + NAME_VALUE_SEPARATOR + String.valueOf(value));
		return this;
	}

	/**
	 * @methodtype mutate
	 *
	 * Adds the following to the LogMessage: ", <name>=<value>".
	 */
	public LogBuilder addParameter(String name, String value) {
		add(name + NAME_VALUE_SEPARATOR + value);
		return this;
	}

	/**
	 * @methodtype mutate
	 *
	 * Adds the following to the LogMessage: ", <name>=<value>.toString()".
	 */
	public LogBuilder addParameter(String name, Object value) {
		add(name + NAME_VALUE_SEPARATOR + value.toString());
		return this;
	}

	/**
	 * @methodtype mutate
	 *
	 * Adds the message to the LogMessage: ", <message>".
	 */
	public LogBuilder addMessage(String message) {
		add(message);
		return this;
	}

	/**
	 * @methodtype mutate
	 *
	 * Adds the stacktrace and the <code>exceptionMessage</code> to the log message.
	 */
	public LogBuilder addException(String exceptionMessage, Throwable throwable) {
		add(EXCEPTION_REASON + NAME_VALUE_SEPARATOR + exceptionMessage);
		StringWriter sw = new StringWriter();
		throwable.printStackTrace(new PrintWriter(sw));
		add(STACKTRACE + NAME_VALUE_SEPARATOR + sw.toString());
		return this;
	}


	// build-method ----------------------------------------------------------------------------------------------------

	/**
	 * @methodtype mutate
	 *
	 * Adds the info that the action is performed the log message: "action=<action>".
	 */
	public LogBuilder addAction(String action) {
		add(ACTION + NAME_VALUE_SEPARATOR + action);
		return this;
	}


	// hidden setter and getter methods --------------------------------------------------------------------------------

	/**
	 * @methodtype conversion
	 *
	 * Puts everything together that has been added to the LogMessage before.
	 */
	@Override
	public String toString() {

		assert logMessage != null;
		assert logMessage.length() > 0;

		return logMessage.toString();
	}
}