Loading web application properties

Question

When I build project by maven, it's OK, but when deploy it by Tomkat, I have NullPointerException. Class, where can be problem - PropertiesManager. logline: PropertiesManager.getApplicationProperties(PropertiesManager.java:31)

public class PropertiesManager {
    private static final String PROPERTY_FILE_NAME =
            "resources/application.properties";
    private static PropertiesManager Instance;
    private Properties properties;

    private PropertiesManager() {
    }

    public static PropertiesManager getInstance() {
        if (Instance == null) {
            Instance = new PropertiesManager();
        }
        return Instance;
    }

    public Properties getApplicationProperties() {
        if (properties == null) {
            properties = new Properties();
            try (InputStream stream = Thread.currentThread()
                    .getContextClassLoader()
                    .getResourceAsStream(PROPERTY_FILE_NAME)) {
                properties.load(stream);
            } catch (IOException e) {
                throw new ApplicationException("Failed to load property file", e);
            }
        }
        return properties;
    }
}

And logline: ApplicationLifecycleListener.contextInitialized(ApplicationLifecycleListener.java:14) Class ApplicationLifecycleListener:

public class ApplicationLifecycleListener implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        Properties applicationProperties = PropertiesManager.getInstance().getApplicationProperties();
        DBManager.getInstance().initialize(applicationProperties);
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        DBManager.getInstance().stopDb();
    }
}

What is problem can be?

How do you deploy it? in a standalone Tomcat instance, wamp, inside eclipse or something else? If you use a relative path, I guess that could be relevant in your issue... — Rafael Palomino, Sep 13 '18 at 18:11

carloseugenio · Accepted Answer · 2018-09-16T13:49:21.930

Without providing the file with the exact line you see the NullPointerException (none of the files you provided have the lines shown in log), it is difficult to be sure. But one hint is that although you put your resources files to be built with Maven in the '<project>/src/main/resources' folder, when built and packing the war file, it will put your application resource files in the 'WEB-INF/classes' folder which is part of the application default classpath. Therefore, to correctly reference them using the method Thread.currentThread().getContextClassLoader().getResourceAsStream(...) you should not add the 'resources\...' prefix to the file name, since this method already look files in the default application classpath. Remove the prefix and see if it works. Please, refer to this answer for more detail.

Loading web application properties

1 Answers1