parent
...pom.xml
...servlet-app
......pom.xml ( specifies simple-lib as a dependency )
...simple-lib
......src/main/resources/config.properties
......src/main/java/package1/Config.java
......src/main/java/package1/HelloQuartzJob.java

public class Config{

    static final String PROPERTILES_FILE = "config.properties";
    static Properties props;
    static{
        log.info("Loading Config properties from {}", PROPERTILES_FILE);
        props = new Properties();

        try {
            InputStream is = ClassLoader.getSystemResourceAsStream(PROPERTILES_FILE);
            if (is == null) {
                log.info("Loading through ClassLoader as root");
                is = ClassLoader.getSystemResourceAsStream("/"+PROPERTILES_FILE);
            }
            if (is == null) {
                log.info("Loading through Config.class. root");
                is = Config.class.getResourceAsStream("/"+PROPERTILES_FILE);
            }
            if (is == null) {
                log.info("Loading through Config.class. relative");
                is = Config.class.getResourceAsStream(PROPERTILES_FILE);
            }
            if( is == null ) {
                log.info("Thread class loader root");
                is = Thread.currentThread().getContextClassLoader().getResourceAsStream("/"+PROPERTILES_FILE);
            }
            props.load(is);
        } catch (Throwable e) {
            log.error("Config properties loading error ", e);
            throw new RuntimeException(e);
        }
    }
}

InputStream is = ClassLoader.getSystemResourceAsStream(PROPERTILES_FILE);

InputStream is = Config.class.getClassLoader().getResourceAsStream(PROPERTILES_FILE);

is = ClassLoader.getSystemResourceAsStream("/"+PROPERTILES_FILE);

is = Thread.currentThread().getContextClassLoader().getResourceAsStream("/"+PROPERTILES_FILE);

String url = Config.class.getClassLoader().getResource("config.properties");
InputStream is = Config.class.getClassLoader().getResourceAsStream("config.properties");

String url = getClass().getClassLoader().getResource("config.properties");
InputStream is = getClass().getClassLoader().getResourceAsStream("config.properties");