}

    /**
     * Gets the system properties to use for interpolation and profile activation. The system properties are collected
     * from the runtime environment like {@link System#getProperties()} and environment variables.
     *
     * @return The system properties, never {@code null}.
     */
    public Properties getSystemProperties() {
        return request.getSystemProperties();
    }

*----+------+------+
| <<<*>>> | Java system properties (see {{{https://docs.oracle.com/javase/8/docs/api/java/lang/System.html#getProperties()}JDK reference}}) | <<<$\{user.home\}>>>\
 | | <<<$\{java.home\}>>> |
*----+------+------+
| <<<*>>> | User properties | <<<$\{foo\}>>> |
*----+------+------+
| <<<env.*>>>\

     *
     * @param path
     *            The path to the properties file. Must not be {@literal null} or empty string.
     * @return The properties file.
     */
    public static Properties getProperties(final String path) {
        assertArgumentNotEmpty("path", path);

        final Properties props = new Properties();
        final InputStream is = getResourceAsStream(path);
        try {

        Activation defaultActivation = new Activation();

        defaultActivation.setActiveByDefault(true);

        defaultActivated.setActivation(defaultActivation);

        Properties props = System.getProperties();

        ProfileManager profileManager = new DefaultProfileManager(getContainer(), props);

        profileManager.addProfile(notActivated);
        profileManager.addProfile(defaultActivated);

        model.addProperty("key1", "value1");
        model.addProperty("key2", "value2");
        assertEquals(2, model.getProperties().size());

        // This should not throw NullPointerException
        model.getProperties().clear();
        assertEquals(0, model.getProperties().size());
    }

                            BUILD_POM_CLASSIFIER,
                            main.getExtension(),
                            main.getVersion(),
                            main.getProperties(),
                            main.getPath()));
                }
                // If deployBuildPom is false, we simply don't add the build POM to the result
            }

        Model out = interpolator.interpolateModel(model, new File("."), createModelBuildingRequest(context), collector);
        assertProblemFree(collector);

        assertEquals("/path/to/home", out.getProperties().get("outputDirectory"));
    }

    @Test
    public void envarExpressionThatEvaluatesToNullReturnsTheLiteralString() throws Exception {

        Map<String, String> modelProperties = new HashMap<>();

        final Method m = ClassUtil.getMethod(getClass(), "testGetProperties");
        final Annotation anno = m.getAnnotation(Hoge.class);
        final Map<String, Object> props = AnnotationUtil.getProperties(anno);
        assertThat((String) props.get("aaa"), is("123"));
        assertThat((String) props.get("bbb"), is("3"));
        assertThat(props.get("ccc"), is(nullValue()));
    }

        }

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        try (ObjectOutputStream oos = new ObjectOutputStream(baos)) {
            oos.writeObject(model.getProperties());
            oos.writeObject(model.getBuild().getPlugins());
        }
    }

    }
  }

  public void testNoNullValues() {
    for (StandardSystemProperty property : StandardSystemProperty.values()) {
      // Even though the contract in System.getProperties() specifies that a value will exist for
      // all of the listed keys, for some reason the "java.compiler" key returns null in some JVMs.
      if (property == JAVA_COMPILER) {
        continue;
      }