how to get mock ApplicationContext when i use PowerMockito

when i use PowerMockito to test a method,the code is

public class RedisLockUtil {

    private static final StringRedisTemplate STRING_REDIS_TEMPLATE = SpringContextUtil.getBean(StringRedisTemplate.class);

    public static boolean getLock(String lockId, long second) {
        log.info("lock by key:[{}],last :[{}] s", lockId, second);
        Boolean success = STRING_REDIS_TEMPLATE.opsForValue().setIfAbsent(lockId, "lock",
            second, TimeUnit.SECONDS);
        return success != null && success;
    }
}

@Component
public class SpringContextUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        SpringContextUtil.applicationContext = applicationContext;
    }

    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    public static Object getBean(String name) {
        return getApplicationContext().getBean(name);
    }

    public static <T> T getBean(Class<T> clazz) {
        return getApplicationContext().getBean(clazz);
    }

@RunWith(PowerMockRunner.class)
@PrepareForTest({RedisLockUtil.class})
public class Mock {

    @Before
    public void setUp() {
        PowerMockito.mockStatic(RedisLockUtil.class);
        MockitoAnnotations.initMocks(this);
    }
    @Test
    public void test(){
        RedisLockUtil.getLock("test",1L);
    }
}

i need to test the createUserLockKey method,but the STRING_REDIS_TEMPLATE need to be initialized。but i dont konw how to set ApplicationContext,so the method-getApplicationContext() will return null,and when RedisLockUtil invoke the getBean,it will throw NullPointException.

so how can i make the ApplicationContext not null?