NullPointer Exception when trying to Unit Test using SpringRunner

Question

Hi I am trying to run my unit test using SpringRunner.class. I am creating a new instance for jdbcTemaplte in my test class. I am using H2 DB for unit test and i am able to use the jdbcTemplate instance to create or update the tables.It works fine. but when it goes to the actual class its testing the jdbcTemplate is null which throws NullPointerException

Below is the code:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration
public class MyClassTest {

@InjectMocks
private ClassToTest classToTest;

@Autowired
private JdbcTemplate jdbcTemplate;

@org.springframework.context.annotation.Configuration
static class Config {

    @Bean(name = "jdbcTemplate")
    public JdbcTemplate orderService() {
        BasicDataSource dataSourceConfig = new BasicDataSource();
        dataSourceConfig.setDriverClassName("org.h2.Driver");
        dataSourceConfig.setUrl("jdbc:h2:mem:db");
        dataSourceConfig.setUsername("someUserName");
        dataSourceConfig.setPassword("somePassword");

        return new JdbcTemplate(dataSourceConfig);
    }
}
@Before
public void setUp() throws Exception {
//Use the jdbcTemplate to create Queries in H2 which works fine.
}

}

ClassToTest.java

 public class ClassToTest{
    @Autowired
    JdbcTemplate jdbcTemplate;

   //someMethod in DAO using jdbcTemplate to make sql Operations.

}

the JDBC Template is null in ClassToTest and throws a nullPointerException when trying to test the method.

I am just not sure why the Autowire is not wiring the dependency i have created. I have tried to use @Primary to explicitly take this jdbcTemplate when necessary but not sure why its not working.

Any suggestions are helpful here. Thanks In Advance.

Answer 1

I see many factors that could be in cause :

• Your class "ClassToTest" isn't a Spring service/component, the autowire cannot work. Why won't you annotate it with @Component ?
• Good practices with Spring advice to put autowires in the constructor.

Like :

@Component
public class ClassToTest {
    private JdbcTemplate template;

    @Autowired // Although it's not even required when you have only one constructor : it's by default autowired
    public ClassToTest(JdbcTemplate template) {
        this.template = template;
    }
}

Try this, tell us what worked. Good luck

Answer 2

You’re using @InjectMocks annotation on your object under test but you’re not mocking anything, instead you want to load spring context and inject the jdbcTemplate bean into it. Try to replace @InjectMocks with @Autowired on ClassToTest and remove jdbcTemplate field. jdbcTemplate bean should be initialized in Config and be autowired into ClassToTest. Also you might want to specify the Config class in @ContextConfiguration. Hope it helps.