How to test constructor of a class that has a @PostConstruct method using Spring?

Question

If I have a class with a @PostConstruct method, how can I test its constructor and thus its @PostConstruct method using JUnit and Spring? I can't simply use new ClassName(param, param) because then it's not using Spring -- the @PostConstruct method is not getting fired.

Am I missing something obvious here?

public class Connection {
    private String x1;
    private String x2;

    public Connection(String x1, String x2) {
        this.x1 = x1;
        this.x2 = x2;
    }

    @PostConstruct
    public void init() {
        x1 = "arf arf arf";
    }

}


@Test
public void test() {
    Connection c = new Connection("dog", "ruff");
    assertEquals("arf arf arf", c.getX1());
}

I have something similar (though slightly more complex) than this and the @PostConstruct method does not get hit.

Answer 1

Have a look at Spring JUnit Runner.

You need to inject your class in your test class so that spring will construct your class and will also call post construct method. Refer the pet clinic example.

eg:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:your-test-context-xml.xml")
public class SpringJunitTests {

    @Autowired
    private Connection c;

    @Test
    public void tests() {
        assertEquals("arf arf arf", c.getX1();
    }

    // ...

Answer 2

If the only container managed part of Connection is your @PostContruct method, just call it manually in a test method:

@Test
public void test() {
  Connection c = new Connection("dog", "ruff");
  c.init();
  assertEquals("arf arf arf", c.getX1());
}

If there is more than that, like dependencies and so on you can still either inject them manually or - as Sridhar stated - use spring test framework.

Answer 3

@PostConstruct must be changing the state of the object. So, in JUnit test case, after getting the bean check the state of the object. If it is same as the state set by @PostConstruct, then the test is success.

Answer 4

By default, Spring will not aware of the @PostConstruct and @PreDestroy annotation. To enable it, you have to either register ‘CommonAnnotationBeanPostProcessor‘ or specify the ‘‘ in bean configuration file.

<bean class="org.springframework.context.annotation.CommonAnnotationBeanPostProcessor" />

or

<context:annotation-config />