Java – Spring not autowiring in unit tests with JUnit

javajunitspring

I test the following DAO with JUnit:

@Repository
public class MyDao {

    @Autowired
    private SessionFactory sessionFactory;

    // Other stuff here

}

As you can see, the sessionFactory is autowired using Spring. When I run the test, sessionFactory remains null and I get a null pointer exception.

This is the sessionFactory configuration in Spring:

<bean id="sessionFactory"
    class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource" />
    <property name="configLocation">
        <value>classpath:hibernate.cfg.xml</value>
    </property>
    <property name="configurationClass">
        <value>org.hibernate.cfg.AnnotationConfiguration</value>
    </property>
    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">${jdbc.dialect}</prop>
            <prop key="hibernate.show_sql">true</prop>
        </props>
    </property>
</bean>

What's wrong? How can I enable autowiring for unit testings too?

Update: I don't know if it's the only way to run JUnit tests, but note that I'm running it in Eclipse with right-clicking on the test file and selecting "run as"->"JUnit test"

Best Answer

Add something like this to your root unit test class:

@RunWith( SpringJUnit4ClassRunner.class )
@ContextConfiguration

This will use the XML in your default path. If you need to specify a non-default path then you can supply a locations property to the ContextConfiguration annotation.

http://static.springsource.org/spring/docs/2.5.6/reference/testing.html

Related Solutions

Java – How to assert that a certain exception is thrown in JUnit 4 tests

It depends on the JUnit version and what assert libraries you use.

For JUnit5 and 4.13 see answer https://stackoverflow.com/a/2935935/2986984
If you use assertJ or google-truth, see answer https://stackoverflow.com/a/41019785/2986984

The original answer for JUnit <= 4.12 was:

@Test(expected = IndexOutOfBoundsException.class)
public void testIndexOutOfBoundsException() {

    ArrayList emptyList = new ArrayList();
    Object o = emptyList.get(0);

}

Though answer https://stackoverflow.com/a/31826781/2986984 has more options for JUnit <= 4.12.

Reference :

JUnit Test-FAQ

Java – How does autowiring work in Spring

First, and most important - all Spring beans are managed - they "live" inside a container, called "application context".

Second, each application has an entry point to that context. Web applications have a Servlet, JSF uses a el-resolver, etc. Also, there is a place where the application context is bootstrapped and all beans - autowired. In web applications this can be a startup listener.

Autowiring happens by placing an instance of one bean into the desired field in an instance of another bean. Both classes should be beans, i.e. they should be defined to live in the application context.

What is "living" in the application context? This means that the context instantiates the objects, not you. I.e. - you never make new UserServiceImpl() - the container finds each injection point and sets an instance there.

In your controllers, you just have the following:

@Controller // Defines that this class is a spring bean
@RequestMapping("/users")
public class SomeController {

    // Tells the application context to inject an instance of UserService here
    @Autowired
    private UserService userService;

    @RequestMapping("/login")
    public void login(@RequestParam("username") String username,
           @RequestParam("password") String password) {

        // The UserServiceImpl is already injected and you can use it
        userService.login(username, password);

    }
}

A few notes:

In your applicationContext.xml you should enable the <context:component-scan> so that classes are scanned for the @Controller, @Service, etc. annotations.
The entry point for a Spring-MVC application is the DispatcherServlet, but it is hidden from you, and hence the direct interaction and bootstrapping of the application context happens behind the scene.
UserServiceImpl should also be defined as bean - either using <bean id=".." class=".."> or using the @Service annotation. Since it will be the only implementor of UserService, it will be injected.
Apart from the @Autowired annotation, Spring can use XML-configurable autowiring. In that case all fields that have a name or type that matches with an existing bean automatically get a bean injected. In fact, that was the initial idea of autowiring - to have fields injected with dependencies without any configuration. Other annotations like @Inject, @Resource can also be used.

Best Answer

Related Solutions

Java – How to assert that a certain exception is thrown in JUnit 4 tests

Java – How does autowiring work in Spring

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