How to test a spring bean with prototype scope?

Question

I have a configuration class and a test class as below:

@Configuration
public class SimpleConfiguration {
    @Bean
    @Scope(scopeName = ConfigurableBeanFactory.SCOPE_PROTOTYPE)
    public String hello() {
        return "hello";
    }
}

@RunWith(SpringRunner.class)
@ContextConfiguration(classes = SimpleConfiguration.class)
public class SimpleTest {
    @Autowired
    private String hello;

    @Autowired
    private String another;

    @Test
    public void should_not_same() {
        Assert.assertNotSame(hello, another);
    }
}

According to the definition of prototype scope, the hello and another object should be not same, but this test failed. Why? Thanks!

For your experiment you picked about the only type that's not suitable for a Spring Bean: a String. Also, why are you trying to test Spring Framework code? — kryger, Sep 23 '16 at 12:46

score 1 · Answer 1 · edited May 23 '17 at 10:27

Strings in Java are pooled for effeciency. You can read more about it here: What is the Java string pool and how is "s" different from new String("s")?

So, even though Spring will call your hello() method multiple times to try to create a new object (since you want prototype scope), the JVM will return the same String instance anyway.

If you would do the following, the test should be ok:

public String hello() {
    return new String("hello");
}

Note that is is bad practise to create a String like this, but for the purpose of your test, this is how you can do it.

score 0 · Answer 2 · answered Sep 23 '16 at 06:09

0

Seems like same String is being reused to construct both hello and another from String pool.

If you create a class, say Person, and do the same test it is passing the test.

answered Sep 23 '16 at 06:09

K. Siva Prasad Reddy

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How to test a spring bean with prototype scope?

2 Answers2