SpringJUnit4ClassRunner是否为每个测试初始化​​bean？

Question

The following test illustrates that this test bean is initialized twice by Spring. I'm hoping someone can tell me why this is so, since it should only be once. Here's the test:

import org.apache.log4j.Logger;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;


@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {} )
public class TestAfterPropsSet implements InitializingBean {

private static final Logger logger = Logger.getLogger(TestAfterPropsSet.class);

@Test
public void test1() {
    logger.debug("Test1");
}

@Test
public void test2() {
    logger.debug("Test2");      
}

public void afterPropertiesSet() throws Exception {
    logger.debug("Bean Initialized");       
}
} // end class

Here's the bean file:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd">
</beans>

and here's the output:

2009-10-13 21:20:04,393 [TestAfterPropsSet.java 26] DEBUG - Bean Initialized
2009-10-13 21:20:04,393 [TestAfterPropsSet.java 17] DEBUG - Test1
2009-10-13 21:20:04,393 [TestAfterPropsSet.java 26] DEBUG - Bean Initialized
2009-10-13 21:20:04,393 [TestAfterPropsSet.java 22] DEBUG - Test2

Answer 1

It's not a Spring convention. You should be following JUnit conventions, ie suite-wide initialization or deconstruction should be done in @BeforeClass and @AfterClass accordingly, or you can use @Autowire and let Spring handle the object's scope.

A new suite will be constructed for each test. This is more apparent in JUnit3 where you had to create a new suite using a specified test name.

Take a look at the JavaDoc :

The Test annotation tells JUnit that the public void method to which it is attached can be run as a test case. To run the method, JUnit first constructs a fresh instance of the class then invokes the annotated method. Any exceptions thrown by the test will be reported by JUnit as a failure. If no exceptions are thrown, the test is assumed to have succeeded.

Your use case is a bit puzzling since your test isn't actually doing anything and there is no bean, which you reference. By default, Spring beans are declared with the default scope="singleton" attribute, so had you actually declared a bean, it would have been a cached singleton. However, this has nothing to do with method execution.