Spring @Inject

This annotation has the following execution paths, listed by precedence:
1、Match by Type
2、Match by Qualifier
3、Match by Name

These execution paths are applicable to both setter and field injection.

---

<dependency>
    <groupId>javax.injectgroupId>
    <artifactId>javax.injectartifactId>
    <version>1version>
dependency>

---

Field Injection

Match by Type

@Component
public class ArbitraryDependency {

    private final String label = "Arbitrary Dependency";

    public String toString() {
        return label;
    }
}

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(loader=AnnotationConfigContextLoader.class, classes=ApplicationContextTestInjectType.class)
public class FieldInjectIntegrationTest {

    @Inject
    private ArbitraryDependency fieldInjectDependency;

    @Test
    public void givenInjectAnnotation_WhenOnField_ThenValidDependency(){
        assertNotNull(fieldInjectDependency);
        assertEquals("Arbitrary Dependency",fieldInjectDependency.toString());
    }
}

Match by Qualifier

What if there are multiple implementations of a particular class type, and a certain class requires a specific bean?

public class AnotherArbitraryDependency extends ArbitraryDependency {
    private final String label = "Another Arbitrary Dependency";
    public String toString() {
        return label;
    }
}

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(loader=AnnotationConfigContextLoader.class,classes=ApplicationContextTestInjectQualifier.class)
public class FieldQualifierInjectIntegrationTest {

	# NoUniqueBeanDefinitionException 
	@Inject
	private ArbitraryDependency defaultDependency;
	@Inject
	private ArbitraryDependency namedDependency;
	
	# 解决方案
	@Inject
	@Qualifier("defaultFile")
	private ArbitraryDependency defaultDependency;
	@Inject
	@Qualifier("namedFile")
	private ArbitraryDependency namedDependency;
	
    @Test
    public void givenInjectQualifier_WhenOnField_ThenDefaultFileValid(){
        assertNotNull(defaultDependency);
        assertEquals("Arbitrary Dependency",defaultDependency.toString());
    }

    @Test
    public void givenInjectQualifier_WhenOnField_ThenNamedFileValid(){
        assertNotNull(defaultDependency);
        assertEquals("Another Arbitrary Dependency",namedDependency.toString());
    }
}

Match by Name

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(loader=AnnotationConfigContextLoader.class,classes=ApplicationContextTestInjectName.class)
public class FieldByNameInjectIntegrationTest {

    @Inject
    @Named("yetAnotherFieldInjectDependency")
    private ArbitraryDependency yetAnotherFieldInjectDependency;

    @Test
    public void givenInjectQualifier_WhenSetOnField_ThenDependencyValid(){
        assertNotNull(yetAnotherFieldInjectDependency);
        assertEquals("Yet Another Arbitrary Dependency",yetAnotherFieldInjectDependency.toString());
    }
}

@Configuration
public class ApplicationContextTestInjectName {
    @Bean
    public ArbitraryDependency yetAnotherFieldInjectDependency() {
        ArbitraryDependency yetAnotherFieldInjectDependency = new YetAnotherArbitraryDependency();
        return yetAnotherFieldInjectDependency;
    }
}

如果名字不匹配 ☞ a NoSuchBeanDefinitionException will be thrown.

Setter Injection

如上雷同

参考：Wiring in Spring: @Autowired, @Resource and @Inject