@Resources, @Inject和@Autowired的区别是什么

这篇文章主要介绍“@Resources, @Inject和@Autowired的区别是什么”，在日常操作中，相信很多人在@Resources, @Inject和@Autowired的区别是什么问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答”@Resources, @Inject和@Autowired的区别是什么”的疑惑有所帮助！接下来，请跟着小编一起来学习吧！

@Resources

官方文档里对@Resources的说明：

The @Resource annotation is part of the JSR-250 annotation collection and is packaged with Jakarta EE.

什么是JSR-250呢？访问这个链接：https://id=250https://id=330

注入的优先级：

1. Match by Type

2. Match by Qualifier

3. Match by Name

Match by Type

注意@Inject注入的最高优先级方式为Match by Type，而非@Resource的Match by Name.

任意定义一个待注入的Component：

@Componentpublic class ArbitraryDependency {
    private final String label = "Arbitrary Dependency";
    public String toString() {
        return label;
    }}

使用@Inject注入：

@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

定义一个新的待注入组件：

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

测试代码：

@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(
  loader=AnnotationConfigContextLoader.class,
  classes=ApplicationContextTestInjectQualifier.class)public class FieldQualifierInjectIntegrationTest {
    @Inject
    private ArbitraryDependency defaultDependency;
    @Inject
    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());
    }}

和之前@Resource的第一次试图通过Match by Type注入一样失败，遇到异常：NoUniqueBeanDefinitionException

利用@Qualifier避免这个异常：

@Inject@Qualifier("defaultFile")private ArbitraryDependency defaultDependency;@Inject@Qualifier("namedFile")private ArbitraryDependency namedDependency;

Match by Name

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

消费者代码：

@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());
    }}

application context代码：

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

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