When to Choose @Autowired vs @Resource in Spring? A Deep Dive

@Autowired is a Spring-provided annotation that can be placed on constructors, fields, and method parameters to enable automatic dependency injection based on type.

public class Service {
    // Constructor injection
    @Autowired
    public Service(Service service) {
        this.service = service;
    }

    // Field injection
    @Autowired
    private Service service;

    // Setter injection
    @Autowired
    public void setService(Service service) {
        this.service = service;
    }
}

@Resource is a JDK annotation defined by JSR‑250, available since JDK 1.6. It works in any Java framework and supports both type‑based and name‑based injection.

public class Service {
    @Resource(name = "service1")
    private Service service1;

    @Resource(name = "service2")
    private Service service2;
}

The two annotations differ in several aspects:

Annotation parameters: @Autowired has a single required attribute (default true); @Resource defines multiple attributes such as name, type, lookup, authenticationType, etc.

Default injection mode: @Autowired defaults to by‑type; @Resource defaults to by‑name.

Applicable targets: @Autowired can be used on constructors, fields, method parameters, and other annotations; @Resource can be used on classes, fields, and method parameters.

Origin: @Autowired is defined by Spring; @Resource follows the JSR‑250 specification and is part of the JDK.

Resolution order: @Autowired first attempts by‑type, then by‑name; @Resource follows a flow illustrated in the following diagram.

public @interface Autowired {
    boolean required() default true;
}

public @interface Resource {
    String name() default "";
    String lookup() default "";
    Class<?> type() default java.lang.Object.class;
    enum AuthenticationType { CONTAINER, APPLICATION }
    AuthenticationType authenticationType() default AuthenticationType.CONTAINER;
    boolean shareable() default true;
    String mappedName() default "";
    String description() default "";
}

Injection order for @Autowired:

Injection order for @Resource varies depending on whether name and/or type are specified, as shown in the following diagrams.

A summary table comparing the two annotations is provided below.

Interview tip

When asked about the differences between @Autowired and @Resource, explain the five points above and emphasize that @Autowired is Spring‑specific while @Resource is framework‑agnostic, making the former preferable in pure Spring projects.