Comparison of @Resource and @Autowired for Bean Injection in Spring

@Resource and @Autowired are both used for bean injection in Spring. @Resource is not a Spring annotation; it belongs to javax.annotation.Resource and requires the corresponding import, but Spring supports its injection.

Common points

Both annotations can be placed on fields and setter methods. When placed on a field, a setter method is not required.

Differences

@Autowired

@Autowired is provided by Spring and requires importing org.springframework.beans.factory.annotation.Autowired. It performs injection by type (byType).

public class TestServiceImpl {
    // Either of the following @Autowired can be used
    @Autowired
    private UserDao userDao; // field injection

    @Autowired
    public void setUserDao(UserDao userDao) {
        // setter injection
        this.userDao = userDao;
    }
}

@Autowired injects dependencies by type and, by default, requires the dependency to be present. To allow null values, set required=false. For name‑based injection, combine it with @Qualifier:

public class TestServiceImpl {
    @Autowired
    @Qualifier("userDao")
    private UserDao userDao;
}

IDEA often shows a warning for field injection, recommending constructor‑based injection as suggested by the Spring team.

@Resource

@Resource is a JDK 1.6 annotation provided by J2EE and requires importing javax.annotation.Resource. By default it injects by name; the name attribute can specify the bean name, and it also supports injection by type.

The two important attributes of @Resource are name and type. Spring resolves name to the bean name and type to the bean class.

@Resource(name = "userDaoImpl2", type = UserDaoImpl.class)
private UserDao userDao;

If name is omitted and the annotation is on a field, the field name is used as the bean name. When placed on a setter, the property name is used. If no matching bean name is found, Spring falls back to type‑based injection, unless name is explicitly set, in which case only name‑based injection is performed.

public class TestServiceImpl {
    // Either of the following @Resource can be used
    @Resource(name="userDao")
    private UserDao userDao; // field injection

    @Resource(name="userDao")
    public void setUserDao(UserDao userDao) {
        // setter injection
        this.userDao = userDao;
    }
}

Note: It is preferable to place @Resource on setter methods to follow object‑oriented principles.

@Resource Injection Order

1. If both name and type are specified, Spring looks for a unique bean matching both; otherwise an exception is thrown.

2. If only name is specified, Spring searches for a bean with that name; failure results in an exception.

3. If only type is specified, Spring searches for a unique bean of that type; multiple or no matches cause an exception.

4. If neither name nor type is specified, Spring first attempts name‑based injection; if no match is found, it falls back to type‑based injection.

In effect, @Resource behaves similarly to @Autowired, but @Autowired defaults to by‑type injection while @Resource defaults to by‑name.