Resource vs Autowired

Question

Which annotation   Resource  jsr250  or  Autowired  Spring-specific  should I use in DI   I have successfully used both in the past   Resource name  blah   and  Autowired  Qualifier  blah    My instinct is to stick with the  Resource tag since it s been ratified by the jsr people  Anyone has strong thoughts on this

User · Answer

I would like to emphasize one comment from @Jules on this answer to this question. The comment brings a useful link: Spring Injection with @Resource, @Autowired and @Inject. I encourage you to read it entirely, however here is a quick summary of its usefulness:

How annotations select the right implementation?

@Autowired and @Inject

Matches by Type
Restricts by Qualifiers
Matches by Name

@Resource

Matches by Name
Matches by Type
Restricts by Qualifiers (ignored if match is found by name)

Which annotations (or combination of) should I use for injecting my beans?

Explicitly name your component [@Component("beanName")]
Use @Resource with the name attribute [@Resource(name="beanName")]

Why should I not use `@Qualifier`?

Avoid @Qualifier annotations unless you want to create a list of similar beans. For example you may want to mark a set of rules with a specific @Qualifier annotation. This approach makes it simple to inject a group of rule classes into a list that can be used for processing data.

Does bean injection slow my program?

Scan specific packages for components [context:component-scan base-package="com.sourceallies.person"]. While this will result in more component-scan configurations it reduces the chance that you’ll add unnecessary components to your Spring context.

Reference: Spring Injection with @Resource, @Autowired and @Inject

User · Answer

Autowired    Qualifier will work only with spring DI  if you want to use some other DI in future  Resource is good option   other difference which I found very significant is  Qualifier does not support dynamic bean wiring  as  Qualifier does not support placeholder  while  Resource does it very well   For example  if you have an interface with multiple implementations like this  interface parent       Service  actualService   class ActualService implements parent      Service  stubbedService   class SubbedService implements parent       with  Autowired  amp   Qualifier you need to set specific child implementation  like    Autowired  Qualifier  actualService   or   Qualifier  stubbedService    Parent object    which does not provide placeholder while with  Resource you can put placeholder and use property file to inject specific child implementation like   Resource name    service name    Parent object      where service name is set in property file as     service name actualService  service name stubbedService   Hope that helps someone

User · Answer

With  Resource you can do bean self-injection  it might be needed in order to run all extra logic added by bean post processors like transactional or security related stuff   With Spring 4 3   Autowired is also capable of doing this

User · Answer

Both  Autowired  or  Inject  and  Resource work equally well  But there is a conceptual difference or a difference in the meaning    Resource means get me a known resource by name  The name is extracted from the name of the annotated setter or field  or it is taken from the name-Parameter   Inject or  Autowired try to wire in a suitable other component by type    So  basically these are two quite distinct concepts  Unfortunately the Spring-Implementation of  Resource has a built-in fallback  which kicks in when resolution by-name fails  In this case  it falls back to the  Autowired-kind resolution by-type  While this fallback is convenient  IMHO it causes a lot of confusion  because people are unaware of the conceptual difference and tend to use  Resource for type-based autowiring

User · Answer

This is what I got from the Spring 3 0 x Reference Manual  -     Tip       If you intend to express annotation-driven injection by name  do   not primarily use  Autowired  even if is technically capable of   referring to a bean name through  Qualifier values  Instead  use the   JSR-250  Resource annotation  which is semantically defined to   identify a specific target component by its unique name  with the   declared type being irrelevant for the matching process       As a specific consequence of this semantic difference  beans that are   themselves defined as a collection or map type cannot be injected   through  Autowired  because type matching is not properly applicable   to them  Use  Resource for such beans  referring to the specific   collection or map bean by unique name        Autowired applies to fields  constructors  and multi-argument   methods  allowing for narrowing through qualifier annotations at the   parameter level  By contrast   Resource is supported only for fields   and bean property setter methods with a single argument  As a   consequence  stick with qualifiers if your injection target is a   constructor or a multi-argument method

User · Answer

The primary difference is   Autowired is a spring annotation  Whereas  Resource is specified by the JSR-250  as you pointed out yourself  So the latter is part of Java whereas the former is Spring specific   Hence  you are right in suggesting that  in a sense  I found folks use  Autowired with  Qualifier because it is more powerful  Moving from some framework to some other is considered very unlikely  if not myth  especially in the case of Spring

User · Answer

Both of them are equally good  The advantage of using Resource is in future if you want to another DI framework other than spring  your code changes will be much simpler  Using Autowired your code is tightly coupled with springs DI

User · Answer

Resource is often used by high-level objects  defined via JNDI   Autowired or  Inject will be used by more common beans   As far as I know  it s not a specification  nor even a convention  It s more the logical way standard code will use these annotations

User · Answer

As a note here  SpringBeanAutowiringSupport processInjectionBasedOnCurrentContext and SpringBeanAutowiringSupport processInjectionBasedOnServletContext DOES NOT work with  Resource  annotation  So  there are difference

User · Answer

When you analyze critically from the base classes of these two annotations You will realize the following differences    Autowired uses AutowiredAnnotationBeanPostProcessor  to inject dependencies   Resource uses CommonAnnotationBeanPostProcessor to inject dependencies   Even though they use different post processor classes they all behave nearly identically  The differences critically lie in their execution paths  which I have highlighted below    Autowired    Inject   1 Matches by Type 2 Restricts by Qualifiers 3 Matches by Name   Resource   1 Matches by Name 2 Matches by Type 3 Restricts by Qualifiers  ignored if match is found by name

User · Answer

In spring pre-3 0 it doesn t matter which one   In spring 3 0 there s support for the standard  JSR-330  annotation  javax inject Inject - use it  with a combination of  Qualifier  Note that spring now also supports the  javax inject Qualifier meta-annotation    Qualifier  Retention RUNTIME  public  interface YourQualifier      So you can have   lt bean class  com pkg SomeBean  gt      lt qualifier type  YourQualifier   gt   lt  bean gt    or   YourQualifier  Component public class SomeBean implements Foo          And then    Inject  YourQualifier private Foo foo    This makes less use of String-names  which can be misspelled and are harder to maintain     As for the original question  both  without specifying any attributes of the annotation  perform injection by type  The difference is     Resource allows you to specify a name of the injected bean  Autowired allows you to mark it as non-mandatory

[java] @Resource vs @Autowired

How annotations select the right implementation?

Which annotations (or combination of) should I use for injecting my beans?

Why should I not use `@Qualifier`?

Does bean injection slow my program?

Examples related to java

Examples related to spring

Examples related to dependency-injection

Examples related to annotations

Examples related to autowired

[java] @Resource vs @Autowired

How annotations select the right implementation?

Which annotations (or combination of) should I use for injecting my beans?

Why should I not use @Qualifier?

Does bean injection slow my program?

Examples related to java

Examples related to spring

Examples related to dependency-injection

Examples related to annotations

Examples related to autowired

Why should I not use `@Qualifier`?