Spring autowire a list

Question

Is it possible to use @Autowired with a list?

Like I have properties file with mimetypes and in my class file I have something like this

@Autowired
private List<String> mimeTypes = new ArrayList<String>();

Answer 1

Spring 4 and older support the ability to automatically collect all beans of a given type and inject them into a collection or array.

Here is an example:

@Component
public class Car implements Vehicle {
}

@Component
public class Bus implements Vehicle {
}

@Component
public class User {
   @Autowired
   List<Vehicle> vehicles; // contains both car and bus
}

Ref: Spring 4 Ordering Autowired Collections

Answer 2

@Qualifier("..") is discouraged, instead try to autowire-by-name using

private @Resource(name="..") List<Strings> mimeTypes;

See also How to autowire factorybean.

Answer 3

You can even create a java.util.List within your spring .xml and inject this via @Qualifier into your application. From the springsource http://static.springsource.org/spring/docs/current/reference/xsd-config.html :

 <!-- creates a java.util.List instance with the supplied values -->
 <util:list id="emails">
   <value>pechorin@hero.org</value>
   <value>raskolnikov@slums.org</value>
   <value>stavrogin@gov.org</value>
   <value>porfiry@gov.org</value>
 </util:list>

So this would change your wiring to:

 @Autowired
 @Qualifier("emails")
 private List<String> mimeTypes = new ArrayList<String>();

I would suggest this approach since you're injecting a list of strings anyways.

cheers!

EDIT

If you want to inject properties, have a look at this How can I inject a property value into a Spring Bean which was configured using annotations?

Answer 4

I think you'll need a qualifier at minimum. And the call to "new" seems contrary to the idea of using Spring. You have Spring's role confused. If you call "new", then the object isn't under Spring's control.

Answer 5

If the autowired bean is declared in the same (@Configuration) class and you need it to declare another bean, then following works:

@Bean
public BeanWithMimeTypes beanWithMimeTypes() {
    return new BeanWithMimeTypes(mimeTypes());
}

@Bean
public List<String> mimeTypes() {
    return Arrays.<String>asList("text/html", "application/json);
}

Naturally it behaves correctly even if you override the mimeTypes bean in another config. No need for explicit @Qualifier or @Resource annotations.

Answer 6

You should be able to autowire it as long as the list is a bean. You'd then use the @Qualifier to tell Spring which bean/list to use. See http://static.springsource.org/spring/docs/3.0.x/reference/beans.html#beans-autowired-annotation-qualifiers