How to Autowire Bean of generic type <T> in Spring?
Simple solution is to upgrade to Spring 4.0 as it will automatically consider generics as a form of @Qualifier
, as below:
@Autowired
private Item<String> strItem; // Injects the stringItem bean
@Autowired
private Item<Integer> intItem; // Injects the integerItem bean
Infact, you can even autowire nested generics when injecting into a list, as below:
// Inject all Item beans as long as they have an <Integer> generic
// Item<String> beans will not appear in this list
@Autowired
private List<Item<Integer>> intItems;
How this Works?
The new ResolvableType
class provides the logic of actually working with generic types. You can use it yourself to easily navigate and resolve type information. Most methods on ResolvableType
will themselves return a ResolvableType
, for example:
// Assuming 'field' refers to 'intItems' above
ResolvableType t1 = ResolvableType.forField(field); // List<Item<Integer>>
ResolvableType t2 = t1.getGeneric(); // Item<Integer>
ResolvableType t3 = t2.getGeneric(); // Integer
Class<?> c = t3.resolve(); // Integer.class
// or more succinctly
Class<?> c = ResolvableType.forField(field).resolveGeneric(0, 0);
Check out the Examples & Tutorials at below links.
- Spring Framework 4.0 and Java Generics
- Spring and Autowiring of Generic Types
Hope this helps you.
If you dont want to upgrade to Spring 4 you have to autowire by name as below :
@Autowired
@Qualifier("stringItem")
private Item<String> strItem; // Injects the stringItem bean
@Autowired
@Qualifier("integerItem")
private Item<Integer> intItem; // Injects the integerItem bean