I have @Autowired
service which has to be used from within a static method. I know this is wrong but I cannot change the current design as it would require a lot of work, so I need some simple hack for that. I can't change randomMethod()
to be non-static and I need to use this autowired bean. Any clues how to do that?
@Service
public class Foo {
public int doStuff() {
return 1;
}
}
public class Boo {
@Autowired
Foo foo;
public static void randomMethod() {
foo.doStuff();
}
}
It sucks but you can get the bean by using the ApplicationContextAware
interface. Something like :
public class Boo implements ApplicationContextAware {
private static ApplicationContext appContext;
@Autowired
Foo foo;
public static void randomMethod() {
Foo fooInstance = appContext.getBean(Foo.class);
fooInstance.doStuff();
}
@Override
public void setApplicationContext(ApplicationContext appContext) {
Boo.appContext = appContext;
}
}
What you can do is @Autowired
a setter method and have it set a new static field.
public class Boo {
@Autowired
Foo foo;
static Foo staticFoo;
@Autowired
public void setStaticFoo(Foo foo) {
Boo.staticFoo = foo;
}
public static void randomMethod() {
staticFoo.doStuff();
}
}
When the bean gets processed, Spring will inject a Foo
implementation instance into the instance field foo
. It will then also inject the same Foo
instance into the setStaticFoo()
argument list, which will be used to set the static field.
This is a terrible workaround and will fail if you try to use randomMethod()
before Spring has processed an instance of Boo
.
You have to workaround this via static application context accessor approach:
@Component
public class StaticContextAccessor {
private static StaticContextAccessor instance;
@Autowired
private ApplicationContext applicationContext;
@PostConstruct
public void registerInstance() {
instance = this;
}
public static <T> T getBean(Class<T> clazz) {
return instance.applicationContext.getBean(clazz);
}
}
Then you can access bean instances in a static manner.
public class Boo {
public static void randomMethod() {
StaticContextAccessor.getBean(Foo.class).doStuff();
}
}
Use AppContext. Make sure you create a bean in your context file.
private final static Foo foo = AppContext.getApplicationContext().getBean(Foo.class);
public static void randomMethod() {
foo.doStuff();
}
This builds upon @Pavel's answer, to solve the possibility of Spring context not being initialized when accessing from the static getBean method:
@Component
public class Spring {
private static final Logger LOG = LoggerFactory.getLogger (Spring.class);
private static Spring spring;
@Autowired
private ApplicationContext context;
@PostConstruct
public void registerInstance () {
spring = this;
}
private Spring (ApplicationContext context) {
this.context = context;
}
private static synchronized void initContext () {
if (spring == null) {
LOG.info ("Initializing Spring Context...");
ApplicationContext context = new AnnotationConfigApplicationContext (io.zeniq.spring.BaseConfig.class);
spring = new Spring (context);
}
}
public static <T> T getBean(String name, Class<T> className) throws BeansException {
initContext();
return spring.context.getBean(name, className);
}
public static <T> T getBean(Class<T> className) throws BeansException {
initContext();
return spring.context.getBean(className);
}
public static AutowireCapableBeanFactory getBeanFactory() throws IllegalStateException {
initContext();
return spring.context.getAutowireCapableBeanFactory ();
}
}
The important piece here is the initContext
method. It ensures that the context will always get initialized. But, do note that initContext
will be a point of contention in your code as it is synchronized. If your application is heavily parallelized (for eg: the backend of a high traffic site), this might not be a good solution for you.
Source: Stackoverflow.com