Guice , afterPropertiesSet

问题:

Someone knows some way that how can I achieve the same functionality in Guice as the 'afterPropertiesSet' interface in spring ? ( its a post construction hook )

回答1:

By far the simplest solution, if you're using constructor injection and not doing anything too crazy, is to create a post-construction method and annotate it with @Inject:

final class FooImpl implements Foo {   private final Bar bar;    @Inject   FooImpl(Bar bar) {     this.bar = bar;      ...   }    @Inject   void init() {     // Post-construction code goes here!   } } 

When Guice provides FooImpl, it'll see it has an @Inject constructor, call it, and then search for methods annotated with @Inject and call those. The intended use case for this is setter injection, but even if an @Inject method has no params, Guice will call it.

I don't recommend using this if you're using setter or field injection to inject deps since I don't know if Guice makes any guarantees about the order in which @Inject methods are called (that is, your init() method might not be guaranteed to be called last). That said, constructor injection is the preferred approach anyway, so that should be a non-issue.

回答2:

I guess using @PostConstruct is the way to go.

Here is a related blog post : http://macstrac.blogspot.com/2008/10/adding-support-for-postconstruct.html

And here is an addon library that provides the support : http://code.google.com/p/guiceyfruit/

Adding lifecycle support via Guiceyfruit is described here : http://code.google.com/p/guiceyfruit/wiki/Lifecycle

回答3:

It seems it is not yet supported , so for everyone how wants this work , here is small solution.

public class PostConstructListener implements TypeListener{      private static Logger logger = Logger.getLogger(PostConstructListener.class);      @Override     public <I> void hear(TypeLiteral<I> iTypeLiteral,final TypeEncounter<I> iTypeEncounter) {          Class<? super I> type = iTypeLiteral.getRawType();          ReflectionUtils.MethodFilter mf = new ReflectionUtils.MethodFilter() {             @Override             public boolean matches(Method method) {                 return method.isAnnotationPresent(PostConstruct.class);             }         };          ReflectionUtils.MethodCallback mc = new ReflectionUtils.MethodCallback() {             @Override             public void doWith(Method method) throws IllegalArgumentException, IllegalAccessException {                 if (!(method.getReturnType().equals(Void.TYPE) && method.getParameterTypes().length == 0))                 {                     logger.warn("Only VOID methods having 0 parameters are supported by the PostConstruct annotation!" +                             "method " + method.getName() + " skipped!");                     return;                  }                 iTypeEncounter.register(new PostConstructInvoker<I>(method));             }         };          ReflectionUtils.doWithMethods(type,mc,mf);     }      class PostConstructInvoker<I> implements InjectionListener<I>{          private Method method;          public PostConstructInvoker(Method method) {             this.method = method;         }          @Override         public void afterInjection(I o) {             try {                 method.invoke(o);             } catch (Throwable e) {                 logger.error(e);             }         }     } } 

The ReflectionUtils package is defined in spring.

Bind this listener to any event with :

bindListener(Matchers.any(),new PostConstructListener()); 

in your guice module. Have fun

回答4:

You'll want to read the CustomInjections page on the Guice wiki:

In addition to the standard @Inject-driven injections, Guice includes hooks for custom injections. This enables Guice to host other frameworks that have their own injection semantics or annotations. Most developers won't use custom injections directly; but they may see their use in extensions and third-party libraries. Each custom injection requires a type listener, an injection listener, and registration of each.

文章来源: Guice , afterPropertiesSet