Using with Spring and Injection frameworks

The Juneau REST server API is compatible with dependency injection frameworks such as Spring.

The important class is the {@link oajr.RestResourceResolver} class which is used to resolve child servlet/resource implementation classes inside parent contexts. In other words, it's used for resolving {@link oajr.annotation.RestResource#children() @RestResource(children)} instances.

The general approach starts with defining a resolver that uses the Spring application context for resolution:

public class SpringRestResourceResolver extends RestResourceResolverSimple { private final ApplicationContext appContext; public SpringRestResourceResolver(ApplicationContext appContext) { this.appContext = appContext; } @Override /* RestResourceResolverSimple */ public Object resolve(Class<?> resourceType, RestContextBuilder builder) throws Exception { Object resource = appContext.getBean(type); // If Spring can't resolve it, use default resolution (just look for no-arg constructor). if (resource == null) { resource = super.resolve(resourceType, builder); } return resource; } }

Next, define the Spring configuration to return our resolver:

@Configuration public abstract class MySpringConfiguration { @Autowired private static ApplicationContext appContext; public static ApplicationContext getAppContext(){ return appContext; } public static void setAppContext(ApplicationContext appContext){ MySpringConfiguration.appContext = appContext; } @Bean public RestResourceResolver restResourceResolver(ApplicationContext appContext) { return new SpringRestResourceResolver(appContext); } }

Finally, define your `Root` resource with a constructor that takes in our rest resource resolver and sets it on the config object during initialization.

@RestResource( children={ ... } ) public class Root extends BasicRestServletGroup { private final RestResourceResolver resolver; @Inject public Root(RestResourceResolver resolver) { this.resolver = resolver; } @RestHook(INIT) public void initSpring(RestContextBuilder builder) throws Exception { builder.setResourceResolver(resolver); } }

After that, just define constructors on your child resources to take in Spring beans:

@RestResource( path="/child" ) public class MyChildResource extends BasicRestServlet { private final Bean1 bean1; private final Bean2 bean2; private final Bean3 bean3; @Inject public MyChildResource(Bean1 bean1, Bean2 bean2, Bean3 bean3) { this.bean1 = bean1; this.bean2 = bean2; this.bean3 = bean3; }