问题
Continuation of topic Jersey 2 + HK2 - @ApplicationScoped not working.
I already know, how to bind classes in order to @Inject them properly.
Do you have any ideas, how to automize this process? Putting every single service in bind statements seems like very bad smell in my application.
回答1:
After using Google's Guice for a number of years, I am accustomed to the availability of a Just-In-Time binder, allowing the injection of arbitrary types without requiring any upfront configuration.
I too found the idea of having to explicitly bind every service to be a bad code smell. I'm also not crazy about the need to use a special build step and the added initialization code for the populator.
So I came up with the following JustInTimeResolver implementation:
/**
* Mimic GUICE's ability to satisfy injection points automatically,
* without needing to explicitly bind every class, and without needing
* to add an extra build step.
*/
@Service
public class JustInTimeServiceResolver implements JustInTimeInjectionResolver {
@Inject
private ServiceLocator serviceLocator;
@Override
public boolean justInTimeResolution( Injectee injectee ) {
final Type requiredType = injectee.getRequiredType();
if ( injectee.getRequiredQualifiers().isEmpty() && requiredType instanceof Class ) {
final Class<?> requiredClass = (Class<?>) requiredType;
// IMPORTANT: check the package name, so we don't accidentally preempt other framework JIT resolvers
if ( requiredClass.getName().startsWith( "com.fastmodel" )) {
final List<ActiveDescriptor<?>> descriptors = ServiceLocatorUtilities.addClasses( serviceLocator, requiredClass );
if ( !descriptors.isEmpty() ) {
return true;
}
}
}
return false;
}
}
With this in my project, I simply added the following to my binder in my Jersey application configuration:
bind( JustInTimeServiceResolver.class ).to( JustInTimeInjectionResolver.class );
and I get automatic binding creation like I did in Guice.
回答2:
I would suggest first looking here: Automatic Service Population.
The basic process is to use @Service annotations on your classes and use the JSR-269 (APT) processor (Metadata Generator) at build time. Doing so will add some metadata to your jar files (normally under META-INF/hk2-locator/default).
You can then make sure these services get picked up automatically rather than having to do all those pesky binds by using a Populator which you get from the Dynamic Configuration Service which is available in every ServiceLocator.
The pseudo-code would be something like this:
public void populate(ServiceLocator locator) throws Exception {
DynamicConfigurationService dcs = locator.getService(DynamicConfigurationService.class);
Populator populator = dcs.getPopulator();
populator.populate(new ClasspathDescriptorFileFinder(getClass().getClassLoader()));
}
In the above code the ClasspathDescriptorFileFinder is used to search through the classpath to find the metadata. Other strategies could be used in environments like OSGi.
IMO this is a much better way to add services rather than doing all the binds by yourself.
回答3:
I Have a sugestion that solved my problem here, i've tried proposed solution and not worked here. In my solution it's necessary annotate each class with @MyInjectable annotation.
1-Create an Annotation
@Retention(RUNTIME)
@Target(ElementType.TYPE)
public @interface MyInjectable {
}
2-Create a AbstractBinder implementation
public class MyApplicationBinder extends AbstractBinder {
@Override
protected void configure() {
bindFactory(EMFFactory.class).to(EntityManagerFactory.class).in(Singleton.class);
bindFactory(EMFactory.class).to(EntityManager.class).in(RequestScoped.class);
bind(Environment.class).to(Environment.class);
scanAndBind("com.yourpackage.here");
}
private void scanAndBind(String packageName) {
try {
Class[] classes = getClasses(packageName);
for (Class<?> klazz:
classes) {
MyInjectable annotation = klazz.getAnnotation(MyInjectable.class);
if (annotation!= null) {
bind(klazz).to(klazz);
}
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
private static Class[] getClasses(String packageName)
throws ClassNotFoundException, IOException {
ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
assert classLoader != null;
String path = packageName.replace('.', '/');
Enumeration<URL> resources = classLoader.getResources(path);
List<File> dirs = new ArrayList<>();
while (resources.hasMoreElements()) {
URL resource = resources.nextElement();
dirs.add(new File(resource.getFile()));
}
ArrayList<Class> classes = new ArrayList<Class>();
for (File directory : dirs) {
classes.addAll(findClasses(directory, packageName));
}
return classes.toArray(new Class[classes.size()]);
}
private static List<Class> findClasses(File directory, String packageName) throws ClassNotFoundException {
List<Class> classes = new ArrayList<Class>();
if (!directory.exists()) {
return classes;
}
File[] files = directory.listFiles();
for (File file : files) {
if (file.isDirectory()) {
assert !file.getName().contains(".");
classes.addAll(findClasses(file, packageName + "." + file.getName()));
} else if (file.getName().endsWith(".class")) {
classes.add(Class.forName(packageName + '.' + file.getName().substring(0, file.getName().length() - 6)));
}
}
return classes;
}
}
3-Create a ResourceConfig
public class MyApplication extends ResourceConfig {
@Inject
public MyApplication(ServiceLocator locator) {
ServiceLocatorUtilities.enableImmediateScope(locator);
....
register(new MyApplicationBinder());
}
}
4-Configure properly in web.xml
<servlet>
<servlet-name>Jersey Web Application</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>br.com.solutiontrue.ws</param-value>
</init-param>
<init-param>
<param-name>com.sun.jersey.api.json.POJOMappingFeature</param-name>
<param-value>true</param-value>
</init-param>
<init-param>
<param-name>javax.ws.rs.Application</param-name>
<param-value>your.package.name.MyApplication</param-value>
</init-param>
<init-param>
<param-name>jersey.config.server.resource.validation.disable</param-name>
<param-value>true</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
来源：https://stackoverflow.com/questions/37794144/jersey-2-hk2-automatic-binding-of-classess