java - Constructor parameter injection using guice -

this different question other answered questions constructor parameter (or @ least that's think so, course may wrong). using mapbinder store bunch of implementations , pick 1 during runtime based of criteria. here code:

public interface messageservice {   void send(); }  public class facebookmessageservice implements messageservice {   private final string name;    @inject   public facebookmessageservice(string name) {     this.name = name;   }    public void send() {     system.out.println("sending message via facebook service " + name);   } }  public class messagemodule extends abstractmodule {   @override   protected void configure() {     mapbinder<string, messageservice> mapbinder = mapbinder.newmapbinder<.....>     mapbinder.addbinding("facebook").to(facebookmessageservice.class);   } }  public class messageclient {   @inject   map<string, messageservice> map; //mapbinder being injected    public void callsender() {     injector injector = guice.createinjector(new messagemodule());     injector.injectmembers(this);      messageservice service = map.get("facebook");     service.send();   } } 

i unable figure out how facebookmessageservice name parameter? if use assistedinject factory not able figure out how inject implementation mapbinder.

you can inject 'name' parameter.

public class facebookmessageservice implements messageservice {     private final string name;      @inject     public facebookmessageservice(@named("facebookservicename") string name) {        this.name = name;     } }  public class messagemodule extends abstractmodule {     @override     protected void configure() {         // bind "facebookservicename"         // think binding should exist before map binding         bindconstant().annotatedwith(names.named("facebookservicename"))                       .to("insert argument here");          mapbinder<string, messageservice> mapbinder = mapbinder.newmapbinder<.....>         mapbinder.addbinding("facebook").to(facebookmessageservice.class);     } } 

put debug point in facebookmessageservice constructor see whether works.