java - Changed & Improved passing data from WebServlet to a WebService -

i'm pretty new writing servlet , rest services, i'm @ problem i'm not sure if i'm doing correctly. service this:

@post @produces ("application/json") @path ("/register") public string register(     @formparam("name") string name,     @formparam("username") string username,     @formparam("password") string password,     @context httpservletresponse servletresponse) throws ioexception {      if( this.user_taken(username) ) return "username_taken";     user user = new user(name,username,password);      .....      return mapper.writevalueasstring(user);  } 

so can see service takes care of doing end (database , creating user) servlet on other hand in charge of taking request form, validating , passing service. servlet code:

... validate user input form ...  clientconfig config = new defaultclientconfig(); client client = client.create(config); webresource service = client.resource("http://localhost/jaba");  string map = mapper.writevalueasstring(request.getparametermap()); multivaluedmap<string, string> obj = mapper.readvalue(map, multivaluedmap.class);  string result =      service.path("api").path("register")         .accept("application/json")         .post(string.class, obj); 

as can see client (servlet) has lot of nasty work, pass data service. how can changed/improved/optimized or better yet refactored ? i'm trying follow best practices , how in real life example.

here might do:

instead of doing

string result =      service.path("api").path("register")         .accept("application/json")         .post(string.class, obj); 

i more creating dto object, filling out , passing service. apply aspect along jsr validation , annotations (you can on have won't nice) on client call.

example:

@aspect public class dtovalidator {      private validator validator;      public dtovalidator() {     }      public dtovalidator(validator validator) {         this.validator = validator;     }      public void dovalidation(joinpoint jp){         for( object arg : jp.getargs() ){             if (arg != null) {                 set<constraintviolation<object>> violations = validator.validate(arg);                 if( violations.size() > 0 ){                     throw builderror(violations);                 }             }         }     }      private static badrequestexception builderror( set<constraintviolation<object>> violations ){         map<string, string> errormap = new hashmap<string, string>();         for( constraintviolation error : violations ){             errormap.put(error.getpropertypath().tostring(), error.getmessage());         }         return new badrequestexception(errormap);     } } 

you can annotatively declare aspect or can in config (makes reusable). such:

<aop:config proxy-target-class="true">     <aop:aspect id="dtovalidator" ref="dtovalidator" order="10">         <aop:before method="dovalidation" pointcut="execution(public * com.mycompany.client.*.*(..))"/>     </aop:aspect> </aop:config> 

now can have dto this:

@xmlaccessortype(xmlaccesstype.field) @xmlrootelement public class loginrequest extends abstractdto{      @notnull     private string username;      @notnull     private string password;      private loginrequest() {     }      public loginrequest(string username, string password) {         this.username = username;         this.password = password;     }      public string getusername() {         return username;     }      public string getpassword() {         return password;     }  } 

when fails @notnull checks this:

{    "message":"{username=must not null",    "httpstatuscode":400,    "httpmessage":"bad request",    "details":{       "username":"must not null"    } } 

then use restoperation client such

org.springframework.web.client.restoperations restclient ... restclient.postforobject(url,new dto(...),args);   

place aspect around restclient , you're golden (and, measure, on service calls too).