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Repetition is bad, repetition is bad

Michele Giacobazzi – WellD SaglVoxxed days Ticino 18 april 2015www.welld.ch

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A «harder» case of repetition Repeated code is above and below the «Dynamic» part Use of variables and resources makes refactoring harder In our example there are 6 main actions:

1. User retrieval2. Connection to remote system3. Dynamic call4. Exception handling5. Closing the connection6. Action auditing (log)

REPETITION

CODE

REPETITION

public Squid findSquids(String token, Map<String,Object> criteria) {BEConnector connector = null;Squid result = null;//1 Get the operatorVoxxedOperator operator = login.getOperator(token);if (operator == null) {

logger.warn("invalid operator token " + token); return null;

}try {

//2 estabilish connection and get remote service facadeconnector = ConnUtility.getBEConnector();VoxxedFacade service = ConnUtility.getVoxxedFacade(connector);//3 The real action!result = service.findSquidByCriteria(operator, criteria);

} catch (Exception e) { //4 log and handle exceptionlogger.error("Error in findSquids", e);result = null;

} finally {//5 release the connectionConnUtility.releaseBEConnector(connector);

}// 6 audit the action (log)logger.info("findSquids executed with params " + criteria + " and result " + result);return result;

}

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Java reflection - Method java.lang.reflect.Method Obtained with class.getMethod(String name, Class<?>... parameterTypes) Executed with method.invoke(Object context, Object... parameters)

public class BeMethodCall{

//Token. To be provided.private String token;

private Method method;

private Object[] params;

public BeMethodCall(Method method, String token, Object[] params) {

super();this.token = token;

}

//[getters and setters]

}

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Java reflection - Method Standard Java Only single method call Returns Object Needs wrapper object Verbose syntax

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Callable Task java.util.concurrent.Callable Interface Callable<V> A simple method call() that returns V.

public abstract class BeTask<T> implements Callable<T> {

//Token. To be provided.private String token;//Facade. Injected by BetaskExecutor.private VoxxedFacade service;//Operator. Injected by BetaskExecutor.private VoxxedOperator operator;

 public BeTask(String token) {

super();this.token = token;

}

//[..] Getters and setters}

public Squid getSquidsWithTask(String token, final Map<String,Object> criteria) {

Squid result= beTaskExecutor.executeBeCall(new BeTask<Squid>(token) {

@Overridepublic Squid call() throws Exception {

return this.getService().findSquidByCriteria(this.getOperator(),criteria);

}

});

// 6 audit the action (log)logger.info("getSquidsWithTask executed with params " + criteria

+ " and result " + result);return result;

}

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Callable Task Standard Java Simple code in DAO Allows the use of generic Parameters must be final Resources must be injected Does not allow auditing (log)

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Java 8 function java.lang.FunctionalInterface Must have a single method Can be used with lambdas Common function types in java.util.function Create your own

@FunctionalInterfacepublic interface BeFunctionInterface<T> {

T execute(VoxxedOperator operator, VoxxedFacade service);

}

public abstract class BeFunction<T> implements BeFunctionInterface<T>{

private String token;

public BeFunction(String myToken) {super();this.token = myToken;}

public String getToken(){return token;}

 public abstract T execute(VoxxedOperator operator, VoxxedFacade service);

 }

public Squid getSquidsWithFunction(String token, final Map<String,Object> criteria) {

Squid result= beFunctionExecutor.executeFunction(new BeFunction<Squid>(token) { 

@Overridepublic Squid execute(VoxxedOperator operator, VoxxedFacade service) {

return service.findSquidByCriteria(operator, criteria);}

});

// 6 audit the action (log)logger.info("getSquidWithFunction executed with params " + criteria

+ " and result " + result);return result;

}

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Java 8 function Needs Java 8 Better syntax and parameter handling Does not allow auditing (log) Parameters must be final

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Interceptor javax.interceptor.Interceptor Annotate a method with AroundInvoke Access to InvocationContext Returns a result

@LogMethod@BeConnectionpublic Squid findSquids(@BeFacade VoxxedFacade service, String token, Map<String,Object> criteria) {

Squid result = null;//1 Get the operatorVoxxedOperator operator = loginManager.getOperator(token);if (operator == null) {

logger.warn("invalid operator token " + token); return null;

}

//3 The real action!result = service.findSquidByCriteria(operator, criteria);

 //Exception and Connection close handling in interceptor.

//Log handled in interceptor.return result;

}

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Interceptor Needs container support Wraps the method execution Has access to method data Can manipulate parameter Relies on method signature

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A small comparison

Support Syntax Completeness

Method Standard Java Mah.. Full

Task Standard Java Acceptable Partial (no log)

Function Java 8 Good! Partial (no log)

Interceptor Container library Depends Partial

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Our solution: function + interceptor

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Discussion! Questions and suggestions Find me around or at WellD stand Other approaches: dependency injection, decorator, filters… Contacts: Michele.Giacobazzi@Welld.ch Twitter: @Smirne WellD: www.welld.ch