Repetition is Bad, Repetition is Bad

Quickie Talk at Voxxed Days Ticino 2016 about repetition in Java code.

Transcript

1. title subtitle Repetition is bad, repetition is bad Michele Giacobazzi – WellD Sagl Voxxed days Ticino 18 april 2015 www.welld.ch
2. article title 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 retrieval 2. Connection to remote system 3. Dynamic call 4. Exception handling 5. Closing the connection 6. Action auditing (log) REPETITION CODE REPETITION
3. public Squid findSquids(String token, Map<String,Object> criteria) { BEConnector connector = null; Squid result = null; //1 Get the operator VoxxedOperator operator = login.getOperator(token); if (operator == null) { logger.warn("invalid operator token " + token); return null; } try { //2 estabilish connection and get remote service facade connector = ConnUtility.getBEConnector(); VoxxedFacade service = ConnUtility.getVoxxedFacade(connector); //3 The real action! result = service.findSquidByCriteria(operator, criteria); } catch (Exception e) { //4 log and handle exception logger.error("Error in findSquids", e); result = null; } finally { //5 release the connection ConnUtility.releaseBEConnector(connector); } // 6 audit the action (log) logger.info("findSquids executed with params " + criteria + " and result " + result); return result; }
4. public Octopus findOctopusById(String token, long id) { BEConnector connector = null; Squid result = null; //1 Get the operator VoxxedOperator operator = login.getOperator(token); if (operator == null) { logger.warn("invalid operator token " + token); return null; } try { //2 estabilish connection and get remote service facade connector = ConnUtility.getBEConnector(); VoxxedFacade service = ConnUtility.getVoxxedFacade(connector); //3 The real action! result = service.findOctopusById(operator, id); } catch (Exception e) { //4 log and handle exception logger.error("Error in findOctopusById" + token, e); result = null; } finally { //5 release the connection ConnUtility.releaseBEConnector(connector); } // 6 audit the action (log) logger.info(“findOctopusById executed with params " + id + " and result " + result); return result; }
5. article title Java reflection - Method  java.lang.reflect.Method  Obtained with class.getMethod(String name, Class<?>... parameterTypes)  Executed with method.invoke(Object context, Object... parameters)
6. public Object executeMethod(Method method){ BEConnector connector = null; Object result = null; //1 Get the operator VoxxedOperator operator = loginManager.getOperator(token); if (operator == null) { logger.warn("invalid operator token " + token); return null; } try { //2 estabilish connection and get remote service facade connector = ConnUtility.getBEConnector(); VoxxedFacade service = ConnUtility.getVoxxedFacade(connector); //Invoke the method method.invoke(service, params); } catch (Exception e) { //4 log and handle exception logger.error("Error in retrieving objectType1 for user" + call.getParams(), e); result = null; } finally { //5 release the connection ConnUtility.releaseBEConnector(connector); } // 6 audit the action (log) logger.info(call.getMethod().getName() + " executed with params " + call.getParams() + " and result " + result); return result; }
7. public Object executeMethod(Method method){ BEConnector connector = null; Object result = null; //1 Get the operator VoxxedOperator operator = loginManager.getOperator(token); if (operator == null) { logger.warn("invalid operator token " + token); return null; } try { //2 estabilish connection and get remote service facade connector = ConnUtility.getBEConnector(); VoxxedFacade service = ConnUtility.getVoxxedFacade(connector); //Invoke the method method.invoke(service, params); } catch (Exception e) { //4 log and handle exception logger.error("Error in retrieving objectType1 for user" + call.getParams(), e); result = null; } finally { //5 release the connection ConnUtility.releaseBEConnector(connector); } // 6 audit the action (log) logger.info(call.getMethod().getName() + " executed with params " + call.getParams() + " and result " + result); return result; }
8. 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] }
9. public Object executeMethod(BeMethodCall call){ BEConnector connector = null; Object result = null; //1 Get the operator VoxxedOperator operator = loginManager.getOperator(call.getToken()); if (operator == null) { logger.warn("invalid operator token " + call.getToken()); return null; } try { //2 estabilish connection and get remote service facade connector = ConnUtility.getBEConnector(); VoxxedFacade service = ConnUtility.getVoxxedFacade(connector); //3 Copy the param array, set the operator as first param and execute. Object[] params = new Object[call.getParams().length + 1]; System.arraycopy(call.getParams(), 0, params, 1, call.getParams().length); params[0] = operator; call.getMethod().invoke(service, params); } catch (Exception e) { //4 log and handle exception logger.error("Error in retrieving objectType1 for user" + call.getParams(), e); result = null; } finally { //5 release the connection ConnUtility.releaseBEConnector(connector); } // 6 audit the action (log) logger.info(call.getMethod().getName() + " executed with params " + call.getParams() + " and result " + result); return result; }
10. public Squid getSquidsWithMethod(String token, final Map<String,Object> criteria) { Method method = null; try { method = VoxxedFacade.class.getMethod("findSquidByCriteria", new Class<?>[] {criteria.getClass()}); } catch (NoSuchMethodException | SecurityException e) { logger.warn("Could not create method findSquidByCriteria", e); return null; } BeMethodCall call = new BeMethodCall(method, token, new Object[]{criteria}); Object maybeSquid = beMethodExecutor.executeMethod(call); if (maybeSquid instanceof Squid){ return (Squid) maybeSquid; }else{ logger.warn("Unexpected return object " + maybeSquid); return null; } }
11. article title Java reflection - Method  Standard Java  Only single method call  Returns Object  Needs wrapper object  Verbose syntax
12. article title Callable Task  java.util.concurrent.Callable  Interface Callable<V>  A simple method call() that returns V.
13. public <T> T executeBeCall(BeTask<T> task){ BEConnector connector = null; T result = null; //1 Get the operator VoxxedOperator operator = loginManager.getOperator(task.getToken()); if (operator == null) { logger.warn("invalid operator token " + task.getToken()); return null; } try { //2 estabilish connection and get remote service facade connector = ConnUtility.getBEConnector(); VoxxedFacade service = ConnUtility.getVoxxedFacade(connector); //3 Set variables to task and run! task.setService(service); task.setOperator(operator); return task.call(); } catch (Exception e) { //4 log and handle exception logger.error("Error in retrieving objectType1 for user" + task.getToken(), e); result = null; } finally { //5 release the connection ConnUtility.releaseBEConnector(connector); } // 6 audit the action (log) not possible here return result; }
14. 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 }
15. public Squid getSquidsWithTask(String token, final Map<String,Object> criteria) { Squid result= beTaskExecutor.executeBeCall(new BeTask<Squid>(token) { @Override public 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; }
16. article title 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)
17. article title 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
18. @FunctionalInterface public 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); }
19. public <T> T executeFunction(BeFunction<T> call){ BEConnector connector = null; T result = null; //1 Get the operator VoxxedOperator operator = loginManager.getOperator(call.getToken()); if (operator == null) { logger.warn("invalid operator token " + call.getToken()); return null; } try { //2 estabilish connection and get remote service facade connector = ConnUtility.getBEConnector(); VoxxedFacade service = ConnUtility.getVoxxedFacade(connector); //3 Execute the function! call.execute(operator, service); } catch (Exception e) { //4 log and handle exception logger.error("Error in function call", e); result = null; } finally { //5 release the connection ConnUtility.releaseBEConnector(connector); } // cannot log return result; }
20. public Squid getSquidsWithFunction(String token, final Map<String,Object> criteria) { Squid result= beFunctionExecutor.executeFunction(new BeFunction<Squid>(token) { @Override public 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; }
21. article title Java 8 function  Needs Java 8  Better syntax and parameter handling  Does not allow auditing (log)  Parameters must be final
22. article title Interceptor  javax.interceptor.Interceptor  Annotate a method with AroundInvoke  Access to InvocationContext  Returns a result
23. @Interceptor @LogMethod //Methods annotated with @Logit would be intercepted by logMethodEntry public class LogInterceptor { private static final Logger LOGGER = Logger.getLogger(LogInterceptor.class); @AroundInvoke public Object logMethodEntry(InvocationContext ctx) throws Exception { //Execute the method Object b = ctx.proceed(); //Print method name and params. LOGGER.info(ctx.getMethod().getName() + " executed with params " + ctx.getParameters()); return b; } }
24. @Interceptor @BEConnection public class ConnectionInterceptor{ @AroundInvoke public Object injectFacade(InvocationContext ctx) throws Exception { BEConnector connector = null; try { connector = ConnUtility.getBEConnector(); VoxxedFacade service = ConnUtility.getVoxxedFacade(connector); ctx.getParameters()[0] = service; Object b = ctx.proceed(); return b; } catch(OperatorNotFoundException oE){ logger.warn("Operator not found " , oE); return null; }catch (Exception e) { logger.warn("Error in be call", e); return null; } finally { ConnUtility.releaseBEConnector(connector); } }
25. @LogMethod @BeConnection public Squid findSquids(@BeFacade VoxxedFacade service, String token, Map<String,Object> criteria) { Squid result = null; //1 Get the operator VoxxedOperator 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; }
26. article title Interceptor  Needs container support  Wraps the method execution  Has access to method data  Can manipulate parameter  Relies on method signature
27. article title 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
28. article title Our solution: function + interceptor @LogMethod public Squid getSquidsWithFunctionAndLog(String token, final Map<String,Object> criteria) { return beFunctionExecutor.executeFunction(new BeFunction<Squid>(token) { @Override public Squid execute(VoxxedOperator operator, VoxxedFacade service) { return service.findSquidByCriteria(operator, criteria); } }); }
29. article title 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