为你的基于SPRING的应用增加简单规则引擎2

public class SpringRuleEngineTest extends TestCase {

   public void testSuccessfulFlow() throws Exception {
      SpringRuleEngine engine = LoanProcessRuleEngine.getEngine("SharkysExpressLoansApplicationProcessor");
      LoanApplication application = new LoanApplication();
      application.setFirstName("John");
      application.setLastName("Doe");
      application.setStateCode("TX");
      application.setExpences(4500);
      application.setIncome(7000);
      engine.processRequest(application);
      assertEquals(LoanApplication.APPROVED, application.getStatus());
   }
  
   public void testInvalidState() throws Exception {
      SpringRuleEngine engine = LoanProcessRuleEngine.getEngine("SharkysExpressLoansApplicationProcessor");
      LoanApplication application = new LoanApplication();
      application.setFirstName("John");
      application.setLastName("Doe");
      application.setStateCode("OK");
      application.setExpences(4500);
      application.setIncome(7000);
      engine.processRequest(application);
      assertEquals(LoanApplication.INVALID_STATE, application.getStatus());
   }
  
   public void testInvalidRatio() throws Exception {
      SpringRuleEngine engine = LoanProcessRuleEngine.getEngine("SharkysExpressLoansApplicationProcessor");
      LoanApplication application = new LoanApplication();
      application.setFirstName("John");
      application.setLastName("Doe");
      application.setStateCode("MI");
      application.setIncome(7000);
      application.setExpences(0.80 * 7000); //too high     
      engine.processRequest(application);
      assertEquals(LoanApplication.INVALID_INCOME_EXPENSE_RATIO, application.getStatus());
   }
  
   public void testIncompleteApplication() throws Exception {     
      SpringRuleEngine engine = LoanProcessRuleEngine.getEngine("SharkysExpressLoansApplicationProcessor");
      LoanApplication application = new LoanApplication();
      engine.processRequest(application);
      assertEquals(LoanApplication.INSUFFICIENT_DATA, application.getStatus());
   }

　　显然单元测试会失败因为我们还没有实现任何的逻辑。然而，随着项目的进展，越来越多的测试通过，最后JUnit测试就全部通过了。

　　让我们继续操作和规则的实现。我们希望操作与持久服务交互因此我们需要一个通用基类:

public abstract class AbstractPersistenceAwareAction extends AbstractAction {
   private LoanApplicationPersistenceInterface persistenceService;
   public void setPersistenceService(LoanApplicationPersistenceInterface persistenceService) {
      this.persistenceService = persistenceService;
   }
   public LoanApplicationPersistenceInterface getPersistenceService() {
      return persistenceService;
   }
}

　　在我们的进程中第一个请求贷款申请的业务规则已经完成:

public class ValidApplicationRule extends AbstractRule {
   protected boolean makeDecision(Object arg) throws Exception {
      LoanApplication application = (LoanApplication) arg;
      if(application.getExpences() == 0 ||
            application.getFirstName() == null ||
            application.getIncome() == 0 ||
            application.getLastName() == null ||
            application.getStateCode() == null) {
         application.setStatus(LoanApplication.INSUFFICIENT_DATA);
         return false;
      }
      return true;
   }
}

　　注意这个类的一些有趣的现象:他是完全自包含的。他可以由自己实例化或者任何外部的应用容器，而类中的逻辑可以独立的开发和测试。这些现象使类成为基于规则应用的完美的程序块。