Task 3: Debugging a rule

You create a query to find the action rule that uses the variable monthly repayment, and then add a breakpoint to track the rule.

1. Run the decision service as shown in Task 1: Using automatic exception handling.
   In the results, you see that the report does not show the correct monthly repayment value. You want to find the source of this value to determine how to fix it.
2. In the Rule Explorer, expand the Loan Validation Service project.
3. Right-click the queries folder, and click New > Query.
4. Enter Monthly as the name in the New Query dialog, and click Finish.
5. Click <enter a condition> and add search parameters to form the following query:
   

   Tip: The search function is case sensitive. Enter the name of the variable as you expect to find it in the action rule.
6. Click Run query, and click Yes in the Save Resource dialog.
   The Search view shows the repayment action rule because it contains the word monthly:

   
7. Double-click the action rule in the Search view to open it in the rule editor.
   You see that the first action, line 7, sets the value of the monthly repayment variable.
8. Open the ARL tab.
   It shows the language that is applied by the action rule (see Advanced Rule Language (ARL)).

   The rule has three main parts: the definition of the variables, the condition beginning with when, and the action beginning with then. In the action part, you see that the rule calls the loan.LoanUtil.getMonthlyRepayment method to calculate the monthly repayment rate. You must step into this method.

9. Right-click line 7, and then click Toggle Breakpoint in the pop-up menu.
   A breakpoint is displayed next to the line:

   

   In the next step, you debug the action rule.

You run a debugging session. When it stops at breakpoints, you look for reasons for the monthly repayment error.

1. Run the run loan validation configuration in the Debug Configurations.
2. Click OK in the Save and Launch dialog if it opens, and click Yes in the Confirm Perspective Switch dialog.
   The Debug perspective opens.
3. The debugger stops at the validation task in the loanvalidation ruleflow. Right-click the task, and click Toggle Breakpoint to remove the breakpoint.
   You do not need this breakpoint for this task.
4. Click the Resume button .
   The Content view now shows the repayment action rule.
5. Open the Variables tab and expand report.
   The monthlyRepayment variable shows 0.0.
6. Click the Step Into button . The debugger stops at LoanUtil.java.
   The Java code shows the following method at the breakpoint:

   

   The function computes a monthly repayment rate by dividing yearlyRate by MonthsInYear. In the Variables view, you see that the value of MonthsInYear is 0. The error is that the function is dividing by 0, when it should divide by 12.

7. Stop the debugging session by clicking the Terminate button .

You change the value of the MonthsInYear variable to 12, and run the decision service to check the results.

1. Switch to LoanUtil.java in the Rule perspective.
2. Change the value of the MonthsInYear variable to 12:
   
3. Save your changes, and run the decision service normally by selecting run loan validation in the Run Configurations.
   The Console now shows the correct monthly repayment rate of 570.83:

   

   However, the decision service still does not approve the loan, so you have more work to do.

4. Remove all the breakpoints because you no longer need them:
   1. Open Window > Show view > Other.
   2. In the filter field, type breakpoints, select Breakpoints in the list, and click OK.
   3. Click the Remove All Breakpoints button .
5. Save your work.