AccumulateTest.java

    @Test
    public void testAccumulateLambdaToString() {

        SecurityManager origSecurityManager = System.getSecurityManager();
        try {
            System.setSecurityManager(new SecurityManager() {
                @Override
                public void checkPermission(Permission perm) {
                    if (perm instanceof RuntimePermission && "accessDeclaredMembers".equals(perm.getName())) {
                        for (StackTraceElement elem : Thread.currentThread().getStackTrace()) {
                            if (elem.toString().contains("LambdaIntrospector.getExpressionHash") || elem.toString().contains("DummyLambdaPrinter.getExpressionHash")) {
                                fail("Introspector getExpressionHash is called : elem = " + elem);
                            }
                        }
                    }
                }
            });

            String str =
                    "import " + Person.class.getCanonicalName() + ";" +
                         "import " + Result.class.getCanonicalName() + ";" +
                         "rule X when\n" +
                         "  accumulate ( $p: Person ( getName().startsWith(\"M\") ); \n" +
                         "                $sum : sum($p.getAge())  \n" +
                         "              )                          \n" +
                         "then\n" +
                         "  insert(new Result($sum));\n" +
                         "end";

            KieSession ksession = getKieSession(str);

            RuleImpl rule = (RuleImpl) ksession.getKieBase().getKiePackage("defaultpkg").getRules().iterator().next();
            Pattern accumulatePattern = (Pattern) rule.getLhs().getChildren().get(0);// AccumulatePattern
            SingleAccumulate singleAccumulate = (SingleAccumulate) accumulatePattern.getSource();
            Accumulator accumulator = singleAccumulate.getAccumulators()[0];
            if (accumulator instanceof LambdaAccumulator.BindingAcc) {
                LambdaAccumulator.BindingAcc accumulator1 = (LambdaAccumulator.BindingAcc) accumulator;
                BindingEvaluator bindingEvaluator = accumulator1.getBindingEvaluator();
                BindViewItem1 binding = (BindViewItem1) bindingEvaluator.getBinding();
                String result = binding.getBindingFunction().toString();
                System.out.println("toString : " + result);
            }
        } finally {
            System.setSecurityManager(origSecurityManager);
        }
    }