add stricter validation for Metervalues as described in #241

Author: mmauksch

ocpp-v1_6/src/main/java/eu/chargetime/ocpp/model/core/MeterValue.java

@@ -67,7 +67,7 @@ public MeterValue(ZonedDateTime timestamp, SampledValue[] sampledValue) {
 
   @Override
   public boolean validate() {
-    boolean valid = timestamp != null && sampledValue != null;
+    boolean valid = timestamp != null && sampledValue != null && sampledValue.length > 0;
 
     if (valid) {
       for (SampledValue value : sampledValue) {

ocpp-v1_6/src/main/java/eu/chargetime/ocpp/model/core/MeterValuesRequest.java

@@ -64,7 +64,7 @@ public MeterValuesRequest(Integer connectorId) {
 
   @Override
   public boolean validate() {
-    boolean valid = this.connectorId != null && this.connectorId >= 0 && this.meterValue != null;
+    boolean valid = this.connectorId != null && this.connectorId >= 0 && this.meterValue != null && meterValue.length > 0;
 
     if (valid) {
       for (MeterValue current : this.meterValue) {

ocpp-v1_6/src/test/java/eu/chargetime/ocpp/model/core/MeterValuesRequestTest.java

@@ -0,0 +1,32 @@
+package eu.chargetime.ocpp.model.core;
+
+import junit.framework.TestCase;
+
+import java.time.ZonedDateTime;
+
+public class MeterValuesRequestTest extends TestCase {
+
+    public void testEmptyMeterValuesArray_FailsValidation() {
+        MeterValuesRequest request = new MeterValuesRequest(1);
+        request.setTransactionId(2);
+        request.setMeterValue(new MeterValue[]{});
+        assertFalse(request.validate());
+    }
+
+    public void testEmptySampledValuesArray_failsValidation() {
+        MeterValuesRequest request = new MeterValuesRequest(1);
+        MeterValue measured = new MeterValue(ZonedDateTime.now(), new SampledValue[]{});
+        request.setTransactionId(2);
+        request.setMeterValue(new MeterValue[]{measured});
+        assertFalse(request.validate());
+    }
+
+    public void testMeterValuesWithAtLeastOneMeasurementPassesValidation() {
+        MeterValuesRequest request = new MeterValuesRequest(1);
+        SampledValue sample = new SampledValue("5");
+        MeterValue measured = new MeterValue(ZonedDateTime.now(), new SampledValue[]{sample});
+        request.setTransactionId(2);
+        request.setMeterValue(new MeterValue[]{measured});
+        assertTrue(request.validate());
+    }
+}