Dropwizard based custom metric client - code review

Author: DeyanZhelyazkov

cf-java-monitoring-custom-metrics-clients/cf-custom-metrics-clients-core/src/test/java/com/sap/cloud/cf/monitoring/client/configuration/CustomMetricsConfigurationFactoryTest.java

@@ -20,8 +20,7 @@ public void testMatches_WithoutEnv() throws Exception {
 
     @Test
     public void testMatches_WithEmptyEnv() throws Exception {
-        String[] CUSTOM_METRICS_ENV = new String[] { "CUSTOM_METRICS", "" };
-        EnvUtils.setEnvs(new String[][] { CUSTOM_METRICS_ENV });
+        EnvUtils.setEnvs(new String[][] { { "CUSTOM_METRICS", "" } });
 
         testDefault();
     }
@@ -78,10 +77,10 @@ private static String[] getCustomMetricsEnv(String interval) {
 
     private static String getJson(String interval) {
         return "{\n" + //
-                "    \"interval\": \"" + interval + "\",\n" + //
-                "    \"enabled\": \"false\",\n" + //
-                "    \"metrics\": [\"timer\", \"summary\"],\n" + //
-                "    \"metricQuantiles\": \"true\"\n" + //
-                "}";
+               "    \"interval\": \"" + interval + "\",\n" + //
+               "    \"enabled\": \"false\",\n" + //
+               "    \"metrics\": [\"timer\", \"summary\"],\n" + //
+               "    \"metricQuantiles\": \"true\"\n" + //
+               "}";
     }
 }

cf-java-monitoring-custom-metrics-clients/cf-custom-metrics-clients-java/src/main/java/com/sap/cloud/cf/monitoring/java/converter/GaugeConverter.java

@@ -18,7 +18,7 @@ protected List<Metric> convertMetricEntry(Entry<String, Gauge> metricEntry, long
             result.add(buildCustomMetric(metricEntry.getKey() + ".value", number.doubleValue(), MetricType.GAUGE,
                                          timestamp));
         } else {
-            throw new IllegalArgumentException(String.format("The type for Gauge {%s} is invalid. The supported type is {%s}", gaugeValue.getClass().getName(), Number.class.getName()));
+            throw new IllegalArgumentException(String.format("The type {%s} for Gauge {%s} is invalid. The supported type is {%s}", gaugeValue.getClass().getName(), metricEntry.getKey(), Number.class.getName()));
         }
         return result;
     }

cf-java-monitoring-custom-metrics-clients/cf-custom-metrics-clients-java/src/main/java/com/sap/cloud/cf/monitoring/java/converter/MetricConverter.java

@@ -1,18 +1,18 @@
 package com.sap.cloud.cf.monitoring.java.converter;
 
-import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.stream.Collectors;
 
 import com.sap.cloud.cf.monitoring.client.model.Metric;
 
 public abstract class MetricConverter<T> {
     private static final String KEY_TYPE = "type";
 
     public enum MetricType {
-                     TIMER("timer"), HISTOGRAM("histogram"), GAUGE("gauge"), METER("meter"), COUNTER("counter");
+                            TIMER("timer"), HISTOGRAM("histogram"), GAUGE("gauge"), METER("meter"), COUNTER("counter");
 
         private final String metricTypeName;
 
@@ -26,11 +26,11 @@ private MetricType(String metricTypeName) {
     }
 
     public List<Metric> convert(Map<String, T> metrics, long timestamp) {
-        ArrayList<Metric> result = new ArrayList<>();
-        for (Entry<String, T> entry: metrics.entrySet()) {
-            result.addAll(convertMetricEntry(entry, timestamp));
-        }
-        return result;
+        return metrics.entrySet()
+                .stream()
+                .map(entry -> convertMetricEntry(entry, timestamp))
+                .flatMap(List::stream)
+                .collect(Collectors.toList());
     }
 
     protected abstract List<Metric> convertMetricEntry(Entry<String, T> metricEntry, long timestamp);
@@ -40,4 +40,4 @@ protected Metric buildCustomMetric(String name, double value, MetricType type, l
         tags.put(KEY_TYPE, type.getMetricTypeName());
         return new Metric(name, value, timestamp, tags);
     }
-}
+}

cf-java-monitoring-custom-metrics-clients/cf-custom-metrics-clients-java/src/test/java/com/sap/cloud/cf/monitoring/java/converter/GaugeConverterTest.java

@@ -56,7 +56,7 @@ public String getValue() {
         gauges.put(GAUGE_METRIC, gauge);
 
         expectedException.expect(IllegalArgumentException.class);
-        expectedException.expectMessage(String.format("The type for Gauge {%s} is invalid. The supported type is {%s}", gauge.getValue().getClass().getName(), Number.class.getName()));
+        expectedException.expectMessage(String.format("The type {%s} for Gauge {%s} is invalid. The supported type is {%s}", gauge.getValue().getClass().getName(), GAUGE_METRIC, Number.class.getName()));
 
         new GaugeConverter().convert(gauges, currentTimeMillis);
     }