Simplification and tests

dhis-2/dhis-web-api/src/main/java/org/hisp/dhis/webapi/controller/datasummary/DataSummaryController.java

@@ -117,32 +117,18 @@ public DataSummaryController(DataStatisticsService dataStatisticsService) {
     metrics.helpLine("data_summary_system_info", "System information");
     metrics.typeLine("data_summary_system_info", "gauge");
     if (summary.getSystem() != null) {
-      if (summary.getSystem() != null) {
-        if (summary.getSystem().getVersion() != null) {
-          metrics.appendStaticKeyValue(
-              "data_summary_system_info", "version", summary.getSystem().getVersion());
-        }
-        if (summary.getSystem().getRevision() != null) {
-          metrics.appendStaticKeyValue(
-              "data_summary_system_info", "revision", summary.getSystem().getRevision());
-        }
-        if (summary.getSystem().getBuildTime() != null) {
-          metrics.appendStaticKeyValue(
-              "data_summary_system_info",
-              "build_time",
-              summary.getSystem().getBuildTime().toString());
-        }
-        if (summary.getSystem().getSystemId() != null) {
-          metrics.appendStaticKeyValue(
-              "data_summary_system_info", "system_id", summary.getSystem().getSystemId());
-        }
-        if (summary.getSystem().getServerDate() != null) {
-          metrics.appendStaticKeyValue(
-              "data_summary_system_info",
-              "server_date",
-              summary.getSystem().getServerDate().toString());
-        }
-      }
+      metrics.appendStaticKeyValue(
+          "data_summary_system_info", "version", summary.getSystem().getVersion());
+      metrics.appendStaticKeyValue(
+          "data_summary_system_info", "revision", summary.getSystem().getRevision());
+      metrics.appendStaticKeyValue(
+          "data_summary_system_info", "build_time", summary.getSystem().getBuildTime().toString());
+      metrics.appendStaticKeyValue(
+          "data_summary_system_info", "system_id", summary.getSystem().getSystemId());
+      metrics.appendStaticKeyValue(
+          "data_summary_system_info",
+          "server_date",
+          summary.getSystem().getServerDate().toString());
     }
 
     return metrics.getMetrics();

dhis-2/dhis-web-api/src/main/java/org/hisp/dhis/webapi/utils/PrometheusTextBuilder.java

@@ -30,9 +30,8 @@
 import java.util.Map;
 
 /**
- * A simple utility class to build Prometheus text format metrics. Note that there is no validation
- * of the input, so the user should make sure that the input is correct. The Prometheus text format
- * is documented here: https://prometheus.io/docs/instrumenting/exposition_formats/
+ * A simple utility class to build Prometheus text format metrics. The Prometheus text format is
+ * documented here: https://prometheus.io/docs/instrumenting/exposition_formats/
  *
  * @author Jason P. Pickering
  */
@@ -41,34 +40,59 @@ public class PrometheusTextBuilder {
   private StringBuilder metrics = new StringBuilder();
 
   public void helpLine(String metricName, String help) {
-    metrics.append("# HELP ").append(metricName).append(" ").append(help).append("%n");
+    metrics.append(String.format("# HELP %s %s%n", metricName, help));
   }
 
+  /**
+   * Appends a Prometheus metric type line to the metrics.
+   *
+   * @param metricName the name of the metric
+   * @param type the type of the metric (e.g., counter, gauge)
+   */
   public void typeLine(String metricName, String type) {
-    metrics.append("# TYPE ").append(metricName).append(" ").append(type).append("%n");
+    metrics.append(String.format("# TYPE %s %s%n", metricName, type));
   }
 
+  /**
+   * Transform a Map<String, ?> into a Prometheus text format metric. Note that the key is assumed
+   * to be a string, and the value should be a number which is capable of being converted to a
+   * string.
+   *
+   * @param map the map containing the metrics data
+   * @param metricName the name of the metric
+   * @param keyName the name of the key in the metric
+   * @param help the help text for the metric
+   * @param type the type of the metric
+   */
   public void updateMetricsFromMap(
       Map<?, ?> map, String metricName, String keyName, String help, String type) {
     helpLine(metricName, help);
     typeLine(metricName, type);
     map.forEach(
         (key, value) ->
-            metrics.append("%s{%s=\"%s\" } %s%n".formatted(metricName, keyName, key, value)));
+            metrics.append("%s{%s=\"%s\"} %s%n".formatted(metricName, keyName, key, value)));
   }
 
+  /**
+   * Appends a static key-value pair to the Prometheus metrics. This is most useful for representing
+   * labels in the Prometheus text format such as build time, version, etc. This will produce a
+   * metric with a static value of 1.
+   *
+   * @param metricName the name of the metric
+   * @param key the key for the metric
+   * @param value the value for the metric
+   */
   public void appendStaticKeyValue(String metricName, String key, String value) {
     if (value != null) {
-      metrics
-          .append(metricName)
-          .append("{key=\"")
-          .append(key)
-          .append("\", value=\"")
-          .append(value)
-          .append("\"} 1%n");
+      metrics.append(String.format("%s{key=\"%s\", value=\"%s\"} 1%n", metricName, key, value));
     }
   }
 
+  /**
+   * Returns the Prometheus metrics as a string.
+   *
+   * @return the metrics in Prometheus text format
+   */
   public String getMetrics() {
     return metrics.toString();
   }

dhis-2/dhis-web-api/src/test/java/org/hisp/dhis/webapi/utils/PrometheusTextBuilderTest.java

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2004-2025, University of Oslo
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * Redistributions of source code must retain the above copyright notice, this
+ * list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * Neither the name of the HISP project nor the names of its contributors may
+ * be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.hisp.dhis.webapi.utils;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for the PrometheusTextBuilder class.
+ *
+ * @author Jason P. Pickering
+ */
+public class PrometheusTextBuilderTest {
+  @Test
+  void getMetricsReturnsEmptyStringWhenNoMetrics() {
+    PrometheusTextBuilder builder = new PrometheusTextBuilder();
+    assertEquals("", builder.getMetrics());
+  }
+
+  @Test
+  void helpLineAppendsHelpText() {
+    PrometheusTextBuilder builder = new PrometheusTextBuilder();
+    builder.helpLine("test_metric", "This is a test metric");
+    assertEquals("# HELP test_metric This is a test metric\n", builder.getMetrics());
+  }
+
+  @Test
+  void typeLineAppendsTypeText() {
+    PrometheusTextBuilder builder = new PrometheusTextBuilder();
+    builder.typeLine("test_metric", "counter");
+    assertEquals("# TYPE test_metric counter\n", builder.getMetrics());
+  }
+
+  @Test
+  void updateMetricsFromMapAppendsMetrics() {
+    PrometheusTextBuilder builder = new PrometheusTextBuilder();
+    Map<String, Integer> map = Map.of("key1", 1);
+    builder.updateMetricsFromMap(map, "test_metric", "key", "Test help", "gauge");
+    String expected =
+        "# HELP test_metric Test help\n"
+            + "# TYPE test_metric gauge\n"
+            + "test_metric{key=\"key1\"} 1\n";
+    assertEquals(expected, builder.getMetrics());
+  }
+
+  @Test
+  void appendStaticKeyValueAppendsKeyValue() {
+    PrometheusTextBuilder builder = new PrometheusTextBuilder();
+    builder.appendStaticKeyValue("test_metric", "key", "value");
+    assertEquals("test_metric{key=\"key\", value=\"value\"} 1\n", builder.getMetrics());
+  }
+
+  @Test
+  void appendStaticKeyValueIgnoresNullValue() {
+    PrometheusTextBuilder builder = new PrometheusTextBuilder();
+    builder.appendStaticKeyValue("test_metric", "key", null);
+    assertEquals("", builder.getMetrics());
+  }
+}