#1871 - Add ability to write metrics in JSON form to Appendable

src/main/java/io/ebean/meta/ServerMetricsAsJson.java

@@ -33,6 +33,18 @@ public interface ServerMetricsAsJson {
    */
   ServerMetricsAsJson withNewLine(boolean withNewLine);
 
+  /**
+   * Set to include a heading of the database name.
+   * <p>
+   * When this is false the metrics are written without json array start or array end.
+   */
+  ServerMetricsAsJson withHeader(boolean withHeader);
+
+    /**
+     * Collect and write metrics as JSON to the given buffer.
+     */
+  void write(Appendable buffer);
+
   /**
    * Return the metrics in raw JSON.
    */

src/main/java/io/ebeaninternal/server/core/DumpMetricsJson.java

@@ -10,6 +10,7 @@ import io.ebean.meta.ServerMetrics;
 import io.ebean.meta.ServerMetricsAsJson;
 import io.ebean.meta.SortMetric;
 
+import java.io.IOException;
 import java.io.StringWriter;
 import java.util.Comparator;
 import java.util.List;
@@ -18,8 +19,9 @@ class DumpMetricsJson implements ServerMetricsAsJson {
 
   private final Database database;
 
-  private final StringWriter writer = new StringWriter();
+  private Appendable writer;
 
+  private boolean withHeader = true;
   private boolean withHash = true;
   private boolean withSql = true;
   private boolean withLocation = true;
@@ -34,6 +36,12 @@ class DumpMetricsJson implements ServerMetricsAsJson {
     this.database = database;
   }
 
+  @Override
+  public ServerMetricsAsJson withHeader(boolean withHeader) {
+    this.withHeader = withHeader;
+    return this;
+  }
+
   @Override
   public ServerMetricsAsJson withLocation(boolean withLocation) {
     this.withLocation = withLocation;
@@ -66,97 +74,111 @@ class DumpMetricsJson implements ServerMetricsAsJson {
 
   @Override
   public String json() {
+    writer = new StringWriter();
     collect(database.getMetaInfoManager().collectMetrics());
     return writer.toString();
   }
 
+  @Override
+  public void write(Appendable buffer) {
+    writer = buffer;
+    collect(database.getMetaInfoManager().collectMetrics());
+  }
+
   private void collect(ServerMetrics serverMetrics) {
+    try {
+      start();
+      for (MetaTimedMetric metric : serverMetrics.getTimedMetrics()) {
+        log(metric);
+      }
 
-    start();
-    for (MetaTimedMetric metric : serverMetrics.getTimedMetrics()) {
-      log(metric);
-    }
+      List<MetaCountMetric> countMetrics = serverMetrics.getCountMetrics();
+      if (!countMetrics.isEmpty()) {
+        if (sortBy != null) {
+          countMetrics.sort(SortMetric.COUNT_NAME);
+        }
+        for (MetaCountMetric metric : countMetrics) {
+          logCount(metric);
+        }
+      }
 
-    List<MetaCountMetric> countMetrics = serverMetrics.getCountMetrics();
-    if (!countMetrics.isEmpty()) {
-      if (sortBy != null) {
-        countMetrics.sort(SortMetric.COUNT_NAME);
+      List<MetaOrmQueryMetric> ormQueryMetrics = serverMetrics.getOrmQueryMetrics();
+      if (!ormQueryMetrics.isEmpty()) {
+        if (sortBy != null) {
+          ormQueryMetrics.sort(sortBy);
+        }
+        for (MetaOrmQueryMetric metric : ormQueryMetrics) {
+          logQuery(metric);
+        }
       }
-      for (MetaCountMetric metric : countMetrics) {
-        logCount(metric);
-      }
-    }
 
-    List<MetaOrmQueryMetric> ormQueryMetrics = serverMetrics.getOrmQueryMetrics();
-    if (!ormQueryMetrics.isEmpty()) {
-      if (sortBy != null) {
-        ormQueryMetrics.sort(sortBy);
-      }
-      for (MetaOrmQueryMetric metric : ormQueryMetrics) {
-        logQuery(metric);
+      List<MetaQueryMetric> dtoQueryMetrics = serverMetrics.getDtoQueryMetrics();
+      if (!dtoQueryMetrics.isEmpty()) {
+        if (sortBy != null) {
+          dtoQueryMetrics.sort(sortBy);
+        }
+        for (MetaQueryMetric metric : dtoQueryMetrics) {
+          logDtoQuery(metric);
+        }
       }
+      end();
+    } catch (IOException e) {
+      throw new RuntimeException("Error writing metrics as JSON", e);
     }
-
-    List<MetaQueryMetric> dtoQueryMetrics = serverMetrics.getDtoQueryMetrics();
-    if (!dtoQueryMetrics.isEmpty()) {
-      if (sortBy != null) {
-        dtoQueryMetrics.sort(sortBy);
-      }
-      for (MetaQueryMetric metric : dtoQueryMetrics) {
-        logDtoQuery(metric);
-      }
-    }
-    end();
   }
 
-  private void start() {
-    objStart();
-    key("db");
-    val(database.getName());
-    key("metrics");
-    listStart();
+  private void start() throws IOException {
+    if (withHeader) {
+      objStart();
+      key("db");
+      val(database.getName());
+      key("metrics");
+      listStart();
+    }
   }
 
-  private void end() {
-    listEnd();
-    objEnd();
+  private void end() throws IOException {
+    if (withHeader) {
+      listEnd();
+      objEnd();
+    }
   }
 
-  private void objStart() {
+  private void objStart() throws IOException {
     objKeyCounter = 0;
     writer.append("{");
   }
 
-  private void objEnd() {
+  private void objEnd() throws IOException {
     writer.append("}");
   }
 
-  private void listStart() {
+  private void listStart() throws IOException {
     listCounter = 0;
     writer.append("[");
     writer.append(newLine);
   }
 
-  private void listEnd() {
+  private void listEnd() throws IOException {
     writer.append("]");
   }
 
-  private void key(String key) {
+  private void key(String key) throws IOException {
     if (objKeyCounter++ > 0) {
       writer.append(", ");
     }
     writer.append("\"").append(key).append("\":");
   }
 
-  private void val(long count) {
+  private void val(long count) throws IOException {
     writer.append(Long.toString(count));
   }
 
-  private void val(String val) {
+  private void val(String val) throws IOException {
     writer.append("\"").append(val).append("\"");
   }
 
-  private void metricStart(MetaMetric metric) {
+  private void metricStart(MetaMetric metric) throws IOException {
     if (listCounter++ > 0) {
       writer.append(",").append(newLine);
     }
@@ -167,11 +189,11 @@ class DumpMetricsJson implements ServerMetricsAsJson {
     val(metric.getMetricType().name());
   }
 
-  private void metricEnd() {
+  private void metricEnd() throws IOException {
     objEnd();
   }
 
-  private void log(MetaTimedMetric metric) {
+  private void log(MetaTimedMetric metric) throws IOException {
     metricStart(metric);
     appendCounters(metric);
     if (withLocation) {
@@ -180,14 +202,14 @@ class DumpMetricsJson implements ServerMetricsAsJson {
     metricEnd();
   }
 
-  private void logCount(MetaCountMetric metric) {
+  private void logCount(MetaCountMetric metric) throws IOException {
     metricStart(metric);
     key("count");
     val(metric.getCount());
     metricEnd();
   }
 
-  private void logQuery(MetaOrmQueryMetric metric) {
+  private void logQuery(MetaOrmQueryMetric metric) throws IOException {
     metricStart(metric);
     appendCounters(metric);
     if (withHash) {
@@ -198,14 +220,14 @@ class DumpMetricsJson implements ServerMetricsAsJson {
     metricEnd();
   }
 
-  private void logDtoQuery(MetaQueryMetric metric) {
+  private void logDtoQuery(MetaQueryMetric metric) throws IOException {
     metricStart(metric);
     appendCounters(metric);
     appendLocationAndSql(metric);
     metricEnd();
   }
 
-  private void appendLocationAndSql(MetaQueryMetric metric) {
+  private void appendLocationAndSql(MetaQueryMetric metric) throws IOException {
     if (withLocation) {
       appendLocation(metric.getLocation());
     }
@@ -215,14 +237,14 @@ class DumpMetricsJson implements ServerMetricsAsJson {
     }
   }
 
-  private void appendLocation(String location) {
+  private void appendLocation(String location) throws IOException {
     if (location != null) {
       key("loc");
       val(location);
     }
   }
 
-  private void appendCounters(MetaTimedMetric timedMetric) {
+  private void appendCounters(MetaTimedMetric timedMetric) throws IOException {
     key("count");
     val(timedMetric.getCount());
     key("total");