Unify field collection providers

loki-logback-appender/src/main/java/com/github/loki4j/logback/json/AbstractFieldCollectionJsonProvider.java

@@ -0,0 +1,110 @@
+package com.github.loki4j.logback.json;
+
+import java.util.Collection;
+import java.util.HashSet;
+import java.util.Set;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+
+/**
+ * An abstract provider that writes a collection of JSON fields
+ */
+public abstract class AbstractFieldCollectionJsonProvider<E, T extends Collection<E>> extends AbstractJsonProvider {
+
+    /**
+     * A prefix added to all the keys (field names) in this collection.
+     */
+    private String prefix;
+
+    /**
+     * Whether to omit the prefix and use field names from this collection as they are.
+     */
+    private boolean noPrefix;
+
+    /**
+     * A set of keys to exclude from JSON payload.
+     * Exclude list has a precedence over include list.
+     * If not specified, all keys are included.
+     */
+    private Set<String> excludeKeys = new HashSet<>();
+
+    /**
+     * A set of keys to include into JSON payload.
+     * If not specified, all keys are included.
+     */
+    private Set<String> includeKeys = new HashSet<>();
+
+    @Override
+    public boolean canWrite(ILoggingEvent event) {
+        var entries = extractEntries(event);
+        return entries != null && !entries.isEmpty();
+    }
+
+    @Override
+    public boolean writeTo(JsonEventWriter writer, ILoggingEvent event, boolean startWithSeparator) {
+        var entries = extractEntries(event);
+        var firstFieldWritten = false;
+        for (E entry : entries) {
+            var key = extractKey(entry);
+            var value = extractValue(entry);
+            // skip empty records
+            if (key == null || value == null)
+                continue;
+
+            // check exclude list, if defined
+            if (!excludeKeys.isEmpty() && excludeKeys.contains(key))
+                continue;
+
+            // check include list, if defined
+            if (!includeKeys.isEmpty() && !includeKeys.contains(key))
+                continue;
+
+            if (startWithSeparator || firstFieldWritten)
+                writer.writeFieldSeparator();
+            var name = noPrefix ? key : prefix + key;
+            writer.writeObjectField(name, value);
+            firstFieldWritten = true;
+        }
+        return firstFieldWritten;
+    }
+
+    /**
+     * Extract the collection of entries (i.e. fields) from the logging event.
+     * @param event Current logback event.
+     */
+    protected abstract T extractEntries(ILoggingEvent event);
+
+    /**
+     * Extract the key (i.e. field name) from the collection entry.
+     */
+    protected abstract String extractKey(E entry);
+
+    /**
+     * Extract the value (i.e. field value) from the collection entry.
+     */
+    protected abstract Object extractValue(E entry);
+
+    public void addExclude(String key) {
+        excludeKeys.add(key);
+    }
+
+    public void addInclude(String key) {
+        includeKeys.add(key);
+    }
+
+    public String getPrefix() {
+        return prefix;
+    }
+
+    public void setPrefix(String prefix) {
+        this.prefix = prefix;
+    }
+
+    public boolean isNoPrefix() {
+        return noPrefix;
+    }
+
+    public void setNoPrefix(boolean noPrefix) {
+        this.noPrefix = noPrefix;
+    }
+}

loki-logback-appender/src/main/java/com/github/loki4j/logback/json/AbstractFieldJsonProvider.java

@@ -1,22 +1,17 @@
 package com.github.loki4j.logback.json;
 
 import ch.qos.logback.classic.spi.ILoggingEvent;
-import ch.qos.logback.core.spi.ContextAwareBase;
 
 /**
- * An abstract provider that writes a certain aspect of a logging event as a JSON field
+ * An abstract provider that writes a single JSON field
  */
-public abstract class AbstractFieldJsonProvider extends ContextAwareBase implements JsonProvider<ILoggingEvent> {
-
-    private boolean enabled = true;
+public abstract class AbstractFieldJsonProvider extends AbstractJsonProvider {
 
     /**
      * A JSON field name to use for this provider.
      */
     private String fieldName;
 
-    private volatile boolean started;
-
     @Override
     public boolean canWrite(ILoggingEvent event) {
         return true;
@@ -37,30 +32,6 @@ public boolean writeTo(JsonEventWriter writer, ILoggingEvent event, boolean star
      */
     protected abstract void writeExactlyOneField(JsonEventWriter writer, ILoggingEvent event);
 
-    @Override
-    public void start() {
-        started = true;
-    }
-
-    @Override
-    public void stop() {
-        started = false;
-    }
-
-    @Override
-    public boolean isStarted() {
-        return started;
-    }
-
-    @Override
-    public boolean isEnabled() {
-        return enabled;
-    }
-
-    public void setEnabled(boolean enabled) {
-        this.enabled = enabled;
-    }
-
     public String getFieldName() {
         return fieldName;
     }

loki-logback-appender/src/main/java/com/github/loki4j/logback/json/AbstractJsonProvider.java

@@ -0,0 +1,38 @@
+package com.github.loki4j.logback.json;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.spi.ContextAwareBase;
+
+/**
+ * An abstract provider that writes a certain aspect of a logging event as a JSON fragment
+ */
+public abstract class AbstractJsonProvider extends ContextAwareBase implements JsonProvider<ILoggingEvent> {
+
+    private boolean enabled = true;
+
+    private volatile boolean started;
+
+    @Override
+    public void start() {
+        started = true;
+    }
+
+    @Override
+    public void stop() {
+        started = false;
+    }
+
+    @Override
+    public boolean isStarted() {
+        return started;
+    }
+
+    @Override
+    public boolean isEnabled() {
+        return enabled;
+    }
+
+    public void setEnabled(boolean enabled) {
+        this.enabled = enabled;
+    }
+}

loki-logback-appender/src/main/java/com/github/loki4j/logback/json/KeyValuePairsJsonProvider.java

@@ -1,77 +1,32 @@
 package com.github.loki4j.logback.json;
 
-import java.util.HashSet;
 import java.util.List;
-import java.util.Set;
 
 import org.slf4j.event.KeyValuePair;
 
 import ch.qos.logback.classic.spi.ILoggingEvent;
 
-public class KeyValuePairsJsonProvider extends AbstractFieldJsonProvider {
+public class KeyValuePairsJsonProvider extends AbstractFieldCollectionJsonProvider<KeyValuePair, List<KeyValuePair>> {
 
     public static final String FIELD_KVP_PREFIX = "kvp_";
 
-    /**
-     * A set of keys to exclude from JSON payload.
-     * Exclude list has a precedence over include list.
-     * If not specified, all keys are included.
-     */
-    private Set<String> excludeKeys = new HashSet<>();
-
-    /**
-     * A set of keys to include into JSON payload.
-     * If not specified, all keys are included.
-     */
-    private Set<String> includeKeys = new HashSet<>();
-
     public KeyValuePairsJsonProvider() {
-        setFieldName(FIELD_KVP_PREFIX);
+        setPrefix(FIELD_KVP_PREFIX);
     }
 
     @Override
-    public boolean canWrite(ILoggingEvent event) {
-        List<KeyValuePair> kvPairs = event.getKeyValuePairs();
-        return kvPairs != null && !kvPairs.isEmpty();
+    protected List<KeyValuePair> extractEntries(ILoggingEvent event) {
+        return event.getKeyValuePairs();
     }
 
     @Override
-    public boolean writeTo(JsonEventWriter writer, ILoggingEvent event, boolean startWithSeparator) {
-        List<KeyValuePair> kvPairs = event.getKeyValuePairs();
-        var firstFieldWritten = false;
-        for (KeyValuePair entry : kvPairs) {
-            // skip empty records
-            if (entry.key == null || entry.value == null)
-                continue;
-
-            // check exclude list, if defined
-            if (!excludeKeys.isEmpty() && excludeKeys.contains(entry.key))
-                continue;
-
-            // check include list, if defined
-            if (!includeKeys.isEmpty() && !includeKeys.contains(entry.key))
-                continue;
-
-            if (startWithSeparator || firstFieldWritten)
-                writer.writeFieldSeparator();
-            writer.writeObjectField(getFieldName() + entry.key, entry.value);
-            firstFieldWritten = true;
-        }
-        return firstFieldWritten;
+    protected String extractKey(KeyValuePair entry) {
+        return entry.key;
     }
 
     @Override
-    protected void writeExactlyOneField(JsonEventWriter writer, ILoggingEvent event) {
-        throw new UnsupportedOperationException(
-            "KeyValuePairsJsonProvider can write an arbitrary number of fields. `writeExactlyOneField` should never be called for KeyValuePairsJsonProvider.");
-    }
-
-    public void addExclude(String key) {
-        excludeKeys.add(key);
-    }
-
-    public void addInclude(String key) {
-        includeKeys.add(key);
+    protected Object extractValue(KeyValuePair entry) {
+        return entry.value;
     }
 
 }

loki-logback-appender/src/main/java/com/github/loki4j/logback/json/MdcJsonProvider.java

@@ -1,75 +1,33 @@
 package com.github.loki4j.logback.json;
 
-import java.util.HashSet;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Set;
 
 import ch.qos.logback.classic.spi.ILoggingEvent;
 
-public class MdcJsonProvider extends AbstractFieldJsonProvider {
+public class MdcJsonProvider extends AbstractFieldCollectionJsonProvider<Map.Entry<String, String>, Set<Map.Entry<String, String>>> {
 
     public static final String FIELD_MDC_PREFIX = "mdc_";
 
-    /**
-     * A set of MDC keys to exclude from JSON payload.
-     * Exclude list has a precedence over include list.
-     * If not specified, all keys are included.
-     */
-    private Set<String> excludeKeys = new HashSet<>();
-
-    /**
-     * A set of MDC keys to include into JSON payload.
-     * If not specified, all keys are included.
-     */
-    private Set<String> includeKeys = new HashSet<>();
-
     public MdcJsonProvider() {
-        setFieldName(FIELD_MDC_PREFIX);
+        setPrefix(FIELD_MDC_PREFIX);
     }
 
     @Override
-    public boolean canWrite(ILoggingEvent event) {
-        Map<String, String> mdcProperties = event.getMDCPropertyMap();
-        return mdcProperties != null && !mdcProperties.isEmpty();
+    protected Set<Entry<String, String>> extractEntries(ILoggingEvent event) {
+        var mdcProperties = event.getMDCPropertyMap();
+        return mdcProperties == null ? null : mdcProperties.entrySet();
     }
 
     @Override
-    public boolean writeTo(JsonEventWriter writer, ILoggingEvent event, boolean startWithSeparator) {
-        Map<String, String> mdcProperties = event.getMDCPropertyMap();
-        var firstFieldWritten = false;
-        for (Map.Entry<String, String> entry : mdcProperties.entrySet()) {
-            // skip empty records
-            if (entry.getKey() == null || entry.getValue() == null)
-                continue;
-
-            // check exclude list, if defined
-            if (!excludeKeys.isEmpty() && excludeKeys.contains(entry.getKey()))
-                continue;
-
-            // check include list, if defined
-            if (!includeKeys.isEmpty() && !includeKeys.contains(entry.getKey()))
-                continue;
-
-            if (startWithSeparator || firstFieldWritten)
-                writer.writeFieldSeparator();
-            writer.writeStringField(getFieldName() + entry.getKey(), entry.getValue());
-            firstFieldWritten = true;
-        }
-        return firstFieldWritten;
+    protected String extractKey(Entry<String, String> entry) {
+        return entry.getKey();
     }
 
     @Override
-    protected void writeExactlyOneField(JsonEventWriter writer, ILoggingEvent event) {
-        throw new UnsupportedOperationException(
-            "MdcJsonProvider can write an arbitrary number of fields. `writeExactlyOneField` should never be called for MdcJsonProvider.");
-    }
-
-    public void addExclude(String key) {
-        excludeKeys.add(key);
-    }
-
-    public void addInclude(String key) {
-        includeKeys.add(key);
+    protected String extractValue(Entry<String, String> entry) {
+        return entry.getValue();
     }
 
 }

loki-logback-appender/src/test/java/com/github/loki4j/logback/json/JsonEventWriterTest.java

@@ -3,7 +3,7 @@
 import static org.junit.Assert.assertEquals;
 
 import java.util.List;
-import java.util.Set;
+import java.util.TreeSet;
 
 import org.junit.Test;
 
@@ -89,7 +89,7 @@ public void testWriteListOfStrings() {
     public void testWriteSetOfInts() {
         var writer = new JsonEventWriter(10);
         writer.writeBeginObject();
-        writer.writeObjectField("it", Set.of(1, 2, 3));
+        writer.writeObjectField("it", new TreeSet<Integer>(List.of(1, 2, 3)));
         writer.writeEndObject();
 
         assertEquals("{\"it\":[1,2,3]}", writer.toString());