Customizable field serializer

loki4j · Dec 15, 2024 · 8fbf930 · 8fbf930
1 parent c6d5500
commit 8fbf930
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Showing 3 changed files with 52 additions and 5 deletions.
diff --git a/loki-logback-appender/src/main/java/com/github/loki4j/logback/json/JsonEventWriter.java b/loki-logback-appender/src/main/java/com/github/loki4j/logback/json/JsonEventWriter.java
@@ -41,7 +41,7 @@ public void writeArraySeparator() {
     }
 
     public void writeObjectField(String fieldName, Object value) {
-        serializeFieldName(fieldName);
+        writeFieldName(fieldName);
         writeObjectValue(value);
     }
 
@@ -69,7 +69,7 @@ else if (value instanceof RawJsonString)
     }
 
     public void writeStringField(String fieldName, String value) {
-        serializeFieldName(fieldName);
+        writeFieldName(fieldName);
         writeStringValue(value);
     }
 
@@ -83,15 +83,15 @@ public void writeStringValue(String value) {
     }
 
     public void writeNumericField(String fieldName, long value) {
-        serializeFieldName(fieldName);
+        writeFieldName(fieldName);
         writeNumericValue(value);
     }
 
     public void writeNumericValue(long value) {
         NumberConverter.serialize(value, raw);
     }
 
-    private void serializeFieldName(String fieldName) {
+    public void writeFieldName(String fieldName) {
         raw.writeString(fieldName);
         raw.writeByte(SEMI);
     }

diff --git a/...back-appender/src/main/java/com/github/loki4j/logback/json/KeyValuePairsJsonProvider.java b/...back-appender/src/main/java/com/github/loki4j/logback/json/KeyValuePairsJsonProvider.java
@@ -10,6 +10,11 @@ public class KeyValuePairsJsonProvider extends AbstractFieldCollectionJsonProvid
 
     public static final String FIELD_KVP_PREFIX = "kvp_";
 
+    /**
+     * Json serializer to use for each field specified for this KVP provider.
+     */
+    private JsonFieldSerializer fieldSerializer = (writer, name, value) -> writer.writeObjectField(name, value);
+
     public KeyValuePairsJsonProvider() {
         setPrefix(FIELD_KVP_PREFIX);
     }
@@ -31,6 +36,14 @@ protected Object extractValue(KeyValuePair entry) {
 
     @Override
     protected void writeField(JsonEventWriter writer, String fieldName, Object fieldValue) {
-        writer.writeObjectField(fieldName, fieldValue);
+        fieldSerializer.writeField(writer, fieldName, fieldValue);
+    }
+
+    public JsonFieldSerializer getFieldSerializer() {
+        return fieldSerializer;
+    }
+
+    public void setFieldSerializer(JsonFieldSerializer fieldSerializer) {
+        this.fieldSerializer = fieldSerializer;
     }
 }
diff --git a/...-appender/src/test/java/com/github/loki4j/logback/json/KeyValuePairsJsonProviderTest.java b/...-appender/src/test/java/com/github/loki4j/logback/json/KeyValuePairsJsonProviderTest.java
@@ -111,4 +111,38 @@ public void testOmitPrefix() {
 
         provider.stop();
     }
+
+    @Test
+    public void testCustomFieldSerializer() {
+        var event = loggingEvent(101L, Level.DEBUG, "io.test.TestApp", "thread-1", "m2-line1", null);
+        event.setKeyValuePairs(Arrays.asList(
+                new KeyValuePair("property1", "value1"),
+                new KeyValuePair("property2", "value2")
+        ));
+
+        var provider = new KeyValuePairsJsonProvider();
+        provider.setFieldSerializer(
+                (writer, name, value) -> {
+                    writer.writeFieldName(name + "_arr");
+                    writer.writeBeginArray();
+                    writer.writeStringValue(name);
+                    writer.writeArraySeparator();
+                    writer.writeStringValue(value.toString());
+                    writer.writeEndArray();
+                }
+        );
+        provider.start();
+
+        assertTrue("canWrite", provider.canWrite(event));
+
+        var writer = new JsonEventWriter(0);
+        provider.writeTo(writer, event, false);
+
+        assertEquals("writeTo",
+                "\"kvp_property1_arr\":[\"kvp_property1\",\"value1\"],\"kvp_property2_arr\":[\"kvp_property2\",\"value2\"]",
+                writer.toString()
+        );
+
+        provider.stop();
+    }
 }