Refactor Logback Log Generation

Use jackson directly to serialise the Logback log events.
Removes the old pattern layout approach.
The new approach provides several callback and customisation
features. They enable users to extend the library within their own
applications. Furthermore, support for custom fields has been
extended to support non-string values for top level fields. Also,
CloudFoundry's VCAP environment variables are no longer added
by default. The user has to opt in those fields

Signed-off-by: Karsten Schnitter <k.schnitter@sap.com>

Author: KarstenSchnitter

cf-java-logging-support-core/src/main/java/com/sap/hcp/cf/logging/common/converter/DefaultCustomFieldsConverter.java

@@ -107,7 +107,7 @@ private void addCustomFields(ArrayComposer<ObjectComposer<JSONComposer<String>>>
 			// Let argument CustomField take precedence over MDC
 			CustomField field = customFields.get(key);
 			if (field != null) {
-				value = field.getValue();
+                value = String.valueOf(field.getValue());
 			}
 			if (value != null) {
 				oc.startObject().put("k", key).put("v", value).put("i", i).end();

cf-java-logging-support-core/src/main/java/com/sap/hcp/cf/logging/common/customfields/CustomField.java

@@ -30,13 +30,13 @@ public String getKey() {
         return key;
     }
 
-    public String getValue() {
-        return String.valueOf(value);
+    public Object getValue() {
+        return value;
     }
 
     @Override
     public String toString() {
-        return key + "=" + getValue();
+        return key + "=" + String.valueOf(value);
     }
 
     private void validateNotNull(Object obj, String msg) throws IllegalArgumentException {

cf-java-logging-support-core/src/main/java/com/sap/hcp/cf/logging/common/request/RequestRecord.java

@@ -3,6 +3,7 @@
 import java.time.Clock;
 import java.time.Duration;
 import java.time.Instant;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
@@ -216,6 +217,11 @@ public String toString() {
         }
     }
 
+    public Map<String, Value> getFields() {
+        finish();
+        return Collections.unmodifiableMap(fields);
+    }
+
     private void setDefaults() {
         LogContext.loadContextFields();
         addValue(Fields.RESPONSE_SIZE_B, Defaults.RESPONSE_SIZE_B);

cf-java-logging-support-core/src/main/java/com/sap/hcp/cf/logging/common/serialization/ContextFieldSupplier.java

@@ -0,0 +1,8 @@
+package com.sap.hcp.cf.logging.common.serialization;
+
+import java.util.Map;
+import java.util.function.Supplier;
+
+@FunctionalInterface
+public interface ContextFieldSupplier extends Supplier<Map<String, Object>> {
+}

cf-java-logging-support-core/src/main/java/com/sap/hcp/cf/logging/common/serialization/FullVcapEnvFieldFupplier.java

@@ -0,0 +1,8 @@
+package com.sap.hcp.cf.logging.common.serialization;
+
+public class FullVcapEnvFieldFupplier extends VcapEnvFieldSupplier {
+
+    public FullVcapEnvFieldFupplier() {
+        super(true);
+    }
+}

cf-java-logging-support-core/src/main/java/com/sap/hcp/cf/logging/common/serialization/VcapEnvFieldSupplier.java

@@ -0,0 +1,32 @@
+package com.sap.hcp.cf.logging.common.serialization;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import com.sap.hcp.cf.logging.common.LogContext;
+import com.sap.hcp.cf.logging.common.VcapEnvReader;
+
+public class VcapEnvFieldSupplier implements ContextFieldSupplier {
+
+    private final Map<String, Object> envMap;
+
+    public VcapEnvFieldSupplier() {
+        this(false);
+    }
+
+    protected VcapEnvFieldSupplier(boolean sendDefaultValues) {
+        Map<String, Object> map = new HashMap<>();
+        map.putAll(VcapEnvReader.getEnvMap());
+        if (sendDefaultValues) {
+            LogContext.getContextFieldsKeys().stream().forEach(k -> map.computeIfAbsent(k, LogContext::getDefault));
+        }
+        this.envMap = Collections.unmodifiableMap(map);
+    }
+
+    @Override
+    public Map<String, Object> get() {
+        return envMap;
+    }
+
+}

cf-java-logging-support-log4j2/src/main/java/com/sap/hcp/cf/log4j2/converter/ContextPropsConverter.java

@@ -76,7 +76,7 @@ private Map<String, String> addCustomFieldsFromArguments(Map<String, String> con
                     result = new HashMap<>(contextData);
                     unchangedContextData = false;
                 }
-                result.put(field.getKey(), field.getValue());
+                result.put(field.getKey(), String.valueOf(field.getValue()));
             }
         }
         return result;