Create Custom Fields from MDC (Log4j)

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

@@ -24,10 +24,6 @@ public void setFieldName(String fieldName) {
         }
     }
 
-    public void convert(Object[] arguments, StringBuilder appendTo) {
-		convert(appendTo, Collections.emptyMap(), arguments);
-    }
-
 	public void convert(StringBuilder appendTo, Map<String, String> mdcCustomFields, Object... arguments) {
 		List<CustomField> customFields = getCustomFields(arguments);
 		if (!customFields.isEmpty() || !mdcCustomFields.isEmpty()) {

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

@@ -0,0 +1,91 @@
+package com.sap.hcp.cf.log4j2.converter;
+
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
+import static java.util.Collections.unmodifiableList;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.logging.log4j.core.LogEvent;
+import org.apache.logging.log4j.core.config.plugins.Plugin;
+import org.apache.logging.log4j.core.pattern.ConverterKeys;
+import org.apache.logging.log4j.core.pattern.LogEventPatternConverter;
+import org.apache.logging.log4j.core.pattern.PatternConverter;
+import org.apache.logging.log4j.message.Message;
+import org.apache.logging.log4j.util.BiConsumer;
+import org.apache.logging.log4j.util.ReadOnlyStringMap;
+
+import com.sap.hcp.cf.logging.common.converter.DefaultCustomFieldsConverter;
+import com.sap.hcp.cf.logging.common.customfields.CustomField;
+
+/**
+ * This is a simple {@link LogEventPatternConverter} implementation that
+ * converts key/value pairs stored in {@link CustomField} instances which have
+ * been passed as arguments.
+ * <p>
+ * We allow to types of addition to a log message, either <i>embedded</i>, i.e.
+ * the key/value pairs appear as a list of JSON fields in the message, or as a
+ * nested object where the field name has been specified as an option to this
+ * converter.
+ */
+@Plugin(name = "ArgsConverter", category = PatternConverter.CATEGORY)
+@ConverterKeys({ "cf" })
+public class CustomFieldsConverter extends LogEventPatternConverter {
+
+	public static final String WORD = "cf";
+
+	private final List<String> customFieldMdcKeyNames;
+	private DefaultCustomFieldsConverter converter = new DefaultCustomFieldsConverter();
+
+	public CustomFieldsConverter(String[] options) {
+		super(WORD, WORD);
+
+		customFieldMdcKeyNames = options == null ? emptyList() : unmodifiableList(asList(options));
+	}
+
+	public static CustomFieldsConverter newInstance(final String[] options) {
+		return new CustomFieldsConverter(options);
+	}
+
+	void setConverter(DefaultCustomFieldsConverter converter) {
+		this.converter = converter;
+	}
+
+	@Override
+	public void format(LogEvent event, StringBuilder appendTo) {
+		converter.convert(appendTo, getCustomFieldsFromMdc(event), getMessageParameters(event));
+	}
+
+	private Object[] getMessageParameters(LogEvent event) {
+		Message message = event.getMessage();
+		return message == null ? null : message.getParameters();
+	}
+
+	private Map<String, String> getCustomFieldsFromMdc(LogEvent event) {
+		ReadOnlyStringMap contextData = event.getContextData();
+		if (contextData == null || contextData.isEmpty()) {
+			return Collections.emptyMap();
+		}
+		CustomFieldsMdcCollector mdcCollector = new CustomFieldsMdcCollector();
+		contextData.forEach(mdcCollector);
+		return mdcCollector.getCustomFields();
+	}
+
+	private class CustomFieldsMdcCollector implements BiConsumer<String, String> {
+		private Map<String, String> customFields = new HashMap<>(customFieldMdcKeyNames.size());
+
+		@Override
+		public void accept(String key, String value) {
+			if (customFieldMdcKeyNames.contains(key)) {
+				customFields.put(key, value);
+			}
+		}
+
+		public Map<String, String> getCustomFields() {
+			return customFields;
+		}
+	}
+}

cf-java-logging-support-log4j2/src/main/java/com/sap/hcp/cf/log4j2/layout/CustomField.java

@@ -0,0 +1,61 @@
+package com.sap.hcp.cf.log4j2.layout;
+
+import org.apache.logging.log4j.core.config.Node;
+import org.apache.logging.log4j.core.config.plugins.Plugin;
+import org.apache.logging.log4j.core.config.plugins.PluginBuilderAttribute;
+import org.apache.logging.log4j.core.config.plugins.PluginBuilderFactory;
+
+@Plugin(name = "customField", category = Node.CATEGORY, printObject = true)
+public class CustomField {
+
+	private final String key;
+	private final boolean retainOriginal;
+
+	private CustomField(Builder builder) {
+		this.key = builder.key;
+		this.retainOriginal = builder.retainOriginal;
+	}
+
+	public String getKey() {
+		return key;
+	}
+
+	public boolean isRetainOriginal() {
+		return retainOriginal;
+	}
+
+	@Override
+	public String toString() {
+		return key + (retainOriginal ? " (retained)" : "");
+	}
+
+	@PluginBuilderFactory
+	public static Builder newBuilder() {
+		return new Builder();
+	}
+
+	public static class Builder implements org.apache.logging.log4j.core.util.Builder<CustomField> {
+
+		@PluginBuilderAttribute("mdcKeyName")
+		private String key;
+
+		@PluginBuilderAttribute("retainOriginal")
+		private boolean retainOriginal;
+
+		public Builder setKey(String key) {
+			this.key = key;
+			return this;
+		}
+
+		public Builder setRetainOriginal(boolean retainOriginal) {
+			this.retainOriginal = retainOriginal;
+			return this;
+		}
+
+		@Override
+		public CustomField build() {
+			return new CustomField(this);
+		}
+
+	}
+}

cf-java-logging-support-log4j2/src/main/java/com/sap/hcp/cf/log4j2/layout/CustomFieldsAdapter.java

@@ -0,0 +1,39 @@
+package com.sap.hcp.cf.log4j2.layout;
+
+import static java.util.Arrays.asList;
+import static java.util.Collections.emptyList;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+import com.sap.hcp.cf.logging.common.LogContext;
+
+public class CustomFieldsAdapter {
+
+	private List<CustomField> customFields;
+
+	public CustomFieldsAdapter(CustomField... customFields) {
+		this.customFields = customFields == null ? emptyList() : asList(customFields);
+	}
+
+	public List<String> getCustomFieldKeyNames() {
+		List<String> result = new ArrayList<>(customFields.size());
+		for (CustomField customField : customFields) {
+			result.add(customField.getKey());
+		}
+		return result;
+	}
+
+	public List<String> getExcludedFieldKeyNames() {
+		Collection<String> contextFieldsKeys = LogContext.getContextFieldsKeys();
+		List<String> result = new ArrayList<>(customFields.size());
+		for (CustomField customField : customFields) {
+			if (!customField.isRetainOriginal() && !contextFieldsKeys.contains(customField.getKey())) {
+				result.add(customField.getKey());
+			}
+		}
+		return result;
+	}
+
+}