[BAEL-1300] Custom Logback Appender (#3193)

* BAEL-1300 Custom logback appender

* BAEL-1300 fix to logback module

* relativePath

logging-modules/logback/src/main/java/com/baeldung/logback/Example.java

@@ -0,0 +1,14 @@
+package com.baeldung.logback;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Example {
+
+    private static final Logger logger = LoggerFactory.getLogger(Example.class);
+
+    public static void main(String[] args) {
+        logger.info("Example log from {}", Example.class.getSimpleName());
+    }
+
+}

logging-modules/logback/src/main/java/com/baeldung/logback/MapAppender.java

@@ -0,0 +1,37 @@
+package com.baeldung.logback;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.AppenderBase;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class MapAppender extends AppenderBase<ILoggingEvent> {
+
+    private final Map<String, ILoggingEvent> eventMap = new HashMap<>();
+
+    private String prefix;
+
+    @Override
+    protected void append(final ILoggingEvent event) {
+        if (prefix == null || "".equals(prefix)) {
+            addError("Prefix is not set for MapAppender.");
+            return;
+        }
+
+        eventMap.put(prefix + System.currentTimeMillis(), event);
+    }
+
+    public String getPrefix() {
+        return prefix;
+    }
+
+    public void setPrefix(final String prefix) {
+        this.prefix = prefix;
+    }
+
+    public Map<String, ILoggingEvent> getEventMap() {
+        return eventMap;
+    }
+
+}

logging-modules/logback/src/main/resources/logback.xml

@@ -0,0 +1,18 @@
+<configuration>
+
+    <appender name="map" class="com.baeldung.logback.MapAppender">
+        <prefix>test</prefix>
+    </appender>
+
+    <appender name="out" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="info">
+        <appender-ref ref="map"/>
+        <appender-ref ref="out"/>
+    </root>
+
+</configuration>