BAEL-9356 Update "Conditional Logging with logback" article

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

@@ -0,0 +1,14 @@
+package com.baeldung.logback;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.boolex.EventEvaluatorBase;
+import ch.qos.logback.core.boolex.EvaluationException;
+
+public class BillingMessageEvaluator extends EventEvaluatorBase<ILoggingEvent> {
+
+    @Override
+    public boolean evaluate(ILoggingEvent event) throws NullPointerException, EvaluationException {
+        String message = event.getMessage();
+        return message.contains("billing");
+    }
+}

logging-modules/logback/src/test/java/com/baeldung/logback/ConditionalLoggingUnitTest.java

@@ -47,4 +47,16 @@ public void whenSystemPropertyIsPresent_thenReturnFileLogger() throws IOExceptio
         String logOutput = FileUtils.readFileToString(new File("conditional.log"));
         assertTrue(logOutput.contains("test prod log"));
     }
+
+    @Test
+    public void whenMatchedWithEvaluatorFilter_thenReturnFilteredLogs() throws IOException {
+        System.setProperty("ENVIRONMENT", "PROD");
+        logger = (Logger) LoggerFactory.getLogger(ConditionalLoggingUnitTest.class);
+        logger.info("billing details: XXXX");
+        logger.info("test prod log");
+
+        String filteredLog = FileUtils.readFileToString(new File("filtered.log"));
+        assertTrue(filteredLog.contains("test prod log"));
+        assertFalse(filteredLog.contains("billing details: XXXX"));
+    }
 }

logging-modules/logback/src/test/resources/logback-conditional.xml

@@ -38,15 +38,13 @@
     <appender name="FILTER_APPENDER" class="ch.qos.logback.core.FileAppender">
         <file>filtered.log</file>
         <filter class="ch.qos.logback.core.filter.EvaluatorFilter">
-            <evaluator>
-                <expression>return message.contains("billing");</expression>
-            </evaluator>
+            <evaluator class="com.baeldung.logback.BillingMessageEvaluator"/>
             <OnMatch>DENY</OnMatch>
             <OnMismatch>NEUTRAL</OnMismatch>
         </filter>
-        <encoder>
-            <pattern>%d %-4relative [%thread] %-5level %logger -%kvp -%msg%n</pattern>
-        </encoder>
+        <layout>
+            <pattern>%d [%thread] %-5level %logger{36} -%kvp- %msg%n</pattern>
+        </layout>
     </appender>
 
     <appender name="CONSOLE_APPENDER" class="ch.qos.logback.core.ConsoleAppender">
@@ -60,4 +58,4 @@
         <appender-ref ref="FILTER_APPENDER" />
         <appender-ref ref="CONSOLE_APPENDER" />
     </root>
-</configuration>
+</configuration>