BAEL-1710 - A Guide to Logback (#4178)

logging-modules/README.md

@@ -5,3 +5,4 @@
 
 - [Creating a Custom Logback Appender](http://www.baeldung.com/custom-logback-appender)
 - [Get Log Output in JSON Format](http://www.baeldung.com/java-log-json-output)
+- [A Guide To Logback](http://www.baeldung.com/a-guide-to-logback)

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

@@ -0,0 +1,89 @@
+package com.baeldung.logback;
+
+import ch.qos.logback.classic.Level;
+import org.junit.Test;
+
+import ch.qos.logback.classic.Logger;
+import org.slf4j.LoggerFactory;
+
+public class LogbackTests {
+
+    @Test
+    public void givenLogHierarchy_MessagesFiltered() {
+
+        ch.qos.logback.classic.Logger parentLogger =
+                (ch.qos.logback.classic.Logger) LoggerFactory.getLogger("com.baeldung.logback");
+
+        parentLogger.setLevel(Level.INFO);
+
+        Logger childlogger = (ch.qos.logback.classic.Logger)LoggerFactory.getLogger("com.baeldung.logback.tests");
+
+        parentLogger.warn("This message is logged because WARN > INFO.");
+
+        // This request is disabled, because DEBUG < INFO.
+        parentLogger.debug("This message is not logged because DEBUG < INFO.");
+
+        childlogger.info("INFO == INFO");
+
+        childlogger.debug("DEBUG < INFO");
+
+    }
+
+    @Test
+    public void givenRootLevel_MessagesFiltered() {
+
+        ch.qos.logback.classic.Logger logger =
+                (ch.qos.logback.classic.Logger) LoggerFactory.getLogger("com.baeldung.logback");
+
+        logger.debug("Hi there!");
+
+        Logger rootLogger = (ch.qos.logback.classic.Logger)LoggerFactory.getLogger(org.slf4j.Logger.ROOT_LOGGER_NAME);
+
+        logger.debug("This message is logged because DEBUG == DEBUG.");
+
+        rootLogger.setLevel(Level.ERROR);
+        logger.warn("This message is not logged because WARN < ERROR.");
+
+        logger.error("This is logged.");
+
+    }
+
+    @Test
+    public void givenParameters_ValuesLogged() {
+
+        Logger logger = (ch.qos.logback.classic.Logger) LoggerFactory.getLogger(LogbackTests.class);
+
+        String message = "This is a String";
+        Integer zero = 0;
+
+        try {
+            logger.debug("Logging message: {}", message);
+            logger.debug("Going to divide {} by {}", 42, zero);
+            int result = 42 / zero;
+        } catch (Exception e) {
+            logger.error("Error dividing {} by {} ", 42, zero, e);
+        }
+    }
+
+    @Test
+    public void givenConfig_MessageFiltered() {
+
+        Logger foobar = (ch.qos.logback.classic.Logger) LoggerFactory.getLogger("com.baeldung.foobar");
+        Logger logger = (ch.qos.logback.classic.Logger) LoggerFactory.getLogger("com.baeldung.logback");
+        Logger testslogger = (ch.qos.logback.classic.Logger) LoggerFactory.getLogger("com.baeldung.logback.tests");
+
+        foobar.debug("This is logged from foobar");
+        logger.debug("This is not logged from logger");
+        logger.info("This is logged from logger");
+        testslogger.info("This is not logged from tests");
+        testslogger.warn("This is logged from tests");
+
+
+    }
+
+
+
+
+
+
+}

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

@@ -0,0 +1,32 @@
+<configuration debug="true">
+
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <!-- encoders are assigned the type
+             ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <appender name="FILE" class="ch.qos.logback.core.FileAppender">
+        <file>tests.log</file>
+        <append>true</append>
+        <!-- set immediateFlush to false for much higher logging throughput -->
+        <immediateFlush>true</immediateFlush>
+        <!-- encoders are assigned the type
+             ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
+        <encoder>
+            <pattern>%-4relative [%thread] %-5level %logger{35} - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+
+    <root level="debug">
+        <appender-ref ref="STDOUT" />
+    </root>
+    <logger name="com.baeldung.logback" level="INFO" />
+    <logger name="com.baeldung.logback.tests" level="WARN">
+        <appender-ref ref="FILE" />
+    </logger>
+
+</configuration>