Merge branch 'master' of https://github.com/JonCook/tutorials

logging-modules/logback/README.md

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+### Relevant Articles:
+
+- [Get Log Output in JSON](https://www.baeldung.com/java-log-json-output)
+- [SLF4J Warning: Class Path Contains Multiple SLF4J Bindings](https://www.baeldung.com/slf4j-classpath-multiple-bindings)

logging-modules/logback/pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
+                             http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>logback</artifactId>
+    <version>0.1-SNAPSHOT</version>
+    <name>logback</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+
+        <dependency>
+            <groupId>ch.qos.logback</groupId>
+            <artifactId>logback-classic</artifactId>
+            <version>${logback.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>ch.qos.logback.contrib</groupId>
+            <artifactId>logback-json-classic</artifactId>
+            <version>${logback.contrib.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>ch.qos.logback.contrib</groupId>
+            <artifactId>logback-jackson</artifactId>
+            <version>${logback.contrib.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <version>${jackson.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.docx4j</groupId>
+            <artifactId>docx4j</artifactId>
+            <version>${docx4j.version}</version>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.slf4j</groupId>
+                    <artifactId>slf4j-log4j12</artifactId>
+                </exclusion>
+                <exclusion>
+                    <groupId>log4j</groupId>
+                    <artifactId>log4j</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+        
+    </dependencies>
+
+    <properties>
+        <logback.version>1.2.3</logback.version>
+        <logback.contrib.version>0.1.5</logback.contrib.version>
+        <docx4j.version>3.3.5</docx4j.version>
+    </properties>
+
+</project>

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

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+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

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+package com.baeldung.logback;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import ch.qos.logback.core.AppenderBase;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+public class MapAppender extends AppenderBase<ILoggingEvent> {
+
+    private final ConcurrentMap<String, ILoggingEvent> eventMap
+      = new ConcurrentHashMap<>();
+
+    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

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+<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>

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

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+package com.baeldung.logback;
+
+import static org.junit.Assert.assertTrue;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.PrintStream;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public class JSONLayoutIntegrationTest {
+
+    private static Logger logger;
+    private ByteArrayOutputStream consoleOutput = new ByteArrayOutputStream();
+    private PrintStream ps = new PrintStream(consoleOutput);
+
+    @Before
+    public void setUp() {
+        // Redirect console output to our stream
+        System.setOut(ps);
+        logger = LoggerFactory.getLogger("jsonLogger");
+    }
+
+    @Test
+    public void whenLogLayoutInJSON_thenOutputIsCorrectJSON() {
+        logger.debug("Debug message");
+        String currentLog = consoleOutput.toString();
+        assertTrue(!currentLog.isEmpty() && isValidJSON(currentLog));
+    }
+
+    public static boolean isValidJSON(String jsonInString) {
+        try {
+            final ObjectMapper mapper = new ObjectMapper();
+            mapper.readTree(jsonInString);
+            return true;
+        } catch (IOException e) {
+            return false;
+        }
+    }
+}

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

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+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 LogbackIntegrationTest {
+
+    @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(LogbackIntegrationTest.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/java/com/baeldung/logback/MapAppenderIntegrationTest.java

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+package com.baeldung.logback;
+
+import ch.qos.logback.classic.Logger;
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.LoggerFactory;
+
+import static org.junit.Assert.assertEquals;
+
+public class MapAppenderIntegrationTest {
+
+    private Logger rootLogger;
+
+    @Before
+    public void setUp() throws Exception {
+        rootLogger = (Logger) LoggerFactory.getLogger("ROOT");
+    }
+
+    @Test
+    public void whenLoggerEmitsLoggingEvent_thenAppenderReceivesEvent() throws Exception {
+        rootLogger.info("Test from {}", this.getClass().getSimpleName());
+        MapAppender appender = (MapAppender) rootLogger.getAppender("map");
+        assertEquals(appender.getEventMap().size(), 1);
+    }
+
+    @Test
+    public void givenNoPrefixSet_whenLoggerEmitsEvent_thenAppenderReceivesNoEvent() throws Exception {
+        rootLogger.info("Test from {}", this.getClass().getSimpleName());
+        MapAppender appender = (MapAppender) rootLogger.getAppender("badMap");
+        assertEquals(appender.getEventMap().size(), 0);
+    }
+
+}

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

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+package com.baeldung.logback;
+
+import ch.qos.logback.classic.Level;
+import ch.qos.logback.classic.LoggerContext;
+import ch.qos.logback.classic.spi.LoggingEvent;
+import ch.qos.logback.core.BasicStatusManager;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class MapAppenderUnitTest {
+
+    private LoggerContext ctx;
+
+    private MapAppender mapAppender = new MapAppender();
+
+    private LoggingEvent event;
+
+    @Before
+    public void setUp() throws Exception {
+        ctx = new LoggerContext();
+        ctx.setName("test context");
+        ctx.setStatusManager(new BasicStatusManager());
+        mapAppender.setContext(ctx);
+        mapAppender.setPrefix("prefix");
+        event = new LoggingEvent("fqcn", ctx.getLogger("logger"), Level.INFO, "Test message for logback appender", null, new Object[0]);
+        ctx.start();
+    }
+
+    @After
+    public void tearDown() throws Exception {
+        ctx.stop();
+        mapAppender.stop();
+    }
+
+    @Test
+    public void whenPrefixIsNull_thenMapAppenderDoesNotLog() throws Exception {
+        mapAppender.setPrefix(null);
+        mapAppender.append(event);
+        assertTrue(mapAppender.getEventMap().isEmpty());
+    }
+
+    @Test
+    public void whenPrefixIsEmpty_thenMapAppenderDoesNotLog() throws Exception {
+        mapAppender.setPrefix("");
+        mapAppender.append(event);
+        assertTrue(mapAppender.getEventMap().isEmpty());
+    }
+
+    @Test
+    public void whenLogMessageIsEmitted_thenMapAppenderReceivesMessage() throws Exception {
+        mapAppender.append(event);
+        assertEquals(mapAppender.getEventMap().size(), 1);
+        mapAppender.getEventMap().forEach((k, v) -> assertTrue(k.startsWith("prefix")));
+    }
+
+}

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

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+<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>

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

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+<configuration debug="false">
+
+    <statusListener class="ch.qos.logback.core.status.NopStatusListener" />
+
+    <appender name="map" class="com.baeldung.logback.MapAppender">
+        <prefix>test</prefix>
+    </appender>
+
+    <appender name="badMap" class="com.baeldung.logback.MapAppender" />
+
+    # JSON appender
+    <appender name="json" class="ch.qos.logback.core.ConsoleAppender">
+        <layout class="ch.qos.logback.contrib.json.classic.JsonLayout">
+            <jsonFormatter
+                class="ch.qos.logback.contrib.jackson.JacksonJsonFormatter">
+                <prettyPrint>true</prettyPrint>
+            </jsonFormatter>
+            <timestampFormat>yyyy-MM-dd' 'HH:mm:ss.SSS</timestampFormat>
+        </layout>
+    </appender>
+
+    <logger name="jsonLogger" level="TRACE">
+        <appender-ref ref="json" />
+    </logger>
+
+    <root level="debug">
+        <appender-ref ref="map" />
+        <appender-ref ref="badMap" />
+    </root>
+
+</configuration>