ログバックの手引き

<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-core</artifactId>
    <version>1.2.3</version>
</dependency>

<dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>slf4j-api</artifactId>
    <version>1.8.0-beta2</version>
    <scope>test</scope>
</dependency>

<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.2.3</version>
</dependency>

private static final Logger logger
  = LoggerFactory.getLogger(Example.class);

logger.info("Example log from {}", Example.class.getSimpleName());

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.");
parentLogger.debug("This message is not logged because DEBUG < INFO.");
childlogger.info("INFO == INFO");
childlogger.debug("DEBUG < INFO");

20:31:29.586[main]WARN com.baeldung.logback - This message is logged because WARN > INFO.
20:31:29.594[main]INFO com.baeldung.logback.tests - INFO == INFO

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.");

20:44:44.241[main]DEBUG com.baeldung.logback - Hi there!
20:44:44.243[main]DEBUG com.baeldung.logback - This message is logged because DEBUG == DEBUG.
20:44:44.243[main]ERROR com.baeldung.logback - This is logged.

log.debug("Current count is " + count);

log.debug("Current count is {}", count);

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);
}

21:32:10.311[main]DEBUG com.baeldung.logback.LogbackTests - Logging message: This is a String
21:32:10.316[main]DEBUG com.baeldung.logback.LogbackTests - Going to divide 42 by 0
21:32:10.316[main]ERROR com.baeldung.logback.LogbackTests - Error dividing 42 by 0
java.lang.ArithmeticException:/by zero
  at com.baeldung.logback.LogbackTests.givenParameters__ValuesLogged(LogbackTests.java:64)
...

<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
        <pattern>%d{HH:mm:ss.SSS}[%thread]%-5level %logger{36} - %msg%n</pattern>
    </encoder>
</appender>

<root level="debug">
    <appender-ref ref="STDOUT"/>
</root>

<configuration debug="true">
  ...
</configuration>

23:54:23,040 |-INFO in ch.qos.logback.classic.LoggerContext[default]- Found resource[logback-test.xml]
  at[file:/Users/egoebelbecker/ideaProjects/logback-guide/out/test/resources/logback-test.xml]23:54:23,230 |-INFO in ch.qos.logback.core.joran.action.AppenderAction - About to instantiate appender
  of type[ch.qos.logback.core.ConsoleAppender]23:54:23,236 |-INFO in ch.qos.logback.core.joran.action.AppenderAction - Naming appender as[STDOUT]23:54:23,247 |-INFO in ch.qos.logback.core.joran.action.NestedComplexPropertyIA - Assuming default type
 [ch.qos.logback.classic.encoder.PatternLayoutEncoder]for[encoder]property
23:54:23,308 |-INFO in ch.qos.logback.classic.joran.action.RootLoggerAction - Setting level of ROOT logger to DEBUG
23:54:23,309 |-INFO in ch.qos.logback.core.joran.action.AppenderRefAction - Attaching appender named[STDOUT]to Logger[ROOT]23:54:23,310 |-INFO in ch.qos.logback.classic.joran.action.ConfigurationAction - End of configuration.
23:54:23,313 |-INFO in[email protected]- Registering current configuration
  as safe fallback point

<configuration>
    <statusListener class="ch.qos.logback.core.status.OnConsoleStatusListener"/>
    ...
</configuration>

<configuration scan="true">
  ...
</configuration>

<configuration scan="true" scanPeriod="15 seconds">
  ...
</configuration>

<configuration>
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss.SSS}[%thread]%-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>
    <logger name="com.baeldung.logback" level="INFO"/>
    <logger name="com.baeldung.logback.tests" level="WARN"/>
    <root level="debug">
        <appender-ref ref="STDOUT"/>
    </root>
</configuration>

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");

00:29:51.787[main]DEBUG com.baeldung.foobar - This is logged from foobar
00:29:51.789[main]INFO com.baeldung.logback - This is logged from logger
00:29:51.789[main]WARN com.baeldung.logback.tests - This is logged from tests

<property name="LOG__DIR" value="/var/log/application"/>
<appender name="FILE" class="ch.qos.logback.core.FileAppender">
    <file>${LOG__DIR}/tests.log</file>
    <append>true</append>
    <encoder>
        <pattern>%-4relative[%thread]%-5level %logger{35} - %msg%n</pattern>
    </encoder>
</appender>

$ java -DLOG__DIR=/var/log/application com.baeldung.logback.LogbackTests

<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>
        <encoder>
            <pattern>%-4relative[%thread]%-5level %logger{35} - %msg%n</pattern>
        </encoder>
    </appender>

    <logger name="com.baeldung.logback" level="INFO"/>
    <logger name="com.baeldung.logback.tests" level="WARN">
        <appender-ref ref="FILE"/>
    </logger>

    <root level="debug">
        <appender-ref ref="STDOUT"/>
    </root>
</configuration>

<logger name="com.baeldung.logback.tests" level="WARN" additivity="false" >
    <appender-ref ref="FILE"/>
</logger>

<root level="debug">
    <appender-ref ref="STDOUT"/>
</root>

<property name="LOG__FILE" value="LogFile"/>
<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${LOG__FILE}.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
        <!-- daily rollover -->
        <fileNamePattern>${LOG__FILE}.%d{yyyy-MM-dd}.gz</fileNamePattern>

        <!-- keep 30 days' worth of history capped at 3GB total size -->
        <maxHistory>30</maxHistory>
        <totalSizeCap>3GB</totalSizeCap>
    </rollingPolicy>
    <encoder>
        <pattern>%-4relative[%thread]%-5level %logger{35} - %msg%n</pattern>
    </encoder>
</appender>

<property name="LOG__FILE" value="LogFile"/>
<property name="LOG__DIR" value="/var/logs/application"/>
<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${LOG__DIR}/${LOG__FILE}.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
        <fileNamePattern>${LOG__DIR}/%d{yyyy/MM}/${LOG__FILE}.gz</fileNamePattern>
        <totalSizeCap>3GB</totalSizeCap>
    </rollingPolicy>