知识分享 – JAVA 应用日志最佳实践

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

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

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// 推荐
logger.info("用户 {} 借走图书 <<{}>> ",  userName, bookTitle);

// 不推荐
logger.info("用户 " + userName + " 借走图书 <<" + bookTitle + ">>");

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void foo() {
    try {
        //  do something ...
    } catch ( Exception e ) {
        logger.error("Bad things : ", e); // 正确

        logger.error(e.getMessage());  // 错误
        logger.error("Bad things : ", e.getMessage()); // 错误
    }
}

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void foo() {
    try{
        // do something...
    } catch ( Exception e ) {
        logger.error("Bad things : ",e );  // 正确

        System.out.println(e.getMessage());  // 错误
        System.err.println(e.getMessage());  // 错误
        e.printStackTrace();  // 错误
    }
}

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if (logger.isDebugEnabled ()) {
    logger.debug("return content:" + content);
}

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<!--Logback 中关闭 additivity-->
<Configuration>
  ...
  <Loggers>
    <Logger name="demo.wood" level="debug" additivity="false">
      <AppenderRef ref="applog" />
    </Logger>
    ...
  </Loggers>
</Configuration>

<!--Log4j2 中关闭 additivity-->
<Configuration>
    ...
    <Loggers>
        <Logger name="org.springframework" level="INFO" additivity="false">
            <AppenderRef ref="Console"/>
        </Logger>
        ...
    </Loggers>
</Configuration>

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// Example 1: 设置 Logback 日志级别
Logger logger = oggerContext.getLogger("需要设置级别的 logger 名");
logger.setLevel(Level.DEBUG);

// Example 2: 设置 Log4j2 日志级别
Logger logger4j = LogManager.getLogger("需要设置级别的 logger 名");
Configurator.setLevel(logger4j.getName(), Level.ERROR);

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<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="true" scanPeriod="60 seconds">
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>${CONSOLE_LOG_PATTERN}</pattern>
            <pattern>[%d{yyyy-MM-dd HH:mm:ss}] -- [%-5p]: [%c] -- %m%n</pattern>
        </encoder>
    </appender>
    <root level="INFO">
        <appender-ref ref="STDOUT"/>
    </root>
</configuration>

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import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.LoggerContext;
import com.google.common.collect.ImmutableMap;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Map;
import java.util.Scanner;

public class DynamicLogbackLevelDemo {
    private static final Logger logger = LoggerFactory.getLogger(DynamicLogbackLevelDemo.class);

    private static final Map<Integer, String> LOG_LEVEL_MAP = new ImmutableMap.Builder<Integer, String>()
            .put(1, "TRACE").put(2, "DEBUG").put(3, "INFO").put(4, "WARN").put(5, "ERROR").build();

    public static void main(String[] args) throws Exception {
        Scanner scanner = new Scanner(System.in);
        String userInput = null;
        do {
            System.out.printf("\nPlease Enter Logback Logger Level (q to quit): 1 - TRACE, 2 - DEBUG, 3 - INFO, 4 - WARN, 5 - ERROR\n");

            userInput = scanner.nextLine().trim();
            if (!StringUtils.isNumeric(userInput)) {
                continue;
            }

            String logLevel = LOG_LEVEL_MAP.get(Integer.parseInt(userInput));
            if (null != logLevel) {

                // 获取 loggert
                LoggerContext loggerContext = (LoggerContext) LoggerFactory.getILoggerFactory();
                ch.qos.logback.classic.Logger tmplogger = loggerContext.getLogger(DynamicLogbackLevelDemo.class);

                // 修改日志级别
                System.out.printf("[current logger level]: %s ---> [new logger level]: %s\n", tmplogger.getLevel(), logLevel);
                tmplogger.setLevel(Level.toLevel(logLevel));

                System.out.println("verifying new logger level:");
                logger.trace("sample trace log");
                logger.debug("sample debug log");
                logger.info("sample info log");
                logger.warn("sample warn log");
                logger.error("sample error log");
            }
        } while (!"q".equalsIgnoreCase(userInput));
        scanner.close();
    }
}

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<?xml version="1.0" encoding="UTF-8"?>
<configuration scan="true" scanPeriod="60 seconds">
    <!-- 开启 JMX -->
    <jmxConfigurator />

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

    <appender name="fileAppender" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>${LOG_PATH}/demoApp.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>demoApp-%d-%i.log</fileNamePattern>
            <MaxHistory>20</MaxHistory>
            <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
                <maxFileSize>500MB</maxFileSize>
            </timeBasedFileNamingAndTriggeringPolicy>
        </rollingPolicy>
        <encoder>
            <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%t] [%-5level] [%logger{36}]: %msg%n</pattern>
            <charset>UTF-8</charset>
        </encoder>
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>INFO</level>
            <onMatch>ACCEPT</onMatch>
            <onMismatch>DENY</onMismatch>
        </filter>
    </appender>

    <logger name="org.springframework" additivity="false">
        <level value="ERROR" />
        <appender-ref ref="STDOUT" />
        <appender-ref ref="fileAppender" />
    </logger>

    <logger name="org.apache.tomcat.util" additivity="false">
        <level value="ERROR"/>
        <appender-ref ref="STDOUT"/>
        <appender-ref ref="fileAppender"/>
    </logger>

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

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