【日常记录-Java】应用引入Slf4J

news2024/10/29 5:17:55

1. 简介

SLF4J(Simple Logging Facade for Java) 是Java的一个简单日志门面，为Java日志访问提供了一套标准、规范的API框架。而具体日志的实现则可以根据这套接口去实现具体的日志框架，以便将来需要更换日志框架时，只替换实现框架即可。常见的具体实现有JUL、log4j、logback、log4j2等。

2. 操作

2.1 引入依赖

<dependency>
  <groupId>org.slf4j</groupId>
  <artifactId>slf4j-api</artifactId>
  <version>2.0.16</version>
</dependency>
<dependency>
  <groupId>ch.qos.logback</groupId>
  <artifactId>logback-classic</artifactId>
  <version>1.5.8</version>
</dependency>

2.2 配置日志实现

对于Logback，通常在类路径下（如src/main/resources目录）创建一个名为logback-config.xml配置文件，在其中定义日志记录级别、格式、输出目的地等。

<?xml version="1.0" encoding="UTF-8"?>  
<configuration scan="true" scanPeriod="60 seconds" debug="false">  
    <!-- 工程名/项目名 -->  
    <contextName>project_name</contextName>  
  
    <!-- 把>=debug的日志输出到控制台 -->  
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">  
        <encoder>  
            <pattern>%-4relative %date{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{35} - %msg %n</pattern>  
             <charset>UTF-8</charset>
        </encoder>  
    </appender>  
  
    <!-- 系统日志输出到文件，并设置滚动策略 -->  
    <appender name="INFO_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">  
        <file>logs/info.log</file>  
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">  
            <fileNamePattern>logs/info.%d{yyyy-MM-dd}.log</fileNamePattern>  
            <maxHistory>30</maxHistory>  
        </rollingPolicy>  
        <encoder>  
            <pattern>%-4relative %date{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{35} - %msg%n</pattern>  
             <charset>UTF-8</charset>
        </encoder>  
        <filter class="ch.qos.logback.classic.filter.LevelFilter">
            <level>ERROR</level>
            <onMatch>DENY</onMatch>
            <onMismatch>ACCEPT</onMismatch>
        </filter>
    </appender>  
  
    <!-- 错误日志输出到文件，并设置滚动策略 -->  
    <appender name="ERROR_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">  
        <file>logs/error.log</file>  
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">  
            <fileNamePattern>logs/error.%d{yyyy-MM-dd}.log</fileNamePattern>  
            <maxHistory>30</maxHistory>  
        </rollingPolicy>  
        <encoder>  
            <pattern>%-4relative %date{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level %logger{35} - %msg%n</pattern>  
             <charset>UTF-8</charset>
        </encoder>  
        <filter class="ch.qos.logback.classic.filter.LevelFilter">  
            <level>ERROR</level>  
            <onMatch>ACCEPT</onMatch>  
            <onMismatch>DENY</onMismatch>  
        </filter>  
    </appender>  
  
    <!-- 根日志级别控制，并引用所有appender -->  
    <root level="INFO">  
        <appender-ref ref="STDOUT"/>  
        <appender-ref ref="INFO_FILE"/>  
        <appender-ref ref="ERROR_FILE"/>  
    </root>  
</configuration>

2.3 启用配置并使用

import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.joran.JoranConfigurator;
import ch.qos.logback.core.joran.spi.JoranException;
import ch.qos.logback.core.util.StatusPrinter2;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.InputStream;

public class Main {

    public static void main(String[] args){
        // step1: 使用配置文件完成配置
        LoggerContext context = (LoggerContext) LoggerFactory.getILoggerFactory();
        try {
            InputStream configStream = Main.class.getClassLoader().getResourceAsStream("logback-config.xml");
            if (configStream == null) {
                throw new RuntimeException("Could not find logback-config.xml");
            }

            JoranConfigurator configurator = new JoranConfigurator();
            configurator.setContext(context);
            context.reset();
            configurator.doConfigure(configStream);
            new StatusPrinter2().printInCaseOfErrorsOrWarnings(context);
        } catch (JoranException je) {
            throw new RuntimeException(je);
        }

        // step2: 进行日志记录
        Logger log = LoggerFactory.getLogger(Main.class);
        log.info("this is a logger!");
    }
}