日志

Logback

Spring Boot使用的日志组件是Logback，这边给出一个logback-spring.xml 示例：

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <include resource="org/springframework/boot/logging/logback/defaults.xml" />
  
  <springProperty scope="context" name="springAppName" source="spring.application.name" />
  <!-- Example for logging into the build folder of your project -->
  <property name="LOG_FILE" value="${BUILD_FOLDER:-build}/${springAppName}" />
  
  <property name="CONSOLE_LOG_PATTERN"
    value="%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(${LOG_LEVEL_PATTERN:-%5p}) %clr([${springAppName:-},%X{X-B3-TraceId:-},%X{X-B3-SpanId:-},%X{X-B3-ParentSpanId:-},%X{X-Span-Export:-}]){yellow} %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n${LOG_EXCEPTION_CONVERSION_WORD:-%wEx}" />

  <!-- Appender to log to console -->
  <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
    <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
      <!-- Minimum logging level to be presented in the console logs -->
      <level>DEBUG</level>
    </filter>
    <encoder>
      <pattern>${CONSOLE_LOG_PATTERN}</pattern>
      <charset>utf8</charset>
    </encoder>
  </appender>

  <!-- Appender to log to file -->
  <appender name="flatfile" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${LOG_FILE}</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
      <fileNamePattern>${LOG_FILE}.%d{yyyy-MM-dd}.gz</fileNamePattern>
      <maxHistory>7</maxHistory>
    </rollingPolicy>
    <encoder>
      <pattern>${CONSOLE_LOG_PATTERN}</pattern>
      <charset>utf8</charset>
    </encoder>
  </appender>
  
  <!-- Appender to log to file in a JSON format -->
  <appender name="logstash" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${LOG_FILE}.json</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
      <fileNamePattern>${LOG_FILE}.json.%d{yyyy-MM-dd}.gz</fileNamePattern>
      <maxHistory>7</maxHistory>
    </rollingPolicy>
    <encoder class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder">
      <providers>
        <timestamp>
          <timeZone>UTC</timeZone>
        </timestamp>
        <pattern>
          <pattern>
            {
              "severity": "%level",
              "service": "${springAppName:-}",
              "trace": "%X{X-B3-TraceId:-}",
              "span": "%X{X-B3-SpanId:-}",
              "parent": "%X{X-B3-ParentSpanId:-}",
              "exportable": "%X{X-Span-Export:-}",
              "pid": "${PID:-}",
              "thread": "%thread",
              "class": "%logger{40}",
              "rest": "%message"
            }
          </pattern>
        </pattern>
      </providers>
    </encoder>
  </appender>
  
  <root level="INFO">
    <appender-ref ref="console" />
    <appender-ref ref="logstash" />
    <!--<appender-ref ref="flatfile"/> -->
  </root>
</configuration>

当然，也可使用Log4j2 替换 logback 。

Log4j2

整合Log4j2的步骤如下：

1. 修改pom.xml文件，排除 spring-boot-starter-logging 的依赖，例如：

   <dependency>
     <groupId>org.springframework.cloud</groupId>
     <artifactId>spring-cloud-netflix-hystrix-stream</artifactId>
     <exclusions>
       <exclusion>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-logging</artifactId>
       </exclusion>
     </exclusions>
   </dependency>

2. 为项目添加Log4j2所需的依赖，如下：

   <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-log4j2</artifactId>
   </dependency>

3. 如需使用YAML文件配置Log4j2，请为项目添加如下依赖：

   <dependency>
     <groupId>com.fasterxml.jackson.dataformat</groupId>
     <artifactId>jackson-dataformat-yaml</artifactId>
   </dependency>
   <dependency>
     <groupId>com.fasterxml.jackson.core</groupId>
     <artifactId>jackson-databind</artifactId>
   </dependency>

4. 在项目的src/main/resources 目录下，建立log4j2.yml ，内容类似如下：

   configutation:
     name: Default
     Properties:
       Property:
         - name: log-path
           value: "logs"
     Appenders:
       #输出到控制台
       Console:
         name: CONSOLE
         target: SYSTEM_OUT
         PatternLayout:
           pattern: "%clr{%d{yyyy-MM-dd HH:mm:ss.SSS}}{faint} %clr{%5p} %X{X-B3-TraceId} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n%xwEx"
       # 输出到文件
       RollingFile:
         - name: FILE
           fileName: ${log-path}/logfile.data
           filePattern: "${log-path}/rollingfile.log.%d{yyyy-MM-dd-hh-mm}.gz"
           PatternLayout:
             pattern: "%clr{%d{yyyy-MM-dd HH:mm:ss.SSS}}{faint} %clr{%5p} %X{X-B3-TraceId} %clr{---}{faint} %clr{[%15.15t]}{faint} %clr{%-40.40c{1.}}{cyan} %clr{:}{faint} %m%n%xwEx"
           Policies:
             SizeBasedTriggeringPolicy:
               size: 100MB
           DefaultRollOverStrategy:
             max: 1
     Loggers:
       Root:
         level: info
         AppenderRef:
           - ref: FILE
           - ref: CONSOLE
       Logger:
         # 测试Sleuth的打印
         - name: org.springframework.web.servlet.DispatcherServlet
           # additivity: false
           level: debug
           AppenderRef:
             - ref: FILE
             - ref: CONSOLE

   这样，项目就会使用Log4j2记录日志了。简单分析一下log4j2.yml ：

   • 定义了一个环境变量log-path ，值为logs
   • 定义了两个Appender：FILE和CONSOLE，其中FILE用于记录文件日志；CONSOLE用于记录日志到控制台
   • 对于FILE这个Appender，它的pattern字段，即：日志打印的行格式。

5. 如项目启动时，报 java.lang.NoClassDefFoundError: org/apache/log4j/Logger 的异常，则为项目添加log4j-over-slf4j 的依赖：

   <dependency>
     <groupId>org.slf4j</groupId>
     <artifactId>log4j-over-slf4j</artifactId>
   </dependency>

6. 检查：请务必检查项目中是否已经不存在spring-boot-starter-logging ，并已存在spring-boot-starter-log4j2 、jackson-databind 、ackson-dataformat-yaml 。

7. 示例：

   <!--整合hystrix，并使用kafka收集数据-->
   <dependency>
     <groupId>org.springframework.cloud</groupId>
     <artifactId>spring-cloud-starter-hystrix</artifactId>
   </dependency>
   <dependency>
   <groupId>org.springframework.cloud</groupId>
   <artifactId>spring-cloud-netflix-hystrix-stream</artifactId>
   <exclusions>
   <exclusion>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-logging</artifactId>
   </exclusion>
   </exclusions>
   </dependency>
   <dependency>
     <groupId>org.springframework.cloud</groupId>
     <artifactId>spring-cloud-starter-stream-kafka</artifactId>
   </dependency>
   
   <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter</artifactId>
     <exclusions>
       <exclusion>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-logging</artifactId>
       </exclusion>
     </exclusions>
   </dependency>
   <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-log4j2</artifactId>
   </dependency>
   <dependency>
     <groupId>com.fasterxml.jackson.dataformat</groupId>
     <artifactId>jackson-dataformat-yaml</artifactId>
   </dependency>
   
   <dependency>
     <groupId>org.slf4j</groupId>
     <artifactId>log4j-over-slf4j</artifactId>
   </dependency>

   ​