An overview of the

In Java applications, logs fall into the following five levels:

  • ERROR ERROR information
  • WARN Warning Information
  • INFO General information
  • DEBUG Debugging information
  • TRACE TRACE information

Spring Boot uses Apache Commons Logging as the internal Logging framework, which is only a Logging interface. In practical applications, the corresponding Logging implementation needs to be specified for this interface.

The default Logging implementation of SpringBt is Java Util Logging, which comes with the JDK. SpringBt also supports popular Logging implementations such as Log4J and Logback.

These logging implementations are collectively referred to as logging frameworks

Let’s put it into practice!

Use the Spring Boot Logging plug-in

  • First add a configuration to the application.properties file:
logging.level.root=INFOCopy the code
  • Part of the controller code is as follows:
package com.hansonwang99.controller; import com.hansonwang99.K8sresctrlApplication; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController @RequestMapping("/testlogging ") public class LoggingTestController { private static Logger logger = LoggerFactory.getLogger(K8sresctrlApplication.class); @GetMapping("/hello ") public String hello() { logger.info("test logging... "); return "hello "; }}Copy the code
  • The results

Because the log level is set to INFO, logs of INFO and higher levels are displayed

As you can see, most of the INFO logs come from the SpringBt framework itself. If we want to mask them, we can set the log level to ERROR so that the framework’s INFO will not be printed. You can then set specific packages in your application to DEBUG level logs so that you can only see DEBUG and above logs in the packages you are interested in.

  • Controls the logging level of a particular package

Change the configuration in application.yml

logging:
  level:
    root: error
    com.hansonwang99.controller: debugCopy the code

It is clear that the root log level is set to ERROR, and then he will com. Hansonwang99. Controller packages of the log level to DEBUG, for this is: the first banned all again allows individual to set method

  • Controller code
package com.hansonwang99.controller; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController @RequestMapping("/testlogging ") public class LoggingTestController { private Logger logger = LoggerFactory.getLogger(this.getClass()); @GetMapping("/hello ") public String hello() { logger.info("test logging... "); return "hello "; }}Copy the code
  • The results

You can see that the framework’s own info-level logs are all hidden, while the logs in the specified package print out smoothly by level

  • Output logs to a file
logging:
  level:
    root: error
    com.hansonwang99.controller: debug
  file: ${user.home}/logs/hello.logCopy the code
  • The results

Using Spring Boot Logging, we found that although the log was exported to a file, a copy was still printed in the console. Org.slf4j.logger was not able to solve this problem

Integrate Log4J logging framework

  • Add dependencies to pom.xml
       <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</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>Copy the code
  • Add it in the Resources directorylog4j2.xmlFile, as follows:
<? XML version="1.0 "encoding="UTF-8 "? > <configuration> <appenders> <File name="file " fileName="${sys:user.home}/logs/hello2.log "> <PatternLayout pattern="%d{HH:mm:ss,SSS} %p %c (%L) - %m%n "/> </File> </appenders> <loggers> <root level="ERROR "> <appender-ref ref="file "/> </root> <logger name="com.hansonwang99.controller " level="DEBUG " /> </loggers> </configuration>Copy the code
  • Everything else remains the same

Running the program found no log output from the console and something in the hello2.log file, which is what we expected:

The log format matches that defined in pattern=”%d{HH:mm:ss,SSS} %p % C (%L) – %m%n”

Log4J takes this a step further

  • Pom. XML configuration:
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</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>Copy the code
  • Log4j2. XML configuration
<? XML version="1.0 "encoding="UTF-8 "? > <configuration status="warn "> <properties> <Property name="app_name ">springboot-web</Property> <Property name="log_path ">logs/${app_name}</Property> </properties> <appenders> <console name="Console " target="SYSTEM_OUT "> <PatternLayout pattern="[%d][%t][%p][%l] %m%n " /> </console> <RollingFile name="RollingFileInfo " fileName="${log_path}/info.log " filePattern="${log_path}/? {date:yyyy-MM}/info-%d{yyyy-MM-dd}-%i.log.gz "> <Filters> <ThresholdFilter level="INFO " /> <ThresholdFilter level="WARN  " onMatch="DENY " onMismatch="NEUTRAL " /> </Filters> <PatternLayout pattern="[%d][%t][%p][%c:%L] %m%n " /> <Policies> <! - archive file every day -- -- > < TimeBasedTriggeringPolicy interval = "1" modulate = "true" / > <! - a single file size limit - > < SizeBasedTriggeringPolicy size = "2 MB" / > < / Policies > <! DefaultRolloverStrategy compressionLevel="0 "Max ="10 "/> </RollingFile> <RollingFile name="RollingFileWarn " fileName="${log_path}/warn.log " filePattern="${log_path}/? {date:yyyy-MM}/warn-%d{yyyy-MM-dd}-%i.log.gz "> <Filters> <ThresholdFilter level="WARN " /> <ThresholdFilter level="ERROR " onMatch="DENY " onMismatch="NEUTRAL " /> </Filters> <PatternLayout pattern="[%d][%t][%p][%c:%L] %m%n " />  <Policies> <! - archive file every day -- -- > < TimeBasedTriggeringPolicy interval = "1" modulate = "true" / > <! - a single file size limit - > < SizeBasedTriggeringPolicy size = "2 MB" / > < / Policies > <! DefaultRolloverStrategy compressionLevel="0 "Max ="10 "/> </RollingFile> <RollingFile name="RollingFileError " fileName="${log_path}/error.log " filePattern="${log_path}/? {date:yyyy-MM}/error-%d{yyyy-MM-dd}-%i.log.gz "> <ThresholdFilter level="ERROR " /> <PatternLayout pattern="[%d][%t][%p][%c:%L] %m%n " /> <Policies> <! - archive file every day -- -- > < TimeBasedTriggeringPolicy interval = "1" modulate = "true" / > <! - a single file size limit - > < SizeBasedTriggeringPolicy size = "2 MB" / > < / Policies > <! DefaultRolloverStrategy compressionLevel="0 "Max ="10 "/> </RollingFile> </appenders> <loggers> <root level="info "> <appender-ref ref="Console " /> <appender-ref ref="RollingFileInfo " /> <appender-ref ref="RollingFileWarn " /> <appender-ref ref="RollingFileError " /> </root> </loggers> </configuration>Copy the code
  • Controller code:
package com.hansonwang99.controller; import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController @RequestMapping("/testlogging ") public class LoggingTestController { private final Logger logger = LogManager.getLogger(this.getClass()); @GetMapping("/hello ") public String hello() { for(int i=0; i<10_0000; i++){ logger.info("info execute index method "); logger.warn("warn execute index method "); logger.error("error execute index method "); } return "My First SpringBoot Application "; }}Copy the code
  • The results

Logs are stored in different files based on different levels. When the size of a log file exceeds 2 MB, it is compressed and stored in multiple files. You are advised to set the size of a log file to 20-50MB in the production environment.

Afterword.

Author of more original articles in the cloud habitat community

The author has more SpringBt practice articles here:

  • ElasticSearch in SpringBoot
  • A preliminary study on Kotlin+SpringBoot joint programming