How to understand Log4j in Spring log
This article will explain in detail how to understand the Log4j in the Spring log. The content of the article is of high quality, so the editor shares it for you as a reference. I hope you will have a certain understanding of the relevant knowledge after reading this article.
Introduction to Slf4j
The full name of slf4j is Simple Loging Facade For Java, that is, it is only a unified interface to provide log output for Java programs, and it is not a specific log implementation, just like JDBC, it is just a rule. Therefore, slf4j alone does not work, and must be matched with other specific logging implementations, such as java.util.logging.Logger and log4j included in apache's org.apache.log4j.Logger,JDK.
The pom.xml configuration is as follows: org.slf4j slf4j-log4j12 1.7.25
Mainly increased org.slf4j:slf4j-log4j12 dependency
Create a log4j.properties profile:
Create a property profile named log4j.properties in the src/main/resources directory
Log4j.rootLogger=INFO, console, filelog4j.appender.console=org.apache.log4j.ConsoleAppenderlog4j.appender.console.layout=org.apache.log4j.PatternLayoutlog4j.appender.console.layout.ConversionPattern=%d% p [% c] -% m%nlog4j.appender.file=org.apache.log4j.DailyRollingFileAppenderlog4j.appender.file.File=logs/log.loglog4j.appender.file.layout=org.apache.log4j.PatternLayoutlog4j.appender.A3.MaxFileSize=1024KBlog4j.appender.A3.MaxBackupIndex=10log4j.appender.file.layout.ConversionPattern=%d% p [% c] -% m% n
Log configuration instructions:
Log4j.rootLogger: root log, configured with log level of INFO, and predefined two appenders named console and file
Log4j.appender.console:console appender, log output is located in the console
Log4j.appender.console.layout:console appendage, using matcher layout mode
Log4j.appender.console.layout.ConversionPattern:console append, log output format is: date log level [class name]-message newline character
Log4j.appender.file:file appendage, which generates a log file every day
Log4j.appender.file.File:file appender, log file output location logs/log.log
Log4j.appender.file.layout:file appendage, using matcher layout mode
Log4j.appender.A3.MaxFileSize: log file maximum
Log4j.appender.A3.MaxBackupIndex: maximum number of files recorded
Log4j.appender.file.layout.ConversionPattern:file append, log output format is: date log level [class name]-message newline character
Test log output
Create a test class and test the log output as follows:
Import org.slf4j.Logger;import org.slf4j.LoggerFactory;public class MyTest {public static final Logger logger = LoggerFactory.getLogger (MyTest.class); public static void main (String [] args) {logger.info ("slf4j for info"); logger.debug ("slf4j for debug"); logger.error ("slf4j for error"); logger.warn ("slf4j for warn"); String message = "Hello SLF4J" Logger.info ("slf4j message is: {}", message); / / {} placeholder}
The console displays as follows:
2018-06-07 05 slf4j for info2018 15 ERROR 42914 [com.hjj.hello.spring.MyTest]-slf4j for info2018-06-07 05 slf4j for info2018 15 ERROR [com.hjj.hello.spring.MyTest]-slf4j for error2018-06-07 05 INFO 15 ERROR [com.hjj.hello.spring.MyTest]-slf4j for warn2018-06-07 05 15 INFO [com.hjj.hello.spring.MyTest]-slf4j message is: Hello SLF4J
Logs/log.log directories and files will also be added to the root directory of the project.
Attached: placeholder ({}) description
uses {} placeholders when logging, so there is no string concatenation, reducing the number of useless String objects and saving memory. And remember, before producing the string of the final log information, this method checks to see if a specific log level is turned on, which not only reduces memory consumption but also reduces the time CPU takes to process string concatenation commands in advance.
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