Why write the log output code after SpringApplication.run() , it will not be executed, while other c-CodePudding

I create a demo program use SpringInitializr。

jdk8 maven 3.6.3 windows11

import

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.5.10</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>demo</description>
<properties>
    <java.version>1.8</java.version>
</properties>
<dependencies>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
    
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-logging</artifactId>
    </dependency>

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

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

main application

package com.example.demo;

import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@Slf4j
public class Application {

    public static void main(String[] args) {
        log.info("log output before SpringApplication.run");
        SpringApplication.run(Application.class, args);
        System.out.println("after SpringApplication.run first System.out.println");
        log.info("log output after SpringApplication.run");
        System.out.println("System.out.println end");
    }
}

result enter image description here

03:23:26.850 [main] INFO com.example.demo.Application - log output before             SpringApplication.run

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::               (v2.5.10)

after SpringApplication.run first System.out.println
System.out.println end

Why the console does not output log.info(), but can output System.out.println()? I tried to change the logback version, or use log4j，has the same result

Thank you very much for helping me

CodePudding user response：

It happens because you set logging level to WARN or ERROR in your application.properties file (or other logger-configuration file).

For example, in application.properties

logging.level.root=WARN

By default it is INFO - that is why you see the printed log before Spring application starts.

Then Spring application starts and changes level to one of the below INFO: ERROR or WARN - according to configuration you have provided.