Spring boot + slf4j + log4j + class org.apache.logging.slf4j.SLF4JLoggerContext cannot be cast to class

Question

I have Spring boot 2.3.1

• pom.xml

<?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>2.3.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>logger</groupId>
    <artifactId>logger</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>logger</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>11</java.version>
        <lombok.version>1.18.12</lombok.version>
        <log4j.version>1.2.17</log4j.version>
        <slf4j.version>1.7.30</slf4j.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <exclusions>
                <exclusion>
                    <artifactId>logback-classic</artifactId>
                    <groupId>ch.qos.logback</groupId>
                </exclusion>
            </exclusions>
        </dependency>


        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>${lombok.version}</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>${slf4j.version}</version>
        </dependency>

        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>${log4j.version}</version>
        </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>

</project>

• class

@Slf4j
@SpringBootApplication
public class LoggerApplication {

    public static void main(String[] args) {

        log.info("++++++++++++++++++++++++TEST+++++++++++++++++++++++++++++");

        SpringApplication.run(LoggerApplication.class, args);
    }

}

• application.properties

logging.config=classpath:log4j.properties

• log4j.properties

log4j.rootLogger=INFO, console
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.Target=System.out
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.conversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} %-5p - %m%n

I tried to find a solution, looked at similar topics on the forum, tried various options for excluding dependencies.

Exception in thread "main" java.lang.ClassCastException: class org.apache.logging.slf4j.SLF4JLoggerContext cannot be cast to class org.apache.logging.log4j.core.LoggerContext (org.apache.logging.slf4j.SLF4JLoggerContext and org.apache.logging.log4j.core.LoggerContext are in unnamed module of loader 'app') at

I also tried to exclude some dependencies

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <exclusions>
                <exclusion>
                    <artifactId>logback-classic</artifactId>
                    <groupId>ch.qos.logback</groupId>
                </exclusion>

                    <exclusion>
                        <groupId>log4j</groupId>
                        <artifactId>*</artifactId>
                    </exclusion>
                    <exclusion>
                        <groupId>org.slf4j</groupId>
                        <artifactId>*</artifactId>
                    </exclusion>
                    <exclusion>
                        <groupId>org.apache.logging.log4j</groupId>
                        <artifactId>*</artifactId>
                    </exclusion>

            </exclusions>
        </dependency>

But again an error, but now it is no longer possible to format logs.

2021-01-13 19:12:15,881 INFO - ++++++++++++++++++++++++TEST+++++++++++++++++++++++++++++ ERROR StatusLogger Unrecognized format specifier [d] ERROR StatusLogger Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. ERROR StatusLogger Unrecognized format specifier [thread] ERROR StatusLogger Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. ERROR StatusLogger Unrecognized format specifier [level] ERROR StatusLogger Unrecognized conversion specifier [level] starting at position 35 in conversion pattern.

...

ERROR StatusLogger Unrecognized format specifier [n] ERROR StatusLogger Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. WARNING: sun.reflect.Reflection.getCallerClass is not supported. This will impact performance.

Can anyone have any ideas how to fix it ?

Answer 1

I found a workaround for this problem. As it turned out, the problem was in the conflict of one of the private libraries (the appender for elastik).

I executed the command:

mvn dependency:tree

then found transitive dependencies and excluded them on the path to all classes to exclude the library conflicts needed for logging.

• pom.xml

<dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
      <exclusions>
        <exclusion>
          <artifactId>logback-classic</artifactId>
          <groupId>ch.qos.logback</groupId>
        </exclusion>
        <exclusion>
          <artifactId>log4j-to-slf4j</artifactId>
          <groupId>org.apache.logging.log4j</groupId>
        </exclusion>
      </exclusions>
    </dependency>

    <dependency>
      <artifactId>springfox-boot-starter</artifactId>
      <groupId>io.springfox</groupId>
      <version>3.0.0</version>
        <exclusions>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

 <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>${lombok.version}</version>
      <scope>provided</scope>
    </dependency>

    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>${log4j.version}</version>
    </dependency>

      <dependency>
          <groupId>org.apache.logging.log4j</groupId>
          <artifactId>log4j-core</artifactId>
          <version>${version.log4j.core}</version>
      </dependency>

    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>${slf4j.version}</version>
    </dependency>