Was tricky to find through google, but I found that replacing the log4j
entries in the new POM (bottom of the original email) with the following
will solve the issue:
<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>
If I understood the explanation, it seems that the spring boot starter
(parent) defaults to slf4j and that the code above removes that support
while replacing it with log4j2.
On 1/25/2022 11:33 AM, Bruno Melloni wrote:
I wrote and used a custom library that includes some log4j aware
classes. Was working perfectly when built as a standard Java JAR. I
am converting the POM to rely on a few Spring Boot starters as a way
to simplify it.
All went well until I run "Maven Install", when I got the following
ClassCastException even though my code never uses slf4j: "*class
org.apache.logging.slf4j.SLF4JLogger cannot be cast to class
org.apache.logging.log4j.core.Logger
(org.apache.logging.slf4j.SLF4JLogger and
org.apache.logging.log4j.core.Logger are in unnamed module of loader
'app')*"
The issue is probably trivial and I suspect that one or more of the
starters (possibly the TEST portion) relies on slf4j and I somehow
need to provide a library to accept slf4j and automatically convert to
log4j logging.
Can anybody see where I messed up, and know how to fix it?
*This is the old (good) POM*:
<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>
<groupId>net.cndc</groupId>
<artifactId>libCore</artifactId>
<version>0.0.1-SNAPSHOT</version>
<properties>
<oshi.version>5.8.2</oshi.version>
</properties>
<dependencies>
<!-- Apache commons -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-text</artifactId>
<version>1.9</version>
</dependency>
<!-- Log4j -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>2.15.0</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.15.0</version>
</dependency>
<!-- JJWT, library to add JWT bearer token support -->
<dependency>
<groupId>io.jsonwebtoken</groupId>
<artifactId>jjwt</artifactId>
<version>0.9.1</version>
</dependency>
<dependency>
<groupId>javax.xml.bind</groupId>
<artifactId>jaxb-api</artifactId>
<version>2.3.1</version>
</dependency>
<!-- Jackson JSON -->
<dependency> <!-- Jackson -->
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.12.5</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.13</version>
</dependency>
<!-- Server compatible -->
<dependency> <!-- Servlet API -->
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
<!-- Spring -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>5.3.9</version>
</dependency>
<!-- SpringSecurity -->
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-web</artifactId>
<version>5.5.2</version>
</dependency>
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-core</artifactId>
<version>5.5.2</version>
</dependency>
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-config</artifactId>
<version>5.5.2</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>5.3.10</version>
</dependency>
<dependency>
<groupId>com.github.oshi</groupId>
<artifactId>oshi-core</artifactId>
<version>${oshi.version}</version>
</dependency>
<!-- Misc -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.12.0</version>
</dependency>
<!-- Other -->
<dependency> <!-- JUnit -->
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13.2</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<release>15</release>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
*And this is the POM that causes the error*:
<?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>2.6.3</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>net.cndc</groupId>
<artifactId>core-lib</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>core-lib</name>
<description>Core library for all CNDC apps</description>
<properties>
<java.version>17</java.version>
<oshi.version>5.8.2</oshi.version>
</properties>
<dependencies>
<!-- starters -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</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>
<dependency>
<groupId>org.springframework.security</groupId>
<artifactId>spring-security-test</artifactId>
<scope>test</scope>
</dependency>
<!-- Apache commons -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-text</artifactId>
<version>1.9</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
</dependency>
<!-- Log4j -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
</dependency>
<!-- Hardware -->
<dependency>
<groupId>com.github.oshi</groupId>
<artifactId>oshi-core</artifactId>
<version>${oshi.version}</version>
</dependency>
<!-- Jackson JSON -->
<dependency> <!-- Jackson -->
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
<!-- Spring -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
