提取 jar 时，spring boot 运行 JarLauncher

Question

I'm building a fat jar using spring boot , the fat jar works using

java -jar app.jar

the problem is that I'm using docker and I want to expand the jar contents for better usability , I do the following to extract :

unzip app.jar

now I run the jar with the following :

java -cp "." org/springframework/boot/loader/JarLauncher

I get the following error :

 Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'jaxRsServer' defined in class path resource 

so it couldn't find my bean altough it's configured :

@SpringBootApplication(exclude = SecurityAutoConfiguration.class)
@ImportResource("classpath:spring/beans_context.xml")
public class SpringBootJaxrsApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpringBootJaxrsApplication.class, args);
    }

}

beans_context.xml :

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
          http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
          http://www.springframework.org/schema/context
          http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:annotation-config />


<import resource="classpath:META-INF/spring/*_context.xml"/>

Answer 1

Which Spring Boot version are you using? Since 2.3.0, a new layered mode is available for packaging fat JARs. Once you enable the layered mode, you can then do something like this to build the Docker image.

FROM adoptopenjdk:11-jre-hotspot as builder
WORKDIR application
ARG JAR_FILE=target/*.jar
COPY ${JAR_FILE} application.jar
RUN java -Djarmode=layertools -jar application.jar extract

FROM adoptopenjdk:11-jre-hotspot
WORKDIR application
COPY --from=builder application/dependencies/ ./
COPY --from=builder application/snapshot-dependencies/ ./
COPY --from=builder application/resources/ ./
COPY --from=builder application/application/ ./
ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]

Notice that the command is java org.springframework.boot.loader.JarLauncher .

The example is fully explained in this post from the Spring blog. For more information on how layering works in Spring Boot 2.3, you can refer to this post , again from the Spring blog.

Instead, if you're using an older version of Spring Boot, you can build your Dockerfile as explained in this post . In this case, the entrypoint will be java -cp app:app/lib/* hello.Application .

FROM openjdk:8-jdk-alpine
RUN addgroup -S spring && adduser -S spring -G spring
USER spring:spring
ARG DEPENDENCY=target/dependency
COPY ${DEPENDENCY}/BOOT-INF/lib /app/lib
COPY ${DEPENDENCY}/META-INF /app/META-INF
COPY ${DEPENDENCY}/BOOT-INF/classes /app
ENTRYPOINT ["java","-cp","app:app/lib/*","hello.Application"]