Scenario
Let’s say you built spring-boot executable jar and uploaded it into nexus repository. To deploy your spring-boot application you create a Dockerfile that downloads your jar using nexus rest search and download API. For example:
FROM openjdk:8-jre-alpine MAINTAINER itzap <mailer@itzap.com> WORKDIR / RUN wget -O app-service.jar \ 'https://nexus.companyUrl.com/nexus/service/rest/v1/search/assets/download?group=com.mycompany.service&name=app-service&repository=company-snapshots&sort=version&direction=des' EXPOSE 8080 ENTRYPOINT [ "java", "-jar","app-service.jar"]
When you run docker container you see the following error message:
no main manifest attribute, in app-service.jar
Diagnostic
When you build and run jar locally everything is working fine. app-service.jar inside docker container appears to be corrupted. To diagnose the issue run the wget command from the terminal:
wget -O app-service.jar \ 'https://nexus.companyUrl.com/nexus/service/rest/v1/search/assets/download?group=com.mycompany.service&name=app-service&repository=company-snapshots&sort=version&direction=des'
Notice the following results on the command line:
$ wget -O app-service.jar 'https://nexus.companyUrl.com/nexus/service/rest/v1/search/assets/download?group=com.mycompany.service&name=app-service&repository=company-snapshots&sort=version&direction=desc' --2019-10-21 21:48:27-- https://nexus.companyUrl.com/nexus/service/rest/v1/search/assets/download?group=com.mycompany.service&name=app-service&repository=company-snapshots&sort=version&direction=desc Распознаётся nexus.compnyUrl.com (nexus.companyUrl.com)… 00.00.00.00 Подключение к nexus.compnyUrl.com (nexus.compnyUrl.com)|00.00.00.00|:443... соединение установлено. HTTP-запрос отправлен. Ожидание ответа… 302 Found Адрес: https://nexus.compnyUrl.com/nexus/repository/company-snapshots/com/mycompany/service/app-service/0.0.1-SNAPSHOT/app-service-0.0.1-20191021.220127-1-javadoc.jar [переход] --2019-10-21 21:48:28-- https://nexus.compnyUrl.com/nexus/repository/app-snapshots/com/mycompany/service/app-service/0.0.1-SNAPSHOT/app-service-0.0.1-20191021.220127-1-javadoc.jar Повторное использование соединения с nexus.compnyUrl.com:443. HTTP-запрос отправлен. Ожидание ответа… 200 OK Длина: 247463 (242K) [application/java-archive] Сохранение в: «app-service.jar»
Do not get all these messages in Russian fool you. This is not a Russian hacker attack. Pay attention to what is actually being downloaded. app-service-0.0.1-20191021.220127-1-javadoc.jar javadoc!!!
Solution
Solution to this issue can be found in sonatype Search API. Looking through documentation I came across this query parameter maven.classifier This issue happens when your repository contains javadoc jar alnog side your artifact. &sort=version&direction=desc parameters are also critical to insure you are downloading the latest version, but not enough to uniquely identify artifact. Final URL that works looks like this:
'https://nexus.companyUrl.com/nexus/service/rest/v1/search/assets/download?group=com.mycompany.service&name=app-service&repository=company-snapshots&sort=version&direction=desc&maven.classifier'