openjdk6 builds failed with "NB: JAVA_HOME should point to a JDK not a JRE"

[shuaichang]

Recent openjdk6 builds failed with below messages, one example https://travis-ci.org/aliyun/fc-java-sdk/jobs/276211613, java -Xmx32m -version shows java 1.8. I saw a similar issue #8423 that was closed as a duplicate of #7884, but that only mentioned switching from oraclejdk7 to openjdk7.

Any idea what happened to openjdk6?

$ export PATH=$JAVA_HOME/bin:$PATH
$ java -Xmx32m -version
Picked up _JAVA_OPTIONS: -Xmx2048m -Xms512m
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)
$ javac -J-Xmx32m -version
Picked up _JAVA_OPTIONS: -Xmx2048m -Xms512m
javac 1.8.0_144
0.02s$ mvn clean package install -DskipTests -Dgpg.skip
The JAVA_HOME environment variable is not defined correctly
This environment variable is needed to run this program
NB: JAVA_HOME should point to a JDK not a JRE

[shuaichang]

Seems openjdk6 is not coming along with trusty VM as described in #8199 (comment)

After adding addon openjdk6, the build will be likely to fail with Exception in thread "main" java.lang.UnsupportedClassVersionError: org/apache/maven/cli/MavenCli : Unsupported major.minor version 51.0, which is caused by newer version Maven is incompatible with openjdk6, using an older version of Maven could fix the issue

To make everything working, below travis config can be helpful, credit: travis-ci/enterprise-installation#14 (comment)

language: java

addons:
  apt:
    packages:
      - openjdk-6-jdk

jdk:
  - openjdk6
  - openjdk7
  - oraclejdk8

install:
  - echo "Downloading Maven 3.0";
  - wget https://archive.apache.org/dist/maven/binaries/apache-maven-3.0-bin.zip || travis_terminate 1
  - unzip -qq apache-maven-3.0-bin.zip || travis_terminate 1
  - export M2_HOME=$PWD/apache-maven-3.0
  - export PATH=$M2_HOME/bin:$PATH
  - mvn -version
  - mvn clean package install -DskipTests -Dgpg.skip
script:
  - mvn test

[shuaichang]

Closing