use Java >11.0.2 instead of Java 12 on Travis (FINERACT-937)

by ditching Travis' own sad state of Java (cough) 'support'

and just re-installing it ourselves instead

.travis.yml

@@ -16,14 +16,11 @@
 # under the License.
 #
 
-# https://issues.apache.org/jira/browse/FINERACT-763
+# https://docs.travis-ci.com/user/reference/linux/
+# Must use a fixed distribution (and remember to occassionally upgrade..)
+# to avoid surprise changes such as https://issues.apache.org/jira/browse/FINERACT-763
 dist: bionic
 
-language: java
-
-jdk:
-  - openjdk12
-
 services:
   - mysql
   - docker
@@ -34,7 +31,20 @@ addons:
     # https://httpie.org is used by the docker-compose test below
     - httpie
 
+# See https://issues.apache.org/jira/browse/FINERACT-937 for background re. what below is all about..
+# We basically remove the outdated OpenJDK 11.0.2 which Travis image grabbed from java.net in
+# https://github.com/travis-ci/travis-cookbooks/blob/master/cookbooks/travis_jdk/files/install-jdk.sh#L200
+# (which has 11.0.2 hard-coded!), and instead replace it with the latest openjdk-11-jdk-headless Ubuntu package.
+# NB /usr/local/lib/jvm/openjdk11/bin is also on the PATH, but there's no need to change it (because we rm -rf anyway)
 before_install:
+  - echo $JAVA_HOME
+  - which java
+  - sudo rm -rf /usr/local/lib/jvm/
+  - sudo apt-get install -y openjdk-11-jdk-headless
+  - export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64/
+  - which java
+  - java -version
+  - $JAVA_HOME/bin/java -version
   - echo "USE mysql;\nALTER USER 'root'@'localhost' IDENTIFIED BY 'mysql';\n" | mysql -u root
   - mysql -u root -pmysql -e 'CREATE DATABASE IF NOT EXISTS `fineract_tenants`;'
   - mysql -u root -pmysql -e 'CREATE DATABASE IF NOT EXISTS `fineract_default`;'