Steps to migrate from oracle jdk-8 to openJDK-11

Table of Content

upgrade build tools
Add missing Java dependencies in jdk11
Remove findbug and add Spotbugs
Changes in GC options
- Runtime GC log changes
- GC info
Fork-join Thread pool
Class-Loader
IDE-setup

Upgrade build tools

for gradle,
minimum version should be 5.0
for maven, upgrade maven compiler plugin

<plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-compiler-plugin</artifactId>
   <version>3.8.0</version>
   <configuration>
       <release>11</release>
   </configuration>
</plugin>

Add missing Java dependencies in jdk11

// jdk 11 migration dependencies
implementation "javax.xml.bind:jaxb-api:2.3.1"
implementation "com.sun.xml.bind:jaxb-core:2.3.0.1"
implementation "com.sun.xml.bind:jaxb-impl:2.3.1"
implementation "com.sun.activation:javax.activation:1.2.0"
implementation("javax.annotation:javax.annotation-api:1.3.2")
// https://mvnrepository.com/artifact/org.ow2.asm/asm
compile group: 'org.ow2.asm', name: 'asm', version: '7.1'

compileOnly "com.github.spotbugs:spotbugs-annotations:$spotbugsannotationsVersion"
testCompile("javax.xml.ws:jaxws-api:2.3.1")
// end of jdk 11 migration dependencies

Refs: https://blog.joda.org/2018/09/time-to-look-beyond-oracles-jdk.html

https://adoptopenjdk.net/installation.html

https://stackoverflow.com/a/43574427/2987755

https://blog.codefx.org/java/java-11-migration-guide/

https://www.dariawan.com/tutorials/java/using-jaxb-java-11/

https://medium.com/criciumadev/its-time-migrating-to-java-11-5eb3868354f9

Remove findbug and add Spotbugs

if you have spotbug config in different file other than build.gradle, then you need to specify

older way of specifying plugins(using buildscript) in gradle like
build.gradle

buildscript {

   repositories {
      mavenLocal()
      mavenCentral()
      maven { url "https://repo.spring.io/libs-release" }
  }
  dependencies {
      classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
      classpath("gradle.plugin.com.github.spotbugs:spotbugs-gradle-plugin:2.0.0")
  }
}

project.extensions.extraProperties.set('SpotBugsTask', com.github.spotbugs.SpotBugsTask)

apply from: file('gradle/spotbugs.gradle')

dependencies {
     compile("org.ow2.asm:asm:${asmVersion}")
}

sprotbugs.gradle file

allprojects {
     apply plugin: 'com.github.spotbugs'
     apply plugin: 'jacoco'
     apply plugin: "pmd"
     
    // pmd, ./gradlew pmdMain     
    pmd {
        toolVersion = '6.17.0'
        ignoreFailures = true
        pmdTest.enabled = true
    }
    
    //pmd task, wich will run along with ./gradlew clean build
    tasks.withType(Pmd) {
        reports {
            xml.enabled = false
            html.enabled = true
        }
    }
    
    // To get report ./gradlew clean build; ./gradlew jacocoTestReport;
    jacoco {
        toolVersion = "0.8.4"
    }
    
    jacocoTestReport {
        reports {
            xml.enabled false
            csv.enabled false
            html.enabled true
        }
    }

    spotbugs {
        toolVersion = '3.1.12'
        // continue build despite warnings
        ignoreFailures = true
    }
    //To view spotbugs report in html format.
    tasks.withType(SpotBugsTask) {
        effort = 'max'
        reports.xml.enabled = false
        reports.html.enabled = true
        maxHeapSize '2g'
    }
}

Changes in GC options

change to java-11 java in console

Two flavours of open-jdk

AdoptOpenJdk(VM AdoptOpenJDK)

openjdk version "11.0.2" 2019-01-15
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.2+9)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.2+9, mixed mode)

Oracle's-openjdk(VM 18.9)

openjdk version "11.0.2" 2019-01-15
OpenJDK Runtime Environment 18.9 (build 11.0.2+9)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.2+9, mixed mode)

You can check release.txt file at jdk home

Check avilability of flags in java 11 from here

-Xloggc:/myfolder/gc.log is deprecated and needs to be -Xlog:gc:/myfolder/gc.log instead

change following options from/to

-XX:+PrintGCDetails
-Xloggc:/tmp/application.gc.log
-XX:NumberOfGCLogFiles=5
-XX:GCLogFileSize=1M  

changed to

-Xlog:gc*:file=/tmp/application.gc.log:uptime,level,tags:filecount=5,filesize=1M

#for safepoint

-Xlog:safepoint*:file=safepoints-%p-%t.log:tags,uptime,time,level:filecount=10,filesize=50m

#remove -XX:+UseGCLogFileRotation
#remove -XX:+PrintGCTimeStamps

Unrecognized in OpenJDK 11:

-d64
PrintGCTimeStamps
UseGCLogFileRotation
NumberOfGCLogFiles
GCLogFileSize

format:
-Xlog : <tags to log>[=<log level>] [: <output> [: <decorations> ]] Ref
execute

java -Xlog:help

if you do not want to add which decorator, it is optional, and you can write it as

-Xlog:gc*:file=/tmp/application.gc.log::filecount=5,filesize=1M

Runtime GC log changes

jps
Get the processid
jcmd <processid> VM.log what=gc*

That's it.

GC info

-Xlog Usage: -Xlog[:[what][:[output][:[decorators][:output-options]]]]
     where 'what' is a combination of tags and levels of the form tag1[+tag2...][*][=level][,...]
     Unless wildcard (*) is specified, only log messages tagged with exactly the tags specified will be matched.

Available log levels:
 off, trace, debug, info, warning, error

Available log decorators: 
 time (t), utctime (utc), uptime (u), timemillis (tm), uptimemillis (um), timenanos (tn), uptimenanos (un), hostname (hn), pid (p), tid (ti), level (l), tags (tg)
 Decorators can also be specified as 'none' for no decoration.

Available log tags:
 add, age, alloc, aot, annotation, arguments, attach, barrier, biasedlocking, blocks, bot, breakpoint, cds, census, class,
 classhisto, cleanup, codecache, compaction, compilation, constraints, constantpool, container, coops, cpu, cset, data,
 datacreation, defaultmethods, dump, ergo, exceptions, exit, fingerprint, freelist, gc, handshake, hashtables, heap,
 humongous, ihop, iklass, init, inlining, interpreter, itables, jit, jni, jvmti, liveness, load, loader, logging, mark,
 marking, membername, memops, methodcomparator, metadata, metaspace, mmu, module, monitorinflation, monitormismatch,
 nmethod, normalize, objecttagging, obsolete, oopmap, os, pagesize, patch, path, perf, phases, plab, promotion, preorder,
 protectiondomain, ref, redefine, refine, region, remset, purge, resolve, safepoint, scavenge, scrub, smr, stacktrace,
 stackwalk, start, startuptime, state, stats, stringdedup, stringtable, stackmap, subclass, survivor, sweep, table, task,
 thread, tlab, time, timer, update, unload, unshareable, verification, verify, vmoperation, vmthread, vtables, workgang
 
Specifying 'all' instead of a tag combination matches all tag combinations.

Described tag combinations:
 logging: Logging for the log framework itself

Available log outputs:
 stdout, stderr, file=<filename>
 Specifying %p and/or %t in the filename will expand to the JVM's PID and startup timestamp, respectively.

Some examples:
 -Xlog
     Log all messages using 'info' level to stdout with 'uptime', 'levels' and 'tags' decorations.
     (Equivalent to -Xlog:all=info:stdout:uptime,levels,tags).

 -Xlog:gc
     Log messages tagged with 'gc' tag using 'info' level to stdout, with default decorations.

 -Xlog:gc,safepoint
     Log messages tagged either with 'gc' or 'safepoint' tags, both using 'info' level, to stdout, with default decorations.
     (Messages tagged with both 'gc' and 'safepoint' will not be logged.)

 -Xlog:gc+ref=debug
     Log messages tagged with both 'gc' and 'ref' tags, using 'debug' level, to stdout, with default decorations.
     (Messages tagged only with one of the two tags will not be logged.)

 -Xlog:gc=debug:file=gc.txt:none
     Log messages tagged with 'gc' tag using 'debug' level to file 'gc.txt' with no decorations.

 -Xlog:gc=trace:file=gctrace.txt:uptimemillis,pids:filecount=5,filesize=1m
     Log messages tagged with 'gc' tag using 'trace' level to a rotating fileset of 5 files of size 1MB,
     using the base name 'gctrace.txt', with 'uptimemillis' and 'pid' decorations.

 -Xlog:gc::uptime,tid
     Log messages tagged with 'gc' tag using 'info' level to output 'stdout', using 'uptime' and 'tid' decorations.

 -Xlog:gc*=info,safepoint*=off
     Log messages tagged with at least 'gc' using 'info' level, but turn off logging of messages tagged with 'safepoint'.
     (Messages tagged with both 'gc' and 'safepoint' will not be logged.)

 -Xlog:disable -Xlog:safepoint=trace:safepointtrace.txt
     Turn off all logging, including warnings and errors,
     and then enable messages tagged with 'safepoint' using 'trace' level to file 'safepointtrace.txt'.

Finally,

HZ related options

-Dhazelcast.jmx=true -Dhazelcast.logging.type=slf4j -javaagent:jolokia-jvm-agent.jar

Keystore options

-Djavax.net.ssl.keyStore=keystore -Djavax.net.ssl.keyStorePassword=xxxx -Djavax.net.ssl.keyStoreType=PKCS12 -Djavax.net.ssl.trustStore=truststorefile -Djavax.net.ssl.trustStorePassword=xxxx -Djavax.net.ssl.trustStoreType=JKS

JAVA_OPTS=" -Djava.awt.headless=true -Djava.io.tmpdir=/tmp -Djava.net.preferIPv4Stack=true -Dspring.config.location=application.properties -Xms4198m -Xmx4198m -XX:NewRatio=3 -XX:+HeapDumpOnOutOfMemoryError -XX:MaxGCPauseMillis=200 -XX:+UseG1GC -XX:+UseStringDeduplication -XX:HeapDumpPath=/tmp/ -Xlog:gc*:file=/tmp/a.gc.log::filecount=5,filesize=1M -XX:+PrintCommandLineFlags"

Fork-Join Thread Pool

Ref: https://www.oracle.com/technetwork/java/javase/9-notes-3745703.html#JDK-8172726

final ClassLoader parentThreadClassLoader = Thread.currentThread().getContextClassLoader();
final Runnable a = () -> {
    Thread.currentThread().setContextClassLoader(parentThreadClassLoader);
}

forkJoinPool.submit(a);