OpenJDK
Posted on :: JVM Java Kotlin

Java Commands

1. Create Source Code Structure
$ mkdir -p src/{main,test}/{java,resources}
2. Preview features
$ javac --enable-preview -release 24 Foo.java
$ java  --enable-preview Foo
3. Java Platform Module Systems (JPMS)
$ java --list-modules
$ java --describe-module java.se
$ java --show-module-resolution java.base

# Replace upgradeable modules in the runtime image
$ java --upgrade-module-path $DIR
4. Disassembles a class
$ javap -p -v <classfile>

# Show the class version
$ javap -p -v build.classes.kotlin.main.App | grep version
5. App CDS
# Before JDK 18
if [ ! -f app.jsa ]; then
  java -XX:ArchiveClassesAtExit=app.jsa -jar app.jar
else
  java -XX:ShareArchiveFile=app.jsa -jar app.jar
fi

# Since JDK 19, auto generate the CDS archive
$ java -XX:+AutoCreateSharedArchive -XX:SharedArchiveFile=app.jsa -jar app.jar

# Create default CDS archive
$ jlink-runtime/java -Xshare:dump [-XX:-UseCompressedOops]
# Check if it worked, this will fail if it can't map the archive (lib/server/classes.jsa)
$ jlink-runtime/java -Xshare:on --version
  • https://ionutbalosin.com/2022/04/application-dynamic-class-data-sharing-in-hotspot-jvm
  • https://dev.java/learn/class-data-sharing-and-application-class-data-sharing-in-hotspot
  • https://mbien.dev/blog/entry/custom-java-runtimes-with-jlink
6. Show Java VMProperty Settings
$ java --version
$ java -Xinternalversion

# Show Java Version (Useful for shell scripts)
$ java -XshowSettings:properties -version 2>&1 | grep "java.specification.version =" | awk '{print $3}'
$ jshell --feedback=silent -  <<< 'System.out.println(System.getProperty("java.specification.version"))'

# Show all settings
$ java -XshowSettings:all --version

# Show all Javac linter options
$ javac --help-lint

# Show all system properties
$ java -XshowSettings:properties --version

# VM extra options
$  java -XX:+UnlockExperimentalVMOptions -XX:+UnlockDiagnosticVMOptions -XX:+PrintFlagsFinal --version

# Java JIT compiler options
$ java -Xcomp            forces compilation of methods on first invocation (slow startup)
$ java -Xint             interpreted mode execution only (fast startup)
$ java -Xmixed           mixed mode execution (default)
7. Scan deprecated APIs
# Print dependency summary
$ jdeps -summary  app.jar

# Check the dependencies on JDK internal APIs
$ jdeps --jdk-internals --classpath libs.jar app.jar

# List of module dependences to be used in JLink
$ jdeps --ignore-missing-deps --print-module-deps  app.jar

# List all service providers
$ jlink --suggest-providers java.security.Provider

# List all jlink plugins
$ jlink --list-plugins

# Generate module-info
$ jdeps --generate-module-info ./  app.jar

# List all deprecated APIs for a release
$ jdeprscan --for-removal --release 24 --list

# Scan deprecated APIs
$ jdeprscan --for-removal --release 24 app.jar
8. JPMS
# Start ModuleMainClass
$ java -m jdk.httpserver -b 127.0.0.1

# Compile all modules at once (Start from the main module)
$ javac  --enable-preview \
         --release 24 \
         -parameters  \    // Optional, Generate metadata for reflection on method parameters
         --add-modules ALL-MODULE-PATH \  // Optional, Root modules to resolve in addition to the initial modules
         --module-path ... \           // Optional, where to find application modules
         --module-source-path "src" \  // Source files for multiple modules
         -d classes  \
         --module MainApp              // Compile only the specified module(s)

# Package all modules (Create for all modules)
$ jar --create \
      --file mods/app.jar \
      --main-class dev.suresh.MainKt \
      --module-version 1.0 \    // Optional
      -C app/ classes resources // Or *.class

# Launch app
$ java  --enable-preview \
        --show-version \
        --show-module-resolution \
        --module-path mods \
        --module app   // OR <module>/<mainclass>

# Build native image from modular jars
$ native-image \
    -p base-module.jar:main-module.jar \
    -m dev.suresh.Main

# JavaFX 24 using jlink & jpackage
$ wget "https://download.java.net/java/early_access/.../openjfx-xxx_macos-aarch64_bin-jmods.tar.gz"
$ tar -xvzf openjfx-xxx_macos-aarch64_bin-jmods.tar.gz

$ jlink --output javafx-jdk \
        --module-path $JAVA_HOME/jmods:javafx-jmods-24 \
        --add-modules javafx.controls,java.desktop,java.logging
#       --add-modules ALL-MODULE-PATH

$ javafx-jdk/bin/java --list-modules

$ jpackage --main-jar app.jar \
           --runtime-image javafx-jdk \
           --type app-image \
           --name app \
           --java-options "-Xmx64m" \
           --arguments "arg" \
           --icon app.ico \
           --input app \
           --dest bin
9. JShell
# JShell with preview feature enabled
$ jshell --enable-preview
$ jshell --show-version --enable-preview  --enable-native-access --startup JAVASE --feedback concise

# Use custom startup script
$ jshell --enable-preview --startup DEFAULT --startup ~/calc.repl

# Query system properties/run java code
$ fileEncoding="$(echo 'System.out.println(System.getProperty("file.encoding"))' | jshell -s -)"
10. Java TEMP Config
$ echo "-------- TMP PATH for $OSTYPE --------"
$ MKTEMP_PATH="$(dirname "$(mktemp -u)")/"
$ JAVA_TMP_DIR="$(java -XshowSettings:properties -version 2>&1 | awk 'tolower($0) ~ /java.io.tmpdir/{print $NF}')/"
$ JAVA_FILE_ENC="$(echo 'System.out.println(System.getProperty("file.encoding"))' | jshell -s -)"

$ echo "MKTEMP_PATH    = $MKTEMP_PATH"
$ echo "TMP            = $TMP"
$ echo "TEMP           = $TEMP"
$ echo "TMPDIR (Mac)   = $TMPDIR"
$ echo "RUNNER_TEMP    = $RUNNER_TEMP"
$ echo "JAVA_IO_TMPDIR = $JAVA_TMP_DIR"
$ echo "JAVA_FILE_ENC  = $JAVA_FILE_ENC"
$ echo "/TMP           = $(ls -l /tmp)"

IDEs and Tools

  • IntelliJ Selection Modes

    • All Actions - CMD + SHIFT + A

    • Select all occurrences - CMD + CTRL + G

    • Column selection mode - CMD + SHIFT + 8

    • Multiple Cursors - SHIFT + ALT + Left Click

    • Multi Selection - SHIFT + ALT + Select as usual

    • Caret Cloning - SHIFT + ALT + Middle click on end line

    • Move line - SHIFT + ALT + Arrow UP/DOWN

  • Plugin Version Update

    $ PLUGIN_VERSION="1.2.6.2594"
$ wget --content-disposition "https://plugins.jetbrains.com/plugin/download?rel=true&updateId=331908"
$ unzip github-copilot-intellij-${PLUGIN_VERSION}.zip
$ cd github-copilot-intellij/lib
$ jar -tvf github-copilot-intellij-${PLUGIN_VERSION}.jar | grep plugin.xml
$ unzip github-copilot-intellij-${PLUGIN_VERSION}.jar
# Change until-build="223.*"
$ vi META-INF/plugin.xml
$ zip -r github-copilot-intellij-${PLUGIN_VERSION}.jar META-INF
$ rm -rf META-INF
$ cd ../../
$ zip -r github-copilot-intellij-${PLUGIN_VERSION}.zip github-copilot-intellij/
$ rm -rf github-copilot-intellij

# Now upload github-copilot-intellij-${PLUGIN_VERSION}.zip (Preferences -> Plugins -> ⚙️ -> Install Plugin from Disk)

  • IntelliJ Plugin Channels

    • https://plugins.jetbrains.com/plugins/beta/list
    • https://plugins.jetbrains.com/plugins/snapshots/org.jetbrains.compose.desktop.ide

Networking & Security

🚨Security Developer’s Guide

1. Allow Unsafe Server Cert Change
# This is Unsafe. Don't use in prod.
-Djdk.tls.allowUnsafeServerCertChange=true
-Dsun.security.ssl.allowUnsafeRenegotiation=true
2. Debugging TLS

  • https://docs.oracle.com/en/java/javase/24/security/java-secure-socket-extension-jsse-reference-guide.html#GUID-4D421910-C36D-40A2-8BA2-7D42CCBED3C6

  • https://docs.oracle.com/en/java/javase/24/security/java-secure-socket-extension-jsse-reference-guide.html

  • https://github.com/sureshg/InstallCerts/blob/master/src/main/kotlin/io/github/sureshg/extn/Certs.kt

    # Turn on all debugging
$ java -Djavax.net.debug=all

# Override HostsFileNameService
$ java -Djdk.net.hosts.file=/etc/host/style/file

# Force IPv4
$ java -Djava.net.preferIPv4Stack=true

# The entropy gathering device can also be specified with the system property
$ java -Djava.security.egd=file:/dev/./urandom
3. Java Networking Properties
  • http://htmlpreview.github.io/?https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/net/doc-files/net-properties.html
  • https://docs.oracle.com/en/java/javase/24/docs/api/java.base/java/net/doc-files/net-properties.html
  • All Java Networking System Properties
  • https://docs.oracle.com/javase/8/docs/technotes/guides/net/proxies.html
ConfigDescription
http.proxyHostThe host name of the proxy server
http.proxyPortThe port number, the default value being 80
http.nonProxyHosts

  • HTTP

    # Use JAVA_TOOL_OPTIONS
$ export JAVA_TOOL_OPTIONS="
${JAVA_TOOL_OPTIONS}
-Dhttp.useProxy=true
-Dhttps.useProxy=true
-Dhttp.proxyHost=172.10.10.1
-Dhttp.proxyPort=8100
-Dhttps.proxyHost=172.10.10.1
-Dhttps.proxyPort=8100
-Dhttp.nonProxyHosts='localhost|127.0.0.1|cdn.test.org|*-prod.app.com|slack.com'"

# OR use system properties
$ java -Dhttp.proxyHost=webcache.example.com -Dhttp.proxyPort=8080 -Dhttp.nonProxyHosts="localhost|host.example.com" <URL>

  • Env vars

    export HTTP_PROXY=http://USERNAME:PASSWORD@10.0.1.1:8080/
export HTTPS_PROXY=https://USERNAME:PASSWORD@10.0.0.1:8080/
export NO_PROXY=master.hostname.example.com
4. HTTP Client Properties
-Djdk.internal.httpclient.disableHostnameVerification
-Djdk.httpclient.HttpClient.log=headers
-Djdk.internal.httpclient.debug=false
-Djdk.tls.client.protocols="TLSv1.2"

Gradle Kotlin DSL

1. Docs
2. Name Abbrevation
$ ./gradlew --console=plain \
            --continuous \
            --dry-run \
            --no-daemon \
            -Dauthor=Suresh \
            -Pmyprop=myvalue \
            cle dU
3. Configure/Create Tasks
  • Eager
    val p: Jar = getByName<Jar>("jar")       // Get existing task
val q: Jar = create<Jar>("jar") {}       // Create new task
val r: Jar by getting(Jar::class)        // Get task using property delegate
val s: Copy by creating(Copy::class) {}  // Create task using property delegate
  • Lazy (Configuration Avoidance API)
    val t: TaskProvider<Jar> = named<Jar>("jar"){}        // Get existing task
val u: TaskProvider<Jar> = register<Jar>("jar"){}     // Create new task
val v: TaskProvider<Jar> by registering(Jar::class){} // Create task using property delegate
val jar: TaskProvider<Task> by existing // Get task using property delegate

val foo: FooTask by existing            // Take Task type from val (Kotlin 1.4)
val bar: BarTask by registering {}      // Take Task type from val (Kotlin 1.4)
4. Reproducible builds
withType<AbstractArchiveTask>().configureEach {
    isPreserveFileTimestamps = false
    isReproducibleFileOrder = true
}
5. Multi Release Jar
// See https://github.com/melix/mrjar-gradle for more on multi release jars
val mrVersion = "11"
if (JavaVersion.current().isJava11Compatible) {
    sourceSets {
        create("java$mrVersion") {
            java {
                srcDirs("src/main/java$mrVersion")
            }
        }
    }

    tasks {
        // For each source set, Gradle will automatically create a compile task.
        val mrJavaCompile = named<JavaCompile>("compileJava${mrVersion}Java") {
            sourceCompatibility = mrVersion
            targetCompatibility = mrVersion
            options.compilerArgs = listOf("--release", mrVersion)
        }

        named<Jar>("jar") {
            into("META-INF/versions/$mrVersion") {
                from(sourceSets.named("java$mrVersion").get().output)
            }
            manifest.attributes(
                "Multi-Release" to "true"
            )

            dependsOn(mrJavaCompile)
        }
    }
}
6. Dependencies
# Direct dependencies
$ ./gradlew -q dependencies --configuration implementation
# Transitive dependencies
$ ./gradlew -q dependencies --configuration runtimeClasspath

# Dependencies insight for a dependency group.
$ ./gradlew -q dependencyInsight --configuration runtimeClasspath --dependency kotlin
$ ./gradlew -q dependencyInsight --dependency log4j-core

# Task Dependencies
$ ./gradlew clean build --dry-run

# Dependency updates
$ ./gradlew clean dependencyUpdates -Drevision=release
# Force Gradle to execute all tasks ignoring up-to-date checks
$ ./gradlew clean build --rerun-tasks

# Don't reuse outputs from previous builds (org.gradle.caching=false)
$ ./gradlew clean build --no-build-cache

# To refresh all dependencies in the dependency cache
$ ./gradlew clean build --refresh-dependencies

Maven

1. Create a Project
$ mvn archetype:generate -DgroupId=dev.suresh -DartifactId=my-app -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4 -DinteractiveMode=false
2. Enabling Java preview feature
<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.6.2</version>
            <configuration>
                <release>15</release>
                <compilerArg>--enable-preview</compilerArg>
            </configuration>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <configuration>
                <argLine>--enable-preview</argLine>
            </configuration>
        </plugin>

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-failsafe-plugin</artifactId>
            <configuration>
                <argLine>--enable-preview</argLine>
            </configuration>
        </plugin>
    </plugins>
</build>
3. Reproducible Builds
<properties>
    <project.build.outputTimestamp>2020-04-02T08:04:00Z</project.build.outputTimestamp>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
4. Maven Wrapper
$ mvn wrapper:wrapper -Dmaven=3.8.5
5. Update Version number
$ ./mvnw versions:set -DnewVersion=1.0.1-SNAPSHOT -DprocessAllModules -DgenerateBackupPoms=false
$ ./mvnw versions:revert // Rollback
$ ./mvnw versions:commit
6. Dependency Tree
# Show all orginal versions, not the resolved ones.
$ ./mvnw dependency:tree
$ ./mvnw dependency:tree -Ddetail=true
$ ./mvnw dependency:tree -Dverbose -Dincludes=org.jetbrains.kotlin:kotlin-stdlib
$ ./mvnw clean verify

# Dependency and plugin updates
$ ./mvnw clean versions:display-dependency-updates versions:display-plugin-updates

# Search Artifacts by class
https://search.maven.org/search?q=fc:kotlin.text.Regex

Microservices Starters

1. SpringBoot
$ curl https://start.spring.io/starter.zip \
    -d dependencies=devtools,web \
    -d type=gradle-project \
    -d language=kotlin \
    -d javaVersion=11 \
    -d packaging=jar \
    -d platformVersion=2.2.6.RELEASE \
    -d name=helloworld \
    -d groupId=dev.suresh \
    -d artifactId=helloworld \
    -d packageName=dev.suresh \
    -d description=Hello%20World%20App \
    -d baseDir=helloworld \
    -o helloworld.zip

Misc

  • Github Registry

    $ VERSION=$(date +%s)
$ docker build . --file Dockerfile --tag docker.pkg.github.com/sureshg/repo/app:${VERSION}
$ docker login docker.pkg.github.com --username sureshg --password ${{ secrets.GITHUB_TOKEN }}
$ docker push docker.pkg.github.com/sureshg/repo/app:${VERSION}

  • Install Command Line Tools

    $ xcode-select --install

OpenJDK Build

$ sdk install java 24-open
$ git clone https://github.com/openjdk/jdk.git
$ cd jdk
# $ make clean
$ bash configure
$ make images
$ build/*/images/jdk/bin/java --version

Oracle A1 Flex

# Reset the password
# https://docs.oracle.com/en-us/iaas/Content/Compute/References/serialconsole.htm#four__opcpasswordreset
$ /usr/sbin/load_policy -i
$ sudo /bin/mount -o remount, rw /
$ sudo passwd opc
$ sudo reboot -f

# Install softwares
$ sudo yum upgrade -y
$ sudo yum install curl wget tree docker git zsh -y
$ sh -c "$(curl -fsSL https://raw.github.com/ohmyzsh/ohmyzsh/master/tools/install.sh)"
$ curl -s "https://get.sdkman.io" | bash
$ sdk i java 24.ea-open

# For Github self hosted runners on Aarch64
export LD_LIBRARY_PATH=/opt/oracle/oracle-armtoolset-8/root/usr/lib64:/usr/local/lib:/usr/lib:/usr/local/lib64:/usr/lib64
export DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=1
export JAVA_HOME_11_X64=/home/opc/.sdkman/candidates/java/11.0.11.hs-adpt

# Install EPEL
$ sudo rpm -Uvh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

  • Open Ports

     # Networking > Virtual cloud networks > Security List > Add Ingress Rules (open tcp/8080)
 $ firewall-cmd  --permanent --zone=public --add-port=8080/tcp
 $ firewall-cmd  --reload
 $ http://ip:8080

Awesome Svgs

Illustrations
  • https://undraw.co/illustrations
  • https://www.manypixels.co/gallery/
  • https://www.pixeltrue.com/free-illustrations
Background
  • https://www.svgbackgrounds.com/
Icons
  • https://icons.getbootstrap.com/
  • https://material.io/resources/icons/?style=baseline (not sag)
  • https://fontawesome.com/v4.7.0/icons/ (not sag)
  • https://simpleicons.org/ (Brand Icons - good one)
  • https://github.com/microsoft/fluentui-system-icons
  • https://tablericons.com/
  • https://tabler-icons.io/
  • https://systemuicons.com/
  • https://github.com/c5inco/intellij-icons-compose
  • https://www.visiwig.com/icons/
  • https://standart.io/
  • https://thenounproject.com/
  • https://www.flaticon.com/
  • https://www.iconfinder.com/
  • https://ionicons.com/
  • https://icons8.com/
  • https://github.com/game-icons/icons
Emojis
  • https://emojipedia.org/search/
  • https://github.com/twitter/twemoji/tree/master/assets
Awesome List
  • https://github.com/vkarampinis/awesome-icons
  • https://github.com/notlmn/awesome-icons
  • https://github.com/ikatyang/emoji-cheat-sheet
Tools
  • https://jakearchibald.github.io/svgomg/
  • https://css-tricks.com/tools-for-optimizing-svg/
  • https://imageoptim.com/mac
  • https://xmlgraphics.apache.org/batik/
  • https://github.com/svg/svgo-osx-folder-action
$ pip3 install mkdocs-macros-plugin
$ ./gradlew dokka
$ cp  docs/mkdocs.yml build/dokka
$ cp -R docs/images build/dokka/my-app
$ cp CHANGELOG.md build/dokka/my-app/CHANGELOG.md
$ cp README.md build/dokka/my-app/Overview.md
$ Fix the img reference on Overview.md
$ cd build/dokka
$ mkdocs build
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