Java8: Compact Profiles

Java8 provides a feature that enables Java Applications to use subset of the APIs provided by entire JDK. This feature is called compact profiles. Using compact profiles, we can deploy the application with the subset APIs instead of entire JDK APIs.

 

Why Compact Profiles?

Prior to Java8, to deploy a Java application, we need to deploy entire Java APIs also. With compact profiles, we can reduce memory footprint by deploying only subset profile. Compact profiles are interim solution to Java9 modularity system (Project Jigsaw).

 

Java8 defines 3 compact profiles (compact1, compact2 and compact3). Each profile is a subset of its predecessor. For example, compact2 contains all the copact1 packages plus some new packages.

 

Following table summarizes the compact profiles and their comprising packages.

 

compact1	compact2	compact3
java.io   java.lang   java.lang.annotation   java.lang.invoke   java.lang.ref   java.lang.reflect   java.math   java.net   java.nio   java.nio.channels   java.nio.channels.spi   java.nio.charset   java.nio.charset.spi   java.nio.file   java.nio.file.attribute   java.nio.file.spi   java.security   java.security.cert   java.security.interfaces   java.security.spec   java.text   java.text.spi   java.time   java.time.chrono   java.time.format   java.time.temporal   java.time.zone   java.util   java.util.concurrent   java.util.concurrent.atomic   java.util.concurrent.locks   java.util.function   java.util.jar   java.util.logging   java.util.regex   java.util.spi   java.util.stream   java.util.zip   javax.net   javax.net.ssl   javax.script   javax.security.auth   javax.security.auth.callback   javax.security.auth.login   javax.security.auth.spi   javax.security.auth.x500   javax.security.cert	java.rmi   java.rmi.activation   java.rmi.dgc   java.rmi.registry   java.rmi.server   java.sql   javax.rmi.ssl   javax.sql   javax.transaction   javax.transaction.xa   javax.xml   javax.xml.datatype   javax.xml.namespace   javax.xml.parsers   javax.xml.stream   javax.xml.stream.events   javax.xml.stream.util   javax.xml.transform   javax.xml.transform.dom   javax.xml.transform.sax   javax.xml.transform.stax   javax.xml.transform.stream   javax.xml.validation   javax.xml.xpath   org.w3c.dom   org.w3c.dom.bootstrap   org.w3c.dom.events   org.w3c.dom.ls   org.w3c.dom.views   org.xml.sax   org.xml.sax.ext   org.xml.sax.helpers	java.lang.instrument   java.lang.management   java.security.acl   java.util.prefs   javax.annotation.processing   javax.lang.model   javax.lang.model.element   javax.lang.model.type   javax.lang.model.util   javax.management   javax.management.loading   javax.management.modelmbean   javax.management.monitor   javax.management.openmbean   javax.management.relation   javax.management.remote   javax.management.remote.rmi   javax.management.timer   javax.naming   javax.naming.directory   javax.naming.event   javax.naming.ldap   javax.naming.spi   javax.security.auth.kerberos   javax.security.sasl   javax.sql.rowset   javax.sql.rowset.serial   javax.sql.rowset.spi   javax.tools   javax.xml.crypto   javax.xml.crypto.dom   javax.xml.crypto.dsig   javax.xml.crypto.dsig.dom   javax.xml.crypto.dsig.keyinfo   javax.xml.crypto.dsig.spec   org.ietf.jgss

 

How to compile a class using given compact profile?

Syntax

javac -profile {compact1|compact2|compact3} JavaClass

 

Example

javac -profile compact1 App.java

 

App.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class App {

	public static void main(String args[]) throws IOException {

		try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in));) {
			System.out.println("Enter your name");
			String name = br.readLine();

			System.out.println("Hello " + name);
		}

	}
}

Since java.io package is part of compact1 profile, we can use this profile to compile App.java. Execute the command ‘javac -profile compact1 App.java’ to compile App.java using compact1 profile.

$javac -profile compact1 App.java
$ls
App.class	App.java

How to list dependencies in a class file?

Use jdeps tool to list the dependencies in a class file.

 

jdeps App.class

 

This command generate below output.

$jdeps App.class 
App.class -> /Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/rt.jar
   <unnamed> (App.class)
      -> java.io                                            
      -> java.lang

You can even get more verbose output using -verbose option.

$jdeps -verbose -P App.class
App.class -> /Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/rt.jar (compact1)
   App                                                -> java.io.BufferedReader                             compact1
   App                                                -> java.io.IOException                                compact1
   App                                                -> java.io.InputStream                                compact1
   App                                                -> java.io.InputStreamReader                          compact1
   App                                                -> java.io.PrintStream                                compact1
   App                                                -> java.io.Reader                                     compact1
   App                                                -> java.lang.Object                                   compact1
   App                                                -> java.lang.String                                   compact1
   App                                                -> java.lang.StringBuilder                            compact1
   App                                                -> java.lang.System                                   compact1
   App                                                -> java.lang.Throwable                                compact1

Create smaller Java Platform using jrecreate tool

Download ‘Oracle Java SE Embedded version 8’ from below link.

https://www.oracle.com/java/technologies/java-embedded-java-se-downloads.html

 

Extract the downloaded zip file. You will see ‘ejdk1.8.0/’ folder after extraction.

 

Go to ‘bin’ directory of ejdk1.8.0 folder, you will see jrecreate.sh file.

$ls
jrecreate.bat        jrecreate.config.properties   jrecreate.sh

Execute following command to generate jre with compact1 profile.

 

jrecreate.sh -d ./compact1-jre/ -p compact1

 

Above command generates a folder ‘compact1-jre’ in current directory.

$jrecreate.sh -d ./compact1-jre/ -p compact1
Building JRE using Options {
    ejdk-home: /Users/krishna/Downloads/ejdk1.8.0
    dest: /Users/krishna/Documents/technical-documents/programs/./compact1-jre
    target: linux_arm_vfp_hflt
    vm: minimal
    runtime: compact1 profile
    debug: false
    keep-debug-info: false
    no-compression: false
    dry-run: false
    verbose: false
    extension: []
}

Target JRE Size is 10,513 KB (on disk usage may be greater).

Embedded JRE created successfully

 

Now you can use compact1-jre to ship App.class file. Hopw you enjoyed this tutorial.

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