Maven java version setting

Maven Java Compiler Version

The default Java compiler version used by Maven is Java 1.5 . Why that is still the default Java compiler version is a good question, since Java 5 was released in 2004. To make Maven compile your Java code with a newer version of the Java compiler, you need to specify the Java compiler explicitly in your project’s POM file ( pom.xml ).

Exactly how you specify the Java compiler version depends on whether you are using Java 8 or earlier, or Java 9 or later. From Java 9 Java got modules which complicates the compilation somewhat in the short run, but should help in the long run.

Maven Java Compiler for Java 8 and Earlier

From Java 8 and earlier, there are two ways to set the Java compiler version in a Maven POM file:

Both of these methods to set the Java compiler version in Maven will be explained in the following sections.

Maven Java Compiler Properties

The first, newest and easiest way to set the Java compiler version in your Maven POM file, is via the Maven Java compiler properties. Here is how the Maven Java compiler properties look:

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These properties have to be included in the properties element of your POM file. I usually have the properties element as the last element in my POM files.

Maven Java Compiler Plugin

The second, oldest, and more verbose to set the Java compiler version in your Maven POM files, is via the Maven Java compiler plugin. Here is how the configuration of the Maven Java compiler plugin looks:

   org.apache.maven.plugins maven-compiler-plugin 3.6.1 1.8 1.8     

Full Maven POM File With Java Compiler Version Set

For your convenience, here is a full Maven POM file with the Java compiler version set using both of the above mechanisms. Please note, that only one of the mechanisms should be used in your POM file. The example only shows both examples so you can see where in the POM file they are to be placed.

 4.0.0 com.nanosai grid-ops 0.8.0 jar  junit junit 4.12 test     org.apache.maven.plugins maven-compiler-plugin 3.6.1 1.8 1.8      UTF-8 1.8 1.8   

Maven Java Compiler for Java 9 and Later

For Java 9 and later, you need to use a slight variant of the Java compiler plugin. Instead of the source and target properties, you need to use the release property. Here is an example of how the Maven Java compiler plugin looks with a release property instead:

 org.apache.maven.plugins maven-compiler-plugin 3.8.0 11   

This example sets the Java version to 11 — inside the release property. Java 11 is the latest long-term-support (LTS) version of Java at the time of writing.

Notice also that the version of the Maven Java compiler plugin has changed from 3.6.1 to 3.8.0 .

Please keep in mind, that when you upgrade to Java 9+ you will most likely get more issues, like assuring that all Maven plugins and dependencies your Java project uses, are also Java 9+ compatible. Going into detail about how this is done is beyond the scope of this Maven Java compiler tutorial though.

Enable Preview Features

Some of the later Java versions (Java 10, 12 and 13 at least) have had some features which were in preview. A feature in preview is a feature that the Java SDK team has implemented but are not yet sure if should stay in the Java SDK long term. These features are not enabled in the Java SDK by default. To use them you must explicitly enable them. To enable Java preview features in your Maven POM file, insert the compilerArgs element into the compiler configuration, as shown below:

 org.apache.maven.plugins maven-compiler-plugin 3.8.0 11 --enable-preview   

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Setting Java Compiler Version in Maven

This document demonstrates ways to set the java compiler version in maven via the maven.compiler.target property and the maven-compiler-plugin configuration section.

Prerequisite

Setting the java compiler via maven property

Setting the java compiler via the plugin config

  • For maven-compiler-version below version 3.8.0 has the default compiler set to 1.5
  • Since maven-compiler-version 3.8.0, the default java compiler version is now 1.6
    • See also: maven-compiler-plugin doc.
       1.10 3.8.0     org.apache.maven.plugins maven-compiler-plugin $  $ $    

    Compiler Error Message

    The following is displayed when a compiler mismatch is detected during compile phase. In this example, the java compiler used (1.7) is less than the required version (1.10).

    $ java -version java version "1.7.0_40" Java(TM) SE Runtime Environment (build 1.7.0_40-b43) Java HotSpot(TM) 64-Bit Server VM (build 24.0-b56, mixed mode) 

    Error Message

    The error message as shown on Line 25 of the Maven Console Log

    [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.0:compile (default-compile) on project mvn-demo-java-compiler-version: Fatal error compiling: invalid target release: 1.10 -> [Help 1] 

    Maven Compile Command

    Maven Console Log

    Example Maven Repo

    Github

    Clone the Repo

    $ git clone https://github.com/kapresoft/mvn_set_java_compiler_version.git 

    Project pom.xml

     xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"> 4.0.0 com.kapresoft.demo mvn-demo-java-compiler-version jar 1.0-SNAPSHOT mvn-demo-java-compiler-version http://maven.apache.org  1.10  $ $ UTF-8 UTF-8 3.8.0    junit junit 3.8.1 test      org.apache.maven.plugins maven-compiler-plugin $ $ $ -->    

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