[java] Ant is using wrong java version

I'm using Ant 1.7.0 and installed java 1.6 which is in JAVA_HOME.

I want to build a project using java 1.5, so I've exported JAVA_HOME to be my java 1.5 directory.

java -version

says "1.5". When I run Ant it uses java 1.6.

By default the Ant will considered the JRE as the workspace JRE version. You need to change according to your required version by following the below.

In Eclipse:

• Right click on your build.xml click "Run As", click on "External Tool Configurations..." Select tab JRE.

• Select the JRE you are using.

• Re-run the task, it should be fine now.

You can also specify in a javac task what level of compatibility ( 1.4, 1.5, 1.6 ) you want to use, you can set the "source" and "target" level values, check the docs here : Javac task documentation

In Eclipse:

• Right click on your build.xml

• click "Run As", click on "External Tool Configurations..."

• Select tab JRE. Select the JRE you are using.

Re-run the task, it should be fine now.

You can run the ant task echoproperties and look for "java.version" or ant -v and look for "Java version", e.g. on my machine

ant echoproperties | grep java.version

shows

[echoproperties] java.version=11.0.9.1

and

ant -v | grep -i "java version"

shows

Detected Java version: 11 in: /opt/java/zulu11.43.55-ca-jdk11.0.9.1-linux_x64

According to the ant manual, setting JAVA_HOME should work - are you sure the changed setting is visible to ant?

Alternatively, you could use the JAVACMD variable.

If you run Ant from eclipse, the eclipse will use jdk or jre that is configured in the class-path(build path).

According to the Ant Documentation, set JAVACMD environment variable to complete path to java.exe of the JRE version that you want to run Ant under.

Build file:

<target name="print-version"> 
   <echo>Java/JVM version: ${ant.java.version}</echo> 
   <echo>Java/JVM detail version: ${java.version}</echo> 
</target>

Output:

[echo] Java/JVM version: 1.5
[echo] Java/JVM detail version: 1.5.0_08

Set your JAVA_HOME environment variable with the required java version (in your case java 1.5), then in build.xml use executable="${JAVA_HOME}/bin/javac" inside <javac></javac> tag .

example:

<target name="java compiler" description="Compiles the java code">
    <javac executable="${JAVA_HOME}/bin/javac" srcdir="./src" 
        destdir="${build.dir}/classes"> 
    </javac> 
</target>

You can use the target and source properties on the javac tag to set a target runtime. The example below will compile any source code to target version 1.4 on any compiler that supports version 1.4 or later.

<javac compiler="classic" taskname="javac" includeAntRuntime="no" fork=" deprecation="true" target="1.4" source="1.4" srcdir="${src}" destdir="${classes}">

Note: The 'srcdir' and 'destdir' are property values set else where in the build script, e.g. <property name="classes" value="c:/classes" />

This is rather an old question, but I will add my notes for future references.

I had a similar issue and fixed it by changing the order of the exports in the PATH variable.

For example I was using a method of concatenating strings to my PATH by doing (this is just an example):

$> export PATH='$PATH:'$JAVA_HOME

If my variable PATH already had a java in it, the last value would be meaningless, thus the order would matter. To solve this I started inverting it by adding my variable first, then adding the PATH.

Following this idea I inverted the order that ANT_HOME was being exported. Adding JAVA_HOME before ANT_HOME.

This could be just a coincidence, but it worked for me.

Just had this issue, it happened because I'd first added the build file to the ant-view when the default JRE was 1.6.

There was no project-specific JRE and I changed the default to 1.5, even eclipse was running in 1.5, and JAVA_HOME was 1.5 too. Running the ant target from the command line used JRE 1.5, but within eclipse it still used 1.6.

I had to right-click the ant target, select Run As... and change the JRE under the JRE tab. This setting is remembered for subsequent runs.

Use the following 2 properties for javac tag:

fork="yes"  
executable="full-path-to-the-javac-you-want-to-use".

Explaination of the properties can be found here

If you are not using eclipse. Then you can change the ant java property directly on the file as mentioned here.

http://pissedoff-techie.blogspot.in/2014/09/ant-picks-up-incorrect-java-version.html

Run ant in verbose mode : ant -v and looks for clues.

You could achieve that with following steps, if you are using Eclipse IDE:

1. Right click on the task in your ant build file (build.xml).

2. Mouse over "Run As", click on "External Tool Configurations...".

3. Add followings to "Arguments":

   -Dant.build.javac.target=1.5 -Dant.build.javac.source=1.5
   

JAVACMD is an Ant specific environment variable. Ant doc says:

JAVACMD—full path of the Java executable. Use this to invoke a different JVM than JAVA_HOME/bin/java(.exe).

So, if your java.exe full path is: C:\Program Files\Java\jdk1.8.0_211\bin\java.exe, create a new environment variable called JAVACMD and set its value to the mentioned path (including \java.exe). Note that you need to close and reopen your terminal (cmd, Powershell, etc) so the new environment variable takes effect.