Problem

You need to modify code of a Java NetBeans project but you neither have or want to install that IDE in order to re-compile it.

Solution

Use Apache Ant to compile your Java code.

Instructions

• Create a folder (e.g. lib) in your project, at the same level of nbproject, and save all dependencies (jars) there.

  ~$ cd /path/to/your/app && mkdir lib && cp /path/to/jars lib/

• Save there also org-netbeans-modules-java-j2seproject-copylibstask.jar. This jar is required to execute NetBeans build.xml.

  • Where do I find this jar?

    Its path can be extracted from build.properties in folder nbproject

  • What if not available there?

    If you had an old version of NetBeans installed, check .netbeans/<version>/build.properties

• Create a wrapper (e.g. build-ext.xml) for NetBeans build.xml, at the same level of nbproject, to overwrite properties from the environment variables.

  For example ${platforms.nameofyourplatform.home} was defined either in nbproject/build-impl.xml or nbproject/build.properties as platforms.java

• Fill in the wrapper with something similar to the following

<?xml version="1.0"?>
<project name="BUILD-EXT" default="build-ext" basedir=".">
    <import file="build.xml"/>
    <property environment="env"/>
    <property name="platforms.java" value="${env.JAVA_HOME}" />
    <target name="build-ext" depends="default"/>
</project>

• Run ant by executing ~$ ant -Dlibs.CopyLibs.classpath=lib/org-netbeans-modules-java-j2seproject-copylibstask.jar -f build-ext.xml

  • Got error copylibs doesn't support the "excludeFromCopy" attribute?

    At line XX (specified in the error) of build-impl.xml remove setting excludeFromCopy, save and run ant command again

Sources and research material

• https://netbeans.org/bugzilla/show_bug.cgi?id=231468