Could not initialize class sun.awt.X11GraphicsEnvironment for frevvo module in Oracle® BPM Suite 12.2.1

The problem

BPM Composer in Oracle® BPM Suite 12.2.1 fails when open enterprise maps, and the SOA server's out file says:

<Mar 1, 2016 7:31:43 AM UTC> <Error> <HTTP> <BEA-101017> <[ServletContext@881844748[app:frevvo module:/frevvo path:null spec-version:3.1]] Root cause of ServletException.

java.lang.NoClassDefFoundError: Could not initialize class sun.awt.X11GraphicsEnvironment

    at java.lang.Class.forName0(Native Method)

    at java.lang.Class.forName(Class.java:264)

    at java.awt.GraphicsEnvironment.createGE(GraphicsEnvironment.java:103)

    at java.awt.GraphicsEnvironment.getLocalGraphicsEnvironment(GraphicsEnvironment.java:82)

    at sun.awt.X11FontManager.isHeadless(X11FontManager.java:511)

    Truncated. see log file for complete stacktrace

>

The cause

The JVM was not running headless, and it did not have a DISPLAY variable set to point to a X server.

The solution

Added -Djava.awt.headless=true to the soa server, and restarted it.