As of fall 2024, the following version constraints are known.
No version of Java before 9 is supported. The PL/Java code makes use of Java features first appearing in Java 9.
As for later versions of Java, backward compatibility in the language is generally good. Before Java 8, most likely problem areas with a new Java version tended to be additions to the JDBC API that PL/Java had not yet implemented. Since Java 8, even JDBC additions have not caused problems for existing PL/Java code, as they have taken advantage of the default-methods feature introduced in that release.
In the PL/Java 1.6.x series, the build can be done with Java 9 or newer.
Once built, PL/Java is able to use another Java 9 or later JVM at run time,
simply by setting
the pljava.libjvm_location variable to the desired version's library.
PL/Java can run application code written for a later Java version than PL/Java itself was built with, as long as that later JRE version is used at run time. That also allows PL/Java to take advantage of recent Java implementation advances such as class data sharing.
Some builds of Java 20 are affected by a bug, JDK-8309515. PL/Java will report an error if it detects it is affected by that bug, and the solution can be to use a Java version earlier than 20, or one recent enough to have the bug fixed. The bug was fixed in Java 21.
PL/Java has been successfully used with Oracle Java and with OpenJDK, which is available with either the Hotspot or the OpenJ9 JVM. It can also be built and used with GraalVM.
If building with GraalVM, please add -Dpolyglot.js.nashorn-compat=true on
the mvn command line.
PL/Java can be built with Maven versions as far back as 3.5.2. Maven's requirements can be seen in the Maven release history.
If you are building on a platform where gcc is the compiler,
versions 4.3.0 or later are recommended in order to avoid a
sea of unhelpful compiler messages.
The PL/Java 1.6 series does not support PostgreSQL earlier than 9.5.
More current PostgreSQL versions, naturally, are the focus of development and receive more attention in testing.
PL/Java 1.6.8 has been successfully built and run on at least one platform with PostgreSQL versions from 17 to 9.5, the latest maintenance release for each.