JavaOne – Project Jigsaw – Integration with Tools

“Project Jigsaw – Integration with Tools”

Speaker: Alexandru Jecan (author of Java 9 Modularity Revealed)

For more blog posts from JavaOne, see the table of contents


What expect build tools and IDEs to do

  • Code completion (IDEs only)
  • Make things easier
  • Work with class path and module path

Maven

  • Only Maven 3+ supports Java 9.
  • No changes to Maven core to run on Java 9
  • presence of module-info.java decides if Maven uses module path
  • Need Maven compiler plugin 3.6.1 to compile Java 9 code
  • Discourages using automatic module name
  • GAV not related to module name. Continue to use GAV.
  • Use module name in module-info.java – double work
  • Maven does not generate “requires” clauses for module-info.java
  • Can add <compilerArgs> options for -add-modules or -add-exports
  • New tag <release> which takes precedence over source/target tags. Recomended compiling twice or backward compatbility. once for java 9 modules and once for java 8. [why? isn’t that what multi release ars are for?]
  • maven-exec-plugin – can configure module path
  • taked abut updating maven toolchain file [not clear how this differs than prior versions of java]
  • maven-jdeps-plugin – can automatically generate module descriptor [but said earlier couldn’t]
  • maven-jmod-plugin – new plugin; not yet released. Creates and lists content of jmod files. Merge native code into jar
  • maven-jlink-plugin – new plugin; not yet released. Creates runtime images
  • maven-depdendency-plugin – said lists GAV [not clear how changed

Gradle
No first class support for Java 9 yet. Coming soon. [but said using; puzled?]

Ant
Ant 1.9.8+ support JDK 9 modules for java/javac/junit. [yet Ant doesn’t support JUnit 5]

Loom

  • New build tool for Java 9
  • Uses YAML config. Uses Maaven repo.
  • Supports JUnit 5,

loom.builders

Moditect
Maven plugin that generates module-info.java based on dependencies. Says helps a little but doesn’t do all the work. [how?]

SonarJava
SonarJava 4.11+ recognizes module keywords

Graphviz
Open source visualization software
Reads jdeps input to generate graphical representation of Jigsaw. As can IDES

IDEs

  • NetBeans, Eclipse and IntelliJ all understand modules clauses [if you count pre-release versions]
  • Also offer autocompletion, syntax higlighting, etc
  • NetBeans 9 – not yet released; must build yourself. Showed editing module path, visual of module dependencies, jshell, jlink
  • Eclipse Oxygen with Java 9 support – came out 9/27/17. Ten second demo
  • IntelliJ 2017.1+ – Mark directory as source root so directory name matches module name. Errors on common module errors, Showed module editing, module dependencies and other features

Open source readiness

How to modularize your app

  • Introduce modue-info.java by creating manually or running jdeps to generate
  • Problems: using JDK internal APIs (ignore warning or fix), using odule not availalbe such as xml bindings (add-modules at compile and runtime), cyclic dependencies (can have at runtime but not compile time), split packages (Oracle plans to make change in later version of Java to deal with this)
  • [Note: He recommended renaming packags as a solution to spit packages. That sounds like a horrible idea unless you can guarantee only you call that code]

    My take before session: You know how they say that first impressions matter? The speaker is wearing a suit. 90% of the people in the room are wearing jeans. Two people in the room are wearing a suit The speaker and someone he knows. Then he showed the table of contents. There are 29 points in 45 minutes in the outline. Preparing to have my head spin!

    My take after session: He is in fact technical. The suit was misleading! The pace was way too fast though; drinking from a fire hose. Not enough time to understand/process many of the points. He talks fast (as do I), but key is to *pause* if you talk fast so people can catch up. Also the side transitions were distracting. A cube transition is cute. But if you are reading when it moves, it is disorienting. And due to the speed, there was a good chance of being reading when transitions started. This was good information, but should have been two sessions so split up and a decent pace. And omiting how to migrate your libraries; that’s a talk on its own There is a Maven BOF tonight; maybe folks can discuss more then!

    One minute after the official end time, he asked if there were questions. My head was spinning with questions. [I didn’t even have time to process which was most important]. Another attendee asked if having JUnit tests in a parallel directory with the same package name is a split package. The speaker said yes and went on to say to wait for Java 10 or rename. I interjected at that point. Unless you are distributing a test jar, I don’t think this is a problem. In fact, most IDEs compile both the /src/main/java and /test/main/java directories to the same folder. I stated this and asked the speaker if he agreed. He said yes.

ant vs java – using ** to match directories

Suppose I have the following files:
/MyFiles/dir/a.txt
/MyFiles/dir/child/b.txt

In Ant, this is how you write code to output all text files in any subdirectory of a “dir” directory.

<fileset id="jb" dir="/MyFiles">
  <include name="**/dir/**/*.txt" />
</fileset>

<pathconvert pathsep="${line.separator}" property="out" refid="jb"/>
<echo>${out}</echo>

In Java, the equivalent is

public class MyPathMatcher extends SimpleFileVisitor<Path> {
  private PathMatcher matcher =
     FileSystems.getDefault().getPathMatcher( "glob:**/dir/**.txt");

 @Override
 public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
   if (matcher.matches(file)) {
     System.out.println("File " + file);
   }
   return FileVisitResult.CONTINUE;
 }

  public static void main(String[] args) throws Exception {
    MyPathMatcher dirs = new MyPathMatcher();
    Files.walkFileTree(Paths.get("/MyFiles"), dirs);
   }
}

The Java documentation says “Two asterisks, **, works like * but crosses directory boundaries. This syntax is generally used for matching complete paths”. Whereas in the Ant documentation, “When ** is used as the name of a directory in the pattern, it matches zero or more directories.”

The Ant approach probably feels more natural to me because I’ve been using it longer. But the Java approach seems more logical because it doesn’t have the extra slash that doesn’t actually get matched.

upgrading to mavericks – problems including broke eclipse/ant java for jmockit – and how to fix

I didn’t upgrade to Mavericks right away because I was getting FIOS.  If there were internet problems, I wanted to know they were Verizon’s fault and not be in a position where they could claim it was my computer’s problem.  I’ve had Mavericks long enough that I can write about the experience.

The problems describe here:

  • git
  • Eclipse/Java/Ant/JMockIt
  • OpenOffice crashing

How long it took

Not counting the download, the install took 2 hours.  Much of which was Apple saying there were “17 minutes” left.  I left it alone and it didn’t finish though.  I’ve seen reports of significantly faster installs though.

Problem #1 – git

The first problem I ran into was the error message The “git” command requires the command line developer tools.  Not a big deal.  It was a two minute install.  I was just surprised as I was expecting what was installed before the upgrade to  be installed after.

Problem #2 – Java and Eclipse

And now for the meat of this.  Being able to develop again in Eclipse was by no means seemless.

Error: Ant can’t find Java

Exact message: Specified VM install not found: type MacOS X VM, name Java SE 6 (MacOS X Default)

Solution – for each Ant build:

  • Run > External Tools Configuration
  • Run in same JRE as the workspace

Error: JUnit tests don’t run in Eclipse view

When running from Eclipse, I got the stack trace:


java.lang.IllegalStateException: Unable to load Java agent; please add lib/tools.jar from your JDK to the classpath

at mockit.internal.startup.JDK6AgentLoader.getVirtualMachineImplementationFromEmbeddedOnes(JDK6AgentLoader.java:102)

at mockit.internal.startup.JDK6AgentLoader.loadAgent(JDK6AgentLoader.java:74)

at mockit.internal.startup.AgentInitialization.initializeAccordingToJDKVersion(AgentInitialization.java:41)

at mockit.internal.startup.Startup.initializeIfNeeded(Startup.java:271)

at org.junit.runner.Runner.<clinit>(Runner.java:25)

at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)

at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)

at java.lang.reflect.Constructor.newInstance(Constructor.java:525)

at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:35)

at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:24)

at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:57)

at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:29)

at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:57)

at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:24)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.<init>(JUnit4TestReference.java:33)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestClassReference.<init>(JUnit4TestClassReference.java:25)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.createTest(JUnit4TestLoader.java:48)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.loadTests(JUnit4TestLoader.java:38)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:452)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

java.lang.NoClassDefFoundError: org.junit.runner.Runner

at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)

at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:24)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.<init>(JUnit4TestReference.java:33)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestClassReference.<init>(JUnit4TestClassReference.java:25)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.createTest(JUnit4TestLoader.java:48)

at org.eclipse.jdt.internal.junit4.runner.JUnit4TestLoader.loadTests(JUnit4TestLoader.java:38)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:452)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)

at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

Solution:

First I tried switching creating a new installed JVM of type MacOS X JVM.  That didn’t help directly.  I left it like that since I didn’t want to muck around with my original configuration.  Then I added tools.jar to the installed JRE.

  1. Eclipse > Preferences
  2. Java > Installed JREs
  3. Click target JRE
  4. Edit
  5. Add external jars
  6. Add  /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/lib/tools.jar

Warning: The first time I tried this procedure, Eclipse hung.  I had it to kill it.  When I opened my workspace, I saw “unable to load plugin x” in every single view.  I used Time Machine to restore to before I tried changing the JREs and then re-did that change.  The second time it was successful.

I could have added tools.jar to my classpath for the project instead.  I choose not to because I was hoping updating it in the JVM install would solve the Ant problem (described below) as well.  It didn’t.  I also didn’t want to change the project .classpath as that is shared in Subversion and I didn’t want to make a change that affects others.

This whole exercise felt like a hack until I read the JMockIt instructions.  This leads me to believe I was running with a different JDK before the Mavericks upgrade.

If you are developing on a JDK of version 1.6 or newer on Mac OS X, add <jdkDir>/lib/tools.jar to the classpath, where <jdkDir> is the home directory for your local JDK 1.6 installation.

Error: JUnit tests don’t run from Ant

When running from Ant, every test failed with:

Caused an ERROR</span>
<pre>
null

java.lang.reflect.InvocationTargetException

at java.lang.reflect.Constructor.newInstance(Constructor.java:525)

What I learned:

  • I tried setting JAVA_HOME at the command line to no avail.  I confirmed javac is on the path. (/usr/bin/javac); it was.
  • I tried adding tools.jar to the classpath in launch configuration in Eclipse for running Ant.
  • If I change to fork=”no” in the <junit> task in the Ant script, most of the tests pass.  (Some of them require the JVM be forked which is why it was in the first place.) Showing the problem is when a new JVM is created, it doesn’t inherit the tools.jar from the previous step.
  • If I hard code the classpath entry for tools.jar in the Ant build file, all of the tests pass.

Solution:

If you need to fork the JVM, add the following insider you <junit> task.

<classpath location="/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/lib/tools222.jar" />

I don’t like this solution.  I also didn’t like the hack for Eclipse so my unease is pretty uniform here.  Luckily Ant doesn’t choke if you include a file (or disk or filesystem) in the classpath that doesn’t exist.  Which means this won’t hurt others working on the same project.

Problem #3 – Open Office crashes when opening a document

The solution was to upgrade from Open Office 3.3.0 to the latest (4)

My favorite new feature

It’s a minor one, but I like the feature to synchronization of “Read Later” between my Mac and iPad.  (I haven’t tried it yet so it may not be that nice in practice.)  Most of the new features are things I don’t need.