Extension loading from classpath #71

moving extra classpath loading outside of the kernel startup and into the JJava.main(..) logic

Author: andrus

jjava-distro/src/main/java/org/dflib/jjava/distro/JJava.java

@@ -55,7 +55,6 @@ public static void main(String[] args) throws Exception {
                 .extensionsEnabled(Env.extensionsEnabled())
                 .startupSnippets(Env.startupSnippets())
                 .compilerOpts(Env.compilerOpts())
-                .extraClasspath(Env.extraClasspath())
                 .timeout(Env.timeout())
 
                 .lineMagic("load", new LoadCodeMagic("", ".jsh", ".jshell", ".java", ".jjava"))
@@ -72,9 +71,14 @@ public static void main(String[] args) throws Exception {
 
                 .build();
 
+        // this inits built-in Extensions
         kernel.onStartup();
-        kernel.becomeHandlerForConnection(connection);
 
+        // adds custom jars to classpath, loads Extensions from them
+        kernel.addToClasspath(Env.extraClasspath());
+
+        // connect to Jupyter
+        kernel.becomeHandlerForConnection(connection);
         connection.connect();
         connection.waitUntilClose();
     }

jjava-jupyter/src/main/java/org/dflib/jjava/jupyter/kernel/BaseKernel.java

@@ -80,7 +80,6 @@ public abstract class BaseKernel {
     protected final MagicsRegistry magicsRegistry;
     protected final Map<String, Extension> extensions;
     protected final boolean extensionsEnabled;
-    protected final String extraClasspath;
     protected final StringStyler errorStyler;
     protected final AtomicInteger executionCount;
 
@@ -96,7 +95,6 @@ protected BaseKernel(
             MagicParser magicParser,
             MagicsRegistry magicsRegistry,
             boolean extensionsEnabled,
-            String extraClasspath,
             StringStyler errorStyler) {
 
         this.name = name;
@@ -113,7 +111,6 @@ protected BaseKernel(
         this.magicParser = magicParser;
         this.magicsRegistry = magicsRegistry;
         this.extensionsEnabled = extensionsEnabled;
-        this.extraClasspath = extraClasspath;
         this.extensions = new ConcurrentHashMap<>();
         this.errorStyler = Objects.requireNonNull(errorStyler);
 
@@ -288,13 +285,6 @@ public DisplayData eval(String expr) {
     public void onStartup() {
         if (extensionsEnabled) {
             installDefaultExtensions();
-
-            if (extraClasspath != null) {
-                // TODO: ClassLoader with "extraClasspath" will inherit system classpath, so maybe if there is an
-                //  "extraClasspath", we don't need to call installDefaultExtensions() ?
-
-                installExtensionsFromClasspath(extraClasspath);
-            }
         }
     }
 

jjava-kernel/src/main/java/org/dflib/jjava/kernel/JavaKernel.java

@@ -20,6 +20,7 @@
 import org.dflib.jjava.jupyter.kernel.magic.MagicTranspiler;
 import org.dflib.jjava.jupyter.kernel.magic.MagicsRegistry;
 import org.dflib.jjava.jupyter.kernel.util.CharPredicate;
+import org.dflib.jjava.jupyter.kernel.util.PathsHandler;
 import org.dflib.jjava.jupyter.kernel.util.StringStyler;
 import org.dflib.jjava.kernel.execution.CodeEvaluator;
 import org.dflib.jjava.kernel.execution.CompilationException;
@@ -31,7 +32,6 @@
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.Objects;
 import java.util.Set;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -75,7 +75,6 @@ protected JavaKernel(
             MagicParser magicParser,
             MagicsRegistry magicsRegistry,
             boolean extensionsEnabled,
-            String extraClasspath,
             StringStyler errorStyler,
             JShell jShell,
             CodeEvaluator evaluator) {
@@ -92,7 +91,6 @@ protected JavaKernel(
                 magicParser,
                 magicsRegistry,
                 extensionsEnabled,
-                extraClasspath,
                 errorStyler);
 
         this.jShell = jShell;
@@ -105,11 +103,14 @@ protected JavaKernel(
      * @param classpath one or more filesystem paths separated by {@link java.io.File#pathSeparator}.
      */
     public void addToClasspath(String classpath) {
-        Objects.requireNonNull(classpath, "Null classpath");
-        jShell.addToClasspath(classpath);
+        if (classpath == null || classpath.isBlank()) {
+            return;
+        }
 
+        String classpathResolved = PathsHandler.joinPaths(PathsHandler.splitAndResolveGlobs(classpath));
+        jShell.addToClasspath(classpathResolved);
         if (extensionsEnabled) {
-            installExtensionsFromClasspath(classpath);
+            installExtensionsFromClasspath(classpathResolved);
         }
     }
 
@@ -379,7 +380,6 @@ public JavaKernel build() {
                     buildMagicParser(magicTranspiler),
                     buildMagicsRegistry(),
                     buildExtensionsEnabled(),
-                    buildExtraClasspath(),
                     buildErrorStyler(),
                     jShell,
                     buildCodeEvaluator(jShell, jShellExecutionControlProvider)
@@ -392,9 +392,5 @@ protected List<HelpLink> buildHelpLinks() {
                     new HelpLink("JJava homepage", "https://github.com/dflib/jjava")
             );
         }
-
-        private String buildExtraClasspath() {
-            return extraClasspath;
-        }
     }
 }

jjava-kernel/src/main/java/org/dflib/jjava/kernel/JavaKernelBuilder.java

@@ -5,11 +5,9 @@
 import org.dflib.jjava.jupyter.kernel.LanguageInfo;
 import org.dflib.jjava.jupyter.kernel.magic.MagicParser;
 import org.dflib.jjava.jupyter.kernel.magic.MagicTranspiler;
-import org.dflib.jjava.jupyter.kernel.util.PathsHandler;
 import org.dflib.jjava.kernel.execution.CodeEvaluator;
 import org.dflib.jjava.kernel.execution.JJavaExecutionControlProvider;
 
-import java.io.File;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -28,7 +26,6 @@ public abstract class JavaKernelBuilder<
     protected String timeout;
     protected final List<String> startupSnippets;
     protected final List<String> compilerOpts;
-    protected String extraClasspath;
 
     protected JavaKernelBuilder() {
         this.jShellExecControlID = UUID.randomUUID().toString();
@@ -54,16 +51,6 @@ public B compilerOpts(Iterable<String> opts) {
         return (B) this;
     }
 
-    public B extraClasspath(String classpath) {
-        if (classpath != null && !classpath.isEmpty()) {
-            this.extraClasspath = this.extraClasspath != null
-                    ? this.extraClasspath + File.pathSeparator + classpath
-                    : classpath;
-        }
-
-        return (B) this;
-    }
-
     /**
      * Sets the kernel communication timeout. The String should be a number with a {@link java.util.concurrent.TimeUnit}
      * name. E.g. "30 SECONDS"
@@ -85,24 +72,13 @@ protected JShell buildJShell(JJavaExecutionControlProvider jShellExecControlProv
             execControlParams.put(JJavaExecutionControlProvider.TIMEOUT_KEY, timeout);
         }
 
-        JShell shell = JShell.builder()
+        return JShell.builder()
                 .out(System.out)
                 .err(System.err)
                 .in(System.in)
                 .executionEngine(jShellExecControlProvider, execControlParams)
                 .compilerOptions(compilerOpts.toArray(new String[0]))
                 .build();
-
-        if (extraClasspath != null) {
-
-            String extraClasspathResolved = PathsHandler.joinPaths(PathsHandler.splitAndResolveGlobs(extraClasspath));
-
-            // TODO: not loading JJava extensions from classpath here.
-            //  Is this the cause of https://github.com/dflib/jjava/issues/71 ?
-            shell.addToClasspath(extraClasspathResolved);
-        }
-
-        return shell;
     }
 
     protected CodeEvaluator buildCodeEvaluator(JShell jShell, JJavaExecutionControlProvider jShellExecControlProvider) {

jjava-kernel/src/test/java/org/dflib/jjava/kernel/ExtensionsLifecycleTest.java

@@ -39,27 +39,29 @@ void extraClasspathExtensions() throws Exception {
         String extraClasspath = PathsHandler.joinPaths(PathsHandler.resolveGlobs(jar.toAbsolutePath().toString()));
 
         String extensionClassName = "org.dflib.jjava.kernel.test.TestExtension";
-        String installationsProperty = extensionInstallationsProperty(extensionClassName);
-        System.clearProperty(installationsProperty);
+        String extInstalledProp = extensionInstallationsProperty(extensionClassName);
+        System.clearProperty(extInstalledProp);
 
         JavaKernel kernel = JavaKernel
                 .builder()
                 .name("TestKernel")
-                .extraClasspath(extraClasspath)
                 .build();
         try {
             kernel.onStartup();
-            assertEquals("1", System.getProperty(installationsProperty), "Custom extension was not installed");
             assertNotNull(JavaNotebookStatics.kernel, "Built-in extension was not installed");
+            assertNull(System.getProperty(extInstalledProp), "Custom extension should not be installed yet");
 
             kernel.addToClasspath(extraClasspath);
-            assertEquals("1", System.getProperty(installationsProperty));
+            assertEquals("1", System.getProperty(extInstalledProp), "Custom extension was not installed");
+
+            kernel.addToClasspath(extraClasspath);
+            assertEquals("1", System.getProperty(extInstalledProp), "Custom extension was installed more than once?");
         } finally {
             kernel.onShutdown(false);
         }
 
         assertNull(JavaNotebookStatics.kernel);
-        assertNull(System.getProperty(installationsProperty));
+        assertNull(System.getProperty(extInstalledProp));
     }
 
     private static String extensionInstallationsProperty(String className) {