Pass classpath by environment variable

HMCL/src/main/java/org/jackhuang/hmcl/game/LauncherHelper.java

@@ -621,6 +621,11 @@ public final class LauncherHelper {
 
             LOG.info("Launched process: " + command);
 
+            String classpath = process.getClasspath();
+            if (classpath != null) {
+                LOG.info("Process CLASSPATH: " + classpath);
+            }
+
             if (showLogs)
                 Platform.runLater(() -> {
                     logWindow = new LogWindow();

HMCLCore/src/main/java/org/jackhuang/hmcl/launch/DefaultLauncher.java

@@ -354,7 +354,7 @@ public class DefaultLauncher extends Launcher {
 
     @Override
     public ManagedProcess launch() throws IOException, InterruptedException {
-        File nativeFolder = null;
+        File nativeFolder;
         if (options.getNativesDirType() == NativesDirectoryType.VERSION_FOLDER) {
             nativeFolder = repository.getNativeDirectory(version.getId(), options.getJava().getPlatform());
         } else {
@@ -362,7 +362,15 @@ public class DefaultLauncher extends Launcher {
         }
 
         // To guarantee that when failed to generate launch command line, we will not call pre-launch command
-        List<String> rawCommandLine = generateCommandLine(nativeFolder).asList();
+        List<String> rawCommandLine = generateCommandLine(nativeFolder).asMutableList();
+
+        // Pass classpath using the environment variable, to reduce the command length
+        String classpath = null;
+        final int cpIndex = rawCommandLine.indexOf("-cp");
+        if (cpIndex >= 0 && cpIndex < rawCommandLine.size() - 1) {
+            rawCommandLine.remove(cpIndex); // remove "-cp"
+            classpath = rawCommandLine.remove(cpIndex);
+        }
 
         if (rawCommandLine.stream().anyMatch(StringUtils::isBlank)) {
             throw new IllegalStateException("Illegal command line " + rawCommandLine);
@@ -388,13 +396,14 @@ public class DefaultLauncher extends Launcher {
             }
             String appdata = options.getGameDir().getAbsoluteFile().getParent();
             if (appdata != null) builder.environment().put("APPDATA", appdata);
+            if (classpath != null) builder.environment().put("CLASSPATH", classpath);
             builder.environment().putAll(getEnvVars());
             process = builder.start();
         } catch (IOException e) {
             throw new ProcessCreationException(e);
         }
 
-        ManagedProcess p = new ManagedProcess(process, rawCommandLine);
+        ManagedProcess p = new ManagedProcess(process, rawCommandLine, classpath);
         if (listener != null)
             startMonitors(p, listener, daemon);
         return p;

HMCLCore/src/main/java/org/jackhuang/hmcl/util/platform/CommandBuilder.java

@@ -146,6 +146,10 @@ public final class CommandBuilder {
         return raw.stream().map(i -> i.arg).collect(Collectors.toList());
     }
 
+    public List<String> asMutableList() {
+        return raw.stream().map(i -> i.arg).collect(Collectors.toCollection(ArrayList::new));
+    }
+
     private static class Item {
         String arg;
         boolean parse;

HMCLCore/src/main/java/org/jackhuang/hmcl/util/platform/ManagedProcess.java

@@ -31,6 +31,7 @@ public class ManagedProcess {
 
     private final Process process;
     private final List<String> commands;
+    private final String classpath;
     private final Map<String, Object> properties = new HashMap<>();
     private final Queue<String> lines = new ConcurrentLinkedQueue<>();
     private final List<Thread> relatedThreads = new LinkedList<>();
@@ -44,6 +45,20 @@ public class ManagedProcess {
     public ManagedProcess(Process process, List<String> commands) {
         this.process = process;
         this.commands = Collections.unmodifiableList(new ArrayList<>(commands));
+        this.classpath = null;
+    }
+
+    /**
+     * Constructor.
+     *
+     * @param process the raw system process that this instance manages.
+     * @param commands the command line of {@code process}.
+     * @param classpath the classpath of java process
+     */
+    public ManagedProcess(Process process, List<String> commands, String classpath) {
+        this.process = process;
+        this.commands = Collections.unmodifiableList(new ArrayList<>(commands));
+        this.classpath = classpath;
     }
 
     /**
@@ -64,6 +79,15 @@ public class ManagedProcess {
         return commands;
     }
 
+    /**
+     * The classpath.
+     *
+     * @return classpath
+     */
+    public String getClasspath() {
+        return classpath;
+    }
+
     /**
      * To save some information you need.
      */