Allow for task-controlled modification of streams

build.gradle

@@ -130,6 +130,24 @@ dependencies {
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 }
 
+jar {
+    manifest {
+        attributes(
+            'Automatic-Module-Name': 'dev.lukebemish.forkedtaskexecutor'
+        )
+    }
+}
+
+
+
+runnerJar {
+    manifest {
+        attributes(
+            'Automatic-Module-Name': 'dev.lukebemish.forkedtaskexecutor.runner'
+        )
+    }
+}
+
 testing {
     suites {
         def action = { suite ->

src/runner/java/dev/lukebemish/forkedtaskexecutor/runner/Main.java

@@ -3,6 +3,8 @@
 import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.io.IOException;
+import java.io.InputStream;
+import java.io.PrintStream;
 import java.lang.reflect.Constructor;
 import java.net.ServerSocket;
 import java.net.Socket;
@@ -22,6 +24,10 @@ private Main(Task task) throws IOException {
         this.socket = new ServerSocket(0);
     }
 
+    private static final PrintStream OUT = System.out;
+    private static final PrintStream ERR = System.err;
+    private static final InputStream IN = System.in;
+
     public static void main(String[] args) {
         try {
             Class<?> taskClass = Class.forName(args[0], false, Main.class.getClassLoader());
@@ -32,6 +38,11 @@ public static void main(String[] args) {
             String[] otherArgs = new String[args.length - 1];
             System.arraycopy(args, 1, otherArgs, 0, otherArgs.length);
             var task = (Task) constructor.newInstance((Object) otherArgs);
+
+            System.setOut(task.replaceSystemOut(OUT));
+            System.setErr(task.replaceSystemErr(ERR));
+            System.setIn(task.replaceSystemIn(IN));
+
             try (Main runner = new Main(task)) {
                 runner.run();
             }
@@ -44,7 +55,7 @@ public static void main(String[] args) {
 
     private void run() throws IOException {
         // This tells the parent process what port we're listening on
-        System.out.println(socket.getLocalPort());
+        OUT.println(socket.getLocalPort());
         var socket = this.socket.accept();
         // Communication back to the parent is done through this handle, which ensures synchronization on the output stream.
         var socketHandle = new SocketHandle(socket);
@@ -93,9 +104,9 @@ public void close() throws IOException, TimeoutException {
 
     private static void logException(Throwable t) {
         if (STACKTRACE) {
-            t.printStackTrace(System.err);
+            t.printStackTrace(ERR);
         } else {
-            System.err.println(t);
+            ERR.println(t);
         }
     }
 

src/runner/java/dev/lukebemish/forkedtaskexecutor/runner/Task.java

@@ -1,5 +1,20 @@
 package dev.lukebemish.forkedtaskexecutor.runner;
 
+import java.io.InputStream;
+import java.io.PrintStream;
+
 public interface Task {
     byte[] run(byte[] input) throws Exception;
+
+    default PrintStream replaceSystemOut(PrintStream out) {
+        return out;
+    }
+
+    default InputStream replaceSystemIn(InputStream in) {
+        return in;
+    }
+
+    default PrintStream replaceSystemErr(PrintStream err) {
+        return err;
+    }
 }