Use syscall.Exec() on compatible operating systems

Author: rmichela

canteen/README.md

@@ -93,5 +93,6 @@ The `canteen-maven-plugin` uses the same technique to prepend a simple platform
 cross-compiled with Go to the front of a jar.
 
 When you execute a Canteen packaged jar, the bootstrap program captures all the command line arguments and the name
-of the current file. It then spawns a child process as `java -jar $args`, proxying `stdin`, `stdout`, and `stderr`
-between the shell and the child process.
+of the current file. On Windows, the bootstrap spawns a child process as `java -jar $args`, proxying `stdin`, `stdout`,
+and `stderr` between the shell and the child process. On Linux and MacOS, the bootstrap transfers process control to
+Java by invoking `syscall.Exec()`;

canteen/canteen-bootstrap/README.md

@@ -1,17 +1,18 @@
 # Canteen Bootstrap
 
 This module contains the golang bootstrap shim used to invoke `java -jar`. The shim tries to be transparent. It passes
-all command line arguments to the child process, so you can use it as if it were the Java process itself.
+all command line arguments to the java process, so you can use it as if you invoked Java itself.
 
-Once the bootstrap is running, stdin, stdout, and stderr are proxied to the child process. When the child process
-exits, the bootstrap assumes the child's exit code. At the moment, the bootstrap does not proxy signals between the
-shell and the child process.
+On Linux and MacOS, the bootstrap invokes `syscall.Exec()`, transparently transferring control of the process to Java.
+
+On Windows, once the bootstrap is running, stdin, stdout, and stderr are proxied to the child process. When the child
+process exits, the bootstrap assumes the child's exit code. At the moment, the bootstrap does not proxy signals between
+the shell and the child process.
 
 The bootstrap is cross-compiled for 64-bit Linux, MacOS, and Windows as part of the Maven build and attached as
 additional artifacts with classifiers compatible with the [os-maven-plugin](https://github.com/trustin/os-maven-plugin).
 
 ## Improvements
 
-* Propagate signals to and from child process
 * More platforms
 * More architectures

canteen/canteen-bootstrap/src/main/go/main.go

@@ -11,6 +11,7 @@ import (
 	"log"
 	"os"
 	"os/exec"
+	"runtime"
 	"strings"
 	"syscall"
 )
@@ -27,19 +28,26 @@ func main() {
 	args := []string{"-jar", strings.TrimPrefix(jarName, "./")}
 	args = append(args, jarArgs...)
 
-	cmd := exec.Command(binary, args...)
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-	cmd.Stdin = os.Stdin
+	if runtime.GOOS == "windows" {
+		cmd := exec.Command(binary, args...)
+		cmd.Stdout = os.Stdout
+		cmd.Stderr = os.Stderr
+		cmd.Stdin = os.Stdin
 
-	if err := cmd.Run(); err != nil {
-		if err, ok := err.(*exec.ExitError); ok {
-			if status, ok := err.Sys().(syscall.WaitStatus); ok {
-				// Exit with the same code as the Java program
-				os.Exit(status.ExitStatus())
+		if err := cmd.Run(); err != nil {
+			if err, ok := err.(*exec.ExitError); ok {
+				if status, ok := err.Sys().(syscall.WaitStatus); ok {
+					// Exit with the same code as the Java program
+					os.Exit(status.ExitStatus())
+				}
+			} else {
+				log.Fatalf("Bootstrap execution error: %v", err)
 			}
-		} else {
-			log.Fatalf("Bootstrap execution error: %v", err)
+		}
+	} else {
+		err = syscall.Exec(binary, append([]string{"java"}, args...), nil)
+		if err != nil {
+			log.Fatalf("Bootstrap execution error: %v", os.Environ())
 		}
 	}
 }