support for building plain Java jars from Go projects

bind/genjava.go

@@ -1713,7 +1713,6 @@ import go.Seq;
 //
 //   autogenerated by gobind %[1]s %[2]s
 
-#include <android/log.h>
 #include <stdint.h>
 #include "seq.h"
 #include "_cgo_export.h"

bind/java/NativeUtils.java

@@ -0,0 +1,142 @@
+/*
+ * Class NativeUtils is published under the The MIT License:
+ *
+ * Copyright (c) 2012 Adam Heinrich <[email protected]>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package go;
+
+import java.io.*;
+import java.nio.file.FileSystemNotFoundException;
+import java.nio.file.FileSystems;
+import java.nio.file.Files;
+import java.nio.file.ProviderNotFoundException;
+import java.nio.file.StandardCopyOption;
+
+/**
+ * A simple library class which helps with loading dynamic libraries stored in the
+ * JAR archive. These libraries usually contain implementation of some methods in
+ * native code (using JNI - Java Native Interface).
+ * 
+ * @see <a href="http://adamheinrich.com/blog/2012/how-to-load-native-jni-library-from-jar">http://adamheinrich.com/blog/2012/how-to-load-native-jni-library-from-jar</a>
+ * @see <a href="https://github.com/adamheinrich/native-utils">https://github.com/adamheinrich/native-utils</a>
+ *
+ */
+public class NativeUtils {
+
+    /**
+     * The minimum length a prefix for a file has to have according to {@link File#createTempFile(String, String)}}.
+     */
+    private static final int MIN_PREFIX_LENGTH = 3;
+    public static final String NATIVE_FOLDER_PATH_PREFIX = "nativeutils";
+
+    /**
+     * Temporary directory which will contain the DLLs.
+     */
+    private static File temporaryDir;
+
+    /**
+     * Private constructor - this class will never be instanced
+     */
+    private NativeUtils() {
+    }
+
+    /**
+     * Loads library from current JAR archive
+     * 
+     * The file from JAR is copied into system temporary directory and then loaded. The temporary file is deleted after
+     * exiting.
+     * Method uses String as filename because the pathname is "abstract", not system-dependent.
+     * 
+     * @param path The path of file inside JAR as absolute path (beginning with '/'), e.g. /package/File.ext
+     * @throws IOException If temporary file creation or read/write operation fails
+     * @throws IllegalArgumentException If source file (param path) does not exist
+     * @throws IllegalArgumentException If the path is not absolute or if the filename is shorter than three characters
+     * (restriction of {@link File#createTempFile(java.lang.String, java.lang.String)}).
+     * @throws FileNotFoundException If the file could not be found inside the JAR.
+     */
+    public static void loadLibraryFromJar(String path) throws IOException {
+
+        if (null == path || !path.startsWith("/")) {
+            throw new IllegalArgumentException("The path has to be absolute (start with '/').");
+        }
+
+        // Obtain filename from path
+        String[] parts = path.split("/");
+        String filename = (parts.length > 1) ? parts[parts.length - 1] : null;
+
+        // Check if the filename is okay
+        if (filename == null || filename.length() < MIN_PREFIX_LENGTH) {
+            throw new IllegalArgumentException("The filename has to be at least 3 characters long.");
+        }
+
+        // Prepare temporary file
+        if (temporaryDir == null) {
+            temporaryDir = createTempDirectory(NATIVE_FOLDER_PATH_PREFIX);
+            temporaryDir.deleteOnExit();
+        }
+
+        File temp = new File(temporaryDir, filename);
+
+        try (InputStream is = NativeUtils.class.getResourceAsStream(path)) {
+            Files.copy(is, temp.toPath(), StandardCopyOption.REPLACE_EXISTING);
+        } catch (IOException e) {
+            temp.delete();
+            throw e;
+        } catch (NullPointerException e) {
+            temp.delete();
+            throw new FileNotFoundException("File " + path + " was not found inside JAR.");
+        }
+
+        try {
+            System.load(temp.getAbsolutePath());
+        } finally {
+            if (isPosixCompliant()) {
+                // Assume POSIX compliant file system, can be deleted after loading
+                temp.delete();
+            } else {
+                // Assume non-POSIX, and don't delete until last file descriptor closed
+                temp.deleteOnExit();
+            }
+        }
+    }
+
+    private static boolean isPosixCompliant() {
+        try {
+            return FileSystems.getDefault()
+                    .supportedFileAttributeViews()
+                    .contains("posix");
+        } catch (FileSystemNotFoundException
+                | ProviderNotFoundException
+                | SecurityException e) {
+            return false;
+        }
+    }
+
+    private static File createTempDirectory(String prefix) throws IOException {
+        String tempDir = System.getProperty("java.io.tmpdir");
+        File generatedDir = new File(tempDir, prefix + System.nanoTime());
+
+        if (!generatedDir.mkdir())
+            throw new IOException("Failed to create temp directory " + generatedDir.getName());
+
+        return generatedDir;
+    }
+}

bind/java/Seq.java

@@ -4,7 +4,7 @@
 
 package go;
 
-import android.content.Context;
+// import android.content.Context;
 
 import java.lang.ref.PhantomReference;
 import java.lang.ref.Reference;
@@ -34,15 +34,30 @@ public class Seq {
 	private static final GoRefQueue goRefQueue = new GoRefQueue();
 
 	static {
-		System.loadLibrary("gojni");
+		if ("The Android Project".equals(System.getProperty("java.vendor"))) {
+			System.loadLibrary("gojni");
+		} else {
+			String arch = System.getProperty("os.arch");
+			if ("aarch64".equals(arch)) {
+				arch = "arm64";
+			} else if ("x86_64".equals(arch)) {
+				arch = "amd64";
+			}
+			try {
+				NativeUtils.loadLibraryFromJar("/jniLibs/" + arch + "/libgojni.so");
+			} catch (Exception e) {
+				throw new RuntimeException(e);
+			}
+		}
 		init();
 		Universe.touch();
 	}
 
+	// TODO we probably need to make this file go templatable, to support plain JVM and Android better.
 	// setContext sets the context in the go-library to be used in RunOnJvm.
-	public static void setContext(Context context) {
-		setContext((java.lang.Object)context);
-	}
+	// public static void setContext(Context context) {
+	// 	setContext((java.lang.Object)context);
+	// }
 
 	private static native void init();
 

bind/java/context_android.c

@@ -3,7 +3,7 @@
 // license that can be found in the LICENSE file.
 
 #include <jni.h>
-#include "seq_android.h"
+#include "seq_java.h"
 #include "_cgo_export.h"
 
 JNIEXPORT void JNICALL

bind/java/seq_android.c.support

@@ -6,7 +6,6 @@
 // generated gomobile_bind package and compiled along with the
 // generated binding files.
 
-#include <android/log.h>
 #include <errno.h>
 #include <jni.h>
 #include <stdint.h>
@@ -19,6 +18,12 @@
 
 #define NULL_REFNUM 41
 
+#ifndef __GOBIND_ANDROID__
+#define ACT_ENV_CAST (void**)
+#else
+#define ACT_ENV_CAST
+#endif
+
 // initClasses are only exported from Go if reverse bindings are used.
 // If they're not, weakly define a no-op function.
 __attribute__((weak)) void initClasses(void) { }
@@ -55,7 +60,7 @@ static JNIEnv *go_seq_get_thread_env(void) {
 		if (ret != JNI_EDETACHED) {
 			LOG_FATAL("failed to get thread env");
 		}
-		if ((*jvm)->AttachCurrentThread(jvm, &env, NULL) != JNI_OK) {
+		if ((*jvm)->AttachCurrentThread(jvm, ACT_ENV_CAST &env, NULL) != JNI_OK) {
 			LOG_FATAL("failed to attach current thread");
 		}
 		pthread_setspecific(jnienvs, env);

bind/java/seq_android.go.support

@@ -9,11 +9,11 @@ package main
 // files.
 
 //#cgo CFLAGS: -Werror
-//#cgo LDFLAGS: -llog
+//#cgo android LDFLAGS: -llog
 //#include <jni.h>
 //#include <stdint.h>
 //#include <stdlib.h>
-//#include "seq_android.h"
+//#include "seq_java.h"
 import "C"
 import (
 	"unsafe"

bind/java/seq_android.h

@@ -6,18 +6,32 @@
 #define __GO_SEQ_ANDROID_HDR__
 
 #include <stdint.h>
-#include <android/log.h>
 // For abort()
 #include <stdlib.h>
 #include <jni.h>
 
+#ifdef __GOBIND_ANDROID__
+
+#include <android/log.h>
+
 #define LOG_INFO(...) __android_log_print(ANDROID_LOG_INFO, "go/Seq", __VA_ARGS__)
 #define LOG_FATAL(...)                                             \
   {                                                                \
     __android_log_print(ANDROID_LOG_FATAL, "go/Seq", __VA_ARGS__); \
     abort();                                                       \
   }
 
+#else
+
+#define LOG_INFO(...) printf(__VA_ARGS__)
+#define LOG_FATAL(...)            \
+  {                               \
+    fprintf(stderr, __VA_ARGS__); \
+    abort();                      \
+  }
+
+#endif
+
 // Platform specific types
 typedef struct nstring {
 	// UTF16 or UTF8 Encoded string. When converting from Java string to Go

bind/seq.go.support

@@ -9,6 +9,7 @@ package main
 // with the bindings.
 
 // #cgo android CFLAGS: -D__GOBIND_ANDROID__
+// #cgo java CFLAGS: -D__GOBIND_JAVA__
 // #cgo darwin CFLAGS: -D__GOBIND_DARWIN__
 // #include <stdlib.h>
 // #include "seq.h"

cmd/gobind/gen.go

@@ -69,12 +69,12 @@ func genPkg(lang string, p *types.Package, astFiles []*ast.File, allPkg []*types
 			closer()
 		}
 		buf.Reset()
-		w, closer = writer(filepath.Join("src", "gobind", pname+"_android.c"))
+		w, closer = writer(filepath.Join("src", "gobind", pname+"_java.c"))
 		processErr(g.GenC())
 		io.Copy(w, &buf)
 		closer()
 		buf.Reset()
-		w, closer = writer(filepath.Join("src", "gobind", pname+"_android.h"))
+		w, closer = writer(filepath.Join("src", "gobind", pname+"_java.h"))
 		processErr(g.GenH())
 		io.Copy(w, &buf)
 		closer()
@@ -86,7 +86,7 @@ func genPkg(lang string, p *types.Package, astFiles []*ast.File, allPkg []*types
 				return
 			}
 			repo := filepath.Clean(filepath.Join(dir, "..")) // golang.org/x/mobile directory.
-			for _, javaFile := range []string{"Seq.java"} {
+			for _, javaFile := range []string{"Seq.java", "NativeUtils.java"} {
 				src := filepath.Join(repo, "bind/java/"+javaFile)
 				in, err := os.Open(src)
 				if err != nil {
@@ -110,9 +110,9 @@ func genPkg(lang string, p *types.Package, astFiles []*ast.File, allPkg []*types
 				errorf("unable to import bind/java: %v", err)
 				return
 			}
-			copyFile(filepath.Join("src", "gobind", "seq_android.c"), filepath.Join(javaDir, "seq_android.c.support"))
-			copyFile(filepath.Join("src", "gobind", "seq_android.go"), filepath.Join(javaDir, "seq_android.go.support"))
-			copyFile(filepath.Join("src", "gobind", "seq_android.h"), filepath.Join(javaDir, "seq_android.h"))
+			copyFile(filepath.Join("src", "gobind", "seq_java.c"), filepath.Join(javaDir, "seq_android.c.support"))
+			copyFile(filepath.Join("src", "gobind", "seq_java.go"), filepath.Join(javaDir, "seq_android.go.support"))
+			copyFile(filepath.Join("src", "gobind", "seq_java.h"), filepath.Join(javaDir, "seq_android.h"))
 		}
 	case "go":
 		w, closer := writer(filepath.Join("src", "gobind", fname))
@@ -174,10 +174,10 @@ func genPkg(lang string, p *types.Package, astFiles []*ast.File, allPkg []*types
 func genPkgH(w io.Writer, pname string) {
 	fmt.Fprintf(w, `// Code generated by gobind. DO NOT EDIT.
 
-#ifdef __GOBIND_ANDROID__
-#include "%[1]s_android.h"
+#ifdef __GOBIND_JAVA__
+#include "%[1]s_java.h"
 #endif
-#ifdef __GOBIND_DARWIN__
+#if defined(__GOBIND_DARWIN__) && !defined(__GOBIND_JAVA__)
 #include "%[1]s_darwin.h"
 #endif`, pname)
 }
@@ -275,7 +275,7 @@ func genJavaPackages(dir string, classes []*java.Class, embedders []importers.St
 	}
 	buf.Reset()
 	cg.GenGo()
-	if err := ioutil.WriteFile(filepath.Join(goBase, "classes_android.go"), buf.Bytes(), 0600); err != nil {
+	if err := ioutil.WriteFile(filepath.Join(goBase, "classes_java.go"), buf.Bytes(), 0600); err != nil {
 		return err
 	}
 	buf.Reset()
@@ -285,7 +285,7 @@ func genJavaPackages(dir string, classes []*java.Class, embedders []importers.St
 	}
 	buf.Reset()
 	cg.GenC()
-	if err := ioutil.WriteFile(filepath.Join(goBase, "classes_android.c"), buf.Bytes(), 0600); err != nil {
+	if err := ioutil.WriteFile(filepath.Join(goBase, "classes_java.c"), buf.Bytes(), 0600); err != nil {
 		return err
 	}
 	return nil

cmd/gomobile/bind.go

@@ -25,7 +25,7 @@ import (
 var cmdBind = &command{
 	run:   runBind,
 	Name:  "bind",
-	Usage: "[-target android|" + strings.Join(applePlatforms, "|") + "] [-bootclasspath <path>] [-classpath <path>] [-o output] [build flags] [package]",
+	Usage: "[-target android|" + strings.Join(applePlatforms, "|") + "|java] [-bootclasspath <path>] [-classpath <path>] [-o output] [build flags] [package]",
 	Short: "build a library for Android and iOS",
 	Long: `
 Bind generates language bindings for the package named by the import
@@ -133,6 +133,8 @@ func runBind(cmd *command) error {
 			return fmt.Errorf("-target=%q requires Xcode", buildTarget)
 		}
 		return goAppleBind(gobind, pkgs, targets)
+	case isJavaPlatform(targets[0].platform):
+		return goJavaBind(gobind, pkgs, targets)
 	default:
 		return fmt.Errorf(`invalid -target=%q`, buildTarget)
 	}

cmd/gomobile/bind_androidapp.go

@@ -162,7 +162,7 @@ func buildAAR(srcDir, androidDir string, pkgs []*packages.Package, targets []tar
 	if err != nil {
 		return err
 	}
-	if err := buildJar(w, srcDir); err != nil {
+	if err := buildAndroidJar(w, srcDir); err != nil {
 		return err
 	}
 
@@ -249,7 +249,7 @@ const (
 	minAndroidAPI  = 16
 )
 
-func buildJar(w io.Writer, srcDir string) error {
+func buildAndroidJar(w io.Writer, srcDir string) error {
 	var srcFiles []string
 	if buildN {
 		srcFiles = []string{"*.java"}