bind: add Go constructor for bound classes

Signed-off-by: Eric Lagergren <[email protected]>

FORK

@@ -0,0 +1,6 @@
+# Changes
+#
+# 1. Panic when a Java class cannot be found.
+#
+# 2. Add Go constructor for generated Java wrappers of Go code to facilitate
+#    Java calling back into Go.

bind/genclasses.go

@@ -541,7 +541,7 @@ func (g *ClassGen) genGo(cls *java.Class) {
 	g.Printf("C.free(unsafe.Pointer(cls))\n")
 	// Before Go 1.11 clazz was a pointer value, an uintptr after.
 	g.Printf("if uintptr(clazz) == 0 {\n")
-	g.Printf("	return\n")
+	g.Printf("\tpanic(`unable to find class %q`)\n", strings.Replace(cls.FindName, ".", "/", -1))
 	g.Printf("}\n")
 	g.Printf("class_%s = clazz\n", cls.JNIName)
 	for _, fs := range cls.Funcs {

internal/importers/java/java.go

@@ -243,6 +243,33 @@ func (j *Importer) Import(refs *importers.References) ([]*Class, error) {
 			JNIName:     JNIMangle(n),
 			PkgName:     emb.Name,
 			HasNoArgCon: true,
+			Funcs: []*FuncSet{
+				{
+					Name:   n,
+					GoName: "New",
+					Funcs: []*Func{{
+						FuncSig: FuncSig{
+							Name: "new", // or emb.Name
+							Desc: "()V",
+						},
+						JNIName:     JNIMangle(emb.Name),
+						Public:      true,
+						Final:       true,
+						Constructor: true,
+						Ret: &Type{
+							Kind:  Object,
+							Class: n,
+						},
+					}},
+					CommonSig: CommonSig{
+						HasRet: true,
+						Ret: &Type{
+							Kind:  Object,
+							Class: n,
+						},
+					},
+				},
+			},
 		}
 		for _, ref := range emb.Refs {
 			jpkg := strings.Replace(ref.Pkg, "/", ".", -1)