diff --git a/src/Makefile b/src/Makefile
index 6cf9f17..aa2b3f3 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -24,12 +24,16 @@ clean:
 	rm -f org_pEp_jniadapter_*.h
 	rm -f org/pEp/jniadapter/*.class
 	rm -f org/pEp/jniadapter/pEp*.java
+	rm -f org/pEp/jniadapter/Engine.java
 	rm -f throw_pEp_exception.*
 
 org/pEp/jniadapter/pEpException.java: pEp.yml2 gen_java_exceptions.ysl2
 	yml2proc -y gen_java_exceptions.ysl2 $< -o $@
 
-throw_pEp_exception.cc throw_pEp_exception.hh: pEp.yml2 gen_throw_pEp_exception.ysl2
+org/pEp/jniadapter/Engine.java : pEp.yml2 gen_java_Engine.ysl2 types_java.ysl2
+	yml2proc -y gen_java_Engine.ysl2 $< -o $@
+
+throw_pEp_exception.cc throw_pEp_exception.hh: pEp.yml2 gen_throw_pEp_exception.ysl2 textutils.ysl2
 	yml2proc -y gen_throw_pEp_exception.ysl2 $< -o throw_pEp_exception.cc
 
 throw_pEp_exception.o: throw_pEp_exception.cc throw_pEp_exception.hh
diff --git a/src/gen_java_Engine.ysl2 b/src/gen_java_Engine.ysl2
new file mode 100644
index 0000000..def14e8
--- /dev/null
+++ b/src/gen_java_Engine.ysl2
@@ -0,0 +1,32 @@
+include yslt.yml2
+
+tstylesheet {
+    include ./types_java.ysl2
+
+    template "/"
+        ||
+        package org.pEp.jniadapter;
+        
+        final public class Engine extends AbstractEngine {
+            public Engine() throws pEpException { }
+
+            `` apply "namespace/interface/method";
+        }
+        ||
+
+    template "method"
+        ||
+        public native void «@name»(
+        `` apply "parm", 2
+            ) throws pEpException;`if "position()!=last()" > \n`
+        ||
+
+    template "parm" {
+        const "dir", "name(*[1])";
+        const "type", "name(*[2])";
+        const "name", "name(*[3])";
+
+        | `call "toJava" with "type", "$type"` «translate($name,'-','_')»`if "position()!=last()" > ,`
+    }
+}
+
diff --git a/src/org/pEp/jniadapter/Engine.java b/src/org/pEp/jniadapter/Engine.java
deleted file mode 100644
index 45ed16a..0000000
--- a/src/org/pEp/jniadapter/Engine.java
+++ /dev/null
@@ -1,7 +0,0 @@
-package org.pEp.jniadapter;
-
-public class Engine extends AbstractEngine {
-    public Engine() throws pEpException {
-    }
-}
-
diff --git a/src/pEp.yml2 b/src/pEp.yml2
index b8069b7..cb9287b 100644
--- a/src/pEp.yml2
+++ b/src/pEp.yml2
@@ -1,5 +1,7 @@
 decl namespace @name;
 decl enum @name;
+decl interface @name;
+decl method @name;
 
 namespace pEp {
     enum pEp_status {
@@ -45,5 +47,20 @@ namespace pEp {
         pEp_out_of_memory								> -2
         pEp_unknown_error								> -1
     };
+
+    interface message_api {
+        method encrypt_message(
+                in message src,
+                in stringlist extra,
+                creates message dst,
+                in pEp_enc_format enc_format
+            );
+        
+        method decrypt_message(
+                in message src,
+                in pEp_MIME_format mime,
+                creates message dst
+            );
+    };
 };
 
diff --git a/src/textutils.ysl2 b/src/textutils.ysl2
index 567f48e..ded3427 100644
--- a/src/textutils.ysl2
+++ b/src/textutils.ysl2
@@ -12,21 +12,16 @@ function "lcase" {
 
 function "CamelCase" {
     param "text";
+    const "tokens", "str:tokenize($text, '-')";
 
-    choose {
-        when "contains($text, '-')" {
-            const "tokens", "str:tokenize($text, '-')";
-            for "$tokens" {
-                choose {
-                    when ".='pEp'" > pEp
-                    otherwise {
-                        call "UCASE" with "text", "substring(., 1, 1)";
-                        call "lcase" with "text", "substring(., 2)";
-                    }
-                }
+    for "$tokens" {
+        choose {
+            when ".='pEp'" > pEp
+            otherwise {
+                call "UCASE" with "text", "substring(., 1, 1)";
+                call "lcase" with "text", "substring(., 2)";
             }
         }
-        otherwise | unsupported
     }
 }
 
diff --git a/src/types_java.ysl2 b/src/types_java.ysl2
new file mode 100644
index 0000000..311a0db
--- /dev/null
+++ b/src/types_java.ysl2
@@ -0,0 +1,12 @@
+include ./textutils.ysl2
+
+function "toJava" {
+    param "type";
+
+    choose {
+        when "string" > String
+        when "stringlist" > String[]
+        otherwise call "CamelCase" with "text", "$type";
+    }
+}
+