diff --git a/src/Makefile b/src/Makefile
index a18a33b..e4f845d 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -42,12 +42,18 @@ $(LIBRARY): org_pEp_jniadapter_AbstractEngine.o org_pEp_jniadapter_Engine.o org_
 org/pEp/jniadapter/pEpException.java: pEp.yml2 gen_java_exceptions.ysl2
 	yml2proc -y gen_java_exceptions.ysl2 $< -o $@
 
-org/pEp/jniadapter/Engine.java org/pEp/jniadapter/Message.java : pEp.yml2 gen_java_Message.ysl2 types_java.ysl2
+org/pEp/jniadapter/Message.java: pEp.yml2 gen_java_Message.ysl2 types_java.ysl2
 	yml2proc -y gen_java_Message.ysl2 $<
 
-org_pEp_jniadapter_Engine.cc org_pEp_jniadapter_Message.cc : pEp.yml2 gen_cpp_Message.ysl2 types_c.ysl2
+org_pEp_jniadapter_Message.cc: pEp.yml2 gen_cpp_Message.ysl2 types_c.ysl2
 	yml2proc -y gen_cpp_Message.ysl2 $<
 
+org/pEp/jniadapter/Engine.java: pEp.yml2 gen_java_Engine.ysl2 types_java.ysl2
+	yml2proc -y gen_java_Engine.ysl2 $<
+
+org_pEp_jniadapter_Engine.cc: pEp.yml2 gen_cpp_Engine.ysl2 types_c.ysl2
+	yml2proc -y gen_cpp_Engine.ysl2 $<
+
 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
 
diff --git a/src/gen_cpp_Engine.ysl2 b/src/gen_cpp_Engine.ysl2
new file mode 100644
index 0000000..c757f14
--- /dev/null
+++ b/src/gen_cpp_Engine.ysl2
@@ -0,0 +1,7 @@
+include yslt.yml2
+
+tstylesheet {
+    include ./types_c.ysl2
+
+}
+
diff --git a/src/gen_cpp_Message.ysl2 b/src/gen_cpp_Message.ysl2
index 26210e0..de42452 100644
--- a/src/gen_cpp_Message.ysl2
+++ b/src/gen_cpp_Message.ysl2
@@ -116,15 +116,5 @@ tstylesheet {
 
         ||
     }
-
-    function "jni_type" {
-        param "type";
-
-        choose {
-            when "../enum[@name=$type]" > jint
-            when "$type = 'string'" > jbyteArray
-            otherwise > jobject
-        }
-    }
 }
 
diff --git a/src/gen_java_Engine.ysl2 b/src/gen_java_Engine.ysl2
new file mode 100644
index 0000000..db2757a
--- /dev/null
+++ b/src/gen_java_Engine.ysl2
@@ -0,0 +1,181 @@
+include yslt.yml2
+
+tstylesheet {
+    include ./types_java.ysl2
+
+    template "/namespace[@name='pEp']" apply "interface", 0;
+
+    template "interface" {
+        const "cname" call "toJava" with "type", "@name";
+        document("org/pEp/jniadapter/{$cname}.java", "text")
+            ||
+            package org.pEp.jniadapter;
+
+            import java.util.Vector;
+
+            final public class «$cname» extends AbstractEngine {
+                public «$cname»() throws pEpException { }
+
+                `` apply "method"
+            }
+            ||
+    }
+
+    function "returnJava" {
+        const "returning", "count(parm/creates|parm/returns)";
+        const "returntype" call "toJava" with "type", "name(parm[creates|returns]/*[2])";
+
+        choose {
+            when "$returning = 0" > void
+            when "$returning = 1" > «$returntype»
+            otherwise > «@name»_Return
+        }
+    }
+
+    function "returnInter" {
+        const "returning", "count(parm/creates|parm/returns)";
+        const "returntype" call "toIntermediate" with "type", "name(parm[creates|returns]/*[2])";
+
+        choose {
+            when "$returning = 0" > void
+            when "$returning = 1" > «$returntype»
+            otherwise > _«@name»_Return
+        }
+    }
+
+    template "method" {
+        const "convert", "count(parm/stringlist|parm/stringpairlist|parm/string|parm/identity|parm/identitylist|parm/bloblist) > 0";
+        const "singlereturn", "count(parm/creates|parm/returns) = 1";
+        const "multireturn", "count(parm/creates|parm/returns) > 1";
+
+        if "$convert" {
+            if "$multireturn"
+            ||
+            private class _«@name»_Return {
+            `` apply "parm[creates|returns]", 1, mode=intermediate with "public", 1;
+            }
+
+            ||
+            ||
+            private native `call "returnInter"` _«@name»(
+            `` apply "parm[in]", 2, mode=intermediate
+                ) throws pEpException;
+
+            ||
+        }
+
+        if "$multireturn"
+        ||
+        public class «@name»_Return {
+        `` apply "parm[creates|returns]", 1, mode=java with "public", 1;
+        }
+
+        ||
+        ||
+        public `if "not($convert)" > native ``call "returnJava"` «@name»(
+        `` apply "parm[in]", 2, mode=java
+            ) throws pEpException`if "not($convert)" > ;`
+        {
+            `` apply "parm", mode=convertIn;
+            `if "$singlereturn or $multireturn" call "returnInter", copy "' _result = '"`_«@name»(`apply "parm[in]", mode=call`);
+            `` if "$singlereturn" |> return _result;
+            `` if "$multireturn" apply ".", mode=multireturn with "convert", "$convert";
+        }
+
+        ||
+    }
+
+    template "method", mode=multireturn {
+        param "convert";
+
+        choose {
+            when "$convert"
+                ||
+
+                «@name»_Return result = new «@name»_Return();
+                `` apply "parm[creates|returns]", 0, mode=convertOut;
+
+                return result;
+                ||
+            otherwise | return _result;
+        }
+    }
+
+    template "parm", mode=java {
+        param "public", 0;
+        const "dir", "name(*[1])";
+        const "type", "name(*[2])";
+        const "name", "name(*[3])";
+
+        indent(0);
+
+        if "$public" > public 
+        > †$type «translate($name,'-','_')»
+        choose {
+            when "$public" > ;
+            otherwise if "position()!=last()" > ,
+        }
+        > \n
+    }
+
+    template "parm", mode=intermediate {
+        param "public", 0;
+        const "dir", "name(*[1])";
+        const "type", "name(*[2])";
+        const "name", "name(*[3])";
+
+        indent(0);
+
+        if "$public" > public 
+        > ¡$type «translate($name,'-','_')»
+        choose {
+            when "$public" > ;
+            otherwise if "position()!=last()" > ,
+        }
+        > \n
+    }
+
+    template "parm", mode=convertIn {
+        const "dir", "name(*[1])";
+        const "type", "name(*[2])";
+        const "name" call "lcase" with "text", "name(*[3])";
+
+        if "$dir = 'in'" choose {
+            when "$type = 'string'" | ¡$type _«$name» = AbstractEngine.toUTF8(«$name»);
+            when "$type = 'stringlist'"
+                ||
+                Vector<byte[]> _«$name» = new Vector<byte[]>();
+                for (String s : «$name») {
+                    _«$name».add(AbstractEngine.toUTF8(s);
+                }
+                ||
+        }
+    }
+
+    template "parm", mode=convertOut {
+        const "dir", "name(*[1])";
+        const "type", "name(*[2])";
+        const "name" call "lcase" with "text", "name(*[3])";
+
+        if "$dir != 'in'" choose {
+            when "$type = 'string'" | †$type «$name» = AbstractEngine.toUTF16(_«$name»);
+            when "$type = 'stringlist'"
+                ||
+                Vector<String> result.«$name» = new Vector<String>();
+                for (byte[] a : _result._«$name») {
+                    result.«$name».add(AbstractEngine.toUTF16(a);
+                }
+                ||
+            otherwise | result.«$name» = _result.«$name»;
+        }
+    }
+
+    template "parm", mode=call {
+        const "type", "name(*[2])";
+        const "name" call "lcase" with "text", "name(*[3])";
+
+        if "$type = 'string' or $type = 'stringlist'" > _
+        > «$name»`if "position()!=last()" > , `
+    }
+}
+
diff --git a/src/gen_java_Message.ysl2 b/src/gen_java_Message.ysl2
index 01c124a..93be17f 100644
--- a/src/gen_java_Message.ysl2
+++ b/src/gen_java_Message.ysl2
@@ -3,24 +3,7 @@ include yslt.yml2
 tstylesheet {
     include ./types_java.ysl2
 
-    template "/namespace[@name='pEp']" apply "struct|interface|enum", 0;
-
-    template "interface" {
-        const "cname" call "toJava" with "type", "@name";
-        document("org/pEp/jniadapter/{$cname}.java", "text")
-            ||
-            package org.pEp.jniadapter;
-
-            import java.util.ArrayList;
-            import java.util.Vector;
-
-            final public class «$cname» extends AbstractEngine {
-                public «$cname»() throws pEpException { }
-
-                `` apply "interface|method"
-            }
-            ||
-    }
+    template "/namespace[@name='pEp']" apply "struct|enum", 0;
 
     template "struct" {
         const "cname" call "toJava" with "type", "@name";
@@ -28,7 +11,6 @@ tstylesheet {
             ||
             package org.pEp.jniadapter;
 
-            import java.util.ArrayList;
             import java.util.Vector;
             import java.util.Date;
             import java.util.HashMap;
@@ -92,21 +74,6 @@ tstylesheet {
         ||
     }
 
-    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()" > ,`
-    }
-
     template "*", mode=entry {
         const "ctype", "name(.)";
         const "type" call "toJava" with "type", "name(.)";
diff --git a/src/pEp.yml2 b/src/pEp.yml2
index 2242534..c485127 100644
--- a/src/pEp.yml2
+++ b/src/pEp.yml2
@@ -72,8 +72,7 @@ namespace pEp {
         method encrypt_message(
                 in message src,
                 in stringlist extra,
-                creates message dst,
-                in EncFormat enc_format
+                creates message dst
             );
         
         method decrypt_message(
diff --git a/src/types_c.ysl2 b/src/types_c.ysl2
index 585f31f..7b0bcfe 100644
--- a/src/types_c.ysl2
+++ b/src/types_c.ysl2
@@ -18,5 +18,15 @@ function "toC" {
     }
 }
 
+function "jni_type" {
+    param "type";
+
+    choose {
+        when "../enum[@name=$type]" > jint
+        when "$type = 'string'" > jbyteArray
+        otherwise > jobject
+    }
+}
+
 define operator "√([$@]?[a-zA-Z0-9_]+)" as call "toC" with "type", "%1";
 
diff --git a/src/types_java.ysl2 b/src/types_java.ysl2
index ae021d7..b4bcd52 100644
--- a/src/types_java.ysl2
+++ b/src/types_java.ysl2
@@ -4,14 +4,14 @@ function "toJava" {
     param "type";
 
     choose {
-        when "$type='stringlist'" > ArrayList<String>
+        when "$type='stringlist'" > Vector<String>
         when "$type='string'" > String
         when "$type='message'" > Message
         when "$type='identity'" > Identity
-        when "$type='identitylist'" > ArrayList<Identity>
+        when "$type='identitylist'" > Vector<Identity>
         when "$type='timestamp'" > Date
         when "$type='EncFormat'" > Message.EncFormat
-        when "$type='bloblist'" > ArrayList<Blob>
+        when "$type='bloblist'" > Vector<Blob>
         when "$type='stringpairlist'" > Vector<Pair<String, String>>
         when "$type='message'" > Message
 
@@ -23,12 +23,12 @@ function "toIntermediate" {
     param "type";
 
     choose {
-        when "$type='stringlist'" > ArrayList<byte[]>
+        when "$type='stringlist'" > Vector<byte[]>
         when "$type='stringpairlist'" > Vector<Pair<byte[], byte[]>>
         when "$type='string'" > byte[]
         when "$type='identity'" > _Identity
-        when "$type='identitylist'" > ArrayList<_Identity>
-        when "$type='bloblist'" > ArrayList<_Blob>
+        when "$type='identitylist'" > Vector<_Identity>
+        when "$type='bloblist'" > Vector<_Blob>
 
         otherwise call "toJava" with "type", "$type";
     }