diff --git a/src/gen_cpp_Engine.ysl2 b/src/gen_cpp_Engine.ysl2
index 614dd16..106e036 100644
--- a/src/gen_cpp_Engine.ysl2
+++ b/src/gen_cpp_Engine.ysl2
@@ -1,7 +1,9 @@
 include yslt.yml2
 
 tstylesheet {
+    include ./textutils.ysl2
     include ./types_c.ysl2
+    include ./types_java.ysl2
 
     template "/namespace[@name='pEp']" apply "interface", 0;
 
@@ -23,6 +25,9 @@ tstylesheet {
 
     template "method" {
         const "mangled" call "mangle";
+        const "rettype", "name(parm[creates|returns]/*[2])";
+        const "retname", "name(parm[creates|returns]/*[3])";
+        const "jtype" call "toJavaDeclare" with "type", "$rettype";
 
         ||
         JNIEXPORT jobject JNICALL «$mangled»(
@@ -40,30 +45,59 @@ tstylesheet {
         ||
 
         choose {
-            when "count(parm[returns|creates]) > 1"
-                ||
-                    jclass clazz = findClass(env, "org/pEp/jniadapter/_«@name»_Return");
-                ||
-
-            when "count(parm[returns|creates]) = 1" {
-                const "jtype" call "CamelCase" with "text", "name(parm[creates|returns]/*[2])";
-                ||
-                    jclass clazz = findClass(env, "org/pEp/jniadapter/«$jtype»");
-                ||
+            when "count(parm[returns|creates]) > 1" {
+                apply "parm[returns|creates]", mode=return {
+                    with "retname", "'result'";
+                }
+
+            }
+
+            when "count(parm[returns|creates]) = 1" choose {
+                when "$rettype = 'Color'" apply "parm[returns|creates]", mode=return {
+                    with "name", "'result'";
+                    with "jtype", "$jtype";
+                    with "jnitype", "'jint'";
+                    with "retname", "$retname";
+                    with "sig", "'(I)V'";
+                }
+
+                when "$rettype = 'message'" apply "parm[returns|creates]", mode=return {
+                    with "name", "'result'";
+                    with "jtype", "$jtype";
+                    with "jnitype", "'jlong'";
+                    with "retname", "$retname";
+                    with "sig", "'(J)V'";
+                }
+
+                otherwise error | # not implemented: return type "«$rettype»"
             }
         }
 
         ||
-            jmethodID constructor = env->GetMethodID(clazz, "<init>", "()V");
-            assert(constructor);
-            jobject result = env->NewObject(clazz, constructor);
-
             return result;
         }
 
         ||
     }
 
+    template "parm", mode=return {
+        param "jtype" call "toJavaDeclare" with "type", "name(*[2])";
+        param "name", "concat(name(*[3]), '_')";
+        param "jnitype";
+        param "retname";
+        param "sig", "'()V'";
+
+        ||
+        jclass clazz_«$name» = findClass(env, "org/pEp/jniadapter/«$jtype»");
+        jmethodID constructor_«$name» = env->GetMethodID(clazz_«$name», "<init>", "«$sig»");
+        assert(constructor_«$name»);
+        ||
+        indent(0);
+        > jobject «$name» = env->NewObject(clazz_«$name», constructor_«$name»
+        if "$jnitype" > , («$jnitype») _«$retname»
+        > );\n\n
+    }
+
     template "parm", mode=in {
         const "type", "name(*[2])";
         const "name", "name(*[3])";
diff --git a/src/gen_cpp_Message.ysl2 b/src/gen_cpp_Message.ysl2
index de42452..1cd6c1b 100644
--- a/src/gen_cpp_Message.ysl2
+++ b/src/gen_cpp_Message.ysl2
@@ -1,6 +1,7 @@
 include yslt.yml2
 
 tstylesheet {
+    include ./textutils.ysl2
     include ./types_c.ysl2
 
     template "/namespace[@name='pEp']" apply "struct", 0;
diff --git a/src/gen_java_Engine.ysl2 b/src/gen_java_Engine.ysl2
index 80e6821..6366b4c 100644
--- a/src/gen_java_Engine.ysl2
+++ b/src/gen_java_Engine.ysl2
@@ -1,6 +1,7 @@
 include yslt.yml2
 
 tstylesheet {
+    include ./textutils.ysl2
     include ./types_java.ysl2
 
     template "/namespace[@name='pEp']" apply "interface", 0;
diff --git a/src/gen_java_Message.ysl2 b/src/gen_java_Message.ysl2
index 1692ef1..9863d1f 100644
--- a/src/gen_java_Message.ysl2
+++ b/src/gen_java_Message.ysl2
@@ -1,6 +1,7 @@
 include yslt.yml2
 
 tstylesheet {
+    include ./textutils.ysl2
     include ./types_java.ysl2
 
     template "/namespace[@name='pEp']" apply "struct|enum", 0;
@@ -17,7 +18,7 @@ tstylesheet {
             import java.util.HashMap;
 
             public class «$cname» implements AutoCloseable {
-                private final long handle;
+                private long handle;
 
                 native long init();
                 native void release(long handle);
@@ -26,6 +27,10 @@ tstylesheet {
                     handle = init();
                 }
 
+                private «$cname»(long h) {
+                    handle = h;
+                }
+
                 public final void close() {
                     release(handle);
                 }
diff --git a/src/types_c.ysl2 b/src/types_c.ysl2
index 7b0bcfe..2aede77 100644
--- a/src/types_c.ysl2
+++ b/src/types_c.ysl2
@@ -1,5 +1,3 @@
-include ./textutils.ysl2
-
 function "toC" {
     param "type";
 
diff --git a/src/types_java.ysl2 b/src/types_java.ysl2
index 79c7f58..5e918c3 100644
--- a/src/types_java.ysl2
+++ b/src/types_java.ysl2
@@ -1,5 +1,3 @@
-include ./textutils.ysl2
-
 function "toJava" {
     param "type";
 
@@ -19,6 +17,25 @@ function "toJava" {
     }
 }
 
+function "toJavaDeclare" {
+    param "type";
+
+    choose {
+        when "$type='stringlist'" > java.util.Vector
+        when "$type='string'" error | # cannot declare "string"
+        when "$type='message'" > org.pEp.jniadapter.Message
+        when "$type='identity'" > org.pEp.jniadapter._Identity
+        when "$type='identitylist'" > java.util.Vector
+        when "$type='timestamp'" > java.util.Date
+        when "$type='EncFormat'" > org.pEp.jniadapter.Message.EncFormat
+        when "$type='bloblist'" > java.util.Vector
+        when "$type='stringpairlist'" > java.util.ArrayList
+        when "$type='message'" > org.pEp.jniadapter.Message
+        when "$type='Color'" > org.pEp.jniadapter.Color
+
+        otherwise error | # cannot declare "«$type»"
+    }
+}
 function "toIntermediate" {
     param "type";