diff --git a/src/jniutils.cc b/src/jniutils.cc
index 5113bbf..ea16935 100644
--- a/src/jniutils.cc
+++ b/src/jniutils.cc
@@ -44,6 +44,25 @@ namespace pEp {
             return field;
         }
 
+        jint callIntMethod(
+                JNIEnv *env,
+                jobject obj,
+                const char *methodname
+            )
+        {
+            jclass clazz = env->GetObjectClass(obj);
+            assert(clazz);
+
+            jmethodID method = env->GetMethodID(clazz, methodname, "()I");
+            if (method == NULL) {
+                jclass ex = env->FindClass("java/lang/NoSuchMethodError");
+                assert(ex);
+                env->ThrowNew(ex, methodname);
+                throw std::invalid_argument(std::string(methodname));
+            }
+
+            return env->CallIntMethod(obj, method);
+        }
         jlong callLongMethod(
                 JNIEnv *env,
                 jobject obj,
@@ -64,6 +83,50 @@ namespace pEp {
             return env->CallLongMethod(obj, method);
         }
 
+        jobject callObjectMethod(
+                JNIEnv *env,
+                jobject obj,
+                const char *methodname,
+                jint index
+            )
+        {
+            jclass clazz = env->GetObjectClass(obj);
+            assert(clazz);
+
+            jmethodID method = env->GetMethodID(clazz, methodname,
+                    "(I)Ljava/lang/Object;");
+            if (method == NULL) {
+                jclass ex = env->FindClass("java/lang/NoSuchMethodError");
+                assert(ex);
+                env->ThrowNew(ex, methodname);
+                throw std::invalid_argument(std::string(methodname));
+            }
+
+            return env->CallObjectMethod(obj, method, index);
+        }
+
+        jboolean callBooleanMethod(
+                JNIEnv *env,
+                jobject obj,
+                const char *methodname,
+                jobject o
+            )
+        {
+            jclass clazz = env->GetObjectClass(obj);
+            assert(clazz);
+
+            jmethodID method = env->GetMethodID(clazz, methodname,
+                    "(Ljava/lang/Object;)Z");
+            if (method == NULL) {
+                jclass ex = env->FindClass("java/lang/NoSuchMethodError");
+                assert(ex);
+                env->ThrowNew(ex, methodname);
+                throw std::invalid_argument(std::string(methodname));
+            }
+
+            return env->CallLongMethod(obj, method, o);
+        }
+
         jint outOfMemory(JNIEnv *env)
         {
             jclass ex;
@@ -77,27 +140,127 @@ namespace pEp {
         jbyteArray from_string(JNIEnv *env, const char *str)
         {
             if (str && str[0]) {
-                bool isCopy;
-                jbyteArray _str = NewByteArray(env, strlen(str));
-                jbyte *b = GetByteArrayElements(env, str, &isCopy);
+                jboolean isCopy;
+                jbyteArray _str = env->NewByteArray(strlen(str));
+                jbyte *b = env->GetByteArrayElements(_str, &isCopy);
                 strcpy((char *)b, str);
-                ReleaseByteArrayElements(env, str, b, 0);
+                env->ReleaseByteArrayElements(_str, b, 0);
                 return _str;
             }
             else {
-                return NewByteArray(env, 0);
+                return env->NewByteArray(0);
             }
         }
 
         char *to_string(JNIEnv *env, jbyteArray str)
         {
-            bool isCopy;
-            jbyte *b = GetByteArrayElements(env, str, &isCopy);
-            char *_str = strndup((char *)b, (size_t)GetArrayLength(env, str));
-            ReleaseByteArrayElements(env, str, b, JNI_ABORT);
+            jboolean isCopy;
+            jbyte *b = env->GetByteArrayElements(str, &isCopy);
+            char *_str = strndup((char *)b, (size_t)env->GetArrayLength(str));
+            env->ReleaseByteArrayElements(str, b, JNI_ABORT);
             return _str;
         }
 
+        jobject from_stringlist(JNIEnv *env, stringlist_t *sl)
+        {
+            jclass clazz = findClass(env, "java/util/ArrayList");
+            jmethodID constructor = env->GetMethodID(clazz, "<init>", "()V");
+            assert(constructor);
+            jobject obj = env->NewObject(clazz, constructor);
+            assert(obj);
+
+            stringlist_t *_sl;
+            for (_sl = sl; _sl && _sl->value; _sl = _sl->next) {
+                jobject o = from_string(env, _sl->value);
+                callBooleanMethod(env, obj, "add", o);
+            }
+
+            return obj;
+        }
+
+        stringlist_t *to_stringlist(JNIEnv *env, jobject obj)
+        {
+            jint size = callIntMethod(env, obj, "size");
+            if (size == 0)
+                return NULL;
+
+            stringlist_t *sl = new_stringlist(NULL);
+            stringlist_t *_sl;
+            jint i;
+            for (_sl = sl, i = 0; i < (int) size; i++) {
+                jobject o = callObjectMethod(env, obj, "get", i);
+                jbyteArray a = reinterpret_cast<jbyteArray>(o);
+                char * str = to_string(env, a);
+                _sl = stringlist_add(_sl, str);
+                free(str);
+            }
+
+            return sl;
+        }
+
+        jobject from_stringpairlist(JNIEnv *env, stringpair_list_t *sl)
+        {
+            jclass clazz = findClass(env, "java/util/Vector");
+            jclass clazz_pair = findClass(env, "org/pEp/jniadapter/Pair");
+            jmethodID constructor = env->GetMethodID(clazz, "<init>", "()V");
+            assert(constructor);
+            jmethodID constructor_pair = env->GetMethodID(clazz_pair, "<init>",
+                    "([B[B)V");
+            assert(constructor_pair);
+
+            jobject obj = env->NewObject(clazz, constructor);
+            assert(obj);
+
+            stringpair_list_t *_sl;
+            for (_sl = sl; _sl && _sl->value; _sl = _sl->next) {
+                assert(_sl->value->key);
+                assert(_sl->value->value);
+
+                jbyteArray first = from_string(env, _sl->value->key);
+                jbyteArray second = from_string(env, _sl->value->value);
+                jobject pair = env->NewObject(clazz_pair, constructor_pair,
+                        first, second);
+                callBooleanMethod(env, obj, "add", pair);
+            }
+
+            return obj;
+        }
+
+        stringpair_list_t *to_stringpairlist(JNIEnv *env, jobject obj)
+        {
+            jint size = callIntMethod(env, obj, "size");
+            if (size == 0)
+                return NULL;
+
+            jfieldID first_id = getFieldID(env, "org/pEp/jniadapter/Pair",
+                    "first", "Ljava/lang/Object");
+            jfieldID second_id = getFieldID(env, "org/pEp/jniadapter/Pair",
+                    "second", "Ljava/lang/Object");
+
+            stringpair_list_t *sl = new_stringpair_list(NULL);
+            stringpair_list_t *_sl;
+            jint i;
+            for (_sl = sl, i = 0; i < (int) size; i++) {
+                jobject pair = callObjectMethod(env, obj, "get", i);
+                jbyteArray first =
+                    reinterpret_cast<jbyteArray>(env->GetObjectField(pair,
+                                first_id));
+                jbyteArray second =
+                    reinterpret_cast<jbyteArray>(env->GetObjectField(pair,
+                                second_id));
+
+                char *first_str = to_string(env, first);
+                char *second_str = to_string(env, second);
+                stringpair_t *sp = new_stringpair(first_str, second_str);
+                free(first_str);
+                free(second_str);
+
+                _sl = stringpair_list_add(_sl, sp);
+            }
+
+            return sl;
+        }
+
         jobject from_timestamp(JNIEnv *env, timestamp *ts)
         {
             time_t t = timegm(ts);
diff --git a/src/jniutils.hh b/src/jniutils.hh
index a672c8d..929e5eb 100644
--- a/src/jniutils.hh
+++ b/src/jniutils.hh
@@ -1,6 +1,9 @@
 #pragma once
 
 #include <jni.h>
+#include <pEp/stringpair.h>
+#include <pEp/identity_list.h>
+#include <pEp/bloblist.h>
 
 namespace pEp {
     namespace JNIAdapter {
@@ -13,22 +16,42 @@ namespace pEp {
                 const char *signature
             );
 
+        jint callIntMethod(
+                JNIEnv *env,
+                jobject obj,
+                const char *methodname
+            );
+
         jlong callLongMethod(
                 JNIEnv *env,
                 jobject obj,
                 const char *methodname
             );
 
+        jobject callObjectMethod(
+                JNIEnv *env,
+                jobject obj,
+                const char *methodname,
+                jint index
+            );
+
+        jboolean callBooleanMethod(
+                JNIEnv *env,
+                jobject obj,
+                const char *methodname,
+                jobject o
+            );
+
         jint outOfMemory(JNIEnv *env);
 
         jbyteArray from_string(JNIEnv *env, const char *str);
         char *to_string(JNIEnv *env, jbyteArray str);
 
         jobject from_stringlist(JNIEnv *env, stringlist_t *sl);
-        stringlist_t *to_stringlist(JNIEnv *env, jobject sl);
+        stringlist_t *to_stringlist(JNIEnv *env, jobject obj);
 
         jobject from_stringpairlist(JNIEnv *env, stringpair_list_t *sl);
-        stringpair_list_t *to_stringpairlist(JNIEnv *env, jobject sl);
+        stringpair_list_t *to_stringpairlist(JNIEnv *env, jobject obj);
 
         jobject from_timestamp(JNIEnv *env, timestamp *ts);
         timestamp *to_timestamp(JNIEnv *env, jobject date);
@@ -37,10 +60,10 @@ namespace pEp {
         pEp_identity *to_identity(JNIEnv *env, jobject ident);
 
         jobject from_identitylist(JNIEnv *env, identity_list *il);
-        identity_list *to_identitylist(JNIEnv *env, jobject il);
+        identity_list *to_identitylist(JNIEnv *env, jobject obj);
 
         jobject from_bloblist(JNIEnv *env, bloblist_t *bl);
-        bloblist_t *to_bloblist(JNIEnv *env, jobject bl);
+        bloblist_t *to_bloblist(JNIEnv *env, jobject obj);
     };
 };
 
diff --git a/src/org/pEp/jniadapter/Pair.java b/src/org/pEp/jniadapter/Pair.java
index 4cddbc0..421475d 100644
--- a/src/org/pEp/jniadapter/Pair.java
+++ b/src/org/pEp/jniadapter/Pair.java
@@ -3,5 +3,12 @@ package org.pEp.jniadapter;
 public class Pair<F, S> {
     public F first;
     public S second;
+
+    Pair<F, S>() { }
+
+    Pair<F, S>(F f, S s) {
+        first = f;
+        second = s;
+    }
 }