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Converting binary response from JInterface Java app back into list of strings in Elixir

I have a small java app and I have used JInterface to essentially expose it as an OTP process in my elixir app. I can call it and get a response successfully.
My problem is that the response I get back in elixir is of a binary but I cannot figure out how to convert a binary to a list of strings which is what the response is.
The code for my OTP node in Java using JInterface is below:
public void performAction(Object requestData, OtpMbox mbox, OtpErlangPid lastPid){
List<String> sentences = paragraphSplitter.splitParagraphIntoSentences((String) requestData, Locale.JAPAN);
mbox.send(lastPid, new OtpErlangBinary(getOtpStrings(sentences)));
System.out.println("OK");
}
private List<OtpErlangString> getOtpStrings(List<String> sentences) {
List<OtpErlangString> erlangStrings = new ArrayList<>();
for(int i = 0; i < sentences.size(); i++){
erlangStrings.add(new OtpErlangString(sentences.get(i)));
}
return erlangStrings;
}
It is necessary to wrap the response in an OtpErlangBinary and I have concerted the strings to OTPErlangString. I have also tried without converting the strings to OTPErlangString.
On the elixir side I can receive the binary response and IO.inspect it.
Does anybody know how to use JInterface to deserialise the results correctly when it's anything other than a single string? Or maybe, if I have made some mistake, how to build the correct response type so that I can deserialise it correctly?
Any help would be really appreciated as I have been trying to figure this out for ages.
Thanks in advance.

I have been playing around with JInterface and Elixir and I think I've got your problem figured out.
So you are trying to send a list of strings from an Elixir/Erlang node to a Java node, but you cannot get it to de-serialize properly.
Elixir has its own types (e.g., atoms, tuples, ..) and Java has its own types (e.g., Object, String, List<String>,..). There needs to be a conversion from the one type to the other if they're supposed to talk to each other. In the end it's just a bunch of 1's and 0's that get sent over the wire anyway.
If an Erlang list is sent to Java, what arrives can always be interpreted as an OtpErlangObject. It's up to you to then try and guess what the actual type is before we can even begin turning it into a Java value.
// We know that everything is at least an OtpErlangObject value!
OtpErlangObject o = mbox.receive();
But given that you know that it's in fact a list, we can turn it into an OtpErlangList value.
// We know o is an Erlang list!
OtpErlangList erlList = (OtpErlangList) o;
The elements of this list however, are still unknown. So at this point its still a list of OtpErlangObjects.
But, we know that it's a list of strings, so we can interpret the list of OtpErlangObjects as list of OtpErlangStrings, and convert those to Java strings.
public static List<String> ErlangListToStringList(OtpErlangList estrs) {
OtpErlangObject[] erlObjs = estrs.elements();
List<String> strs = new LinkedList<String>();
for (OtpErlangObject erlO : erlObjs) {
strs.add(erlO.toString());
}
return strs;
}
Note that I used the term list here a lot, because it's in fact an Erlang list, in Java it's all represented as an array!
My entire code is listed below.
The way to run this is to paste it into a Java IDE, and start a REPL with the following parameters:
iex --name bob#127.0.0.1 --cookie "secret"
Java part:
import com.ericsson.otp.erlang.*;
import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
public class Main {
public static OtpErlangList StringListToErlangList(List<String> strs) {
OtpErlangObject[] elems = new OtpErlangObject[strs.size()];
int idx = 0;
for (String str : strs) {
elems[idx] = new OtpErlangString(str);
idx++;
}
return new OtpErlangList(elems);
}
public static List<String> ErlangListToStringList(OtpErlangList estrs) {
OtpErlangObject[] erlObjs = estrs.elements();
List<String> strs = new LinkedList<String>();
for (OtpErlangObject erlO : erlObjs) {
strs.add(erlO.toString());
}
return strs;
}
public static void main(String[] args) throws IOException, InterruptedException {
// Do some initial setup.
OtpNode node = new OtpNode("alice", "secret");
OtpMbox mbox = node.createMbox();
mbox.registerName("alice");
// Check that the remote node is actually online.
if (node.ping("bob#127.0.0.1", 2000)) {
System.out.println("remote is up");
} else {
System.out.println("remote is not up");
}
// Create the list of strings that needs to be sent to the other node.
List<String> strs = new LinkedList<String>();
strs.add("foo");
strs.add("bar");
OtpErlangList erlangStrs = StringListToErlangList(strs);
// Create a tuple so the other node can reply to use.
OtpErlangObject[] msg = new OtpErlangObject[2];
msg[0] = mbox.self();
msg[1] = erlangStrs;
OtpErlangTuple tuple = new OtpErlangTuple(msg);
// Send the tuple to the other node.
mbox.send("echo", "bob#127.0.0.1", tuple);
// Await the reply.
while (true) {
try {
System.out.println("Waiting for response!");
OtpErlangObject o = mbox.receive();
if (o instanceof OtpErlangList) {
OtpErlangList erlList = (OtpErlangList) o;
List<String> receivedStrings = ErlangListToStringList(erlList);
for (String s : receivedStrings) {
System.out.println(s);
}
}
if (o instanceof OtpErlangTuple) {
OtpErlangTuple m = (OtpErlangTuple) o;
OtpErlangPid from = (OtpErlangPid) (m.elementAt(0));
OtpErlangList value = (OtpErlangList) m.elementAt(1);
List<String> receivedStrings = ErlangListToStringList(value);
for (String s : receivedStrings) {
System.out.println(s);
}
}
} catch (OtpErlangExit otpErlangExit) {
otpErlangExit.printStackTrace();
} catch (OtpErlangDecodeException e) {
e.printStackTrace();
}
}
}
}

Java Milo OPC-UA add node

I'm using Milo and its example server and client. I'm adding nodes to the server but I can't figure out how to add EuInformation, i.e., unit and description. I thought about using the ExtensionObject but since EuInformation does not implement Serializable I don't know how to pass it to the ExtensionObject. I'd also like to know how I can get the namespace ID and URI on client side. So far I just set them statically as I have access to the classes.
I've implemeted the AddNodes on server side. I can add nodes, read nodes and write to nodes.
Here's what I'm doing on client side:
// Should somehow get the namespace ID and namespace dynamically.
// Maybe by iterating through all nodes??
ExpandedNodeId parentNodeId = new ExpandedNodeId(
new nodeId(2,DatatypeNamespace.NODE_IDENTIFIER),
datatypeNamespace.NAMESPACE_URI, 0);
NodeId referenceTypeId = Identifiers.String;
// Define the new node.
ExpandedNodeId requestedNewNodeId = new ExpandedNodeId(new NodeId(2, "NewNode"),
DatatypeNamespace.NAMESPACE_URI, 0);
QualifiedName browseName = new QualifiedName(2, "NewNode");
// How to get this to the server??
EUInformation euinfo = new EUInformation(null,-1,LocalizedText.english("MyUnit"),
LocalizedText.english("My Description"));
ExpandedNodeId typeDef = new ExpandedNodeId(Identifiers.BaseVariableType,
DatatypeNamespace.NAMESPACE_URI, 0);
AddNodesItem newItem = new AddNodesItem(parentNodeId, referenceTypeId,
requestedNewNodeId,rowseName,NodeClass.VariableType, null, typeDef);
List<AddNodesItem> items = new ArrayList<AddNodesItem>();
items.add(newItem);
client.addNodes(items).get();
EDIT
With the help of Kevin Herron's answer I worked something out: I adjusted the write() in my namespace class. I can now modify the display name and description of the node with the values of the EUInformation. Here's my write() method:
#Override
public void write(WriteContext context, List<WriteValue> writeValues) {
List<StatusCode> results = Lists.newArrayListWithCapacity(writeValues.size());
for (WriteValue writeValue : writeValues) {
ServerNode node = server.getNodeMap().get(writeValue.getNodeId());
if (node != null) {
// Get the type of the variant thats about to be written to the node
NodeId variantType = writeValue.getValue().getValue().getDataType().get();
if (variantType.equals(Identifiers.Structure)) {
ExtensionObject o = (ExtensionObject) writeValue.getValue().getValue().getValue();
if (o.getEncodingTypeId().equals(Identifiers.EUInformation_Encoding_DefaultBinary)) {
EUInformation euInformation = (EUInformation) o.decode();
node.setDescription(euInformation.getDescription());
node.setDisplayName(euInformation.getDisplayName());
System.out.println("Wrote EUInformation " + euInformation);
results.add(StatusCode.GOOD);
context.complete(results);
return;
}
}
try {
node.writeAttribute(new AttributeContext(context), writeValue.getAttributeId(),
writeValue.getValue(), writeValue.getIndexRange());
results.add(StatusCode.GOOD);
System.out.println(String.format("Wrote value %s to %s attribute of %s",
writeValue.getValue().getValue(),
AttributeId.from(writeValue.getAttributeId()).map(Object::toString).orElse("unknown"),
node.getNodeId()));
} catch (UaException e) {
System.out.println(String.format("Unable to write %s", writeValue.getValue()));
results.add(e.getStatusCode());
}
} else {
results.add(new StatusCode(StatusCodes.Bad_NodeIdUnknown));
}
}
context.complete(results);
}

Ok, so you would add a new VaribleNode with a TypeDefinition of Property (Identifiers.PropertyType).
Then you would write to its Value attribute so it contains the EUInformation object:
EUInformation euInformation = ...
Variant v = new Variant(ExtensionObject.encode(euInformation));
...write the value to the node you created...

Converting a DataMap to a String or String Array

I'm in the process of transferring weather data from an Android phone to a Android Wear wearable via DataMap.
I have managed to get the DataMap on the device but need to find a way how to convert it into either one long string (then split into an array) or a string array.
Any ideas?
Current Code on Phone:
DataMap dataMap = new DataMap();
dataMap.putLong("1-#TIME-STAMP:", System.nanoTime());
dataMap.putLong("2-#CONTENT:", 0);
dataMap.putString("time:", currentWeather[0]);
dataMap.putString("summary:", currentWeather[1]);
dataMap.putString("icon:", currentWeather[2]);
dataMap.putString("nearestStormDistance:", currentWeather[3]);
dataMap.putString("nearestStormBEaring:", currentWeather[4]);
dataMap.putString("precipIntensity:", currentWeather[5]);
dataMap.putString("precipPRobability:", currentWeather[6]);
dataMap.putString("temperature:", currentWeather[7]);
dataMap.putString("apparentTemperature:", currentWeather[8]);
dataMap.putString("dewPoint:", currentWeather[9]);
dataMap.putString("humidity:", currentWeather[10]);
dataMap.putString("windSpeed:", currentWeather[11]);
dataMap.putString("windBearing:", currentWeather[12]);
dataMap.putString("visibility:", currentWeather[13]);
dataMap.putString("cloudCover:", currentWeather[14]);
dataMap.putString("pressure:", currentWeather[15]);
dataMap.putString("ozone:", currentWeather[16]);
new SendToDataLayerThread("/data_from_phone", dataMap).start();
Current Code on Wearable:
#Override
public void onDataChanged(DataEventBuffer dataEvents)
{
DataMap dataMap;
for (DataEvent event : dataEvents)
{
Log.v("myTag", "DataMap item: " + DataMapItem.fromDataItem(event.getDataItem()).getDataMap());
}
}

I understand you want all the values in an string array. Once you have your datamap object on device, you can do that in following manner:
ArrayList<String> listOfDataItems = new ArrayList<String>();
for(String key: dataMap.keySet())
{
Object value = get(key);
if(value instanceof Long)
{
listOfDataItems.add(String.valueOf(value));
}
else if(value instanceof String)
{
listOfDataItems.add(value);
}
}
String [] arrayOfDataItems = listOfDataItems.toArray(new String[listOfDataItems.size()]);

Did you try using Gson ? You could directly write Gson.toJsonString(dataMap).

Is there a problem with using DataMap.putStringArray (String key, String[] value)? Looking at your code, it seems you could use that for your entire currentWeather array, if you want it in the same format on the wearable device.
Doumentation: https://developers.google.com/android/reference/com/google/android/gms/wearable/DataMap.html#putStringArray(java.lang.String,%20java.lang.String[])

String[] from ArrayList<Class>

I recently started working on an app that does a request to a server and gets a json response.
The "thing" functioned beautifully until i had to implement new stuff in the list and now i have a hard time to fix it.
Any help is very appreciated:
class RemoteConfig
{
// names and type must match what we get from the remote
String[] username;
ArrayList<accDetails> in_groups;
String[] in_groups_sorted;
class accDetails
{
int group_id;
String group_label;
Boolean _is_system;
}
This is just a part of how the class starts, and here is how the json reponse looks like:
{
"username":[
"mike"
],
"in_groups":[
{
"group_id":2,
"group_label":"All users",
"_is_system":true
},
{
"group_id":4372,
"group_label":"Privileged User",
"_is_system":false
},
{
"group_id":4979,
"group_label":"Supervisor",
"_is_system":false
}
]
}
The problem that i encounter now, is that i have no idea on how to split the in_groups array list and get into String[] in_groups_sorted the value of Group_label if the _is_system value is false.
Any help is highly appreciated.
Thank you,
Mike
After checking the responses, the cleanest and simplest was the one provided by Abbe:
public String[] groupSettings()
{
String[] levels = new String[] {};
if (remoteConfig != null && remoteConfig.in_groups != null){
for (accDetails ad: remoteConfig.in_groups)
{
if (!ad._is_system) {
levels = ArrayUtils.addAll(levels, ad.group_label); ;
}
}
}
return levels;
}

From your question, I suppose the JSON is already parsed and stored in the in_groups field of RemoteConfig class. And you just need to filter the information you need to populate the in_group_sorted field.
Add the following to the RemoteConfig class:
public initGroupSorted() {
// Temporary list, since we don't know the size once filtered
List<String> labels = new ArrayList<>();
for (accDetails ad : in_groups) {
if (ad._is_system) {
groups.add(ad.group_label);
}
}
in_group_sorted = labels.toArray(new String[labels.size()]);
}

if you don´t want to change the way you parse your JSON, you could always do this:
Let accDetails implement Comparable and then use Collections.sort passing in_groups.
if you really want the String[] you could always iterate over in_groups, add to in_groups_sorted and then using Arrays.sort

Mike, let me give you something that should get you going. From your question i got the feeling that your problem was on how to parse the JSON, so before you go write your own parser, consider the following piece of code that i just wrote:
public void createObjects(String rawJSON) {
try {
JSONObject object = new JSONObject(rawJSON);
JSONArray username = object.getJSONArray("username");
JSONArray inGroups = object.getJSONArray("in_groups");
RemoteConfig config = new RemoteConfig();
config.in_groups = new ArrayList<>();
config.username = username.getString(0);
for (int i = 0; i < inGroups.length(); i++) {
JSONObject group = inGroups.getJSONObject(i);
if (!group.getBoolean("_is_system")) {
accDetails details = new accDetails();
details.group_id = group.getInt("group_id");
details.group_label = group.getString("group_label");
details._is_system = false;
config.in_groups.add(details);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}

Here is a Java 8 Solution using Stream's filter,sorted, and map methods:
//ArrayList<accDetails> in_groups is already populated
Stream<accDetails> tempStream= in_groups.stream().filter(p -> p._is_system == false);
tempStream= tempStream.sorted((accDetails o1, accDetails o2) -> o1.group_label.compareTo(o2.group_label));
String[] in_groups_sorted = tempStream.map(s -> s.group_label).toArray(String[]::new);
Separated the calls for visibility, but they can be a one liner:
String[] in_groups_sorted = in_groups.stream().filter(p -> p._is_system == false).sorted((accDetails o1, accDetails o2) -> o1.group_label.compareTo(o2.group_label)).map(s -> s.group_label).toArray(String[]::new);

How to convert from JSObject to Map (viceversa) or list JSObject members

In Javascript i have the following code:
var r=applet.foo({var0:99,var1:'foo',var2:applet});
In my Java applet i have the following:
public JSObject foo(JSObject args){
System.out.println("The function is correctly invoked");
//In fact, the following works perfectly:
System.out.println("var1 is:"+(String)args.getMember("var1"));
JSObject w=JSObject.getWindow(this);
JSObject j=(JSObject)w.eval("new Object();");
Map m=new Hashmap();
//TODO here all the keys and values of args should be added to m
m.put("hello","world");
//TODO here all the keys and values of m should be added to j
return j;
}
How can this be done? (TODOs)
Reading http://docstore.mik.ua/orelly/web/jscript/ch19_06.html, i noticed theres a getSlot method for JSObject but if i do
args.getSlot(0)
all i have is one Exception:
netscape.javascript.JSException: No such slot 0 on JavaScript object
...

Unfortunately, Errandir's solution works only when you know a name of global variable that can be used to access an object you want to get properties' names of. You need to know this name to be able to add keys method to the object, and invoke it using JSObject's call method later. Of course, you can pass a global name of your object to Java if you have it. This solution doesn't look so good especially when you can't refer to your object in global context.
As an alternative, I proposed to use this of JSObject's eval method in the comment supposing that it will do all the work. And it does. But a big disappointent was that it works as expected only in Mozilla Firefox and Opera. In Internet Explorer 9 and Google Chrome (tested under Windows 7 and Ubuntu 12.04 LTS) this of eval method always refers to applet's document window ignoring which JavaScript object JSObject instance actually represents. I don't know whether it's a bug or simply LiveConnect is supported in these browsers very poorly.
The good news is that call method of JSObject executes specified function on the proper context. Keeping that in mind I finally found a solution how a list of names of JavaScript object's properties can be retrieved. The idea is to define a temporary function in global context using eval method. This function has to receive a JavaScript object we want to get properties of and to return names of these properties as an array. After that we can invoke the temporary function through JSObject's call method passing a Java representation of concerned JavaScript object (jsObject in my method below or args as it sounds in the question). At last, temporary function can be removed.
public static ArrayList<String> getJsObjectPropertiesNames(Applet applet, JSObject jsObject) {
if (applet == null || jsObject == null)
return null;
// Retrieving global context - a JSObject representing a window applet belongs to
JSObject globalContext;
try {
globalContext = JSObject.getWindow(applet);
}
catch (JSException ex) {
return null;
}
// Checking whether passed object is not an array
try {
jsObject.getSlot(0);
return null;
}
catch (JSException e) {
}
String keysFunctionName = String.format("_getKeys%d", Calendar.getInstance().getTimeInMillis());
jsObject.eval("window['" + keysFunctionName + "'] = function(jsObject) { return Object.keys(jsObject) }");
JSObject propertiesNamesJsObject = (JSObject)globalContext.call(keysFunctionName, new Object[] { jsObject });
jsObject.eval("delete(window['" + keysFunctionName + "'])");
ArrayList<String> propertiesNames = new ArrayList<>();
try {
int slotIndex = 0;
while (true) {
Object propertyName = propertiesNamesJsObject.getSlot(slotIndex);
if (propertyName instanceof String)
propertiesNames.add((String)propertyName);
slotIndex++;
}
}
catch (JSException e) {
}
return propertiesNames;
}

As a solution, you could define method keys as proposed here (You can do it within your java-code using JSObject.eval(...)). Then you could get keys like:
JSObject keys = (JSObject)args.call("keys", Collections.EMPTY_LIST);
keys.getSlot(0);

Here below I print a String, please modify it to get whatever you need.
public final static String getKeys = "{var keys = [];for (var key in this) {keys.push(key);} keys;}";
private static String printProperties(final Object o,
final boolean printType,
final int level,
final String tab) {
final StringBuilder sb = new StringBuilder(100);
if (printType) {
sb.append("(");
sb.append(o.getClass().getSimpleName());
sb.append(") ");
}
if (o instanceof JSObject) {
sb.append("{\n");
final JSObject js = (JSObject) o;
final JSObject keys = (JSObject) js.eval(getKeys);
boolean needComma = false;
for (int i = 0;; i++) {
final String key = (String) keys.getSlot(i);
if ((key != null) && !(key.equals("undefined"))) {
final Object val = js.getMember(key);
if (!needComma) {
needComma = true;
} else {
sb.append(",\n");
}
sb.append(multitab(tab, level));
sb.append(key);
sb.append(":");
sb.append(printProperties(val, printType, level + 1, tab));
} else {
break;
}
}
sb.append("\n");
sb.append(multitab(tab, level - 1));
sb.append("}");
} else {
sb.append(o);
}
return sb.toString();
}
private final static String tab = " ";
private static String multitab(final String tab,
int i) {
final StringBuilder sb = new StringBuilder();
while (i-- > 0) {
sb.append(tab);
}
return sb.toString();
}