I'm using Java EE, Netbeans and a facade session bean to implement the JPA layer (eclipselink).
I've a two table for example: Garden (1) ---> Tree (n).
(Script A) Now, I execute this snippet:
Garden mGarden = new Garden();
.....
gardenFacade.create(garden)
(Script B) Then:
Tree oneTree = new Tree();
oneTree.setGarden(mGarden);
treeFacade.create(oneTree);
In this way, the entity Tree is correctly added into my database and the foreign key is right.
(Script C) When I invoke:
Garden findGarden = gardenFacade.find(gardenId);
int count = findGarden.getTreeCollection().size();
I've count = 0 !!!
If I restart glassfish or reload my app and I execute these snippets I've count = 1.
So, I think that this is a problem of Persistence Context Synchronization because if I change my script B with:
Tree oneTree = new Tree();
oneTree.setGarden(mGarden);
treeFacade.create(oneTree);
mGarden.getTreeCollection().add(oneTree);
gardenFacade.edit(mGarden);
all works correctly!
How can I solve this issue?
EDIT:
create --> getEntityManager().persist(entity);
edit ----> getEntityManager().merge(entity);
find ----> getEntityManager().find(entityClass, id);
It looks like all those calls are using the same hibernate session, and sinc you failed to properly initialize both sides of the collection, of course you don't get anything in the collection:
Garden mGarden = new Garden(); // create a new Garden instance
session.persist(mGarden); // now this Garden instance is persistent.
// Its state will be written to the database at the
// next flush
Tree oneTree = new Tree(); // create a new Tree instance
oneTree.setGarden(mGarden); // set the garden of the tree. This is a basic, simple
// Java method call. Nothing will magically add the tree
// to the garden collection of trees if you don't do
// it explicitely
session.persist(oneTree); // now this Tree instance is persistent.
// Its state will be written to the database at the
// next flush.
Garden findGarden = session.get(Garden.class, gardenId);
// returns the garden that has the specific ID. It's already in the session:
// you created and attached it to the session at the beginning. And you
// never added anything to its collection of trees
Related
So the problem I am facing is that when the viewModel data updates it doesn't seems to update the state of my bytearrays: ByteArray by (mutableStateOf) and mutableListOf()
When I change pages/come back to the page it does update them again. How can get the view to update for things like lists and bytearrays
Is mutableStateOf the wrong way to update bytearrays and lists? I couldn't really find anything useful.
Example of byte array that doesn't work (using this code with a Float by mutableStateOf works!).
How I retrieve the data in the #Composable:
val Data = BluetoothMonitoring.shared.Data /*from a viewModel class, doesn't update when Data / bytearray /list changes, only when switching pages in app.*/
Class:
class BluetoothMonitoring : ViewModel(){
companion object {
val shared = BluetoothMonitoring()
}
var Data : ByteArray by mutableStateOf( ByteArray(11) { 0x00 })
}
Any help is appreciated and thanks in advance!
You seem to come from IOS/Swift where using Shared objects is a common pattern
In Android, you're not supposed to create a viewmodel instance by hand, you are supposed to use ViewModelFactory, or compose viewModel() function. The ViewModel object basically preserves some data for you across activity recompositions, i.e. when activity is paused, resumed etc
The general good way of structuring your app is using UDF (Unidirectional Data Flow) where, data flows upwards towards the view/composable and events flow downwards towards the viewmodel, data layer etc. We use something called as Flow which is a reactive data stream, which updates the listener whenever some value changes
Keeping in mind these two points, I've created a very brief way of how you could restructure your code, so that it almost always works. Please adapt accordingly to your logic
class MyViewModel: ViewModel(){
// Declare a flow in the viewModel
var myData = MutableStateFlow(0)
fun modifyMyData(newData: Int){
myData = newData
}
}
And in your composable view layer
#Composable
fun YourComposable(){
val myViewModel = viewModel()
val myUiState by myViewModel.myData.collectAsState()
// Now use your value, and change it, it will be changed accordingly and updated everywhere
}
I also recommend reading this codelab
How I handle byte arrays over Bluetooth with kotlin and Android.
I'm talking sic (communication) to arduino over bluetooth in the app I'm making. Kotlin likes Byte and Arduino likes UBYTE so I do all of those translations in the app because Kotlin threads are inline code easy and the phone has more power for such things.
Add toByte() to everthing that is outbound. <- (actual solution)
outS[8] = Color.alpha(word.color).toByte()
outS[9] = Color.red(word.color).toByte()
outS[10] = Color.green(word.color).toByte()
outS[11] = Color.blue(word.color).toByte()
outS[12] = 0.toByte()
outS[13] = 232.toByte()
outS[14] = 34.toByte()
outS[15] = 182.toByte()
//outS[16] = newline working without a newLine!
// outS[16] = newline
val os = getMyOutputStream()
if (os != null) {
os.write(outS)
}
For inbound data...I have to change everything to UByte. <- (actual solution)
val w: Word = wordViewModel.getWord(i)
if (w._id != 0) {
w.rechecked = (byteArray[7].toInt() != 0)
w.recolor = Color.argb(
byteArray[8].toUByte().toInt(),
byteArray[9].toUByte().toInt(),
byteArray[10].toUByte().toInt(),
byteArray[11].toUByte().toInt()
)
//finally update the word
wordViewModel.update(w)
}
My Youtube channel is about model trains not coding there some android and electronics in there. And a video of bluetooth arduino android is coming soon like tonight or tomorrow soon. I've been working on the app for just over a month using it to learn Kotlin. The project is actually working but I have to do the bluetooth connection manually the app actually controls individual neopixels for my model train layout.
I have a maya node myNode, which creates a shadeNode, which inMesh attribute is connected to shapeNode.outMesh and has an attribute distance.
myNode.outMesh -> shapeNode.inMesh
myNode.distance = 10
Then i have a command, which works on the shape node, but requires the distance argument, which it does by iterating over the inMesh connections:
MPlugArray meshConnections;
MPlug inMeshPlug = depNodeFn.findPlug("inMesh");
inMeshPlug.connectedTo(meshConnections, true, false); // in connections
bool node_found = false;
for(uint i = 0; i < numConnections; i++) {
MPlug remotePlug = meshConnections[i];
myNode = remotePlug.node();
if(MFnDependencyNode(myNode ).typeName() == "myNode") {
node_found = true;
break;
}
}
MFnDependencyNode myDepNode(myNode);
MPlug distancePlug = myDepNode.findPlug("distance");
Now i get a problem, when applying another node (of another type) to myShape, because the dependency graph now looks like this:
myNode.outMesh -> myOtherNode.inMesh
myOtherNode.outMesh -> shapeNode.inMesh
myNode.distance = 10
I tried to remove the check for typeName() == "myNode", because i understood the documentation like there should be recursion to the parent node, when the next node return Mstatus::kInvalidParameter for the unknown MPlug, but i cannot reach the distance plug without implementing further graph traversion.
What is the correct way to reliably find an attribute of a parent node, even when some other nodes were added in between?
The command itself should use the distance Plug to either connect to myNode or to some plug which gets the value recursively. If possible i do not want to change myOtherNode to have a distance plug and correspondig connections for forwarding the data.
The usual Maya workflow would be to make the node operate in isolation -- it should not require any knowledge of the graph structure which surrounds it, it just reacts to changes in inputs and emits new data from its outputs. The node needs to work properly if a user manually unhooks the inputs and then manually reconnects them to other objects -- you can't know, for example, that some tool won't insert a deformer upstream of your node changing the graph layout that was there when the node was first created.
You also don't want to pass data around outside the dag graph -- if the data needs to be updated you'll want to pass it as a connection. Otherwise you won't be able to reproduce the scene from the graph alone. You want to make sure that the graph can only ever produce an unambiguous result.
When you do have to do DAG manipulations -- like setting up a network of connectiosn -- put them into an MPXCommand or a mel/python script.
I found the answer in an answer (python code) to the question how to get all nodes in the graph. My code to find the node in the MPxCommand now looks like this:
MPlugArray meshConnections;
MPlug inMeshPlug = depNodeFn.findPlug("inMesh");
MItDependencyGraph depGraphIt(inMeshPlug, MFn::kInvalid, MItDependencyGraph::Direction::kUpstream);
bool offset_mesh_node_found = false;
while(!depGraphIt.isDone()) {
myNode = depGraphIt.currentItem();
if(MFnDependencyNode(myNode).typeName() == "myNode") {
offset_mesh_node_found = true;
break;
}
depGraphIt.next();
}
The MItDependencyGraph can traverse the graph in upstream or downstream direction either starting from an object or a plug. Here i just search for the first instance of myNode, as I assume there will only be one in my use case. It then connects the distance MPlug in the graph, which still works when more mesh transforms are inserted.
The MItDependencyGraph object allows to filter for node ids, but only the numeric node ids not node names. I probably add a filter later, when I have unique maya ids assigned in all plugins.
I'm struggling with a KeyProperty query, and can't see what's wrong.
My model is
class MyList(ndb.Model):
user = ndb.KeyProperty(indexed=True)
status = ndb.BooleanProperty(default=True)
items = ndb.StructuredProperty(MyRef, repeated=True, indexed=False)
I create an instance of MyList with the appropriate data and can run the following properly
cls = MyList
lists = cls.query().fetch()
Returns
[MyList(key=Key('MyList', 12), status=True, items=..., user=Key('User', 11))]
But it fails when I try to filter by user, i.e. finding lists where the user equals a particular entity; even when using the one I've just used for insert, or from the previous query result.
key = lists[0].user
lists = cls.query(cls.user=key).fetch()
Returns
[]
But works fine with status=True as the filter, and I can't see what's missing?
I should add it happens in a unit testing environment with the following v3_stub
self.policy = datastore_stub_util.PseudoRandomHRConsistencyPolicy(probability=0)
self.testbed.init_datastore_v3_stub(
require_indexes=True,
root_path="%s/../"%(os.path.dirname(__file__)),
consistency_policy=self.policy
)
user=Key('User', 11) is a key to a different class: User. Not MyList
Perhaps you meant:
user = ndb.KeyProperty(kind='User', indexed=True)
Your code looks fine, but I have noticed some data integrity issues when developing locally with NDB. I copied your model and code, and I also got the empty list at first, but then after a few more attempts, the data is there.
Try it a few times?
edit: possibly related?
google app engine ndb: put() and then query(), there is always one less item
I'm writing a Hadoop application calculates map data at a certain resolution. My Input files are tiles of a map, named according to the QuadTile principle. I need to subsample those, and stitch those together until I have a certain higher-level tile which covers a larger area but at a lower resolution. Like zooming out in google maps.
Currently my Mapper subsamples tiles and my reducer combines tiles a a certain level and forms tiles of one level up. So for so good. But depending on which tile I need, I need to repeat those map and reduce steps a x times, which I have not been able to do so far.
What would be the best way to do so? Is it possible without explicitly saving the tiles in some temp directory and starting a new mapreduce Job on those temp dirs until I get what I want? What I think would be the perfect solution is something roughly like 'while(context.hasMoreThanOneKey()){iterate mapreduce}'.
Following an answer, I have now written a class TileJob which extends Job. However, the mapreduce is still not chained. Could you tell me what I'm doing wrong?
public boolean waitForCompletion(boolean verbose) throws IOException, InterruptedException, ClassNotFoundException{
if(desiredkeylength != currentinputkeylength-1){
System.out.println("In loop, setting input at " + tempout);
String tempin = tempout;
FileInputFormat.setInputPaths(this, tempin);
tempout = (output + currentinputkeylength + "/");
FileOutputFormat.setOutputPath(this, new Path(tempout));
System.out.println("Setting output at " + tempout);
currentinputkeylength--;
Configuration conf = new Configuration();
TileJob job = new TileJob(conf);
job.setJobName(getJobName());
job.setUpJob(tempin, tempout, tiletogenerate, currentinputkeylength);
return job.waitForCompletion(verbose);
}else{
//desiredkeylength == currentkeylength-1
System.out.println("In else, setting input at " + tempout);
String tempin = tempout;
FileInputFormat.setInputPaths(this, tempin);
tempout = output;
FileOutputFormat.setOutputPath(this, new Path(tempout));
System.out.println("Setting output at " + tempout);
currentinputkeylength--;
Configuration conf = new Configuration();
TileJob job = new TileJob(conf);
job.setJobName(getJobName());
job.setUpJob(tempin, tempout, tiletogenerate, currentinputkeylength);
currentinputkeylength--;
return super.waitForCompletion(verbose);
}
}
Usually you kick a mapreduce step off by having a driver class main method that configures the Job, Configuration and format type (input and output). Once everything's ready to go that main method calls Job::waitForCompletion() which submits the job and waits for the job to complete before continuing.
You can wrap some of that logic in a loop that repeatedly calls Job::waitForCompletion() until your criteria is met. You can implement your criteria using counters. Put logic into your reduce() method to set or increment a counter with the number of keys. Your loop in the driver class can get the value of that (distributed) counter from the Job instance and you code your while expression using that value.
What file locations you use is up to you. Inside this driver loop you can change the file location for the inputs and outputs, or keep them the same.
I should probably add that you ought to go ahead and create a new Job and Configuration instance inside the loop. I don't know that those objects are reusable in this situation.
public static void main(String[] args) {
int keys = 2;
boolean completed = true;
while (completed & (keys > 1)) {
Job job = new Job();
// Do all your job configuration here
completed = job.waitForCompletion();
if (completed) {
keys = job.getCounter().findCounter("Total","Keys").getValue();
}
}
}
I'm making a Windows Phone 7.1 application, and I'm having a lot of trouble submitting changes to my database. Here is the structure of the tables in my database:
Day <-1-----*-> TrainingSession <-many-----1-> Sport
So, a single day can have many training sessions, and a training session has one sport. A single sport can naturally be in many different training sessions.
The primary keys look like this:
Day - DateTime
TrainingSession - int (DB generated)
Sport - nvarchar(200)
Sports will simply have attributes sportName, and an iconFileName.
I've set up Associations by putting EntitySet in both Day and Sport, and TrainingSession has EntityRef and EntityRef. I'm not 100% sure if Sport needs the EntitySet, so please correct me if I'm wrong. For the moment, I just hard-coded some sports in my Sport class for testing, and you'll see me retrieving an ObservableCollection to get those out.
Here is how I am trying to create a collection of days with training sessions, each training session having different sports:
public void CreateDay(DateTime date)
{
FitPlanDataContext calendarDatabase = new FitPlanDataContext(FitPlanDataContext.ConnectionString);
DateTime firstDate = new DateTime(date.Year, date.Month, 1);
DayItem dayItem = new DayItem();
dayItem.DateTime = firstDate;
fillTestDayItemWithRandomData(dayItem);
calendarDatabase.DayItems.InsertOnSubmit(dayItem);
calendarDatabase.SubmitChanges();
}
private void fillTestDayItemWithRandomData(DayItem dayItem)
{
ObservableCollection<SportArt> sportArtCollection = SportArtController.GetAllSports();
dayItem.TrainingSessions = new EntitySet<TrainingSession>();
ObservableCollection<TrainingSession> trainingSessionCollection = new ObservableCollection<TrainingSession>();
TrainingSession trainingSession1 = new TrainingSession();
trainingSession1.DayItem = dayItem;
trainingSession1.SportArt = sportArtCollection[1];
trainingSessionCollection.Add(trainingSession1);
TrainingSession trainingSession2 = new TrainingSession();
trainingSession2.DayItem = dayItem;
trainingSession2.SportArt = sportArtCollection[2];
trainingSessionCollection.Add(trainingSession2);
FitPlanDataContext calendarDatabase = new FitPlanDataContext(FitPlanDataContext.ConnectionString);
calendarDatabase.TrainingSessions.InsertAllOnSubmit<TrainingSession>(trainingSessionCollection);
}
This code is not working for me, and it is giving me the following error:
NotSupportedException was Unhandled:
An attempt has been made to Attach or Add an entity that is not new, perhaps having been loaded from another DataContext. This is not supported.
Before I got this error, I was also getting NullReferenceExceptions.
I've been looking around for a solution, and I saw some people used Detach or workarounds with Attach, but I havent figured out how I could implement it to my code. Could anyone give me a helping hand with this?
Also, I thought the NullReferenceException could be coming from the fact that I'm not saving any sports to the database, could this be so?
So I messed around with it a lot, and today I finally found the solution I was looking for.
It seems I asked the question wrong. I didn't include the query from the database, which is probably important to add. I actually omitted a lot of the code to keep things simple in my question, but looks like I omitted too much.
Anyways, it turned out the way I setup the database structure was correct, and nothing had to be changed there.
So here's what I did to get it working:
-The call to the method that fills the day with training sessions needed to go after submitting changes about the day. This is because days have training sessions, and I cant save training sessions without the day already in the database.
-I added using statements around the places where I need to use the datacontext instead of just creating an instance of the datacontext with a local variable. This ensures that the datacontext lives only in the scope of the using statment.
(I changed the DateTime of the day to be the date given as the parameter to the method)
public void CreateDay(DateTime date)
{
DayItem dayItem = new DayItem();
dayItem.DateTime = date;
using (FitPlanDataContext calendarDatabase = new FitPlanDataContext(FitPlanDataContext.ConnectionString))
{
calendarDatabase.DayItems.InsertOnSubmit(dayItem);
calendarDatabase.SubmitChanges();
}
fillTestDayItemWithRandomData(dayItem);
}
Then, the changes to the method that fills the day with training sessions go like this:
-I open a using statement where I instantiate a new datacontext. Then I access the database to retrieve a list of all the sports, and also the day that I need to update. I find the day I need to update by dayItemParameter. (Remember that retrieving from the database will give you a collection.)
-I create my new training sessions and fill their properties. Note that the day I retrieved from the database is the value of a training session's property because the training session is a child of day, and needs to know who its parent day is.
-I removed the instantiation of EntitySet because I realized that I already instantiate it in the constructor of the DayItem class.
-Lastly, I add all the new training sessions into a collection, and save them all to the database at once using InsertAllOnSubmit(collection).
private void fillTestDayItemWithRandomData(DayItem dayItemParameter)
{
using (FitPlanDataContext calendarDatabase = new FitPlanDataContext(FitPlanDataContext.ConnectionString))
{
ObservableCollection<SportArt> sportArtCollection;
var sportArts = (from SportArt sportArt in calendarDatabase.SportArts
select sportArt);
sportArtCollection = new ObservableCollection<SportArt>(sportArts);
ObservableCollection<DayItem> dayItemCollection;
var dayItems = (from DayItem dayItem in calendarDatabase.DayItems
where dayItem.DateTime == dayItemParameter.DateTime
select dayItem);
dayItemCollection = new ObservableCollection<DayItem>(dayItems);
DayItem foundDayItem = dayItemCollection[0];
ObservableCollection<TrainingSession> trainingSessionCollection = new ObservableCollection<TrainingSession>();
TrainingSession trainingSession1 = new TrainingSession();
trainingSession1.DayItem = foundDayItem;
trainingSession1.SportArt = sportArtCollection[1];
trainingSessionCollection.Add(trainingSession1);
TrainingSession trainingSession2 = new TrainingSession();
trainingSession2.DayItem = foundDayItem;
trainingSession2.SportArt = sportArtCollection[2];
trainingSessionCollection.Add(trainingSession2);
calendarDatabase.TrainingSessions.InsertAllOnSubmit<TrainingSession>(trainingSessionCollection);
calendarDatabase.SubmitChanges();
}
}
Conclusion:
The main problem I was having was that I was trying to save training sessions to a day that wasn't submitted to the database. The next big problem (that I think many others have) is that reading and updating of an entity has to be in the same datacontext. So, you can't create a datacontext to retrieve a day, then use another datacontext to add a training session to that day (even if you saved the value of the day to a local variable). You need to retrieve the day and save training sessions to it all in the same data context.
At the moment, my application is working, but it is quite sluggish. In this question, I'm asking about just one day, but in my actual program, I'm creating hundreds of days, which means a lot of opening and closing of the database. If anyone has suggestions to how I can
optimize the process, I'm open ears.
I realize and apologize that this post got so long, but writing it helped me to understand the situation with more depth, and I really hope that it'll help others too.