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  • Google App Engine - DELETE JPQL Query and Cascading

    - by Taylor Leese
    I noticed that the children of PersistentUser are not deleted when using the JPQL query below. However, the children are deleted if I perform an entityManager.remove(object). Is this expected? Why doesn't the JPQL query below also perform a cascaded delete? @OneToMany(mappedBy = "persistentUser", cascade = CascadeType.ALL) private Collection<PersistentLogin> persistentLogins; ... @Override @Transactional public final void removeUserTokens(final String username) { final Query query = entityManager.createQuery( "DELETE FROM PersistentUser p WHERE username = :username"); query.setParameter("username", username); query.executeUpdate(); }

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  • Need help understanding the MVC design pattern

    - by Doron Sinai
    Hi, I am trying to find a ood example of MVC design pattern in java. This is what i understood from reading about it, please correct me if I am wrong: I have the Model part which is the logic behind the program, let's say if we have a phonebook, so adding and removing contact from the Array will be the model. The Gui is the view and it contains buttons that upon clicking them, the model is changing. What I am trying to undersand what is the controller part, is it the ActionListeners? how to you seperate those modules in practice. thank you

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  • What software design pattern is best for the following scenario (C#)

    - by askjdh
    I have a gps device that records data e.g. datetime, latitude, longitude I have an sdk that reads the data from the device. The way the data is read: A command packet (basically a combination of int values in a struct) is sent to the device. The device responds with the data in fixed size chunks e.g. 64bytes Depending on the command issued I will get back differect data structs e.g. sending command 1 to the device returns a struct like struct x { id int, name char[20] } command 2 returns a collection of the following structs (basically it boils down to an array of the structs - y[12]) struct y { date datetime, lat decimal, lon decimal } I would then want to convert the struct to a class and save the data to a database. What would be the best way to encapsulate the entire process, preferably using some established design pattern? Many thanks M

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  • Google App Engine - Cannot See Children in Datastore Viewer

    - by Taylor L
    I have the following kinds/relationships in my datastore: UserAccount 1-to-1 PersistentLogin 1-to-many PersistentLogins They are all in the same entity group and UserAccount is the parent. Should I expect to see the other kinds in the datastore viewer? Currently, I only see UserAccount entities, but I'm pretty confident the other entities are there because my code is working as expected. Is this just a nuance of the datastore viewer?

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  • Java How to get exact tile location in random tile engine

    - by SYNYST3R1
    I am using the slick2d library. I want to know how to get the exact tile location so when I click on a tile it only changes that tile and not every tile on the screen. My tile generation class public Image[] tiles = new Image[3]; public int width, height; public int[][] index; public Image grass, dirt, selection; boolean selected; int mouseX, mouseY; public void init() throws SlickException { grass = new Image("assets/tiles/grass.png"); dirt = new Image("assets/tiles/dirt.png"); selection = new Image("assets/tiles/selection.png"); tiles[0] = grass; tiles[1] = dirt; width = 50; height = 50; index = new int[width][height]; Random rand = new Random(); for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { index[x][y] = rand.nextInt(2); } } } public void update(GameContainer gc) { Input input = gc.getInput(); mouseX = input.getMouseX(); mouseY = input.getMouseY(); if(input.isMouseButtonDown(Input.MOUSE_LEFT_BUTTON)) { selected = true; } else{ selected = false; } } public void render() { for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { tiles[index[x][y]].draw(x * 64, y *64); if(IsMouseInsideTile(x, y)) selection.draw(x * 64, y * 64); } } } public boolean IsMouseInsideTile(int x, int y) { return (mouseX >= x * 64 && mouseX <= (x + 1) * 64 && mouseY >= y * 64 && mouseY <= (y + 1) * 64); } I have tried a couple different ways to change the tile I am clicking on, but I don't understand how to do it.

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  • Google App Engine PersistenceManager can process multiple objects ?

    - by Frank
    I have some code like this : PersistenceManager pm=PMF.get().getPersistenceManager(); String query="select from "+PayPal_Message.class.getName()+" where processed == false order by time desc"; List<PayPal_Message> messages=(List<PayPal_Message>)pm.newQuery(query).execute(); if (messages.isEmpty()) { } else { for (PayPal_Message g : messages) { Contact_Info_Entry A_Contact_Entry=Process_PayPal_Message_To_Get_A_License(g.getContent().getValue()); pm=PMF.get().getPersistenceManager(); try { pm.makePersistent(A_Contact_Entry); g.setProcessed(true); pm.makePersistent(g); } catch (Exception e) { Send_Email(Email_From,"[email protected]","Servlet Error Message [ "+time+" ]",new Text(e.toString())); } // finally { pm.close(); } } } pm.close(); I wonder if it's ok to use the pm above to process multiple objects before closing it. Or do I have to get and close pm for processing each object ?

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  • Google App Engine django model form does not pick up BlobProperty

    - by Wes
    I have the following model: class Image(db.Model): auction = db.ReferenceProperty(Auction) image = db.BlobProperty() thumb = db.BlobProperty() caption = db.StringProperty() item_to_tag = db.StringProperty() And the following form: class ImageForm(djangoforms.ModelForm): class Meta: model = Image When I call ImageForm(), only the non-Blob fields are created, like this: <tr><th><label for="id_auction">Auction:</label></th><td><select name="auction" id="id_auction"> <option value="" selected="selected">---------</option> <option value="ahRoYXJ0bWFuYXVjdGlvbmVlcmluZ3INCxIHQXVjdGlvbhgKDA">2010-06-19 11:00:00</option> </select></td></tr> <tr><th><label for="id_caption">Caption:</label></th><td><input type="text" name="caption" id="id_caption" /></td></tr> <tr><th><label for="id_item_to_tag">Item to tag:</label></th><td><input type="text" name="item_to_tag" id="id_item_to_tag" /></td></tr> I want the Blob fields to be included in the form as well (as file inputs). What am I doing wrong?

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  • Fetching just the Key/id from a ReferenceProperty in App Engine

    - by ozone
    Hi SO, I could use a little help in AppEngine land... Using the [Python] API I create relationships like this example from the docs: class Author(db.Model): name = db.StringProperty() class Story(db.Model): author = db.ReferenceProperty(Author) story = db.get(story_key) author_name = story.author.name As I understand it, that example will make two datastore queries. One to fetch the Story and then one to deference the Author inorder to access the name. But I want to be able to fetch the id, so do something like: story = db.get(story_key) author_id = story.author.key().id() I want to just get the id from the reference. I do not want to have to deference (therefore query the datastore) the ReferenceProperty value. From reading the documentation it says that the value of a ReferenceProperty is a Key Which leads me to think that I could just call .id() on the reference's value. But it also says: The ReferenceProperty model provides features for Key property values such as automatic dereferencing. I can't find anything that explains when this referencing takes place? Is it safe to call .id() on the ReferenceProperty's value? Can it be assumed that calling .id() will not cause a datastore lookup?

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  • How to let an average user design a boolean expression graphically

    - by Svein Bringsli
    In our application there's a list of customers, and a list of keywords (among other things). Each customer can have a number of keywords, but it's not mandatory. So for instance, one customer can have the keywords "retail" and "chain", one can have only "contractor" and a third can have none at all. I want to let the user make a selection of customers based on these keywords, but not having to write (retail AND chain) or contractor and not wholesale I would like to make it as user-friendly as possible, and ideally with only "simple" controls, like checkboxes, comboboxes etc. Does anyone have any suggestions on how to design this? Or maybe some examples of applications where there are similar functionality?

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  • Delete an entity by key without fetching it first in app engine (using JDO)

    - by Peter Recore
    Is there a way to delete an entity without having to fetch it from the datastore first? I am assuming I already have the key or id for the entity. I'm thinking of something like deleteObjectById that would be an analogue to getObjectById on PersistenceManager. The closest I can think of is using Query.deletePersistentAll() (as seen here) and specifying a query that only relies on the key, but I can't tell if that is going to fetch the entity before deleting it. thanks EDIT: I know how to do this using the low level API, as well as in the python API. I was wondering if there was a way to do it within the JDO layer.

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  • Design pattern for extending Android's activities?

    - by Carl
    While programming on Android, I end up writing a parent activity which is extended by several others. A bit like ListActivity. My parent activity extends Activity. if I intend to use a Map or a List, I can't use my parent activity as superclass - the child activity can only extend one activity obviously. As such I end up writing my parent activities with the same logic for Activity, ListActivity, MapActivity and so forth. What am I looking for is some sort of trait functionality/design pattern which would help in this case. Any suggestions?

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  • Google App Engine - Dealing with concurrency issues of storing an object

    - by Spines
    My User object that I want to create and store in the datastore has an email, and a username. How do I make sure when creating my User object that another User object doesn't also have either the same email or the same username? If I just do a query to see if any other users have already used the username or the email, then there could be a race condition. UPDATE: The solution I'm currently considering is to use the MemCache to implement a locking mechanism. I would acquire 2 locks before trying to store the User object in the datastore. First a lock that locks based on email, then another that locks based on username. Since creating new User objects only happens at user registration time, and it's even rarer that two people try to use either the same username or the same email, I think it's okay to take the performance hit of locking. I'm thinking of using the MemCache locking code that is here: http://appengine-cookbook.appspot.com/recipe/mutex-using-memcache-api/ What do you guys think?

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  • Google App Engine Application Error 5

    - by Sam
    I frequently get this Application error. What does this mean ? File "/base/data/home/apps/0xxopdp/10.347467753731922836/matrices.py", line 215, in insert_into_db obj.put() File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/db/__init__.py", line 895, in put return datastore.Put(self._entity, config=config) File "/base/python_runtime/python_lib/versions/1/google/appengine/api/datastore.py", line 404, in Put return _GetConnection().async_put(config, entities, extra_hook).get_result() File "/base/python_runtime/python_lib/versions/1/google/appengine/datastore/datastore_rpc.py", line 601, in get_result self.check_success() File "/base/python_runtime/python_lib/versions/1/google/appengine/datastore/datastore_rpc.py", line 572, in check_success rpc.check_success() File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_stub_map.py", line 502, in check_success self.__rpc.CheckSuccess() File "/base/python_runtime/python_lib/versions/1/google/appengine/api/apiproxy_rpc.py", line 126, in CheckSuccess raise self.exception ApplicationError: ApplicationError: 5 I do make many calls to the datastore. What caused this problem ?

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  • Example where Up-Front Design (Would have) Saved You Time

    - by Winston Ewert
    In various places I've seen the claim that by designing a system up-front, you can significantly reduce development time. I.e. by spending an hour designing you can save a week coding. My problem is that I have never seen a situation where I found this to be true. So I want to know of any examples out there that people have where this would be true: So: What sort of problem arose during coding? (or was avoided?) How could you have avoided (or did avoid) the problem by spending more time doing design? Why was it (or would it have been) hard to fix the problem in the code?

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  • App Engine Django Form Uniqueness Validation?

    - by GeekTantra
    Is there a simpler way to use uniqueness validation with Django Forms in AppEngine? I understand that performance would be problem if we keep an uniqueness constraint but since the amount of data being added is very small performance is not a big concern, rather development time is a concern here. Any help is appreciated.

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  • Doubts on Expression Engine

    - by bparanj
    Is EE better than Plone? Is there a way to allow guest bloggers to post content in EE? Is anyone interested in attending the EE conference this year? There is a discount if we sign up as a group. Please contact me directly if you are interested bparanj at gmail.

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  • Database Design for One to One relationships

    - by Greelmo
    I'm trying to finalize my design of the data model for my project, and am having difficulty figuring out which way to go with it. I have a table of users, and an undetermined number of attributes that apply to that user. The attributes are in almost every case optional, so null values are allowed. Each of these attributes are one to one for the user. Should I put them on the same table, and keep adding columns when attributes are added (making the user table quite wide), or should I put each attribute on a separate table with a foreign key to the user table. I have decided against using the EAV model. Thanks!

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  • Theory of Game Interface Design

    - by anon
    Anyone know of a good book on Game Interface Design (not game play mechanics; the actual UI). I'm particular interested in theories of cognition, and how game interfaces are designed to allow the enduser efficient communication with the game (whether it in FPS, RTS, or so on). In a modern game, the amount of information conveyed to the user, the amount of choices the user can make; and the support for the user to make said decisions is simply astounding (think UIs for Starcraft II / WoW). Any insights into this would be greatly appreciated.

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  • how to send some data to the Thread module on python and google-map-engine

    - by zjm1126
    from google.appengine.ext import db class Log(db.Model): content = db.StringProperty(multiline=True) class MyThread(threading.Thread): def run(self,request): #logs_query = Log.all().order('-date') #logs = logs_query.fetch(3) log=Log() log.content=request.POST.get('content',None) log.put() def Log(request): thr = MyThread() thr.start(request) return HttpResponse('') error is : Exception in thread Thread-1: Traceback (most recent call last): File "D:\Python25\lib\threading.py", line 486, in __bootstrap_inner self.run() File "D:\zjm_code\helloworld\views.py", line 33, in run log.content=request.POST.get('content',None) NameError: global name 'request' is not defined

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  • Reg Google app engine datastore -primarykey

    - by megala
    hi, I created table in google Big table datastore ,In that the i set primary key using @annotations as follows @Id @Column(name = "groupname") private String groupname; @Basic private String groupdesc; I worked corretly,but it override the previous record,how to solve this for eg if i entered groupname=group1 groupdesc=groupdesc than it accept after that i enter same groupname it override previous record for eg groupname=group1 groupdesc=groups this record override previous one.

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