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  • Calling delegate methods and calling selectors

    - by Crystal
    I'm new to the concept of delegates and selectors when used with notifications. So my first question is, 1) Let's say you have a button that has a delegate that implements some doWork method. If you want the same functionality that's in the method, is it 'ok' to just call that method? I didn't know if that was considered good coding practices and/or if you should do that, or do something different in getting that type of functionality. Like if that is ok architecture? 2) Similarly, with NSNotificationCenter, I see some code that posts a notification. Then there's a HandleSegmentedControl:(NSNotification *)notification method. If I want to manually have that functionality, but without pressing the segment control, is it 'ok' to just take that functionality out of that method and put it in a new method so it would look like this: Original: - (void)HandleSegmentedControl:(NSNotification *)notification { NSDictionary *dict = [userInfo notification]; // do stuff with the dictionary } New: - (void)HandleSegmentedControl:(NSNotification *)notification { NSDictionary *dict = [userInfo notification]; [self newMethod:dict]; } - (void)newMethod:(NSDictionary *)dict { // do stuff with the dictionary } - (void)myOtherMethodThatNeedsTheSameFunctionality { NSDictionary *dict = // create some dictionary [self newMethod:dict]; } Sorry if these are basic questions. I'm not sure what the best practices are for things like this and wanted to start the right way. Thanks.

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  • How to get more detail from an exception?

    - by cusimar9
    I have a .NET 4.0 web application which implements an error handler within the Application_Error event of Global.asax. When an exception occurs this intercepts it and sends me an email including a variety of information like the logged in user, the page the error occurred on, the contents of the session etc. This is all great but there is some fundamental detail missing which I seem unable to locate. For instance, this is a subset of an error I would receive and the associated stack trace: Source: Telerik.Web.UI Message: Selection out of range Parameter name: value Stack trace: at Telerik.Web.UI.RadComboBox.PerformDataBinding(IEnumerable dataSource) at Telerik.Web.UI.RadComboBox.OnDataSourceViewSelectCallback(IEnumerable data) at System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) at Telerik.Web.UI.RadComboBox.OnDataBinding(EventArgs e) at Telerik.Web.UI.RadComboBox.PerformSelect() at System.Web.UI.WebControls.BaseDataBoundControl.DataBind() at Telerik.Web.UI.RadComboBox.DataBind() at System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() at Telerik.Web.UI.RadComboBox.OnPreRender(EventArgs e) at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Control.PreRenderRecursiveInternal() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) Now as lovely as this is I could do with knowing a) the name of the control and b) the value which caused the control to be 'out of range'. Any suggestions about how I could get this sort of information? I've run this in debug mode and the objects passed to Global.asax don't seem to hold any more detail that I can see.

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  • ArrayAccess multidimensional (un)set?

    - by anomareh
    I have a class implementing ArrayAccess and I'm trying to get it to work with a multidimensional array. exists and get work. set and unset are giving me a problem though. class ArrayTest implements ArrayAccess { private $_arr = array( 'test' => array( 'bar' => 1, 'baz' => 2 ) ); public function offsetExists($name) { return isset($this->_arr[$name]); } public function offsetSet($name, $value) { $this->_arr[$name] = $value; } public function offsetGet($name) { return $this->_arr[$name]; } public function offsetUnset($name) { unset($this->_arr[$name]); } } $arrTest = new ArrayTest(); isset($arrTest['test']['bar']); // Returns TRUE echo $arrTest['test']['baz']; // Echo's 2 unset($arrTest['test']['bar']; // Error $arrTest['test']['bar'] = 5; // Error I know $_arr could just be made public so you could access it directly, but for my implementation it's not desired and is private. The last 2 lines throw an error: Notice: Indirect modification of overloaded element. I know ArrayAccess just generally doesn't work with multidimensional arrays, but is there anyway around this or any somewhat clean implementation that will allow the desired functionality? The best idea I could come up with is using a character as a separator and testing for it in set and unset and acting accordingly. Though this gets really ugly really fast if you're dealing with a variable depth. Does anyone know why exists and get work so as to maybe copy over the functionality? Thanks for any help anyone can offer.

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  • Java Process.waitFor() and IO streams

    - by lynks
    I have the following code; String[] cmd = { "bash", "-c", "~/path/to/script.sh" }; Process p = Runtime.getRuntime().exec(cmd); PipeThread a = new PipeThread(p.getInputStream(), System.out); PipeThread b = new PipeThread(p.getErrorStream(), System.err); p.waitFor(); a.die(); b.die(); The PipeThread class is quite simple so I will include it in full; public class PipeThread implements Runnable { private BufferedInputStream in; private BufferedOutputStream out; public Thread thread; private boolean die = false; public PipeThread(InputStream i, OutputStream o) { in = new BufferedInputStream(i); out = new BufferedOutputStream(o); thread = new Thread(this); thread.start(); } public void die() { die = true; } public void run() { try { byte[] b = new byte[1024]; while(!die) { int x = in.read(b, 0, 1024); if(x > 0) out.write(b, 0, x); else die(); out.flush(); } } catch(Exception e) { e.printStackTrace(); } try { in.close(); out.close(); } catch(Exception e) { } } } My problem is this; p.waitFor() blocks endlessly, even after the subprocess has terminated. If I do not create the pair of PipeThread instances, then p.waitFor() works perfectly. What is it about the piping of io streams that is causing p.waitFor() to continue blocking? I'm confused as I thought the IO streams would be passive, unable to keep a process alive, or to make Java think the process is still alive.

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  • AnyCPU/x86/x64 for C# application and it's C++/CLI dependency

    - by Soonts
    I'm Windows developer, I'm using Microsoft visual studio 2008 SP1. My developer machine is 64 bit. The software I'm currently working on is managed .exe written in C#. Unfortunately, I was unable to solve the whole problem solely in C#. That's why I also developed a small managed DLL in C++/CLI. Both projects are in the same solution. My C# .exe build target is "Any CPU". When my C++ DLL build target is "x86", the DLL is not loaded. As far as I understood when I googled, the reason is C++/CLI language, unlike other .NET languages, compiles to the native code, not managed code. I switched the C++ DLL build target to x64, and everything works now. However, AFAIK everything will stop working as soon as my client will install my product on a 32-bit OS. I have to support Windows Vista and 7, both 32 and 64 bit versions of each of them. I don't want to fall back to 32 bits. That 250 lines of C++ code in my DLL is only 2% of my codebase. And that DLL is only used in several places, so in the typical usage scenario it's not even loaded. My DLL implements two COM objects with ATL, so I can't use "/clr:safe" project setting. Is there way to configure the solution and the projects so that C# project builds "Any CPU" version, the C++ project builds both 32 bit and 64 bit versions, then in the runtime when the managed .EXE is starting up, it uses either 32-bit DLL or 64-bit DLL depending on the OS? Or maybe there's some better solution I'm not aware of? Thanks in advance!

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  • How do I implement a listener pattern over RMI using Spring?

    - by predhme
    So here is a generalized version of our application desgin: @Controller public class MyController { @Autowired private MyServiceInterface myServiceInterface; @RequestMapping("/myURL") public @ResponseBody String doSomething() { MyListenerInterface listener = new MyListenerInterfaceImpl(); myServiceInterface.doThenCallListener(listener); // do post stuff } } public interface MyListenerInterface { public void callA(); public void callB(); } public class MyListenerInterfaceImpl implements MyListenerInterface { // ... omitted for clarity } public interface MyServiceInterface { public void doThenCallListener(MyListenerInterface listener); } public class MyServiceImpl { public void doThenCallListener(MyListenerInterface listener) { // do stuff listener.callA(); } } Basically I have a controller that is being called via AJAX in which I am looking to return a response as a string. However, I need to make a call to the backend (MyServiceInterface). That guy is exposed through RMI by using Spring (man that was easy). But the service method as described requires a listener to be registered for invokation completion purposes. So what I assume I need to achieve is transparently to the backend make it so that when the listener methods are called, really the call is going over RMI. I would have thought Spring would have a simple way to wrap a POJO (not a service singleton) with RMI calls. I looked through their documentation but they had nothing besides exposing services via RMI. Could someone point me in the right direction?

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  • Dynamically adding controls from an Event after Page_Init

    - by GenericTypeTea
    Might seem like a daft title as you shouldn't add dynamic controls after Page_Init if you want to maintain ViewState, but I couldn't think of a better way of explaining the problem. I have a class similar to the following: public class WebCustomForm : WebControl, IScriptControl { internal CustomRender Content { get { object content = this.Page.Session[this.SESSION_CONTENT_TRACKER]; return content as CustomRender; } private set { this.Page.Session[this.SESSION_CONTENT_TRACKER] = value; } } } CustomRender is an abstract class that implements ITemplate that I use to self-contain a CustomForms module I'm in the middle of writing. On the Page_Init of the page that holds the WebCustomForm, I Initialise the control by passing the relevant Ids to it. Then on the overridden OnInit method of the WebCustomForm I call the Instantiate the CustomRender control that's currently active: if (this.Content != null) { this.Content.InstantiateIn(this); } The problem is that my CustomRender controls need the ability to change the CustomRender control of the WebCustomForm. But when the events that fire on the CustomRender fire, the Page_Init event has obviously already gone off. So, my question is, how can I change the content of the WebCustomForm from a dynamically added control within it? The way I see it, I have two options: I separate the CustomRender controls out into their own stand alone control and basically have an aspx page per control and handle the events myself on the page (although I was hoping to just make a control I drop on the page and forget about) I don't use events and just keep requesting the current page, but with different Request Parameters Or I go back to the drawing board with any better suggetions anyone can give me.

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  • ASP.NET MVC - How to Unit Test boundaries in the Repository pattern?

    - by JK
    Given a basic repository interface: public interface IPersonRepository { void AddPerson(Person person); List<Person> GetAllPeople(); } With a basic implementation: public class PersonRepository: IPersonRepository { public void AddPerson(Person person) { ObjectContext.AddObject(person); } public List<Person> GetAllPeople() { return ObjectSet.AsQueryable().ToList(); } } How can you unit test this in a meaningful way? Since it crosses the boundary and physically updates and reads from the database, thats not a unit test, its an integration test. Or is it wrong to want to unit test this in the first place? Should I only have integration tests on the repository? I've been googling the subject and blogs often say to make a stub that implements the IRepository: public class PersonRepositoryTestStub: IPersonRepository { private List<Person> people = new List<Person>(); public void AddPerson(Person person) { people.Add(person); } public List<Person> GetAllPeople() { return people; } } But that doesnt unit test PersonRepository, it tests the implementation of PersonRepositoryTestStub (not very helpful).

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  • Method for defining simultaneous has-many and has-one associations between two models in CakePHP?

    - by Hobonium
    One thing with which I have long had problems, within the CakePHP framework, is defining simultaneous hasOne and hasMany relationships between two models. For example: BlogEntry hasMany Comment BlogEntry hasOne MostRecentComment (where MostRecentComment is the Comment with the most recent created field) Defining these relationships in the BlogEntry model properties is problematic. CakePHP's ORM implements a has-one relationship as an INNER JOIN, so as soon as there is more than one Comment, BlogEntry::find('all') calls return multiple results per BlogEntry. I've worked around these situations in the past in a few ways: Using a model callback (or, sometimes, even in the controller or view!), I've simulated a MostRecentComment with: $this->data['MostRecentComment'] = $this->data['Comment'][0]; This gets ugly fast if, say, I need to order the Comments any way other than by Comment.created. It also doesn't Cake's in-built pagination features to sort by MostRecentComment fields (e.g. sort BlogEntry results reverse-chronologically by MostRecentComment.created. Maintaining an additional foreign key, BlogEntry.most_recent_comment_id. This is annoying to maintain, and breaks Cake's ORM: the implication is BlogEntry belongsTo MostRecentComment. It works, but just looks...wrong. These solutions left much to be desired, so I sat down with this problem the other day, and worked on a better solution. I've posted my eventual solution below, but I'd be thrilled (and maybe just a little mortified) to discover there is some mind-blowingly simple solution that has escaped me this whole time. Or any other solution that meets my criteria: it must be able to sort by MostRecentComment fields at the Model::find level (ie. not just a massage of the results); it shouldn't require additional fields in the comments or blog_entries tables; it should respect the 'spirit' of the CakePHP ORM. (I'm also not sure the title of this question is as concise/informative as it could be.)

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  • Lost with hibernate - OneToMany resulting in the one being pulled back many times..

    - by Andy
    I have this DB design: CREATE TABLE report ( ID MEDIUMINT PRIMARY KEY NOT NULL AUTO_INCREMENT, user MEDIUMINT NOT NULL, created TIMESTAMP NOT NULL, state INT NOT NULL, FOREIGN KEY (user) REFERENCES user(ID) ON UPDATE CASCADE ON DELETE CASCADE ); CREATE TABLE reportProperties ( ID MEDIUMINT NOT NULL, k VARCHAR(128) NOT NULL, v TEXT NOT NULL, PRIMARY KEY( ID, k ), FOREIGN KEY (ID) REFERENCES report(ID) ON UPDATE CASCADE ON DELETE CASCADE ); and this Hibernate Markup: @Table(name="report") @Entity(name="ReportEntity") public class ReportEntity extends Report{ @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name="ID") private Integer ID; @Column(name="user") private Integer user; @Column(name="created") private Timestamp created; @Column(name="state") private Integer state = ReportState.RUNNING.getLevel(); @OneToMany(mappedBy="pk.ID", fetch=FetchType.EAGER) @JoinColumns( @JoinColumn(name="ID", referencedColumnName="ID") ) @MapKey(name="pk.key") private Map<String, ReportPropertyEntity> reportProperties = new HashMap<String, ReportPropertyEntity>(); } and @Table(name="reportProperties") @Entity(name="ReportPropertyEntity") public class ReportPropertyEntity extends ReportProperty{ @Embeddable public static class ReportPropertyEntityPk implements Serializable{ /** * long#serialVersionUID */ private static final long serialVersionUID = 2545373078182672152L; @Column(name="ID") protected int ID; @Column(name="k") protected String key; } @EmbeddedId protected ReportPropertyEntityPk pk = new ReportPropertyEntityPk(); @Column(name="v") protected String value; } And i have inserted on Report and 4 Properties for that report. Now when i execute this: this.findByCriteria( Order.asc("created"), Restrictions.eq("user", user.getObject(UserField.ID)) ) ); I get back the report 4 times, instead of just the once with a Map with the 4 properties in. I'm not great at Hibernate to be honest, prefer straight SQL but I must learn, but i can't see what it is that is wrong.....? Any suggestions?

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  • Question about decorator pattern and the abstract decorator class?

    - by es11
    This question was asked already here, but rather than answering the specific question, descriptions of how the decorator pattern works were given instead. I'd like to ask it again because the answer is not immediately evident to me just by reading how the decorator pattern works (I've read the wikipedia article and the section in the book Head First Design Patterns). Basically, I want to know why an abstract decorator class must be created which implements (or extends) some interface (or abstract class). Why can't all the new "decorated classes" simply implement (or extend) the base abstract object themselves (instead of extending the abstract decorator class)? To make this more concrete I'll use the example from the design patterns book dealing with coffee beverages: There is an abstract component class called Beverage Simple beverage types such as HouseBlend simply extend Beverage To decorate beverage, an abstract CondimentDecorator class is created which extends Beverage and has an instance of Beverage Say we want to add a "milk" condiment, a class Milk is created which extends CondimentDecorator I'd like to understand why we needed the CondimentDecorator class and why the class Milk couldn't have simply extended the Beverage class itself and been passed an instance of Beverage in its constructor. Hopefully this is clear...if not I'd simply like to know why is the abstract decorator class necessary for this pattern? Thanks. Edit: I tried to implement this, omitting the abstract decorator class, and it seems to still work. Is this abstract class present in all descriptions of this pattern simply because it provides a standard interface for all of the new decorated classes?

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  • ASP.NET ListView, custom DataSources, and editing items

    - by Andrew Shepherd
    The MSDN walkthroughs provide a number of examples where you can drag a DataSource from the toolbox, run through some simple configuration steps, then drag a ListView onto the screen, point it at the DataSource, and hey - you've got full table editing. Now I'm trying to write my own DataSource class (a class that implements System.Web.UI.IDataSource) and my own DataSourceView class. I now assign an instance of this custom DataSource class to the ListView.DataSource propery. The display of all the items is working well. However, updating, inserting and deleting just is not working. I'm overriding every function I can in my DataSourceView class, and they just aren't being called. This is such a huge topic, I'll focus this question on one simple example: When you press the "Edit" button (the button inside the ItemTemplate with a CommandName of "Edit", you expect the ItemTemplate to be replaced by an EditItemTemplate. This did not happen. The only way I could get it to happen was to handle the onitemediting event. protected void _listViewPublicHolidays_ItemEditing(object sender, ListViewEditEventArgs e) { _listViewPublicHolidays.EditIndex = e.NewEditIndex; _listViewPublicHolidays.DataBind(); } This is hardly a problem, but how come I had to do it at all? In the MSDN walkthroughs where I attach a ListView to a LinqDataSource, this code doesn't have to be written. Can someone who's been here before hazard a guess as to what would be different or missing in my custom datasource?

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  • When combo box is selected then display Combo Box and then when any Item in Combo Box is selected then make JTextField visible

    - by Gugz_Singh
    I am having trouble with my code. What i'm trying to do is: 1. Create a Check Box, make it visible 2. When Check Box is selected display Combo Box, which will have few items for example ("1","2") 3. When 1 is selected from Combo Box then make 1 Text Field visible 4. When 2 is selected from Combo Box then make 2 Text Field's visible What I am able to do is when Check Box is clicked, it displays the Combo Box with the items. I am not able provide functionality to the items in the Combo Box, such as when Item1 is clicked then make 1 Text Field visible. Please help needed. My Code: public void replacement_used(){ no_of_part_used_label.setVisible(false); no_part_used_list.setVisible(false); part_no_one_label.setVisible(false); part_no_one_field.setVisible(false); part_no_two_label.setVisible(false); part_no_two_field.setVisible(false); part_no_three_label.setVisible(false); part_no_three_field.setVisible(false); part_no_four_label.setVisible(false); part_no_four_field.setVisible(false); part_no_five_label.setVisible(false); part_no_five_field.setVisible(false); HandlerClass handler = new HandlerClass(); replacement_part_check_box.addItemListener(handler); } private class HandlerClass implements ItemListener{ public void itemStateChanged(ItemEvent event){ if (replacement_part_check_box.isSelected()){ no_of_part_used_label.setVisible(true); no_part_used_list.setVisible(true); } x(); } } public void x(){ System.out.println("Start of x fucntion"); if( no_part_used_list.getSelectedItem().equals("1") ){ System.out.println("It is 1"); part_no_one_label.setVisible(true); part_no_one_field.setVisible(true); } }

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  • Google App Engine how to get an object from the servlet ?

    - by Frank
    I have the following class objects in Google App Engine's dadastore, I can see them from the "Datastore Viewer " : import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.IdentityType; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) Long Id; public static final long serialVersionUID=26362862L; String Contact_Id="",First_Name="",Last_Name="",Company_Name="",Branch_Name="",Address_1="",Address_2="",City="",State="",Zip="",Country=""; double D_1,D_2; boolean B_1,B_2; Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } ...... } How can my java applications get the object from a servlet url ? For instance if have an instance of Contact_Info_Entry who's Contact_Id is "ABC-123", and my App Id is : nm-java When my java program accesses the url : "http://nm-java.appspot.com/Check_Contact_Info?Contact_Id=ABC-123 How will the Check_Contact_Info servlet get the object from datastore and return it to my app ? public class Check_Contact_Info_Servlet extends HttpServlet { static boolean Debug=true; public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { } ... protected void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { doGet(request,response); } } Frank

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  • MouseMotion Sensor Method Call

    - by user321894
    I have a soon-to-be due assignment due in computer science. I have encountered a problem, for which no matter how long I study the API's of the class and superclasses, I can not figure out. Suppose I wish to design a sort of "Breakout game" where the mouse motion controls the motion of a block that is used to bounce a ball, which then destroys multi colored bricks. How do you specifically make the block "listen" to the mouse? The below code is what I have attempted to achieve the desired results. /** Breakout Program*/ public class Breakout extends GraphicsProgram implements MouseMotionListener { ... /** The Paddle Itself */ private GRect paddle = new GRect(0, HEIGHT-PADDLEBOTTOM_OFFSET, PADDLEWIDTH, PADDLEHEIGHT); ... /** Run the Breakout program. */ public void run() { paddle.setFillColor(Color.BLACK); paddle.setFilled(true); add(paddle); paddle.addMouseListener(this); ... } /** Move the horizontal middle of the paddle to the x-coordinate of the mouse position - * -but keep the paddle completely on the board. */ public void mouseMoved(MouseEvent e) { GPoint p= new GPoint(e.getPoint()); double x = p.getX(); paddle.setLocation(x, HEIGHT-PADDLEBOTTOM_OFFSET); } } Any clarification on why/what I am doing incorrectly would be helpful, thanks.

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  • Java enums in generic type

    - by Marcin Cylke
    Hi, I'd like to create a generic enum-based mapper for IBatis. I'm doing this with the below code. This does have compile time errors, which I don't know how to fix. Maybe my solution is just plain wrong (keep in mind the use of IBatis), in such case please suggest something better. Any help appreciated. What I want to achieve is to define subsequent mappers as: public class XEnumTypeHandler extends CommonEnumTypeHandler<X> { } The current code: public class CommonEnumTypeHandler<T extends Enum> implements TypeHandlerCallback { public void setParameter(ParameterSetter ps, Object o) throws SQLException { if (o.getClass().isAssignableFrom(**T**)) { ps.setString(((**T**) o).value().toUpperCase()); } else throw new SQLException("Excpected ParameterType object than: " + o); } public Object getResult(ResultGetter rs) throws SQLException { Object o = valueOf(rs.getString()); if (o == null) throw new SQLException("Unknown parameter type: " + rs.getString()); return o; } public Object valueOf(String s) { for (T pt : T.**values()**) { if (pt.**value()**.equalsIgnoreCase(s)) return pt; } return null; } } I've added error markings to the above code, the error messages are in order: T cannot be resolved The method value() is undefined for the type T The method values() is undefined for the type T The method values() is undefined for the type T

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  • Time complexity to fill hash table (homework)?

    - by Heathcliff
    This is a homework question, but I think there's something missing from it. It asks: Provide a sequence of m keys to fill a hash table implemented with linear probing, such that the time to fill it is minimum. And then Provide another sequence of m keys, but such that the time fill it is maximum. Repeat these two questions if the hash table implements quadratic probing I can only assume that the hash table has size m, both because it's the only number given and because we have been using that letter to address a hash table size before when describing the load factor. But I can't think of any sequence to do the first without knowing the hash function that hashes the sequence into the table. If it is a bad hash function, such that, for instance, it hashes every entry to the same index, then both the minimum and maximum time to fill it will take O(n) time, regardless of what the sequence looks like. And in the average case, where I assume the hash function is OK, how am I suppossed to know how long it will take for that hash function to fill the table? Aren't these questions linked to the hash function stronger than they are to the sequence that is hashed? As for the second question, I can assume that, regardless of the hash function, a sequence of size m with the same key repeated m-times will provide the maximum time, because it will cause linear probing from the second entry on. I think that will take O(n) time. Is that correct? Thanks

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  • Creating futures using Apple's GCD

    - by jer
    I'm working on a library which implements the actor model on top of Grand Central Dispatch (specifically the C level API libdispatch). Basically a brief overview of my system is as such: Communication happens between actors using messages Multicast communication only (one actor to many actors) Senders and receivers are decoupled from one another using a blackboard where messages are pushed to. Messages are sent in the default queue asynchronously using dispatch_group_async() once a message gets pushed onto the blackboard. I'm trying to implement futures in the language right now, so I've created a new type which holds some information: A group of its own The value being 'returned' However, I have a problem since dispatch_block_t is of type void (^)(void) so it doesn't return anything. So my idea of in my future_new() function of setting up another group which can be used to execute a block returning a result, which I can store in my "value" member in my future_t structure, isn't going to work. The rest of the futures implementation is very clear, except it all depends on being able to get the value into the future back from the actor, acting on the message. When using the library, it would greatly reduce its usefulness if I had to ask users (and myself) to be aware when futures were going to be used by other parts of the system—It just isn't practical. I'm wondering if anyone can think of a way around this?

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  • Conventions for the behavior of double or triple "click to select text" features?

    - by John Sullivan
    Almost any mature program that involves text implements "double click to select the word" and, in some cases, "triple click to select additional stuff like an entire line" as a feature. I find these features useful but they are often inconsistent between programs. Example - some programs' double clicks do not select the ending space after a word, but most do. Some recognize the - character as the end of a word, others do not. SO likes to select the entire paragraph as I write this post when I triple click it, VS web developer 2005 has no triple click support, and ultra-edit 32 will select one line upon triple clicking. We could come up with innumerable inconsistencies about how double and triple click pattern matching is implemented across programs. I am concerned about how to implement this behavior in my program if nobody else has achieved a convention about how the pattern matching should work. My question is, does a convention (conventions? maybe an MS or Linux convention?) exist that dictates how these features are supposed to behave to the end user? What, if any, are they?

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  • @PrePersist with entity inheritance

    - by gerry
    I'm having some problems with inheritance and the @PrePersist annotation. My source code looks like the following: _the 'base' class with the annotated updateDates() method: @javax.persistence.Entity @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS) public class Base implements Serializable{ ... @Id @GeneratedValue protected Long id; ... @Column(nullable=false) @Temporal(TemporalType.TIMESTAMP) private Date creationDate; @Column(nullable=false) @Temporal(TemporalType.TIMESTAMP) private Date lastModificationDate; ... public Date getCreationDate() { return creationDate; } public void setCreationDate(Date creationDate) { this.creationDate = creationDate; } public Date getLastModificationDate() { return lastModificationDate; } public void setLastModificationDate(Date lastModificationDate) { this.lastModificationDate = lastModificationDate; } ... @PrePersist protected void updateDates() { if (creationDate == null) { creationDate = new Date(); } lastModificationDate = new Date(); } } _ now the 'Child' class that should inherit all methods "and annotations" from the base class: @javax.persistence.Entity @NamedQueries({ @NamedQuery(name=Sensor.QUERY_FIND_ALL, query="SELECT s FROM Sensor s") }) public class Sensor extends Entity { ... // additional attributes @Column(nullable=false) protected String value; ... // additional getters, setters ... } If I store/persist instances of the Base class to the database, everything works fine. The dates are getting updated. But now, if I want to persist a child instance, the database throws the following exception: MySQLIntegrityConstraintViolationException: Column 'CREATIONDATE' cannot be null So, in my opinion, this is caused because in Child the method "@PrePersist protected void updateDates()" is not called/invoked before persisting the instances to the database. What is wrong with my code?

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  • Should I return IEnumerable<T> or IQueryable<T> from my DAL?

    - by Gary '-'
    I know this could be opinion, but I'm looking for best practices. As I understand, IQueryable implements IEnumerable, so in my DAL, I currently have method signatures like the following: IEnumerable<Product> GetProducts(); IEnumerable<Product> GetProductsByCategory(int cateogoryId); Product GetProduct(int productId); Should I be using IQueryable here? What are the pros and cons of either approach? Note that I am planning on using the Repository pattern so I will have a class like so: public class ProductRepository { DBDataContext db = new DBDataContext(<!-- connection string -->); public IEnumerable<Product> GetProductsNew(int daysOld) { return db.GetProducts() .Where(p => p.AddedDateTime > DateTime.Now.AddDays(-daysOld )); } } Should I change my IEnumerable<T> to IQueryable<T>? What advantages/disadvantages are there to one or the other?

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  • Weird camera Intent behavior

    - by David Erosa
    Hi all. I'm invoking the MediaStore.ACTION_IMAGE_CAPTURE intent with the MediaStore.EXTRA_OUTPUT extra so that it does save the image to that file. On the onActivityResult I can check that the image is being saved in the intended file, which is correct. The weird thing is that anyhow, the image is also saved in a file named something like "/sdcard/Pictures/Camera/1298041488657.jpg" (epoch time in which the image was taken). I've checked the Camera app source (froyo-release branch) and I'm almost sure that the code path is correct and wouldn't have to save the image, but I'm a noob and I'm not completly sure. AFAIK, the image saving process starts with this callback (comments are mine): private final class JpegPictureCallback implements PictureCallback { ... public void onPictureTaken(...){ ... // This is where the image is passed back to the invoking activity. mImageCapture.storeImage(jpegData, camera, mLocation); ... public void storeImage(final byte[] data, android.hardware.Camera camera, Location loc) { if (!mIsImageCaptureIntent) { // Am i an intent? int degree = storeImage(data, loc); // THIS SHOULD NOT BE CALLED WITHIN THE CAPTURE INTENT!! ....... // An finally: private int storeImage(byte[] data, Location loc) { try { long dateTaken = System.currentTimeMillis(); String title = createName(dateTaken); String filename = title + ".jpg"; // Eureka, timestamp filename! ... So, I'm receiving the correct data, but it's also being saved in the "storeImage(data, loc);" method call, which should not be called... It'd not be a problem if I could get the newly created filename from the intent result data, but I can't. When I found this out, I found about 20 image files from my tests that I didn't know were on my sdcard :) I'm getting this behavior both with my Nexus One with Froyo and my Huawei U8110 with Eclair. Could please anyone enlight me? Thanks a lot.

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  • Anyone know exactly which JMS messages will be redelivered in CLIENT_ACKNOWLEDGE mode if the client

    - by user360612
    The spec says "Acknowledging a consumed message automatically acknowledges the receipt of all messages that have been delivered by its session" - but what I need to know is what it means by 'delivered'. For example, if I call consumer.receive() 6 times, and then call .acknowledge on the 3rd message - is it (a) just the first 3 messages that are ack'd, or (b) all 6? I'm really hoping it's option a, i.e. messages after the one you called acknowledge on WILL be redelivered, otherwise it's hard to see how you could prevent message lost in the event of my receiver process crashing before I've had a chance to persist and acknowledge the messages. But the spec is worded such that it's not clear. I get the impression the authors of the JMS spec considered broker failure, but didn't spend too long thinking about how to protect against client failure :o( Anyway, I've been able to test with SonicMQ and found that it implements (a), i.e. messages 'received' later than the message you call .ack on DO get redelivered in the event of a crash, but I'd love to know how other people read the standard, and if anyone knows how any other providers have implemented CLIENT_ACKNOWLEDGE? (i.e. what the 'de facto' standard is) Thanks Ben

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  • Generating a field setter and getter with ASM

    - by ng
    I would like to avoid reflection in an open source project I am developing. Here I have classes like the following. public class PurchaseOrder { @Property private Customer customer; @Property private String name; } I scan for the @Property annotation to determine what I can set and get from the PurchaseOrder reflectively. There are many such classes all using java.lang.reflect.Field.get() and java.lang.reflect.Field.set(). Ideally I would like to generate for each property an invoker like the following. public interface PropertyAccessor<S, V> { public void set(S source, V value); public V get(S source); } Now when I scan the class I can create a static inner class of PurchaseOrder like so. static class customer_Field implements PropertyAccessor<PurchaseOrder, Customer> { public void set(PurchaseOrder order, Customer customer) { order.customer = customer; } public Customer get(PurchaseOrder order) { return order.customer; } } With these I totally avoid the cost of reflection. I can now set and get from my instances with native performance. Can anyone tell me how I would do this. A code example would be great. I have searched the net for a good example but can find nothing like this. The ASM examples are pretty poor also. The key here is that I have an interface that I can pass around. So I can have various implementations, perhaps one with Java Reflection as a default, one with ASM, and maybe one with Javassist? Any help would be greatly appreciated.

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  • WCF service reference namespace differs from original

    - by Thorarin
    I'm having a problem regarding namespaces used by my service references. I have a number of WCF services, say with the namespace MyCompany.Services.MyProduct (the actual namespaces are longer). As part of the product, I'm also providing a sample C# .NET website. This web application uses the namespace MyCompany.MyProduct. During initial development, the service was added as a project reference to the website and uses directly. I used a factory pattern that returns an object instance that implements MyCompany.Services.MyProduct.IMyService. So far, so good. Now I want to change this to use an actual service reference. After adding the reference and typing MyCompany.Services.MyProduct in the namespace textbox, it generates classes in the namespace MyCompany.MyProduct.MyCompany.Services.MyProduct. BAD! I don't want to have to change using directives in several places just because I'm using a proxy class. So I tried prepending the namespace with global::, but that is not accepted. Note that I hadn't even deleted the original assembly references yet, and "reuse types" is enabled, but no reusing was done, apparently. However, I don't want to keep the assembly references around in my sample website for it to work anyway. The only solution I've come up with so far is setting the default namespace for my web application to MyCompany (because it cannot be empty), and adding the service reference as Services.MyProduct. Suppose that a customer wants to use my sample website as a starting point, and they change the default namespace to OtherCompany.Whatever, this will obviously break my workaround. Is there a good solution to this problem? To summarize: I want to generate a service reference proxy in the original namespace, without referencing the assembly. Note: I have seen this question, but there was no solution provided that is acceptable for my use case. Edit: As John Saunders suggested, I've submitted some feedback to Microsoft about this: Feedback item @ Microsoft Connect

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