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  • jpa-Primarykey relationship

    - by megala
    Hi created student entity in gogole app engine datastore using JPA. Student---Coding @Entity @Table(name="StudentPersonalDetails", schema="PUBLIC") public class StudentPersonalDetails { @Id @Column(name = "STUDENTNO") private Long stuno; @Basic @Column(name = "STUDENTNAME") private String stuname; public void setStuname(String stuname) { this.stuname = stuname; } public String getStuname() { return stuname; } public void setStuno(Longstuno) { this.stuno = stuno; } public Long getStuno() { return stuno; } public StudentPersonalDetails(Long stuno,String stuname) { this.stuno = stuno; this.stuname = stuname; } } I stored Property value as follows Stuno Stuname 1 a 2 b If i stored Again Stuno No 1 stuname z means it wont allow to insert the record But. It Overwrite the value Stuno Stuname 1 z 2 b How to solve this?

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  • How do I calculate a good hash code for a list of strings?

    - by Ian Ringrose
    Background: I have a short list of strings. The number of strings is not always the same, but are nearly always of the order of a “handful” In our database will store these strings in a 2nd normalised table These strings are never changed once they are written to the database. We wish to be able to match on these strings quickly in a query without the performance hit of doing lots of joins. So I am thinking of storing a hash code of all these strings in the main table and including it in our index, so the joins are only processed by the database when the hash code matches. So how do I get a good hashcode? I could: Xor the hash codes of all the string together Xor with multiply the result after each string (say by 31) Cat all the string together then get the hashcode Some other way So what do people think? (If you care we are using .NET and SqlServer)

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  • can a .class file be added to the urlpath of a URLClassLoader

    - by java_geek
    I have a custom class loader which extends from a URLClassLoader. I added a .class file to the urlpath using addURL(); but when i do a class.forname() using this loader i get a ClassNotFoundException. However, if i create a jar and add the jar to the urlpath, i do not get any exception. What can be added to the urlpath of a URLClassLoader usign addURL()

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  • Getting N random numbers that the sum is M

    - by marionmaiden
    Hello I want to get N random numbers that the sum of them is a value. For example, let's suppose I want 5 random numbers that their sum is 1 Then, a valid possibility is: 0.2 0.2 0.2 0.2 0.2 Other possibility is: 0.8 0.1 0.03 0.03 0.04 And so on. I need this for the creation of the matrix of belongings of the Fuzzy C-means.

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  • Gson serialization depending on field value

    - by Serj Lotutovici
    I have a POJO that is similar to: public class MyGsonPojo { @Expose @SerializedName("value1") private String valueOne; @Expose @SerializedName("value2") private boolean valueTwo; @Expose @SerializedName("value3") private int valueThree; // Getters and other stuff here } The issue is that this object has to be serialized into a json body for a call to the server. Some fields are optional for the request and if I even send it with default and null values, the API responds differently (Unfortunately changing the api is not an option). So basically I need to exclude fields from serialization if any of them is set to a default value. For example if the field valueOne is null the resulting json should be: { "value2" : true, "value3" : 2 } Any idea how to make this a painless effort? I wouldn't want to build the json body manually. Any help would be great. Thank you in advice.

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  • Hibernate: getting a record but it's being updated in the database?

    - by jack
    For some reason Hibernate seems to be keeping my session open and updating the object without me explicitely invoking a save/update/saveorupdate. I guess the session is staying open and it's beeing marked as dirty. However this is not the desired behaviour, so what's the cleanest way to fix this? The issue seems to occur because I store a phone number without formatting in the database but the getter of the object returns a formatted telephone number. My flow: go to a jsp = controller = service = dao DAO getter function if(userId != 0) { return (User)dbFactory.get(User.class, userId); } return null; The service just passes it to the controller and the controller puts te User object in the request scope. I display it on my JSP page using EL.

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  • Google Data Api returning an invalid access token

    - by kingdavies
    I'm trying to pull a list of contacts from a google account. But Google returns a 401. The url used for requesting an authorization code: String codeUrl = 'https://accounts.google.com/o/oauth2/auth' + '?' + 'client_id=' + EncodingUtil.urlEncode(CLIENT_ID, 'UTF-8') + '&redirect_uri=' + EncodingUtil.urlEncode(MY_URL, 'UTF-8') + '&scope=' + EncodingUtil.urlEncode('https://www.google.com/m8/feeds/', 'UTF-8') + '&access_type=' + 'offline' + '&response_type=' + EncodingUtil.urlEncode('code', 'UTF-8') + '&approval_prompt=' + EncodingUtil.urlEncode('force', 'UTF-8'); Exchanging the returned authorization code for an access token (and refresh token): String params = 'code=' + EncodingUtil.urlEncode(authCode, 'UTF-8') + '&client_id=' + EncodingUtil.urlEncode(CLIENT_ID, 'UTF-8') + '&client_secret=' + EncodingUtil.urlEncode(CLIENT_SECRET, 'UTF-8') + '&redirect_uri=' + EncodingUtil.urlEncode(MY_URL, 'UTF-8') + '&grant_type=' + EncodingUtil.urlEncode('authorization_code', 'UTF-8'); Http con = new Http(); Httprequest req = new Httprequest(); req.setEndpoint('https://accounts.google.com/o/oauth2/token'); req.setHeader('Content-Type', 'application/x-www-form-urlencoded'); req.setBody(params); req.setMethod('POST'); Httpresponse reply = con.send(req); Which returns a JSON array with what looks like a valid access token: { "access_token" : "{access_token}", "token_type" : "Bearer", "expires_in" : 3600, "refresh_token" : "{refresh_token}" } However when I try and use the access token (either in code or curl) Google returns a 401: curl -H "Authorization: Bearer {access_token}" https://www.google.com/m8/feeds/contacts/default/full/ Incidentally the same curl command but with an access token acquired via https://code.google.com/oauthplayground/ works. Which leads me to believe there is something wrong with the exchanging authorization code for access token request as the returned access token does not work. I should add this is all within the expires_in time frame so its not that the access_token has expired

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  • Call HashMap from jsp EL ?

    - by Parhs
    Here is my Entity Class public enum UnitType { HOSPITAL, HEALTHCENTER } public static LinkedHashMap<UnitType, String> unitType = new LinkedHashMap<UnitType, String>() { { put(UnitType.HEALTHCENTER, "???t?? ??e?a?"); put(UnitType.HOSPITAL, "??s???µe??"); } }; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String name; private String address; @Column(columnDefinition = "TEXT") private String info; @Enumerated(EnumType.STRING) private UnitType type; At my jsp <c:forEach var="unit" items="${requestScope.units}"> <tr> <td>${unit.id}</td> <td>${unit.name}</td> <td>${unit.address}</td> <td>??!?</td> <td><a href="#">?e??ss?te?a</a></td> </tr> </c:forEach> How can i place the text value of the enum at ??!? .. Any idea? Tried some ways but nothing worked..

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  • Consistent HashCode() and Equals() results, but inconsistent TreeMap.containsKey() result

    - by smessing
    I have the following object Node: private class Node implements Comparable<Node>(){ private String guid(); ... public boolean equals(Node o){ return (this == o); } public int hashCode(){ return guid.hashCode(); } ... } And I use it in the following TreeMap: TreeMap<Node, TreeSet<Edge>> nodes = new TreeMap<Node, TreeSet<Edge>>(); Now, the tree map is used in a class called Graph to store nodes currently in the graph, along with a set of their edges (from the class Edge). My problem is when I try to execute: public containsNode(n){ for (Node x : nodes.keySet()) { System.out.println("HASH CODE: "); System.out.print(x.hashCode() == n.hashCode()); System.out.println("EQUALS: "); System.out.print(x.equals(n)); System.out.println("CONTAINS: "); System.out.print(nodes.containsKey(n)); System.out.println("N: " + n); System.out.println("X: " + x); } } I sometimes get the following: HASHCODE: true EQUALS: true CONTAINS: false N: foo X: foo Anyone have an idea as to what I'm doing wrong? I'm still new to all this, so I apologize in advance if I'm overlooking something simple (I know hashCode() doesn't really matter for TreeMap, but I figured I'd include it).

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  • Is it okay to pass injected EntityManagers to EJB bean's helper classes and use it?

    - by Zwei steinen
    We have some JavaEE5 stateless EJB bean that passes the injected EntityManager to its helpers. Is this safe? It has worked well until now, but I found out some Oracle document that states its implementation of EntityManager is thread-safe. Now I wonder whether the reason we did not have issues until now, was only because the implementation we were using happened to be thread-safe (we use Oracle). @Stateless class SomeBean { @PersistenceContext private EntityManager em; private SomeHelper helper; @PostConstruct public void init(){ helper = new SomeHelper(em); } @Override public void business(){ helper.doSomethingWithEm(); } } Actually it makes sense.. If EntityManager is thread-unsafe, a container would have to do inercept business() this.em = newEntityManager(); business(); which will not propagate to its helper classes. If so, what is the best practice in this kind of a situation? Passing EntityManagerFactory instead of EntityManager?

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  • Correct handling of return data

    - by Serhiy
    Hello, I have a question related to correct handling of returns of the DAO library I'm writing for one project. This library probably is going to be used by another people and I want to do it correctly. So I would like to know, how I should deal with return statements of the functions of my DAO. Example 1 I have function to getCustomer which should return String. In case query doesn't return any result should I return null, empty string or throw some kind of Exception? Example 2 I have function getCutomerList which return ArrayList. In case query doesn't return any result should I return null, empty ArrayList or throw some Exception? Example 3 Some sql exception was detected, what should I do: throw exception or do try..catch of the block where it can occur? What is the "good" practice or "best" practice to apply in my case? Thanks on advance, Serhiy.

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  • How to design authentication in a thick client, to be fail safe?

    - by Jay
    Here's a use case: I have a desktop application (built using Eclipse RCP) which on start, pops open a dialog box with 'UserName' and 'Password' fields in it. Once the end user, inputs his UserName and Password, a server is contacted (a spring remote-servlet, with the client side being a spring httpclient: similar to the approaches here.), and authentication is performed on the server side. A few questions related to the above mentioned scenario: If said this authentication service were to go down, what would be the best way to handle further proceedings? Authentication is something that I cannot do away with. Would running the desktop client in a "limited" mode be a good idea? For instance, important features/menus/views will be disabled, rest of the application will be accessible? Should I have a back up authentication service running on a different machine, working as a backup? What are the general best-practices in this scenario? I remember reading about google gears and how it would let you edit and do stuff offline - should something like this be designed? Please let me know your design/architectural comments/suggestions. Appreciate your help.

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  • How to declare a warning on field with AspectJ

    - by Ralph
    I want to declare a warning on all fields Annotated with @org.jboss.weld.context.ejb.Ejb in AspectJ. But I do not find a way how to select that field. I guess the aspect should be something like that: public aspect WrongEjbAnnotationWarningAspect { declare warning : within(com.queomedia..*) && ??? (@org.jboss.weld.context.ejb.Ejb) : "WrongEjbAnnotationErrorAspect: use javax.ejb.EJB instead of weld Ejb!"; } Or is it impossible to declare warnings on fields at all?

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  • Strange behavior while returning csv file from spring controller

    - by Fanooos
    I working in a spring application which have an action method that returns a CSV file. This action works fine but in some cases it throws a predefined exception (MyAppException). I have another method that is annotated @ExceptionHandler(MyAppException.class) In the exception handler method I return another csv file but with different contents. The code that returns the csv file is almost the same in the two methods. List<String[]> list= new ArrayList<String[]>(); list.add(new String[]{ integrationRequestErrorLog.getErrorMessage(), Long.toString(integrationRequestErrorLog.getId()), Integer.toString(integrationRequestErrorLog.getErrorCode()) }); CSVWriter writer = new CSVWriter(response.getWriter(), ','); writer.writeAll(list); writer.close(); the difference between the two method is the list of contents. In the first method the file is returned normally while in the exception handler method I have a strange behavior. The exception handler method works fine with Opera browser while it gives me a 404 with FireFox. Opera browser give me 404 also but it download the file while firefox does not? Really I do not understand what is the difference here.

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  • Simple explaination of Arraylists

    - by Jeremy
    I'm new to programming and I'm looking for a simple answer to build my foundation of understanding Arrays. I've used google and searched this site. After a bit of trial and error I get how to make and reference Arrays like thing[3] gets you the fourth thing in the thing array(since 0 is the first). which lets me do something like thing[3].getStupidNumber() to get the StupidNumber of the 4th thing in the thing array. Then I get to ArrayLists which seem to have much more utility but I cant make logical sense of them like Arrays. When i search I cant find this or word this correctly and thus far everything else I've learned clicked easily. so say I make an ArrayList thing with 5 things in it. how do i get to the .getStupidNumber() method inside the fourth thing, if possible? I think if I learn this I can learn the rest on my own. Thanks!

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  • Android pattern for activity "flows"

    - by Otto
    I'm developing an android app that has a bunch of screens (activities) that are supposed to have "continue" and "back" buttons at the top. Can you tell me the right pattern for implementing this? I've seen some iPhone apps that have this but Android apps usually don't (I think partly because the back button is part of the phone). I found a post online about an Activity class that has "sub activities" which kind of seems like what I want to do, but I'm wondering if there's a simpler solution or pattern for creating flows like this (in which several activities are linked with continue/back buttons).

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  • How to define RequestMapping prioritization

    - by James Skidmore
    I have a situation where I need the following RequestMapping: @RequestMapping(value={"/{section}"}) ...method implementation here... @RequestMapping(value={"/support"}) ...method implementation here... There is an obvious conflict. My hope was that Spring would resolve this automatically and map /support to the second method, and everything else to the first, but it instead maps /support to the first method. How can I tell Spring to allow an explicit RequestMapping to override a RequestMapping with a PathVariable in the same place? (Edit - this is simplified, I know that having those two RequestMapping alone wouldn't make much sense)

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  • Is there a concise way to create an InputSupplier for an InputStream in Google Guava?

    - by Fabian Steeg
    There are a few factory methods in Google Guava to create InputSuppliers, e.g. from a byte[]: ByteStreams.newInputStreamSupplier(bytes); Or from a File: Files.newInputStreamSupplier(file); Is there a similar way to to create an InputSupplier for a given InputStream? That is, a way that's more concise than an anonymous class: new InputSupplier<InputStream>() { public InputStream getInput() throws IOException { return inputStream; } }; Background: I'd like to use InputStreams with e.g. Files.copy(...) or ByteStreams.equal(...).

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  • Sun App Server Deployment Error

    - by Nick Long
    Sun App Server Deployment : When choose to precompile JSP : Throw this error com.sun.enterprise.admin.common.exception.MBeanConfigException: Component not registered then have to do asadmin undeploy Anyone know what is the reason for this error?

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  • download file exception handling

    - by klaus-vlad
    Hi, In my application I download several critical files from a server, and I want to write some code that handles the case where the a file download didn't complete for a reason or other ,to retry downloading it at next startup. The function that downloads a file at a time however throws only MalformedURLException and IOException , but if these exceptions are thrown that means that the download didn't even begin. How should I arrange things so I can treat the case where a download failed , even if it began ? download(String file) throws MalformedURLException ,IOException { }

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  • JUnit terminates child threads

    - by Marco
    Hi to all, When i test the execution of a method that creates a child thread, the JUnit test ends before the child thread and kills it. How do i force JUnit to wait for the child thread to complete its execution? Thanks

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  • How did this get 8?

    - by David
    Here's the code: class qual { public static int fibonacci(int n) { if (n == 0 || n == 1) { return 1; } else { return fibonacci(n-1) + fibonacci(n-2); } } public static void main(String[] arg) { System.out.println(fibonacci(5)); } } The output was 8. The output should be 8 but when I look at this I think it should be 7 ((5-1) +(5-2)). Why was the output 8? I think the reasoning behind getting 8 will make recursion maybe stop being confusing for me.

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