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  • java serialization and final fields

    - by mdma
    I have an class defining an immutable value type that I now need to serialize. The immutability comes from the final fields which are set in the constructor. I've tried serializing, and it works (surprisingly?) - but I've no idea how. Here's an example of the class public class MyValueType implements Serializable { private final int value; private transient int derivedValue; public MyValueType(int value) { this.value = value; this.derivedValue = derivedValue(value); } // getters etc... } Given that the class doesn't have a no arg constructor, how can it be instantiated and the final field set? (An aside - I noticed this class particularly because IDEA wasn't generating a "no serialVersionUID" inspection warning for this class, yet successfully generated warnings for other classes that I've just made serializable.)

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  • What are the benefits of using ORM over XML Serialization/Deserialization?

    - by Tequila Jinx
    I've been reading about NHibernate and Microsoft's Entity Framework to perform Object Relational Mapping against my data access layer. I'm interested in the benefits of having an established framework to perform ORM, but I'm curious as to the performance costs of using it against standard XML Serialization and Deserialization. Right now, I develop stored procedures in Oracle and SQL Server that use XML Types for either input or output parameters and return or shred XML depending on need. I use a custom database command object that uses generics to deserialize the XML results into a specified serializable class. By using a combination of generics, xml (de)serialization and Microsoft's DAAB, I've got a process that's fairly simple to develop against regardless of the data source. Moreover, since I exclusively use Stored Procedures to perform database operations, I'm mostly protected from changes in the data structure. Here's an over-simplified example of what I've been doing. static void main() { testXmlClass test = new test(1); test.Name = "Foo"; test.Save(); } // Example Serializable Class ------------------------------------------------ [XmlRootAttribute("test")] class testXmlClass() { [XmlElement(Name="id")] public int ID {set; get;} [XmlElement(Name="name")] public string Name {set; get;} //create an instance of the class loaded with data. public testXmlClass(int id) { GenericDBProvider db = new GenericDBProvider(); this = db.ExecuteSerializable("myGetByIDProcedure"); } //save the class to the database... public Save() { GenericDBProvider db = new GenericDBProvider(); db.AddInParameter("myInputParameter", DbType.XML, this); db.ExecuteSerializableNonQuery("mySaveProcedure"); } } // Database Handler ---------------------------------------------------------- class GenericDBProvider { public T ExecuteSerializable<T>(string commandText) where T : class { XmlSerializer xml = new XmlSerializer(typeof(T)); // connection and command code is assumed for the purposes of this example. // the final results basically just come down to... return xml.Deserialize(commandResults) as T; } public void ExecuteSerializableNonQuery(string commandText) { // once again, connection and command code is assumed... // basically, just execute the command along with the specified // parameters which have been serialized. } public void AddInParameter(string name, DbType type, object value) { StringWriter w = new StringWriter(); XmlSerializer x = new XmlSerializer(value.GetType()); //handle serialization for serializable classes. if (type == DbType.Xml && (value.GetType() != typeof(System.String))) { x.Serialize(w, value); w.Close(); // store serialized object in a DbParameterCollection accessible // to my other methods. } else { //handle all other parameter types } } } I'm starting a new project which will rely heavily on database operations. I'm very curious to know whether my current practices will be sustainable in a high-traffic situation and whether or not I should consider switching to NHibernate or Microsoft's Entity Framework to perform what essentially seems to boil down to the same thing I'm currently doing. I appreciate any advice you may have.

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  • Cannot instantiate abstract class or interface : problem while persisting

    - by sammy
    i have a class campaign that maintains a list of AdGroupInterfaces. im going to persist its implementation @Entity @Table(name = "campaigns") public class Campaign implements Serializable,Comparable<Object>,CampaignInterface { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @OneToMany ( cascade = {CascadeType.ALL}, fetch = FetchType.EAGER, targetEntity=AdGroupInterface.class ) @org.hibernate.annotations.Cascade( value = org.hibernate.annotations.CascadeType.DELETE_ORPHAN ) @org.hibernate.annotations.IndexColumn(name = "CHOICE_POSITION") private List<AdGroupInterface> AdGroup; public Campaign() { super(); } public List<AdGroupInterface> getAdGroup() { return AdGroup; } public void setAdGroup(List<AdGroupInterface> adGroup) { AdGroup = adGroup; } public void set1AdGroup(AdGroupInterface adGroup) { if(AdGroup==null) AdGroup=new LinkedList<AdGroupInterface>(); AdGroup.add(adGroup); } } AdGroupInterface's implementation is AdGroups. when i add an adgroup to the list in campaign, campaign c; c.getAdGroupList().add(new AdGroups()), etc and save campaign it says"Cannot instantiate abstract class or interface :" AdGroupInterface its not recognizing the implementation just before persisting... Whereas Persisting adGroups separately works. when it is a member of another entity, it doesnt get persisted. import java.io.Serializable; import java.util.List; import javax.persistence.*; @Entity @DiscriminatorValue("1") @Table(name = "AdGroups") public class AdGroups implements Serializable,Comparable,AdGroupInterface{ /** * */ private static final long serialVersionUID = 1L; private Long Id; private String Name; private CampaignInterface Campaign; private MonetaryValue DefaultBid; public AdGroups(){ super(); } public AdGroups( String name, CampaignInterface campaign) { super(); this.Campaign=new Campaign(); Name = name; this.Campaign = campaign; DefaultBid = defaultBid; AdList=adList; } @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="AdGroup_Id") public Long getId() { return Id; } public void setId(Long id) { Id = id; } @Column(name="AdGroup_Name") public String getName() { return Name; } public void setName(String name) { Name = name; } @ManyToOne @JoinColumn (name="Cam_ID", nullable = true,insertable = false) public CampaignInterface getCampaign() { return Campaign; } public void setCampaign(CampaignInterface campaign) { this.Campaign = campaign; } } what am i missing?? please look into it ...

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  • How to implement Xml Serialization with inherited classes in C#

    - by liorafar
    I have two classes : base class name Component and inheritd class named DBComponent [Serializable] public class Component { private string name = string.Empty; private string description = string.Empty; } [Serializable] public class DBComponent : Component { private List<string> spFiles = new List<string>(); // Storage Procedure Files [XmlArrayItem("SPFile", typeof(string))] [XmlArray("SPFiles")] public List<string> SPFiles { get { return spFiles; } set { spFiles = value; } } public DBComponent(string name, string description) : base(name, description) { } } [Serializable] public class ComponentsCollection { private static ComponentsCollection instance = null; private List<Component> components = new List<Component>(); public List<Component> Components { get { return components; } set { components = value; } } public static ComponentsCollection GetInstance() { if (ccuInstance == null) { lock (lockObject) { if (instance == null) PopulateComponents(); } } return instance; } private static void PopulateComponents() { instance = new CCUniverse(); XmlSerializer xs = new XmlSerializer(instance.GetType()); instance = xs.Deserialize(XmlReader.Create("Components.xml")) as ComponentsCollection; } } } I want read\write from a Xml file. I know that I need to implement the Serialization for DBComponent class otherwise it will not read it.But i cannot find any simple article for that. all the articles that I found were too complex for this simple scenario. The Xml file looks like this: <?xml version="1.0" encoding="utf-8" ?> <ComponentsCollection> <Components> <DBComponent Name="Tenant Historical Database" Description="Tenant Historical Database"> <SPFiles> <SPFile>Setup\TenantHistoricalSP.sql</SPFile> </SPFiles> </DBComponent> <Component Name="Agent" Description="Desktop Agent" /> </Components> </ComponentsCollection> Can someone please give me a simple example of how to read this kind of xml file and what should be implemented ? Thanks Lior

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  • help me "dry" out this .net XML serialization code

    - by Sarah Vessels
    I have a base collection class and a child collection class, each of which are serializable. In a test, I discovered that simply having the child class's ReadXml method call base.ReadXml resulted in an InvalidCastException later on. First, here's the class structure: Base Class // Collection of Row objects [Serializable] [XmlRoot("Rows")] public class Rows : IList<Row>, ICollection<Row>, IEnumerable<Row>, IEquatable<Rows>, IXmlSerializable { public Collection<Row> Collection { get; protected set; } public void ReadXml(XmlReader reader) { reader.ReadToFollowing(XmlNodeName); do { using (XmlReader rowReader = reader.ReadSubtree()) { var row = new Row(); row.ReadXml(rowReader); Collection.Add(row); } } while (reader.ReadToNextSibling(XmlNodeName)); } } Derived Class // Acts as a collection of SpecificRow objects, which inherit from Row. Uses the same // Collection<Row> that Rows defines which is fine since SpecificRow : Row. [Serializable] [XmlRoot("MySpecificRowList")] public class SpecificRows : Rows, IXmlSerializable { public new void ReadXml(XmlReader reader) { // Trying to just do base.ReadXml(reader) causes a cast exception later reader.ReadToFollowing(XmlNodeName); do { using (XmlReader rowReader = reader.ReadSubtree()) { var row = new SpecificRow(); row.ReadXml(rowReader); Collection.Add(row); } } while (reader.ReadToNextSibling(XmlNodeName)); } public new Row this[int index] { // The cast in this getter is what causes InvalidCastException if I try // to call base.ReadXml from this class's ReadXml get { return (Row)Collection[index]; } set { Collection[index] = value; } } } And here's the code that causes a runtime InvalidCastException if I do not use the version of ReadXml shown in SpecificRows above (i.e., I get the exception if I just call base.ReadXml from within SpecificRows.ReadXml): TextReader reader = new StringReader(serializedResultStr); SpecificRows deserializedResults = (SpecificRows)xs.Deserialize(reader); SpecificRow = deserializedResults[0]; // this throws InvalidCastException So, the code above all compiles and runs exception-free, but it bugs me that Rows.ReadXml and SpecificRows.ReadXml are essentially the same code. The value of XmlNodeName and the new Row()/new SpecificRow() are the differences. How would you suggest I extract out all the common functionality of both versions of ReadXml? Would it be silly to create some generic class just for one method? Sorry for the lengthy code samples, I just wanted to provide the reason I can't simply call base.ReadXml from within SpecificRows.

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  • Are all public read/write members serialized with XmlSerializer?

    - by David
    I have a handful of public read/write members that are not being serialized and I can't figure out why. Reviewing some code, and my root class is marked serializable: [Serializable] public class MyClass I have a default constructor that initializes 10-15 string members. There are about 50 public read/write string members in MyClass with get and set--no explicit serialization attributes are set on any of these. Serialization looks like this: XmlSerializer x = new XmlSerializer(typeof(MyClass)); TextWriter twWriter = new StreamWriter(sFileName); x.Serialize(twWriter, this); twWriter.Close(); only a handful (20-30) of these members are actually seralized to my xml file. what am i missing or misunderstanding about the XmlSerializer class?

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  • Error when compiling c# project in VS2012 when using Postsharp

    - by Thewads
    I am currently working on a project where we were wanting to add PostSharp functionality. I have set up my Postsharp attribute as so [Serializable] public class NLogTraceAttribute : OnMethodBoundaryAspect { private readonly string _logLevel; ILogger logger; public NLogTraceAttribute(string logLevel) { _logLevel = logLevel; logger = new Logger("TraceAttribute"); } public override void OnEntry(MethodExecutionArgs args) { LogAction("Enter", args); } public override void OnExit(MethodExecutionArgs args) { LogAction("Leave", args); } private void LogAction(string action, MethodExecutionArgs args) { var argumentsInfo = args.GetArgumentsInfo(); logger.Log(_logLevel, "{0}: {1}.{2}{3}", action, args.Method.DeclaringType.Name, args.Method.Name, argumentsInfo); } } and trying to use it as [NLogTrace(NLogLevel.Debug)] However when compiling the project I am getting the following error: Error 26 Cannot serialize the aspects: Type 'NLog.Logger' in Assembly 'NLog, Version=2.0.0.0, Culture=neutral, PublicKeyToken=5120e14c03d0593c' is not marked as serializable.. Any help would be appreciated

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  • JSF2 - use view scope managed bean to pass value between navigation

    - by Fekete Kamosh
    Hi all, I am solving how to pass values from one page to another without making use of session scope managed bean. For most managed beans I would like to have only Request scope. I created a very, very simple calculator example which passes Result object resulting from actions on request bean (CalculatorRequestBean) from 5th phase as initializing value for new instance of request bean initialized in next phase lifecycle. In fact - in production environment we need to pass much more complicated data object which is not as primitive as Result defined below. What is your opinion on this solution which considers both possibilities - we stay on the same view or we navigate to the new one. But in both cases I can get to previous value stored passed using view scoped managed bean. Calculator page: <?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html"> <h:head> <title>Calculator</title> </h:head> <h:body> <h:form> <h:panelGrid columns="2"> <h:outputText value="Value to use:"/> <h:inputText value="#{calculatorBeanRequest.valueToAdd}"/> <h:outputText value="Navigate to new view:"/> <h:selectBooleanCheckbox value="#{calculatorBeanRequest.navigateToNewView}"/> <h:commandButton value="Add" action="#{calculatorBeanRequest.add}"/> <h:commandButton value="Subtract" action="#{calculatorBeanRequest.subtract}"/> <h:outputText value="Result:"/> <h:outputText value="#{calculatorBeanRequest.result.value}"/> <h:outputText value="DUMMY" rendered="#{resultBeanView.dummy}"/> </h:panelGrid> </h:form> </h:body> Object to be passed through lifecycle: package cz.test.calculator; import java.io.Serializable; /** * Data object passed among pages. * Lets imagine it holds something much more complicated than primitive int */ public class Result implements Serializable { private int value; public void setValue(int value) { this.value = value; } public int getValue() { return value; } } Request scoped managed bean used on view "calculator.xhtml" package cz.test.calculator; import javax.annotation.PostConstruct; import javax.faces.bean.ManagedBean; import javax.faces.bean.ManagedProperty; import javax.faces.bean.RequestScoped; @ManagedBean @RequestScoped public class CalculatorBeanRequest { @ManagedProperty(value="#{resultBeanView}") ResultBeanView resultBeanView; private Result result; private int valueToAdd; /** * Should perform navigation to */ private boolean navigateToNewView; /** Creates a new instance of CalculatorBeanRequest */ public CalculatorBeanRequest() { } @PostConstruct public void init() { // Remember already saved result from view scoped bean result = resultBeanView.getResult(); } // Dependency injections public void setResultBeanView(ResultBeanView resultBeanView) { this.resultBeanView = resultBeanView; } public ResultBeanView getResultBeanView() { return resultBeanView; } // Getters, setter public void setValueToAdd(int valueToAdd) { this.valueToAdd = valueToAdd; } public int getValueToAdd() { return valueToAdd; } public boolean isNavigateToNewView() { return navigateToNewView; } public void setNavigateToNewView(boolean navigateToNewView) { this.navigateToNewView = navigateToNewView; } public Result getResult() { return result; } // Actions public String add() { result.setValue(result.getValue() + valueToAdd); return isNavigateToNewView() ? "calculator" : null; } public String subtract() { result.setValue(result.getValue() - valueToAdd); return isNavigateToNewView() ? "calculator" : null; } } and finally view scoped managed bean to pass Result variable to new page: package cz.test.calculator; import java.io.Serializable; import javax.annotation.PostConstruct; import javax.faces.bean.ManagedBean; import javax.faces.bean.ViewScoped; import javax.faces.context.FacesContext; @ManagedBean @ViewScoped public class ResultBeanView implements Serializable { private Result result = new Result(); /** Creates a new instance of ResultBeanView */ public ResultBeanView() { } @PostConstruct public void init() { // Try to find request bean ManagedBeanRequest and reset result value CalculatorBeanRequest calculatorBeanRequest = (CalculatorBeanRequest)FacesContext.getCurrentInstance().getExternalContext().getRequestMap().get("calculatorBeanRequest"); if(calculatorBeanRequest != null) { setResult(calculatorBeanRequest.getResult()); } } /** No need to have public modifier as not used on view * but only in managed bean within the same package */ void setResult(Result result) { this.result = result; } /** No need to have public modifier as not used on view * but only in managed bean within the same package */ Result getResult() { return result; } /** * To be called on page to instantiate ResultBeanView in Render view phase */ public boolean isDummy() { return false; } }

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  • @OneToOne and @JoinColumn, auto delete null entity , doable?

    - by smallufo
    I have two Entities , with the following JPA annotations : @Entity @Table(name = "Owner") public class Owner implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id") private long id; @OneToOne(fetch=FetchType.EAGER , cascade=CascadeType.ALL) @JoinColumn(name="Data_id") private Data Data; } @Entity @Table(name = "Data") public class Data implements Serializable { @Id private long id; } Owner and Data has one-to-one mapping , the owning side is Owner. The problem occurs when I execute : owner.setData(null) ; ownerDao.update(owner) ; The "Owner" table's Data_id becomes null , that's correct. But the "Data" row is not deleted automatically. I have to write another DataDao , and another service layer to wrap the two actions ( ownerDao.update(owner) ; dataDao.delete(data); ) Is it possible to make a data row automatically deleted when the owning Owner set it to null ?

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  • Sessions not persisting between requests

    - by klonq
    My session objects are only stored within the request scope on google app engine and I can't figure out how to persist objects between requests. The docs are next to useless on this matter and I can't find anyone who's experienced a similar problem. Please help. When I store session objects in the servlet and forward the request to a JSP using: getServletContext().getRequestDispatcher("/example.jsp").forward(request,response); Everything works like it should. But when I store objects to the session and redirect the request using: response.sendRedirect("/example/url"); The session objects are lost to the ether. In fact when I dump session key/value pairs on new requests there is absolutely nothing, session objects only appear within the request scope of servlets which create session objects. It appears to me that the objects are not being written to Memcache or Datastore. In terms of configuring sessions for my application I have set <sessions-enabled>true</sessions-enabled> In appengine-web.xml. Is there anything else I am missing? The single paragraph of documentation on sessions also notes that only objects which implement Serializable can be stored in the session between requests. I have included an example of the code which is not working below. The obvious solution is to not use redirects, and this might be ok for the example given below but some application data does need to be stored in the session between requests so I need to find a solution to this problem. EXAMPLE: The class FlashMessage gives feedback to the user from server-side operations. if (email.send()) { FlashMessage flash = new FlashMessage(FlashMessage.SUCCESS, "Your message has been sent."); session.setAttribute(FlashMessage.SESSION_KEY, flash); // The flash message will not be available in the session object in the next request response.sendRedirect(URL.HOME); } else { FlashMessage flash = new FlashMessage(FlashMessage.ERROR, FlashMessage.INVALID_FORM_DATA); session.setAttribute(FlashMessage.SESSION_KEY, flash); // The flash message is displayed without problem getServletContext().getRequestDispatcher(Templates.CONTACT_FORM).forward(request,response); } FlashMessage.java import java.io.Serializable; public class FlashMessage implements Serializable { private static final long serialVersionUID = 8109520737272565760L; // I have tried using different, default and no serialVersionUID public static final String SESSION_KEY = "flashMessage"; public static final String ERROR = "error"; public static final String SUCCESS = "success"; public static final String INVALID_FORM_DATA = "Your request failed to validate."; private String message; private String type; public FlashMessage (String type, String message) { this.type = type; this.message = message; } public String display(){ return "<div id='flash' class='" + type + "'>" + message + "</div>"; } }

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  • Collectable<T> serialization, Root Namespaces on T in .xml files.

    - by Stacey
    I have a Repository Class with the following method... public T Single<T>(Predicate<T> expression) { using (var list = (Models.Collectable<T>)System.Xml.Serializer.Deserialize(typeof(Models.Collectable<T>), FileName)) { return list.Find(expression); } } Where Collectable is defined.. [Serializable] public class Collectable<T> : List<T>, IDisposable { public Collectable() { } public void Dispose() { } } And an Item that uses it is defined.. [Serializable] [System.Xml.Serialization.XmlRoot("Titles")] public partial class Titles : Collectable<Title> { } The problem is when I call the method, it expects "Collectable" to be the XmlRoot, but the XmlRoot is "Titles" (all of object Title). I have several classes that are collected in .xml files like this, but it seems pointless to rewrite the basic methods for loading each up when the generic accessors do it - but how can I enforce the proper root name for each file without hard coding methods for each one? The [System.Xml.Serialization.XmlRoot] seems to be ignored.

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  • Getting field of type bytea in helper table when using GenerationType.IDENTITY

    - by dtrunk
    I'm creating my db scheme using Hibernate. There's a Table called "tbl_articles" and another one called "tbl_categories". To have a n-n relationship a helper table ("tbl_articles_categories") is needed. Here are all necessary Entities: @Entity @Table( name = "tbl_articles" ) public class Article implements Serializable { private static final long serialVersionUID = 1L; @Id @Column( nullable = false ) @GeneratedValue( strategy = GenerationType.IDENTITY ) private Integer id; // other fields... public Integer getId() { return id; } public void setId( Integer id ) { this.id = id; } // other fields... } @Entity @Table( name = "tbl_categories" ) public class Category implements Serializable { private static final long serialVersionUID = 1L; @Id @Column( nullable = false ) @GeneratedValue( strategy = GenerationType.IDENTITY ) private Integer id; // other fields public Integer getId() { return id; } public void setId( Integer id ) { this.id = id; } // other fields... } @Entity @Table( name = "tbl_articles_categories" ) @AssociationOverrides({ @AssociationOverride( name = "pk.article", joinColumns = @JoinColumn( name = "article_id" ) ), @AssociationOverride( name = "pk.category", joinColumns = @JoinColumn( name = "category_id" ) ) }) public class ArticleCategory { private ArticleCategoryPK pk = new ArticleCategoryPK(); public void setPk( ArticleCategoryPK pk ) { this.pk = pk; } @EmbeddedId public ArticleCategoryPK getPk() { return pk; } @Transient public Article getArticle() { return pk.getArticle(); } public void setArticle( Article article ) { pk.setArticle( article ); } @Transient public Category getCategory() { return pk.getCategory(); } public void setCategory( Category category ) { pk.setCategory( category ); } } @Embeddable public class ArticleCategoryPK implements Serializable { private static final long serialVersionUID = 1L; @ManyToOne @ForeignKey( name = "tbl_articles_categories_fkey_article_id" ) private Article article; @ManyToOne @ForeignKey( name = "tbl_articles_categories_fkey_category_id" ) private Category category; public ArticleCategoryPK( Article article, Category category ) { setArticle( article ); setCategory( category ); } public ArticleCategoryPK() { } public Article getArticle() { return article; } public void setArticle( Article article ) { this.article = article; } public Category getCategory() { return category; } public void setCategory( Category category ) { this.category = category; } } Now, I'm getting a serial type what I wanted in my articles table as well as in my categories table. But looking into my helper table, there aren't the expected fields article_id and category_id each of type integer - instead there are article and category of type bytea. What's wrong here? EDIT: Sorry, forgot to mention that I'm using PostgreSQL.

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  • Find changed properties of a class

    - by Rohit
    I am using asp.net 3.5 I have a license class containing 10 properties and not marked as serializable. I have to log property changes to the database. License is an entity class,and it is not in my scope to modify it. So I cannot mark it as serializabel neither i can use IpropertyChanged Interface. Now i cannot store it in viewstate as it is not serializable. I wanted to store it so that i can compare it with new values and see which value has changed. How to proceed with this.

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  • How to solve this Java type safety warning? (Struts2)

    - by Nicolas Raoul
    Map session = ActionContext.getContext().getSession(); session.put("user", user); This code generates a warning: Type safety: The method put(Object, Object) belongs to the raw type Map. References to generic type Map should be parameterized. Map<String, Serializable> session = (Map<String, Serializable>)ActionContext.getContext().getSession(); session.put("user", user); This code generates a warning: Type safety: Unchecked cast from Map to Map. The getSession method belongs to Struts2 so I can't modify it. I would like to avoid using @SuppressWarnings because other warnings can be useful. I guess all Struts2 users in the world faced the same problem... is there an elegant solution?

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  • Annotations: methods vs variables

    - by Zenzen
    I was always sure (don't know why) that it's better to add annotations to variables, but while browsing the Hibernate doc http://docs.jboss.org/hibernate/stable/annotations/reference/en/html_single/#entity-hibspec-collection I noticed they tend to annotate the methods. So should I put my annotations before methods, like this: @Entity public class Flight implements Serializable { private long id; @Id @GeneratedValue public long getId() { return id; } public void setId(long id) { this.id = id; } } Or is it better to do it like this: @Entity public class Flight implements Serializable { @Id @GeneratedValue private long id; public long getId() { return id; } public void setId(long id) { this.id = id; } } Or maybe there's no difference?

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  • [app-engine-java-groovy] One-to-Many relationship. Select objects from datastore.

    - by Olexandr
    Hi. I've omitted some code(package declarations, imports, other fields) for shortness. I have here simple One-to-Many relation. It worked fine till this moment. @PersistenceCapable(identityType = IdentityType.APPLICATION, detachable="true") class Restaurant implements Serializable { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) Key id @Persistent(mappedBy = "restaurant") List<RestaurantAddress> addresses = new ArrayList<RestaurantAddress>() } //-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= @PersistenceCapable(identityType = IdentityType.APPLICATION, detachable="true") class RestaurantAddress implements Serializable { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) Key id @Persistent Restaurant restaurant } Now i need to get(select) all the Restaurants from DB: def getRestaurantsToExport(final String dst, final int count) { String field = restaurantExportFields[dst] return transactionExecute() { PersistenceManager pm -> Query q = pm.newQuery(Restaurant.class) q.filter = "$field == null" q.setRange(0, count) return q.execute() } } But there are on problem - query gives me 12 restaurants(as in DB) but every Restaurant has 0 Address but in Datastore every Restaurant has minimum 2 addresses. Have anyone the same problem or knows the solution ?

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  • How to generate entities with Objects?

    - by 01
    I want to generate @Enities with seam-gen from existing database. However its generates very simple version only. For Example @Entity @Table(name = "badges") public class Badges implements java.io.Serializable { private Integer id; private **Integer userId**; private String name; private String date; I want him to generate @Entity @Table(name = "badges") public class Badges implements java.io.Serializable { private Integer id; private **User user**; private String name; private String date; I even have constrain on userId and it points to column User.id P.S. Im using MySQL5 and seam gen is using hbm2java to generate entities.

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  • Creating immutable objects from javabean

    - by redzedi
    Hi All, I am involved in this project where we are building on good bit of legacy code. I have a particular situation about one big java bean object which has to be transferred over wire. So my first thought was to make it immutable and serializable to do the trick .At this point I am faced with a few difficult choices :- 1 Ideally I want some way to automatically generate an immutable, serializable version of this class. I dont have the scope to refactor or alter this class in any way and i would really really hate to have to copy paste the class with a different name ?? 2 Assuming that i gave up on 1 i.e i actually chose to duplicate code of the HUGE javabean class , i still will be in the unsavoury situation of having to write a constructor with some 20-25 parameters to make this class immutable. what is a better way to make a class immutable other than constructor injection ?? Thanks and Regards,

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  • Read and write .NET Objects in SQL Database without serialization.

    - by Mohit
    Hello, I have a small query. I need to create a Caching Service of my own that will write and read .NET Objects to and from the Database. Now, I have achieved that with the help of Binary Serialization. But the Problem is I need to deliberately marked my objects as [Serializable], which makes me think that what if someone will try to add an object which is not marked as [Serializable]. Thus, I need to find a way to read and write Objects to Database without Serialization. I have one thought too.. As we all know Session can store any object in it. Now, we can make sessions to be stored in the DB, outproc. What mechanism it uses to store these objects without serializing or deserializing. Any help will be highly appreciated. Thanks. M.B

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  • JPA Bidirectional OneToMany and ManyToOne?

    - by PhoenixJon
    I'm using Oracle JDeveloper 11g Release 2. I created two tables A and B using SQL developer. Table A has a FK to table B. Using the Entities from Tables function, I created two JPA files from it. A has @ManyToOne annotation on FK. And also B has @OneToMany annotation to A. I don't want this. Can I remove this @OneToMany annotation automatically? public class A implements Serializable { ... @ManyToOne @JoinColumn(name = "FIELD_B") private B b; ... } public class B implements Serializable { ... @OneToMany(mappedBy = "B") private List<A> assetList; ... } I don't need @OneToMany mapping.

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  • Domain entities into (ASP.NET) Session, or better some kind of DTOs?

    - by Robert
    Currently we put Domain Objects into our ASP.NET Sessions. Now we considering moving from InProc sessions to state server. This requires that all objects inside session are serializable. Instead to annotate all objects with the [Serializable] attribute, we thought about creating custom-session objects (DTO Session Objects?), which only contain the information we need: CONS: Entities must be reloaded, which requires additional DB round-trips PROS: Session State is smaller Session information is more specific (could be a CON) No unneeded annotation of Domain-Entities What do you think? Should we use some kind of DTOs to store inside the session, or should we stick with god old entities?

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  • Different types of Session state management options available with ASP.NET

    - by Aamir Hasan
    ASP.NET provides In-Process and Out-of-Process state management.In-Process stores the session in memory on the web server.This requires the a "sticky-server" (or no load-balancing) so that the user is always reconnected to the same web server.Out-of-Process Session state management stores data in an external data source.The external data source may be either a SQL Server or a State Server service.Out-of-Process state management requires that all objects stored in session are serializable.Linkhttp://msdn.microsoft.com/en-us/library/ms178586%28VS.80%29.aspx

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  • How to create a simple adf dashboard application with EJB 3.0

    - by Rodrigues, Raphael
    In this month's Oracle Magazine, Frank Nimphius wrote a very good article about an Oracle ADF Faces dashboard application to support persistent user personalization. You can read this entire article clicking here. The idea in this article is to extend the dashboard application. My idea here is to create a similar dashboard application, but instead ADF BC model layer, I'm intending to use EJB3.0. There are just a one small trick here and I'll show you. I'm using the HR usual oracle schema. The steps are: 1. Create a ADF Fusion Application with EJB as a layer model 2. Generate the entities from table (I'm using Department and Employees only) 3. Create a new Session Bean. I called it: HRSessionEJB 4. Create a new method like that: public List getAllDepartmentsHavingEmployees(){ JpaEntityManager jpaEntityManager = (JpaEntityManager)em.getDelegate(); Query query = jpaEntityManager.createNamedQuery("Departments.allDepartmentsHavingEmployees"); JavaBeanResult.setQueryResultClass(query, AggregatedDepartment.class); return query.getResultList(); } 5. In the Departments entity, create a new native query annotation: @Entity @NamedQueries( { @NamedQuery(name = "Departments.findAll", query = "select o from Departments o") }) @NamedNativeQueries({ @NamedNativeQuery(name="Departments.allDepartmentsHavingEmployees", query = "select e.department_id, d.department_name , sum(e.salary), avg(e.salary) , max(e.salary), min(e.salary) from departments d , employees e where d.department_id = e.department_id group by e.department_id, d.department_name")}) public class Departments implements Serializable {...} 6. Create a new POJO called AggregatedDepartment: package oramag.sample.dashboard.model; import java.io.Serializable; import java.math.BigDecimal; public class AggregatedDepartment implements Serializable{ @SuppressWarnings("compatibility:5167698678781240729") private static final long serialVersionUID = 1L; private BigDecimal departmentId; private String departmentName; private BigDecimal sum; private BigDecimal avg; private BigDecimal max; private BigDecimal min; public AggregatedDepartment() { super(); } public AggregatedDepartment(BigDecimal departmentId, String departmentName, BigDecimal sum, BigDecimal avg, BigDecimal max, BigDecimal min) { super(); this.departmentId = departmentId; this.departmentName = departmentName; this.sum = sum; this.avg = avg; this.max = max; this.min = min; } public void setDepartmentId(BigDecimal departmentId) { this.departmentId = departmentId; } public BigDecimal getDepartmentId() { return departmentId; } public void setDepartmentName(String departmentName) { this.departmentName = departmentName; } public String getDepartmentName() { return departmentName; } public void setSum(BigDecimal sum) { this.sum = sum; } public BigDecimal getSum() { return sum; } public void setAvg(BigDecimal avg) { this.avg = avg; } public BigDecimal getAvg() { return avg; } public void setMax(BigDecimal max) { this.max = max; } public BigDecimal getMax() { return max; } public void setMin(BigDecimal min) { this.min = min; } public BigDecimal getMin() { return min; } } 7. Create the util java class called JavaBeanResult. The function of this class is to configure a native SQL query to return POJOs in a single line of code using the utility class. Credits: http://onpersistence.blogspot.com.br/2010/07/eclipselink-jpa-native-constructor.html package oramag.sample.dashboard.model.util; /******************************************************************************* * Copyright (c) 2010 Oracle. All rights reserved. * This program and the accompanying materials are made available under the * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0 * which accompanies this distribution. * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html * and the Eclipse Distribution License is available at * http://www.eclipse.org/org/documents/edl-v10.php. * * @author shsmith ******************************************************************************/ import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.util.ArrayList; import java.util.List; import javax.persistence.Query; import org.eclipse.persistence.exceptions.ConversionException; import org.eclipse.persistence.internal.helper.ConversionManager; import org.eclipse.persistence.internal.sessions.AbstractRecord; import org.eclipse.persistence.internal.sessions.AbstractSession; import org.eclipse.persistence.jpa.JpaHelper; import org.eclipse.persistence.queries.DatabaseQuery; import org.eclipse.persistence.queries.QueryRedirector; import org.eclipse.persistence.sessions.Record; import org.eclipse.persistence.sessions.Session; /*** * This class is a simple query redirector that intercepts the result of a * native query and builds an instance of the specified JavaBean class from each * result row. The order of the selected columns musts match the JavaBean class * constructor arguments order. * * To configure a JavaBeanResult on a native SQL query use: * JavaBeanResult.setQueryResultClass(query, SomeBeanClass.class); * where query is either a JPA SQL Query or native EclipseLink DatabaseQuery. * * @author shsmith * */ public final class JavaBeanResult implements QueryRedirector { private static final long serialVersionUID = 3025874987115503731L; protected Class resultClass; public static void setQueryResultClass(Query query, Class resultClass) { JavaBeanResult javaBeanResult = new JavaBeanResult(resultClass); DatabaseQuery databaseQuery = JpaHelper.getDatabaseQuery(query); databaseQuery.setRedirector(javaBeanResult); } public static void setQueryResultClass(DatabaseQuery query, Class resultClass) { JavaBeanResult javaBeanResult = new JavaBeanResult(resultClass); query.setRedirector(javaBeanResult); } protected JavaBeanResult(Class resultClass) { this.resultClass = resultClass; } @SuppressWarnings("unchecked") public Object invokeQuery(DatabaseQuery query, Record arguments, Session session) { List results = new ArrayList(); try { Constructor[] constructors = resultClass.getDeclaredConstructors(); Constructor javaBeanClassConstructor = null; // (Constructor) resultClass.getDeclaredConstructors()[0]; Class[] constructorParameterTypes = null; // javaBeanClassConstructor.getParameterTypes(); List rows = (List) query.execute( (AbstractSession) session, (AbstractRecord) arguments); for (Object[] columns : rows) { boolean found = false; for (Constructor constructor : constructors) { javaBeanClassConstructor = constructor; constructorParameterTypes = javaBeanClassConstructor.getParameterTypes(); if (columns.length == constructorParameterTypes.length) { found = true; break; } // if (columns.length != constructorParameterTypes.length) { // throw new ColumnParameterNumberMismatchException( // resultClass); // } } if (!found) throw new ColumnParameterNumberMismatchException( resultClass); Object[] constructorArgs = new Object[constructorParameterTypes.length]; for (int j = 0; j < columns.length; j++) { Object columnValue = columns[j]; Class parameterType = constructorParameterTypes[j]; // convert the column value to the correct type--if possible constructorArgs[j] = ConversionManager.getDefaultManager() .convertObject(columnValue, parameterType); } results.add(javaBeanClassConstructor.newInstance(constructorArgs)); } } catch (ConversionException e) { throw new ColumnParameterMismatchException(e); } catch (IllegalArgumentException e) { throw new ColumnParameterMismatchException(e); } catch (InstantiationException e) { throw new ColumnParameterMismatchException(e); } catch (IllegalAccessException e) { throw new ColumnParameterMismatchException(e); } catch (InvocationTargetException e) { throw new ColumnParameterMismatchException(e); } return results; } public final class ColumnParameterMismatchException extends RuntimeException { private static final long serialVersionUID = 4752000720859502868L; public ColumnParameterMismatchException(Throwable t) { super( "Exception while processing query results-ensure column order matches constructor parameter order", t); } } public final class ColumnParameterNumberMismatchException extends RuntimeException { private static final long serialVersionUID = 1776794744797667755L; public ColumnParameterNumberMismatchException(Class clazz) { super( "Number of selected columns does not match number of constructor arguments for: " + clazz.getName()); } } } 8. Create the DataControl and a jsf or jspx page 9. Drag allDepartmentsHavingEmployees from DataControl and drop in your page 10. Choose Graph > Type: Bar (Normal) > any layout 11. In the wizard screen, Bars label, adds: sum, avg, max, min. In the X Axis label, adds: departmentName, and click in OK button 12. Run the page, the result is showed below: You can download the workspace here . It was using the latest jdeveloper version 11.1.2.2.

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  • ASP.NET ViewState Tips and Tricks #2

    - by João Angelo
    If you need to store complex types in ViewState DO implement IStateManager to control view state persistence and reduce its size. By default a serializable object will be fully stored in view state using BinaryFormatter. A quick comparison for a complex type with two integers and one string property produces the following results measured using ASP.NET tracing: BinaryFormatter: 328 bytes in view state IStateManager: 28 bytes in view state BinaryFormatter sample code: // DO NOT [Serializable] public class Info { public int Id { get; set; } public string Name { get; set; } public int Age { get; set; } } public class ExampleControl : WebControl { protected override void OnLoad(EventArgs e) { base.OnLoad(e); if (!this.Page.IsPostBack) { this.User = new Info { Id = 1, Name = "John Doe", Age = 27 }; } } public Info User { get { object o = this.ViewState["Example_User"]; if (o == null) return null; return (Info)o; } set { this.ViewState["Example_User"] = value; } } } IStateManager sample code: // DO public class Info : IStateManager { public int Id { get; set; } public string Name { get; set; } public int Age { get; set; } private bool isTrackingViewState; bool IStateManager.IsTrackingViewState { get { return this.isTrackingViewState; } } void IStateManager.LoadViewState(object state) { var triplet = (Triplet)state; this.Id = (int)triplet.First; this.Name = (string)triplet.Second; this.Age = (int)triplet.Third; } object IStateManager.SaveViewState() { return new Triplet(this.Id, this.Name, this.Age); } void IStateManager.TrackViewState() { this.isTrackingViewState = true; } } public class ExampleControl : WebControl { protected override void OnLoad(EventArgs e) { base.OnLoad(e); if (!this.Page.IsPostBack) { this.User = new Info { Id = 1, Name = "John Doe", Age = 27 }; } } public Info User { get; set; } protected override object SaveViewState() { return new Pair( ((IStateManager)this.User).SaveViewState(), base.SaveViewState()); } protected override void LoadViewState(object savedState) { if (savedState != null) { var pair = (Pair)savedState; this.User = new Info(); ((IStateManager)this.User).LoadViewState(pair.First); base.LoadViewState(pair.Second); } } }

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