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  • Strange JPA one-to-many behavior when trying to set the "many" on the "one" entity

    - by errr
    I've mapped two entities using JPA (specifically Hibernate). Those entities have a one-to-many relationship (I've simplified for presentation): @Entity public class A { @ManyToOne public B getB() { return b; } } @Entity public Class B { @OneToMany(mappedBy="b") public Set<A> getAs() { return as; } } Now, I'm trying to create a relationship between two instances of these entities by using the setter of the one-side/not-owner-side of the relationship (i.e the table being referenced to): em.getTransaction().begin(); A a = new A(); B b = new B(); Set<A> as = new HashSet<A>(); as.add(a); b.setAs(as); em.persist(a); em.persist(b); em.getTransaction().commit(); But then, the relationship isn't persisted to the DB (the row created for entity A isn't referencing the row created for entity B). Why is it so? I'd excpect it to work. Also, if I remove the "mappedBy" property from the @OneToMany annotation it will work. Again - why is it so? and what are the possible effects for removing the "mappedBy" property?

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  • java: libraries for immutable functional-style data structures

    - by Jason S
    This is very similar to another question (Functional Data Structures in Java) but the answers there are not particularly useful. I need to use immutable versions of the standard Java collections (e.g. HashMap / TreeMap / ArrayList / LinkedList / HashSet / TreeSet). By "immutable" I mean immutable in the functional sense (e.g. purely functional data structures), where updating operations on the data structure do not change the original data, but instead return a new instance of the same kind of data structure. Also typically new and old instances of the data structure will share immutable data to be efficient in time and space. From what I can tell my options include: Functional Java Scala Clojure but I'm not sure whether any of these are particularly appealing to me. I have a few requirements/desirements: the collections in question should be usable directly in Java (with the appropriate libraries in the classpath). FJ would work for me; I'm not sure if I can use Scala's or Clojure's data structures in Java w/o having to use the compilers/interpreters from those languages and w/o having to write Scala or Clojure code. Core operations on lists/maps/sets should be possible w/o having to create function objects with confusing syntaxes (FJ looks slightly iffy) They should be efficient in time and space. I'm looking for a library which ideally has done some performance testing. FJ's TreeMap is based on a red-black tree, not sure how that rates. Documentation / tutorials should be good enough so someone can get started quickly using the data structures. FJ fails on that front. Any suggestions?

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  • Manhattan Heuristic function for A-star (A*)

    - by Shawn Mclean
    I found this algorithm here. I have a problem, I cant seem to understand how to set up and pass my heuristic function. static public Path<TNode> AStar<TNode>(TNode start, TNode destination, Func<TNode, TNode, double> distance, Func<TNode, double> estimate) where TNode : IHasNeighbours<TNode> { var closed = new HashSet<TNode>(); var queue = new PriorityQueue<double, Path<TNode>>(); queue.Enqueue(0, new Path<TNode>(start)); while (!queue.IsEmpty) { var path = queue.Dequeue(); if (closed.Contains(path.LastStep)) continue; if (path.LastStep.Equals(destination)) return path; closed.Add(path.LastStep); foreach (TNode n in path.LastStep.Neighbours) { double d = distance(path.LastStep, n); var newPath = path.AddStep(n, d); queue.Enqueue(newPath.TotalCost + estimate(n), newPath); } } return null; } As you can see, it accepts 2 functions, a distance and a estimate function. Using the Manhattan Heuristic Distance function, I need to take 2 parameters. Do I need to modify his source and change it to accepting 2 parameters of TNode so I can pass a Manhattan estimate to it? This means the 4th param will look like this: Func<TNode, TNode, double> estimate) where TNode : IHasNeighbours<TNode> and change the estimate function to: queue.Enqueue(newPath.TotalCost + estimate(n, path.LastStep), newPath); My Manhattan function is: private float manhattanHeuristic(Vector3 newNode, Vector3 end) { return (Math.Abs(newNode.X - end.X) + Math.Abs(newNode.Y - end.Y)); }

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  • Hash Code for a group of three fields

    - by Gauranga
    I have three fields namely Number1 Number2 Time I am trying to write a function in java that returns a unique hash value (long needs to be the return type of hash) for the above fields. This hash would then be used to store database rows corresponding to the above mentioned fields in a HashSet. I am new to writing a hash code function, can someone please review what I have. Any help would be appreciated. public class HashCode { private long Number1; private long Number2; String Time; public HashCode(long Number1, long Number2, String Time){ this.Number1 = Number1; this.Number2 = Number2; this.Time = Time; } public long getHashCode() { long hash = 3; hash = 47 * hash + (long) (this.Number1 ^ (this.Number1 >>> 32)); hash = 47 * hash + (long) (this.Number2 ^ (this.Number2 >>> 32)); hash = 47 * hash + (this.Time != null ? this.Time.hashCode() : 0); return hash; } }

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  • Problem with 2 levels of inheritance in hibernate mapping

    - by Seth
    Here's my class structure: class A class B extends A class C extends A class D extends C class E extends C And here are my mappings (class bodies omitted for brevity): Class A: @Entity @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @MappedSuperclass @DiscriminatorColumn( name="className", discriminatorType=DiscriminatorType.STRING ) @ForceDiscriminator public abstract class A Class B: @Entity @DiscriminatorValue("B") public class B extends A Class C: @Entity @DiscriminatorValue("C") @MappedSuperclass @DiscriminatorColumn( name="cType", discriminatorType=DiscriminatorType.STRING ) @ForceDiscriminator public abstract class C extends A Class D: @Entity @DiscriminatorValue("D") public class D extends C Class E: @Entity @DiscriminatorValue("E") public class E extends C I've got a class F that contains a set of A: @Entity public class F { ... @OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.ALL) @JoinTable( name="F_A", joinColumns = @JoinColumn(name="A_ID"), inverseJoinColumns = @JoinColumn(name="F_ID") ) private Set<A> aSet = new HashSet<A>(); ... The problem is that whenever I add a new E instance to aSet and then call session.saveOrUpdate(fInstance), hibernate saves with "A" as the discrimiator string. When I try to access the aSet in the F instance, I get the following exception (full stacktrace ommitted for brevity): org.hibernate.InstantiationException: Cannot instantiate abstract class or interface: path.to.class.A Am I mapping the classes incorrectly? How am I supposed to map multiple levels of inheritance? Thanks for the help!

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  • Algorithm complexity question

    - by Itsik
    During a recent job interview, I was asked to give a solution to the following problem: Given a string s (without spaces) and a dictionary, return the words in the dictionary that compose the string. For example, s= peachpie, dic= {peach, pie}, result={peach, pie}. I will ask the the decision variation of this problem: if s can be composed of words in the dictionary return yes, otherwise return no. My solution to this was in backtracking (written in Java) public static boolean words(String s, Set<String> dictionary) { if ("".equals(s)) return true; for (int i=0; i <= s.length(); i++) { String pre = prefix(s,i); // returns s[0..i-1] String suf = suffix(s,i); // returns s[i..s.len] if (dictionary.contains(pre) && words(suf, dictionary)) return true; } return false; } public static void main(String[] args) { Set<String> dic = new HashSet<String>(); dic.add("peach"); dic.add("pie"); dic.add("1"); System.out.println(words("peachpie1", dic)); // true System.out.println(words("peachpie2", dic)); // false } What is the time complexity of this solution? I'm calling recursively in the for loop, but only for the prefix's that are in the dictionary. Any idea's?

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  • This code is not submitting to a form? Why

    - by Ankur
    Since I am using get I expect to see the submitted values appended to the queryString but instead all I see is the URL of the servlet being called with nothing added at the end. <form id="editClassList" name="editClassList" method="get" action="EditClassList"> <% HashMap<Integer,String> classes = new HashMap<Integer,String>(); classes = (HashMap<Integer,String>) request.getAttribute("classes"); %> <% if(classes.size()==0){ %> <label><input class="small-link" type="text" id="add-this-class" size="42" value="" /></label> <% } %> <% Set<Integer> classIds = new HashSet<Integer>(); classIds = classes.keySet(); Iterator<Integer> itr = classIds.iterator(); while(itr.hasNext()){ int nextId = (Integer)itr.next(); %> <label><input class="small-link" type="text" id="<% out.print(nextId); %>" size="42" value="<% out.print(classes.get(nextId)); %>" /> </label> <img id="add-class" src="images/add.png" width="16" height="16" /><br /> <label><input class="small-link" type="text" id="class-to-add" size="42" value="" /></label> <% } %> <label><input type="submit" id="save-class-btn" value="Save Class(es)" /></label> </form>

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  • How do I implement a collection in Scala 2.8?

    - by Simon Reinhardt
    In trying to write an API I'm struggling with Scala's collections in 2.8(.0-beta1). Basically what I need is to write something that: adds functionality to immutable sets of a certain type where all methods like filter and map return a collection of the same type without having to override everything (which is why I went for 2.8 in the first place) where all collections you gain through those methods are constructed with the same parameters the original collection had (similar to how SortedSet hands through an ordering via implicits) which is still a trait in itself, independent of any set implementations. Additionally I want to define a default implementation, for example based on a HashSet. The companion object of the trait might use this default implementation. I'm not sure yet if I need the full power of builder factories to map my collection type to other collection types. I read the paper on the redesign of the collections API but it seems like things have changed a bit since then and I'm missing some details in there. I've also digged through the collections source code but I'm not sure it's very consistent yet. Ideally what I'd like to see is either a hands-on tutorial that tells me step-by-step just the bits that I need or an extensive description of all the details so I can judge myself which bits I need. I liked the chapter on object equality in "Programming in Scala". :-) But I appreciate any pointers to documentation or examples that help me understand the new collections design better.

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  • How to store visited states in iterative deepening / depth limited search?

    - by colinfang
    Update: Search for the first solution. for a normal Depth First Search it is simple, just use a hashset bool DFS (currentState) = { if (myHashSet.Contains(currentState)) { return; } else { myHashSet.Add(currentState); } if (IsSolution(currentState) return true; else { for (var nextState in GetNextStates(currentState)) if (DFS(nextState)) return true; } return false; } However, when it becomes depth limited, i cannot simply do this bool DFS (currentState, maxDepth) = { if (maxDepth = 0) return false; if (myHashSet.Contains(currentState)) { return; } else { myHashSet.Add(currentState); } if (IsSolution(currentState) return true; else { for (var nextState in GetNextStates(currentState)) if (DFS(nextState, maxDepth - 1)) return true; } return false; } Because then it is not going to do a complete search (in a sense of always be able to find a solution if there is any) before maxdepth How should I fix it? Would it add more space complexity to the algorithm? Or it just doesn't require to memoize the state at all. Update: for example, a decision tree is the following: A - B - C - D - E - A | F - G (Goal) Starting from state A. and G is a goal state. Clearly there is a solution under depth 3. However, using my implementation under depth 4, if the direction of search happens to be A(0) -> B(1) -> C(2) -> D(3) -> E(4) -> F(5) exceeds depth, then it would do back track to A, however E is visited, it would ignore the check direction A - E - F - G

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  • Compact data structure for storing a large set of integral values

    - by Odrade
    I'm working on an application that needs to pass around large sets of Int32 values. The sets are expected to contain ~1,000,000-50,000,000 items, where each item is a database key in the range 0-50,000,000. I expect distribution of ids in any given set to be effectively random over this range. The operations I need on the set are dirt simple: Add a new value Iterate over all of the values. There is a serious concern about the memory usage of these sets, so I'm looking for a data structure that can store the ids more efficiently than a simple List<int>or HashSet<int>. I've looked at BitArray, but that can be wasteful depending on how sparse the ids are. I've also considered a bitwise trie, but I'm unsure how to calculate the space efficiency of that solution for the expected data. A Bloom Filter would be great, if only I could tolerate the false negatives. I would appreciate any suggestions of data structures suitable for this purpose. I'm interested in both out-of-the-box and custom solutions. EDIT: To answer your questions: No, the items don't need to be sorted By "pass around" I mean both pass between methods and serialize and send over the wire. I clearly should have mentioned this. There could be a decent number of these sets in memory at once (~100).

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  • How to test a Grails Service that utilizes a criteria query (with spock)?

    - by user569825
    I am trying to test a simple service method. That method mainly just returns the results of a criteria query for which I want to test if it returns the one result or not (depending on what is queried for). The problem is, that I am unaware of how to right the corresponding test correctly. I am trying to accomplish it via spock, but doing the same with any other way of testing also fails. Can one tell me how to amend the test in order to make it work for the task at hand? (BTW I'd like to keep it a unit test, if possible.) The EventService Method public HashSet<Event> listEventsForDate(Date date, int offset, int max) { date.clearTime() def c = Event.createCriteria() def results = c { and { le("startDate", date+1) // starts tonight at midnight or prior? ge("endDate", date) // ends today or later? } maxResults(max) order("startDate", "desc") } return results } The Spock Specification package myapp import grails.plugin.spock.* import spock.lang.* class EventServiceSpec extends Specification { def event def eventService = new EventService() def setup() { event = new Event() event.publisher = Mock(User) event.title = 'et' event.urlTitle = 'ut' event.details = 'details' event.location = 'location' event.startDate = new Date(2010,11,20, 9, 0) event.endDate = new Date(2011, 3, 7,18, 0) } def "list the Events of a specific date"() { given: "An event ranging over multiple days" when: "I look up a date for its respective events" def results = eventService.listEventsForDate(searchDate, 0, 100) then: "The event is found or not - depending on the requested date" numberOfResults == results.size() where: searchDate | numberOfResults new Date(2010,10,19) | 0 // one day before startDate new Date(2010,10,20) | 1 // at startDate new Date(2010,10,21) | 1 // one day after startDate new Date(2011, 1, 1) | 1 // someday during the event range new Date(2011, 3, 6) | 1 // one day before endDate new Date(2011, 3, 7) | 1 // at endDate new Date(2011, 3, 8) | 0 // one day after endDate } } The Error groovy.lang.MissingMethodException: No signature of method: static myapp.Event.createCriteria() is applicable for argument types: () values: [] at myapp.EventService.listEventsForDate(EventService.groovy:47) at myapp.EventServiceSpec.list the Events of a specific date(EventServiceSpec.groovy:29)

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  • Struts2 Hibernate Login with User table and group table

    - by J2ME NewBiew
    My problem is, i have a table User and Table Group (this table use to authorization for user - it mean when user belong to a group like admin, they can login into admincp and other user belong to group member, they just only read and write and can not login into admincp) each user maybe belong to many groups and each group has been contain many users and they have relationship are many to many I use hibernate for persistence storage. and struts 2 to handle business logic. When i want to implement login action from Struts2 how can i get value of group member belong to ? to compare with value i want to know? Example I get user from username and password then get group from user class but i dont know how to get value of group user belong to it mean if user belong to Groupid is 1 and in group table , at column adminpermission is 1, that user can login into admincp, otherwise he can't my code: User.java /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package org.dejavu.software.model; import java.io.Serializable; import java.util.Date; import java.util.HashSet; import java.util.Set; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.JoinTable; import javax.persistence.ManyToMany; import javax.persistence.Table; import javax.persistence.Temporal; /** * * @author Administrator */ @Entity @Table(name="User") public class User implements Serializable{ private static final long serialVersionUID = 2575677114183358003L; private Long userId; private String username; private String password; private String email; private Date DOB; private String address; private String city; private String country; private String avatar; private Set<Group> groups = new HashSet<Group>(0); @Column(name="dob") @Temporal(javax.persistence.TemporalType.DATE) public Date getDOB() { return DOB; } public void setDOB(Date DOB) { this.DOB = DOB; } @Column(name="address") public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Column(name="city") public String getCity() { return city; } public void setCity(String city) { this.city = city; } @Column(name="country") public String getCountry() { return country; } public void setCountry(String country) { this.country = country; } @Column(name="email") public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL) @JoinTable(name="usergroup",joinColumns={@JoinColumn(name="userid")},inverseJoinColumns={@JoinColumn( name="groupid")}) public Set<Group> getGroups() { return groups; } public void setGroups(Set<Group> groups) { this.groups = groups; } @Column(name="password") public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Id @GeneratedValue @Column(name="iduser") public Long getUserId() { return userId; } public void setUserId(Long userId) { this.userId = userId; } @Column(name="username") public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } @Column(name="avatar") public String getAvatar() { return avatar; } public void setAvatar(String avatar) { this.avatar = avatar; } } Group.java /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package org.dejavu.software.model; import java.io.Serializable; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.Table; /** * * @author Administrator */ @Entity @Table(name="Group") public class Group implements Serializable{ private static final long serialVersionUID = -2722005617166945195L; private Long idgroup; private String groupname; private String adminpermission; private String editpermission; private String modpermission; @Column(name="adminpermission") public String getAdminpermission() { return adminpermission; } public void setAdminpermission(String adminpermission) { this.adminpermission = adminpermission; } @Column(name="editpermission") public String getEditpermission() { return editpermission; } public void setEditpermission(String editpermission) { this.editpermission = editpermission; } @Column(name="groupname") public String getGroupname() { return groupname; } public void setGroupname(String groupname) { this.groupname = groupname; } @Id @GeneratedValue @Column (name="idgroup") public Long getIdgroup() { return idgroup; } public void setIdgroup(Long idgroup) { this.idgroup = idgroup; } @Column(name="modpermission") public String getModpermission() { return modpermission; } public void setModpermission(String modpermission) { this.modpermission = modpermission; } } UserDAO /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package org.dejavu.software.dao; import java.util.List; import org.dejavu.software.model.User; import org.dejavu.software.util.HibernateUtil; import org.hibernate.Query; import org.hibernate.Session; /** * * @author Administrator */ public class UserDAO extends HibernateUtil{ public User addUser(User user){ Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); session.save(user); session.getTransaction().commit(); return user; } public List<User> getAllUser(){ Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); List<User> user = null; try { user = session.createQuery("from User").list(); } catch (Exception e) { e.printStackTrace(); session.getTransaction().rollback(); } session.getTransaction().commit(); return user; } public User checkUsernamePassword(String username, String password){ Session session = HibernateUtil.getSessionFactory().getCurrentSession(); session.beginTransaction(); User user = null; try { Query query = session.createQuery("from User where username = :name and password = :password"); query.setString("username", username); query.setString("password", password); user = (User) query.uniqueResult(); } catch (Exception e) { e.printStackTrace(); session.getTransaction().rollback(); } session.getTransaction().commit(); return user; } } AdminLoginAction /* * To change this template, choose Tools | Templates * and open the template in the editor. */ package org.dejavu.software.view; import com.opensymphony.xwork2.ActionSupport; import org.dejavu.software.dao.UserDAO; import org.dejavu.software.model.User; /** * * @author Administrator */ public class AdminLoginAction extends ActionSupport{ private User user; private String username,password; private String role; private UserDAO userDAO; public AdminLoginAction(){ userDAO = new UserDAO(); } @Override public String execute(){ return SUCCESS; } @Override public void validate(){ if(getUsername().length() == 0){ addFieldError("username", "Username is required"); }if(getPassword().length()==0){ addFieldError("password", getText("Password is required")); } } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getRole() { return role; } public void setRole(String role) { this.role = role; } public User getUser() { return user; } public void setUser(User user) { this.user = user; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } } other question. i saw some example about Login, i saw some developers use interceptor, im cant understand why they use it, and what benefit "Interceptor" will be taken for us? Thank You Very Much!

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  • Hibernate HQL m:n join problem

    - by smallufo
    I am very unfamiliar with SQL/HQL , and am currently stuck with this 'maybe' simple problem : I have two many-to-many Entities , with a relation table : Car , CarProblem , and Problem . One Car may have many Problems , One Problem may appear in many Cars, CarProblem is the association table with other properties . Now , I want to find Car(s) with specified Problem , how do I write such HQL ? All ids are Long type . I've tried a lot of join / inner-join combinations , but all in vain.. -- updated : Sorry , forget to mention : Car has many CarProblem Problem has many CarProblem Car and Problem are not directly connected in Java Object. -- update , java code below -- @Entity public class Car extends Model{ @OneToMany(mappedBy="car" , cascade=CascadeType.ALL) public Set<CarProblem> carProblems; } @Entity public class CarProblem extends Model{ @ManyToOne public Car car; @ManyToOne public Problem problem; ... other properties } @Entity public class Problem extends Model { other properties ... // not link to CarProblem , It seems not related to this problem // **This is a very stupid query , I want to get rid of it ...** public List<Car> findCars() { List<CarProblem> list = CarProblem.find("from CarProblem as cp where cp.problem.id = ? ", id).fetch(); Set<Car> result = new HashSet<Car>(); for(CarProblem cp : list) result.add(cp.car); return new ArrayList<Car>(result); } } The Model is from Play! framework , so these properties are all public .

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  • JPA - Can an @JoinColumn be an @Id as well? SerializationException occurs.

    - by Shivago
    Hi everyone, I am trying to use an @JoinColumn as an @Id using JPA and I am getting SerializationExceptions, "Could not serialize." UserRole.java: @Entity @Table(name = "authorities") public class UserRole implements Serializable { @Column(name = "authority") private String role; @Id @ManyToOne @JoinColumn(name = "username") private User owner; ... } User.java: @Entity @Table(name = "users") public class User implements Serializable { @Id @GeneratedValue protected Long id; @Column(name = "username") protected String email; @OneToMany(mappedBy = "owner", fetch = FetchType.LAZY, cascade = CascadeType.ALL) protected Set<UserRole> roles = new HashSet<UserRole>(); .... } "username" is set up as a unique index in my Users table but not as the primary key. Is there any way to make "username" act as the ID for UserRole? I don't want to introduce a numeric key in UserRole. Have I totally lost the plot here? I am using MySQL and Hibernate under the hood.

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  • Unit Testing - Algorithm or Sample based ?

    - by ohadsc
    Say I'm trying to test a simple Set class public IntSet : IEnumerable<int> { Add(int i) {...} //IEnumerable implementation... } And suppose I'm trying to test that no duplicate values can exist in the set. My first option is to insert some sample data into the set, and test for duplicates using my knowledge of the data I used, for example: //OPTION 1 void InsertDuplicateValues_OnlyOneInstancePerValueShouldBeInTheSet() { var set = new IntSet(); //3 will be added 3 times var values = new List<int> {1, 2, 3, 3, 3, 4, 5}; foreach (int i in values) set.Add(i); //I know 3 is the only candidate to appear multiple times int counter = 0; foreach (int i in set) if (i == 3) counter++; Assert.AreEqual(1, counter); } My second option is to test for my condition generically: //OPTION 2 void InsertDuplicateValues_OnlyOneInstancePerValueShouldBeInTheSet() { var set = new IntSet(); //The following could even be a list of random numbers with a duplicate var values = new List<int> { 1, 2, 3, 3, 3, 4, 5}; foreach (int i in values) set.Add(i); //I am not using my prior knowledge of the sample data //the following line would work for any data CollectionAssert.AreEquivalent(new HashSet<int>(values), set); } Of course, in this example, I conveniently have a set implementation to check against, as well as code to compare collections (CollectionAssert). But what if I didn't have either ? This is the situation when you are testing your real life custom business logic. Granted, testing for expected conditions generically covers more cases - but it becomes very similar to implementing the logic again (which is both tedious and useless - you can't use the same code to check itself!). Basically I'm asking whether my tests should look like "insert 1, 2, 3 then check something about 3" or "insert 1, 2, 3 and check for something in general" EDIT - To help me understand, please state in your answer if you prefer OPTION 1 or OPTION 2 (or neither, or that it depends on the case, etc )

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  • My method is too specific. How can I make it more generic?

    - by EricBoersma
    I have a class, the outline of which is basically listed below. import org.apache.commons.math.stat.Frequency; public class WebUsageLog { private Collection<LogLine> logLines; private Collection<Date> dates; WebUsageLog() { this.logLines = new ArrayList<LogLine>(); this.dates = new ArrayList<Date>(); } SortedMap<Double, String> getFrequencyOfVisitedSites() { SortedMap<Double, String> frequencyMap = new TreeMap<Double, String>(Collections.reverseOrder()); //we reverse order to sort from the highest percentage to the lowest. Collection<String> domains = new HashSet<String>(); Frequency freq = new Frequency(); for (LogLine line : this.logLines) { freq.addValue(line.getVisitedDomain()); domains.add(line.getVisitedDomain()); } for (String domain : domains) { frequencyMap.put(freq.getPct(domain), domain); } return frequencyMap; } } The intention of this application is to allow our Human Resources folks to be able to view Web Usage Logs we send to them. However, I'm sure that over time, I'd like to be able to offer the option to view not only the frequency of visited sites, but also other members of LogLine (things like the frequency of assigned categories, accessed types [text/html, img/jpeg, etc...] filter verdicts, and so on). Ideally, I'd like to avoid writing individual methods for compilation of data for each of those types, and they could each end up looking nearly identical to the getFrequencyOfVisitedSites() method. So, my question is twofold: first, can you see anywhere where this method should be improved, from a mechanical standpoint? And secondly, how would you make this method more generic, so that it might be able to handle an arbitrary set of data?

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  • hibernate annotation bi-directional mapping

    - by smithystar
    I'm building a web application using Spring framework and Hibernate with annotation and get stuck with a simple mapping between two entities. I'm trying to create a many-to-many relationship between User and Course. I followed one of the Hibernate tutorials and my implementation is as follows: User class: @Entity @Table(name="USER") public class User { private Long id; private String email; private String password; private Set<Course> courses = new HashSet<Course>(0); @Id @GeneratedValue @Column(name="USER_ID") public Long getId() { return id; } public void setId(Long id) { this.id = id; } @Column(name="USER_EMAIL") public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } @Column(name="USER_PASSWORD") public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @ManyToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_COURSE", joinColumns = { @JoinColumn(name = "USER_ID") }, inverseJoinColumns = { @JoinColumn(name = "COURSE_ID") }) public Set<Course> getCourses() { return courses; } public void setCourses(Set<Course> courses) { this.courses = courses; } } Course class: @Entity @Table(name="COURSE") public class Course { private Long id; private String name; @Id @GeneratedValue @Column(name="COURSE_ID") public Long getId() { return id; } public void setId(Long id) { this.id = id; } @Column(name="NAME") public String getName() { return name; } public void setName(String name) { this.name = name; } } The problem is that this implementation only allows me to go one way user.getCourses() What do I need to change, so I can go in both directions? user.getCourses() course.getUsers() Any help would be appreciated.

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  • What guarantees are there on the run-time complexity (Big-O) of LINQ methods?

    - by tzaman
    I've recently started using LINQ quite a bit, and I haven't really seen any mention of run-time complexity for any of the LINQ methods. Obviously, there are many factors at play here, so let's restrict the discussion to the plain IEnumerable LINQ-to-Objects provider. Further, let's assume that any Func passed in as a selector / mutator / etc. is a cheap O(1) operation. It seems obvious that all the single-pass operations (Select, Where, Count, Take/Skip, Any/All, etc.) will be O(n), since they only need to walk the sequence once; although even this is subject to laziness. Things are murkier for the more complex operations; the set-like operators (Union, Distinct, Except, etc.) work using GetHashCode by default (afaik), so it seems reasonable to assume they're using a hash-table internally, making these operations O(n) as well, in general. What about the versions that use an IEqualityComparer? OrderBy would need a sort, so most likely we're looking at O(n log n). What if it's already sorted? How about if I say OrderBy().ThenBy() and provide the same key to both? I could see GroupBy (and Join) using either sorting, or hashing. Which is it? Contains would be O(n) on a List, but O(1) on a HashSet - does LINQ check the underlying container to see if it can speed things up? And the real question - so far, I've been taking it on faith that the operations are performant. However, can I bank on that? STL containers, for example, clearly specify the complexity of every operation. Are there any similar guarantees on LINQ performance in the .NET library specification?

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  • Union of two or more (hash)maps

    - by javierfp
    I have two Maps that contain the same type of Objects: Map<String, TaskJSO> a = new HashMap<String, TaskJSO>(); Map<String, TaskJSO> b = new HashMap<String, TaskJSO>(); public class TaskJSO { String id; } The map keys are the "id" properties. a.put(taskJSO.getId(), taskJSO); I want to obtain a list with: all values in "Map b" + all values in "Map a" that are not in "Map b". What is the fastest way of doing this operation? Thanks EDIT: The comparaison is done by id. So, two TaskJSOs are considered as equal if they have the same id (equals method is overrided). My intention is to know which is the fastest way of doing this operation from a performance point of view. For instance, is there any difference if I do the "comparaison" in a map (as suggested by Peter): Map<String, TaskJSO> ab = new HashMap<String, TaskJSO>(a); ab.putAll(b); ab.values() or if instead I use a set (as suggested by Nishant): Set s = new Hashset(); s.addAll(a.values()); s.addAll(b.values());

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  • ASP.NET MVC: Converting business objects to select list items

    - by DigiMortal
    Some of our business classes are used to fill dropdown boxes or select lists. And often you have some base class for all your business classes. In this posting I will show you how to use base business class to write extension method that converts collection of business objects to ASP.NET MVC select list items without writing a lot of code. BusinessBase, BaseEntity and other base classes I prefer to have some base class for all my business classes so I can easily use them regardless of their type in contexts I need. NB! Some guys say that it is good idea to have base class for all your business classes and they also suggest you to have mappings done same way in database. Other guys say that it is good to have base class but you don’t have to have one master table in database that contains identities of all your business objects. It is up to you how and what you prefer to do but whatever you do – think and analyze first, please. :) To keep things maximally simple I will use very primitive base class in this example. This class has only Id property and that’s it. public class BaseEntity {     public virtual long Id { get; set; } } Now we have Id in base class and we have one more question to solve – how to better visualize our business objects? To users ID is not enough, they want something more informative. We can define some abstract property that all classes must implement. But there is also another option we can use – overriding ToString() method in our business classes. public class Product : BaseEntity {     public virtual string SKU { get; set; }     public virtual string Name { get; set; }       public override string ToString()     {         if (string.IsNullOrEmpty(Name))             return base.ToString();           return Name;     } } Although you can add more functionality and properties to your base class we are at point where we have what we needed: identity and human readable presentation of business objects. Writing list items converter Now we can write method that creates list items for us. public static class BaseEntityExtensions {            public static IEnumerable<SelectListItem> ToSelectListItems<T>         (this IList<T> baseEntities) where T : BaseEntity     {         return ToSelectListItems((IEnumerator<BaseEntity>)                    baseEntities.GetEnumerator());     }       public static IEnumerable<SelectListItem> ToSelectListItems         (this IEnumerator<BaseEntity> baseEntities)     {         var items = new HashSet<SelectListItem>();           while (baseEntities.MoveNext())         {             var item = new SelectListItem();             var entity = baseEntities.Current;               item.Value = entity.Id.ToString();             item.Text = entity.ToString();               items.Add(item);         }           return items;     } } You can see here to overloads of same method. One works with List<T> and the other with IEnumerator<BaseEntity>. Although mostly my repositories return IList<T> when querying data there are always situations where I can use more abstract types and interfaces. Using extension methods in code In your code you can use ToSelectListItems() extension methods like shown on following code fragment. ... var model = new MyFormModel(); model.Statuses = _myRepository.ListStatuses().ToSelectListItems(); ... You can call this method on all your business classes that extend your base entity. Wanna have some fun with this code? Write overload for extension method that accepts selected item ID.

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  • How to structure game states in an entity/component-based system

    - by Eva
    I'm making a game designed with the entity-component paradigm that uses systems to communicate between components as explained here. I've reached the point in my development that I need to add game states (such as paused, playing, level start, round start, game over, etc.), but I'm not sure how to do it with my framework. I've looked at this code example on game states which everyone seems to reference, but I don't think it fits with my framework. It seems to have each state handling its own drawing and updating. My framework has a SystemManager that handles all the updating using systems. For example, here's my RenderingSystem class: public class RenderingSystem extends GameSystem { private GameView gameView_; /** * Constructor * Creates a new RenderingSystem. * @param gameManager The game manager. Used to get the game components. */ public RenderingSystem(GameManager gameManager) { super(gameManager); } /** * Method: registerGameView * Registers gameView into the RenderingSystem. * @param gameView The game view registered. */ public void registerGameView(GameView gameView) { gameView_ = gameView; } /** * Method: triggerRender * Adds a repaint call to the event queue for the dirty rectangle. */ public void triggerRender() { Rectangle dirtyRect = new Rectangle(); for (GameObject object : getRenderableObjects()) { GraphicsComponent graphicsComponent = object.getComponent(GraphicsComponent.class); dirtyRect.add(graphicsComponent.getDirtyRect()); } gameView_.repaint(dirtyRect); } /** * Method: renderGameView * Renders the game objects onto the game view. * @param g The graphics object that draws the game objects. */ public void renderGameView(Graphics g) { for (GameObject object : getRenderableObjects()) { GraphicsComponent graphicsComponent = object.getComponent(GraphicsComponent.class); if (!graphicsComponent.isVisible()) continue; GraphicsComponent.Shape shape = graphicsComponent.getShape(); BoundsComponent boundsComponent = object.getComponent(BoundsComponent.class); Rectangle bounds = boundsComponent.getBounds(); g.setColor(graphicsComponent.getColor()); if (shape == GraphicsComponent.Shape.RECTANGULAR) { g.fill3DRect(bounds.x, bounds.y, bounds.width, bounds.height, true); } else if (shape == GraphicsComponent.Shape.CIRCULAR) { g.fillOval(bounds.x, bounds.y, bounds.width, bounds.height); } } } /** * Method: getRenderableObjects * @return The renderable game objects. */ private HashSet<GameObject> getRenderableObjects() { return gameManager.getGameObjectManager().getRelevantObjects( getClass()); } } Also all the updating in my game is event-driven. I don't have a loop like theirs that simply updates everything at the same time. I like my framework because it makes it easy to add new GameObjects, but doesn't have the problems some component-based designs encounter when communicating between components. I would hate to chuck it just to get pause to work. Is there a way I can add game states to my game without removing the entity-component design? Does the game state example actually fit my framework, and I'm just missing something? EDIT: I might not have explained my framework well enough. My components are just data. If I was coding in C++, they'd probably be structs. Here's an example of one: public class BoundsComponent implements GameComponent { /** * The position of the game object. */ private Point pos_; /** * The size of the game object. */ private Dimension size_; /** * Constructor * Creates a new BoundsComponent for a game object with initial position * initialPos and initial size initialSize. The position and size combine * to make up the bounds. * @param initialPos The initial position of the game object. * @param initialSize The initial size of the game object. */ public BoundsComponent(Point initialPos, Dimension initialSize) { pos_ = initialPos; size_ = initialSize; } /** * Method: getBounds * @return The bounds of the game object. */ public Rectangle getBounds() { return new Rectangle(pos_, size_); } /** * Method: setPos * Sets the position of the game object to newPos. * @param newPos The value to which the position of the game object is * set. */ public void setPos(Point newPos) { pos_ = newPos; } } My components do not communicate with each other. Systems handle inter-component communication. My systems also do not communicate with each other. They have separate functionality and can easily be kept separate. The MovementSystem doesn't need to know what the RenderingSystem is rendering to move the game objects correctly; it just need to set the right values on the components, so that when the RenderingSystem renders the game objects, it has accurate data. The game state could not be a system, because it needs to interact with the systems rather than the components. It's not setting data; it's determining which functions need to be called. A GameStateComponent wouldn't make sense because all the game objects share one game state. Components are what make up objects and each one is different for each different object. For example, the game objects cannot have the same bounds. They can have overlapping bounds, but if they share a BoundsComponent, they're really the same object. Hopefully, this explanation makes my framework less confusing.

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  • How do you test an ICF based connector using Connector Facade Standalone?

    - by Shashidhar Malyala
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} The following code helps in writing a standalone java program to test an ICF based connector. The sample code in this example takes into account an ICF based flatfile connector. It is possible to test various operations like create, update, delete, search etc... It is also possible to set values to the connector configuration parameters, add/remove attributes and their values. public class FlatFile { private static final java.lang.String BUNDLE_NAME = "<PACKAGE_NAME>"; //Ex: org.info.icf.flatfile private static final java.lang.String BUNDLE_VERSION = "1.0.0"; private static final java.lang.String CONNECTOR_NAME = "org.info.icf.flatfile.FlatFileConnector"; // Name of connector class i.e. the class implemting the connector SPI operations public ConnectorFacade getFacade() throws IOException { ConnectorInfoManagerFactory fact = ConnectorInfoManagerFactory .getInstance(); File bundleDirectory = new File("<BUNDLE_LOCATION>"); //Ex: /usr/oracle/connector_bundles/ URL url = IOUtil.makeURL(bundleDirectory, "org.info.icf.flatfile-1.0.0.jar"); ConnectorInfoManager manager = fact.getLocalManager(url); ConnectorKey key = new ConnectorKey(BUNDLE_NAME, BUNDLE_VERSION, CONNECTOR_NAME); ConnectorInfo info = manager.findConnectorInfo(key); // From the ConnectorInfo object, create the default APIConfiguration. APIConfiguration apiConfig = info.createDefaultAPIConfiguration(); // From the default APIConfiguration, retrieve the // ConfigurationProperties. ConfigurationProperties properties = apiConfig .getConfigurationProperties(); // Print out what the properties are (not necessary) List propertyNames = properties.getPropertyNames(); for (String propName : propertyNames) { ConfigurationProperty prop = properties.getProperty(propName); System.out.println("Property Name: " + prop.getName() + "\tProperty Type: " + prop.getType()); } properties .setPropertyValue("fileLocation", "/usr/oracle/accounts.csv"); // Set all of the ConfigurationProperties needed by the connector. // properties.setPropertyValue("host", FOOBAR_HOST); // properties.setPropertyValue("adminName", FOOBAR_ADMIN); // properties.setPropertyValue("adminPassword", FOOBAR_PASSWORD); // properties.setPropertyValue("useSSL", false); // Use the ConnectorFacadeFactory's newInstance() method to get a new // connector. ConnectorFacade connFacade = ConnectorFacadeFactory.getInstance() .newInstance(apiConfig); // Make sure we have set up the Configuration properly connFacade.validate(); return connFacade; } public static void main(String[] args) throws IOException { FlatFile file = new FlatFile(); ConnectorFacade cfac = file.getFacade(); Set attrSet = new HashSet(); attrSet.add(AttributeBuilder.build(Name.NAME, "Test01")); attrSet.add(AttributeBuilder.build("FIRST_NAME", "Test_First")); attrSet.add(AttributeBuilder.build("LAST_NAME", "Test_Last")); //Create Uid uid = cfac.create(ObjectClass.ACCOUNT, attrSet, null); //Delete Uid uidP = new Uid("Test01"); cfac.delete(ObjectClass.ACCOUNT, uidP, null); } }

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  • Deletes not cascading for self-referencing entities

    - by jwaddell
    I have the following (simplified) Hibernate entities: @Entity @Table(name = "package") public class Package { protected Content content; @OneToOne(cascade = {javax.persistence.CascadeType.ALL}) @JoinColumn(name = "content_id") @Fetch(value = FetchMode.JOIN) public Content getContent() { return content; } public void setContent(Content content) { this.content = content; } } @Entity @Table(name = "content") public class Content { private Set<Content> subContents = new HashSet<Content>(); private ArchivalInformationPackage parentPackage; @OneToMany(fetch = FetchType.EAGER) @JoinTable(name = "subcontents", joinColumns = {@JoinColumn(name = "content_id")}, inverseJoinColumns = {@JoinColumn(name = "elt")}) @Cascade(value = {org.hibernate.annotations.CascadeType.DELETE, org.hibernate.annotations.CascadeType.REPLICATE}) @Fetch(value = FetchMode.SUBSELECT) public Set<Content> getSubContents() { return subContents; } public void setSubContents(Set<Content> subContents) { this.subContents = subContents; } @ManyToOne(cascade = {CascadeType.ALL}) @JoinColumn(name = "parent_package_id") public Package getParentPackage() { return parentPackage; } public void setParentPackage(Package parentPackage) { this.parentPackage = parentPackage; } } So there is one Package, which has one "top" Content. The top Content links back to the Package, with cascade set to ALL. The top Content may have many "sub" Contents, and each sub-Content may have many sub-Contents of its own. Each sub-Content has a parent Package, which may or may not be the same Package as the top Content (ie a many-to-one relationship for Content to Package). The relationships are required to be ManyToOne (Package to Content) and ManyToMany (Content to sub-Contents) but for the case I am currently testing each sub-Content only relates to one Package or Content. The problem is that when I delete a Package and flush the session, I get a Hibernate error stating that I'm violating a foreign key constraint on table subcontents, with a particular content_id still referenced from table subcontents. I've tried specifically (recursively) deleting the Contents before deleting the Package but I get the same error. Is there a reason why this entity tree is not being deleted properly? EDIT: After reading answers/comments I realised that a Content cannot have multiple Packages, and a sub-Content cannot have multiple parent-Contents, so I have modified the annotations from ManyToOne and ManyToMany to OneToOne and OneToMany. Unfortunately that did not fix the problem. I have also added the bi-directional link from Content back to the parent Package which I left out of the simplified code.

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  • Nhibernate: One-To-Many mapping problem - Cannot cascade delete without inverse. Set NULL error

    - by KnaveT
    Hi, I have the current scenario whereby an Article has only 1 Outcome each. Each Article may or may not have an Outcome. In theory, this is a one-to-one mapping, but since NHibernate does not really support one-to-one, I used a One-To-Many to substitute. My Primary Key on the child table is actually the ArticleID (FK). So I have the following setup: Classes public class Article { public virtual Int32 ID { get;set;} private ICollection<ArticleOutcome> _Outcomes {get;set;} public virtual ArticleOutcome Outcome { get { if( this._Outcomes !=null && this._Outcomes.Count > 0 ) return this._Outcomes.First(); return null; } set { if( value == null ) { if( this._Outcomes !=null && this._Outcomes.Count > 0 ) this._Outcomes.Clear(); } else { if( this._Outcomes == null ) this._Outcomes = new HashSet<ArticleOutcome>(); else if ( this._Outcomes.Count >= 1 ) this._Outcomes.Clear(); this._Outcomes.Add( value ); } } } } public class ArticleOutcome { public virtual Int32 ID { get;set; } public virtual Article ParentArticle { get;set;} } Mappings public class ArticleMap : ClassMap<Article> { public ArticleMap() { this.Id( x=> x.ID ).GeneratedBy.Identity(); this.HasMany<ArticleOutcome>( Reveal.Property<Article>("_Outcomes") ) .AsSet().KeyColumn("ArticleID") .Cascade.AllDeleteOrphan() //Cascade.All() doesn't work too. .LazyLoad() .Fetch.Select(); } } public class ArticleOutcomeMap : ClassMap<ArticleOutcome> { public ArticleOutcomeMap(){ this.Id( x=> x.ID, "ArticleID").GeneratedBy.Foreign("ParentArticle"); this.HasOne( x=> x.ParentArticle ).Constrained (); //This do not work also. //this.References( x=> x.ParentArticle, "ArticleID" ).Not.Nullable(); } } Now my problem is this: It works when I do an insert/update of the Outcome. e.g. var article = new Article(); article.Outcome = new ArticleOutcome { xxx = "something" }; session.Save( article ); However, I encounter SQL errors when attempting to delete via the Article itself. var article = session.Get( 123 ); session.Delete( article ); //throws SQL error. The error is something to the like of Cannot insert NULL into ArticleID in ArticleOutcome table. The deletion works if I place Inverse() to the Article's HasMany() mapping, but insertion will fail. Does anyone have a solution for this? Or do I really have to add a surrogate key to the ArticleOutcome table?

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  • Hibernate annotated many-to-one not adding child to parent Collection

    - by Rob Hruska
    I have the following annotated Hibernate entity classes: @Entity public class Cat { @Column(name = "ID") @GeneratedValue(strategy = GenerationType.AUTO) @Id private Long id; @OneToMany(mappedBy = "cat", cascade = CascadeType.ALL, fetch = FetchType.EAGER) private Set<Kitten> kittens = new HashSet<Kitten>(); public void setId(Long id) { this.id = id; } public Long getId() { return id; } public void setKittens(Set<Kitten> kittens) { this.kittens = kittens; } public Set<Kitten> getKittens() { return kittens; } } @Entity public class Kitten { @Column(name = "ID") @GeneratedValue(strategy = GenerationType.AUTO) @Id private Long id; @ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER) private Cat cat; public void setId(Long id) { this.id = id; } public Long getId() { return id; } public void setCat(Cat cat) { this.cat = cat; } public Cat getCat() { return cat; } } My intention here is a bidirectional one-to-many/many-to-one relationship between Cat and Kitten, with Kitten being the "owning side". What I want to happen is when I create a new Cat, followed by a new Kitten referencing the Cat, the Set of kittens on my Cat should contain the new Kitten. However, this does not happen in the following test: @Test public void testAssociations() { Session session = HibernateUtil.getSessionFactory().getCurrentSession(); Transaction tx = session.beginTransaction(); Cat cat = new Cat(); session.save(cat); Kitten kitten = new Kitten(); kitten.setCat(cat); session.save(kitten); tx.commit(); assertNotNull(kitten.getCat()); assertEquals(cat.getId(), kitten.getCat().getId()); assertTrue(cat.getKittens().size() == 1); // <-- ASSERTION FAILS assertEquals(kitten, new ArrayList<Kitten>(cat.getKittens()).get(0)); } Even after re-querying the Cat, the Set is still empty: // added before tx.commit() and assertions cat = (Cat)session.get(Cat.class, cat.getId()); Am I expecting too much from Hibernate here? Or is the burden on me to manage the Collection myself? The (Annotations) documentation doesn't make any indication that I need to create convenience addTo*/removeFrom* methods on my parent object. Can someone please enlighten me on what my expectations should be from Hibernate with this relationship? Or if nothing else, point me to the correct Hibernate documentation that tells me what I should be expecting to happen here. What do I need to do to make the parent Collection automatically contain the child Entity?

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