first post here, hoping someone could perhaps shed some light on an issue I've been trying to juggle...
As a part of a school project we're attempting to build a interface to display points on a map and paths on a map.
For our first sprint I managed to work out storing/retrieving items using Objectify - it went great!
Now we're trying to extend the functionality for our next spring. Having problems now trying to store an object of type MapPath (note MapPath and MapData, our two data types, both extend class Data). Brief code snippets as follows :
#Entity
public class Data extends JavaScriptObject
{
#Id
Long id;
private String name;
private String dataSet;
...getters and setters
}
#Subclass
public class MapData extends Data implements Serializable{
{
private String name;
private String address;
private String dataSet;
#Embedded
private Coordinate location;
....constructors, getters/setters
}
#Subclass
public class PathData extends Data implements Serializable{
private String name;
private String address;
private String dataSet;
#Embedded
private Coordinate[] path;
...etc
}
Now hopefully I haven't lost you yet. I have a DataService class that basically handles all transactions. I have the following unit test :
#Test
public void storeOnePath(){
PathData pd = new PathData();
pd.setName("hi");
DataService.storeSingleton(pd);
Data d = DataService.getSingleton("hi");
assertEquals(pd,d);
}
The implementation of getSingleton is as follows :
public static void storeSingleton(Data d){
Objectify obj = ObjectifyService.begin();
obj.put(d);
}
JUnit complains:
java.lang.ExceptionInInitializerError
at com.teamrawket.tests.DataTest.storeOnePath(DataTest.java:59)
...<taken out>
Caused by: java.lang.IllegalStateException: Attempting to create multiple associations on class com.teamrawket.server.MapData for name
at com.googlecode.objectify.impl.Transmog$Visitor.addRootSetter(Transmog.java:298)
at com.googlecode.objectify.impl.Transmog$Visitor.visitField(Transmog.java:231)
at com.googlecode.objectify.impl.Transmog$Visitor.visitClass(Transmog.java:134)
at com.googlecode.objectify.impl.Transmog.<init>(Transmog.java:319)
at com.googlecode.objectify.impl.ConcreteEntityMetadata.<init>(ConcreteEntityMetadata.java:75)
at com.googlecode.objectify.impl.Registrar.registerPolymorphicHierarchy(Registrar.java:128)
at com.googlecode.objectify.impl.Registrar.register(Registrar.java:62)
at com.googlecode.objectify.ObjectifyFactory.register(ObjectifyFactory.java:209)
at com.googlecode.objectify.ObjectifyService.register(ObjectifyService.java:38)
at com.teamrawket.server.DataService.<clinit>(DataService.java:20)
... 27 more
What exactly does "attempting to create multiple associations on class ... for name" imply?
Sorry for the long post and any formatting issues that may arise.
You have repeated field names in your subclasses. You should not declare 'name' and 'dataSet' in both superclasses and subclasses; remove these fields from MapData and PathData and you should be fine.
com.teamrawket.server.MapData refers to the fullPath name for your MapData file. The name at the end refers to the field String name in your MapData class. This whole exception tries to tell you that it already contains a reference for that specific fullPath.
I would say there is another object with the same fullPath already registered. It would be helpful to know where line 59 is exactly as that is where the error occured.
Related
Mongodb is a no-schema document database, but in spring data, it's necessary to define entity class and repository class, like following:
Entity class:
#Document(collection = "users")
public class User implements UserDetails {
#Id private String userId;
#NotNull #Indexed(unique = true) private String username;
#NotNull private String password;
#NotNull private String name;
#NotNull private String email;
}
Repository class:
public interface UserRepository extends MongoRepository<User, String> {
User findByUsername(String username);
}
Is there anyway to use map not class in spring data mongodb so that the server can accept any dynamic JSON data then store it in BSON without any pre-class define?
First, a few insightful links about schemaless data:
what does “schemaless” even mean anyway?
“schemaless” doesn't mean “schemafree”
Second... one may wonder if Spring, or Java, is the right solution for your problem - why not a more dynamic tool, such a Ruby, Python or the Mongoshell?
That being said, let's focus on the technical issue.
If your goal is only to store random data, you could basically just define your own controller and use the MongoDB Java Driver directly.
If you really insist on having no predefined schema for your domain object class, use this:
#Document(collection = "users")
public class User implements UserDetails {
#Id
private String id;
private Map<String, Object> schemalessData;
// getters/setters omitted
}
Basically it gives you a container in which you can put whatever you want, but watch out for serialization/deserialization issues (this may become tricky if you had ObjectIds and DBRefs in your nested document). Also, updating data may become nasty if your data hierarchy becomes too complex.
Still, at some point, you'll realize your data indeed has a schema that can be pinpointed and put into well-defined POJOs.
Update
A late update since people still happen to read this post in 2020: the Jackson annotations JsonAnyGetter and JsonAnySetter let you hide the root of the schemaless-data container so your unknown fields can be sent as top-level fields in your payload. They will still be stored nested in your MongoDB document, but will appear as top-level fields when the ressource is requested through Spring.
#Document(collection = "users")
public class User implements UserDetails {
#Id
private String id;
// add all other expected fields (getters/setters omitted)
private String foo;
private String bar;
// a container for all unexpected fields
private Map<String, Object> schemalessData;
#JsonAnySetter
public void add(String key, Object value) {
if (null == schemalessData) {
schemalessData = new HashMap<>();
}
schemalessData.put(key, value);
}
#JsonAnyGetter
public Map<String, Object> get() {
return schemalessData;
}
// getters/setters omitted
}
Because the Datastore is shared across multiple versions of an application in App Engine, I'm looking into a way for saving only certain properties of an Entity.
Let's say I have the following class in version 1 of my app:
#Entity
public class ThingA {
#Id private Long id;
private String field1;
private String field2;
}
But in version 2, I changed this class to be:
#Entity
public class ThingA {
#Id private Long id;
private String field1;
private String field2;
private String field3;
}
The problem with saving the whole entity is that every time ThingA is saved on version 1 of the application, it sets "field3" to null.
It would be awesome if there's a way to save only certain fields on ThingA instead of the whole entity.
Thanks
I'm going to answer my own question after Googling a little bit more: The Datastore do not support partial updates to an entity. So that's it.
I have an entity called ReferenceForm which contains an AutoPopulatingList of ReferenceItems. It looks like this:
#Entity
public class ReferenceForm implements Serializable{
private static final long serialVersionUID = -5633788166190438576L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
long id;
#lob
private AutoPopulatingList<ReferenceItem> referenceItems;
}
If I add no annotation at all to the AutoPopulatingList, the field type which hibernate creates is varbinary(255). This causes string truncation errors. To work around this, I used the #lob annotation. This felt questionable at the time, but it worked fine. At this point I was just using HSQLDB.
Now the application needs to run against MSSQL. I have generated the schema using Hibernate, and referenceItems ia an image column on the ReferenceForm table. The items themselves are stored in the ReferenceItem table.
Is #lob an appropriate annotation here?.
EDIT: ReferenceItem looks like this:
#Entity
public class ReferenceItem implements Serializable {
private static final long serialVersionUID = -9077063073733429102L;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
long id;
private Title title;
private String firstName;
private String surname;
private String positionHeld;
private String institutionCompany;
#Embedded
private Address address;
#Embedded
private Telephone telephone;
private String email;
private boolean existingReference;
private String fileName;
public ReferenceItem() {
}
...getters and setters
}
SECOND EDIT:
Thanks to Willome for suggesting using #OneToMany. In the end, this is what worked.
//from
#lob
private AutoPopulatingList<ReferenceItem> referenceItems;
//to
#OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private List<ReferenceItem> referenceItems = new AutoPopulatingList<ReferenceItem>(ReferenceItem.class);
#OneToMany accurately describes the nature of the relationship
Use the interface (List) instead of the implementation when defining the field. See http://docs.jboss.org/hibernate/core/3.3/reference/en/html/collections.html
Define the CascadeType, otherwise this error appears on saving the entity: org.hibernate.TransientObjectException: object references an unsaved transient instance
Make the FetchType EAGER otherwise you cannot load the form in a different transaction: this error appears: failed to lazily initialize a collection of role: ReferenceForm.referenceItems, could not initialize proxy - no Session
You should replace your #Lob annonation with a #OneToMany and replace the AutoPopulatingList with a collection-valued field declared as an interface type (Check out the topic 6.1. Persistent collections on this link http://docs.jboss.org/hibernate/core/3.3/reference/en/html/collections.html.)
//#Lob
#OneToMany(mappedBy = "referenceForm")
private AutoPopulatingList<ReferenceItem> referenceItems; //fail AutoPopulatingList is not an interface
#OneToMany(mappedBy = "referenceForm")
private Set<ReferenceItem> referenceItems; // OK with Set/Collection/List
Thanks to Willome for suggesting using #OneToMany. In the end, this is what worked.
//from
#lob
private AutoPopulatingList<ReferenceItem> referenceItems;
//to
#OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
private List<ReferenceItem> referenceItems = new AutoPopulatingList<ReferenceItem>(ReferenceItem.class);
#OneToMany accurately describes the nature of the relationship
Use the interface (List) instead of the implementation when defining
the field. See
http://docs.jboss.org/hibernate/core/3.3/reference/en/html/collections.html
Define the CascadeType, otherwise this error appears on saving the
entity: org.hibernate.TransientObjectException: object references an
unsaved transient instance
Make the FetchType EAGER otherwise you
cannot load the form in a different transaction: this error appears:
failed to lazily initialize a collection of role:
ReferenceForm.referenceItems, could not initialize proxy - no Session
I'm trying to unmarshal a csv that have composed fields. For instance, in the following example
"order1","foo#email.com","(test1;45),(test2;89)"
The third attribute would represent a list of two items (but the size of the list is variablet), each item having a name and a price. The #Link annotation only works in one-to-one annotation, so it is not an option. The #OneToMany annotation in csv only works for writting so is neither an option.
The csv is written by non technical stuff, so a complex format is not an option either.
Is it possible to manage this requirement?
The java class to instantiate would be, in this case, something like this:
public class Order {
private String name;
private String email;
private List<Item> items;
}
public class Item {
private String name;
private int price;
}
Many thanks in advance
I created one table using Inheritance concept to sore data into google app engine datastore. It contained following coding but it shows error.How to user Inheritance concept.What error in my program
Program 1:
#Entity
#Inheritance(strategy = InheritanceType.JOINED)
public class calender {
#Id
private String EmailId;
#Basic
private String CalName;
#Basic
public void setEmailId(String emailId) {
EmailId = emailId;
}
public String getEmailId() {
return EmailId;
}
public void setCalName(String calName) {
CalName = calName;
}
public String getCalName() {
return CalName;
}
public calender(String EmailId, String CalName) {
this.EmailId = EmailId;
this.CalName = CalName;
}
}
Program 2:
#Entity
public class method extends calender {
#Id
private String method;
public void setMethod(String method) {
this.method = method;
}
public String getMethod() {
return method;
}
public method(String method) {
this.method = method;
}
}
My constraint is I want output like this
Calendartable contain
Emailid
calendarname
and method table contain
Emailid
method
How to achieve this?
It shows the following error in this line public method(String method)
java.lang.Error: Unresolved compilation problem:
Implicit super constructor calender() is undefined. Must explicitly invoke another constructor
According to Using JPA with App Engine, the JOINED inheritance strategy is not supported.
Your code doesn't compile, add a default constructor in Calendar.
I don't think you should annotate the method field with #Id.
The datastore of GAE/J is not an RDBMS so consequently the only "inheritance strategy" that makes any sense is TABLE_PER_CLASS. I would expect GAE/J to throw an exception if you specify that strategy, and if it doesn't then you ought to raise an issue against them
Your error "constructor calender() is undefined" is rather straightforward. You should create constructor without parameters in calendar class (you can make it private if you don't want to use it). That's because compiler can create default constructor by himself only if there aren't another constructors in the class.