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.
Related
I have a general-purpose POJO:
public class Thing {
private String name;
private String etc;
public String getName() {
return name;
}
// other getters and setters
}
I'm using Spring 4.3.9 and Spring-data-mongodb 1.10.4. I want to store instances of this POJO in Mongodb, but I have some constraints:
I can't add Spring annotations to the base class (but I can subclass Thing and annotate that).
I want to use the name field as the Mongodb unique ID (mainly to avoid creating a separate unique index for it).
I want to (redundantly) store the name field as an actual field named "name", so that other consumers of the collection don't have to know that "name" is stored in the _id.
I started out trying this:
public class SpringThing extends Thing {
#Id
#Override
public String getName() {
return super.getName();
}
#Override
public void setName(String name) {
super.setName(name);
}
}
This causes spring to use the value of name for _id, but of course it doesn't store a field named "name" in Mongodb. The documentation says that spring will use a "property or field" named "id" or annotated with #Id. So I tried defining a redundant getter/setter which accesses the name field:
public class SpringThing extends Thing {
#Id
public String getId() {
return super.getName();
}
public void setId(String id) {
super.setName(id);
}
}
Unfortunately, spring ignores getId and setId here, and stores the object with an autogenerated ID. I also tried creating redundant getters/setters annotated with #Field("name"), but spring seems to ignore any getter/setter pair without an actual field.
Adding an actual ID field and storing a copy of the name there does work:
public class SpringThing extends Thing {
#Id
private String id;
#Override
public void setName(String id) {
this.id = id;
super.setName(id);
}
}
But it requires defining a pointless field named "id".
Is there a more reasonable way to get what I want? Is what I'm trying to do reasonable to begin with?
Thanks to a hint by #mp911de, I ended up creating a subclass of Thing that looks like this:
#TypeAlias("thing")
#Document(collection = "things")
public class SpringThing extends Thing {
#Id
#AccessType(Type.PROPERTY)
#JsonIgnore
public String getId() {
return super.getName();
}
public void setId(String taskName) {
super.setName(taskName);
}
}
The #TypeAlias annotation overrides the name which spring would use for the type, to cover up the fact that I've created a subclass just to add annotations.
#Id says that this is the getter for _id.
#AccessType says to access this field through the getter and setter rather than by directly accessing the field. This is what I needed; without it, spring looks for a private member variable named something like id.
#JsonIgnore is the Jackson (JSON library that we're using) annotation to prevent including the id field when serializing these objects to JSON.
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
}
I have a problem with retrieving objects from Google Cloud Datastore using JDO. It is incredibly frustrating, because 99.5% of the time my code works perfectly, but 0.5% of the time some of the data is missing, and I can't find consistent steps to replicate the bug. I'm fairly certain that my issue is with either how I've set up my model or how I'm querying the datastore (I have a suspicion that it may be to do with lazy loading or the default fetch group, but I'm not sure).
Before I explain what's happening it would help to understand the model.
Here is a simplified version of my model:
#PersistenceCapable
#Inheritance(customStrategy = "complete-table")
public class DataObject {
#PrimaryKey
#Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY, defaultFetchGroup="true")
protected Key theKey;
#Persistent()
protected String name;
//...
}
#PersistenceCapable
public class Class1 extends DataObject{
#Persistent()
#Element(dependent="true")
private List<Class2> listOfClass2 = new ArrayList<Class2>();
//...
}
#PersistenceCapable
public class Class2 extends DataObject{
#Persistent()
#Element(dependent="true")
private List<Class3> listOfClass2 = new ArrayList<Class3>();
//...
}
#PersistenceCapable
public class Class3 extends DataObject{
#Persistent()
private String value;
//...
}
And here is the code used to query the data store:
public class DataManager {
public DataObject get(
User user,
Class type,
Long id) throws OAuthRequestException
{
PersistenceManager mgr = getPersistenceManager();
DataObject obj = null;
try
{
obj = mgr.getObjectById(type, id);
getAllChildren(obj);
}
finally
{
mgr.close();
}
if(obj != null)
{
return obj;
}
else
{
throw new EntityNotFoundException("Entity not found");
}
}
/**
* Returns all of the children of the given object
* and their children etc. It is intended to 'touch' every object
* in the tree to accommodate for lazy loading.
*/
private List<StoredDataObject> getAllChildren(DataObject obj)
{
//...
}
}
The problem is that very occasionally, the query will be returned with all of the 'name' fields at a given level empty. For instance, If I retrieve an object of Class1, all of the child Class2 objects will have the 'name' attribute equal to "". The data is definitely in the data store because if I run the query again they will be populated correctly. I have never seen any of the other attributes empty, only the name field. Sometimes it occurs at the Class2 level, sometimes Class3, but never Class1 (as far as I have seen).
It is my understanding that any String attributes should automatically be included in the default fetch group, but am I possibly missing an annotation that forces the 'name' attribute to be retrieved every time?
New observation: When this occurs, it will happen consistently for about 15 minutes as long as I run the same query with the same user credentials. Could this be something to do with caching?
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.
Howdy, ya'll! First question on StackOverflow! :-)
So here's the scenario: We're working on a web app with Silverlight 4 and using WCF RIA Services 1.0 SP1 Beta for the web service. I have my entities in the Entity Framework Designer, but I'm using a slightly-modified ADO.NET C# POCO Entity Generator template to generate the classes.
What I'd like to do is have a method inside a Domain Service with the following signature:
[EnableClientAccess]
public class ResultService : DomainService
{
[Invoke]
public SerializableResult CalculateResult(EntityOne e1, EntityTwo e2);
}
I am returning both EntityOne and EntityTwo to the client through queries in other services, like so:
[EnableClientAccess]
public class EntityOneService : DomainService
{
public IQueryable<EntityOne> GetEntityOnes();
}
[EnableClientAccess]
public class EntityOneService : DomainService
{
public IQueryable<EntityTwo> GetEntityTwos();
}
Those classes are successfully being generated in the Silverlight project. The SerializableResult does not have a key.
When I try to compile, I get the following error: "Operation named 'CalculateResult' does not conform to the required signature. Parameter types must be an entity or complex type, a collection of complex types, or one of the predefined serializable types."
In my research, the most helpful information I found were in the comments of this post by Jeff Handley.
Of note, Peter asked in a comment:
I get an 'does not conform to the required signature ...' compile error if my complex object has an [Key] Attribute. When I remove this attribute I can use the object as parameter for an Invoke operation.
Jeff's response:
This is by design. Complex objects cannot have Key properties. If you have a Key the class gets treated as an Entity.
So it sounds as if any further efforts to try to get my method to work will be futile. However, I was wondering if anyone else has come across this problem, and what they did to solve it.
Thanks very much!
I have the following and it works for me.
namespace BusinessApplication2.Web
{
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.ServiceModel.DomainServices.Hosting;
using System.ServiceModel.DomainServices.Server;
[EnableClientAccess()]
public class DomainService1 : DomainService
{
public IQueryable<EntityOne> GetEntityOnes()
{
return null;
}
public IQueryable<EntityTwo> GetEntityTwos()
{
return null;
}
[Invoke]
public SerializableResult GetSerializableResult(EntityOne one, EntityTwo two)
{
return new SerializableResult() { Result = "It woooooorrrked!" };
}
}
public class EntityOne
{
[Key]
public int Id { get; set; }
}
public class EntityTwo
{
[Key]
public int Id { get; set; }
}
public class SerializableResult
{
public string Result { get; set; }
}
}
Many thanks to Mr. Jeff Handley and Mr. Dinesh Kulkarni for the answer (through Twitter).
In order for an Entity to be used as a parameter in an invoke method, that Entity must be exposed through a query method existing within the same DomainService. The intention for this restriction is that
"Each domain service needs to be able to stand on its own."
By adding two dummy Query methods (see Jeff's answer for an example), I was able to compile my code.