I am having issues with the order classes are scanned in Neo4 OGM.
Take the following minimal Spring Data Rest + Spring Boot application:
#NodeEntity("Country")
public class Country extends CountryRevision {
}
#NodeEntity("CountryRevision")
public class CountryRevision extends RevisionEntity<CountryRevision> {
String name;
}
public abstract class RevisionEntity<T> {
#Id #GeneratedValue(strategy = UuidStrategy.class)
String id;
#Relationship
T previousRevision;
}
#RepositoryRestResource(collectionResourceRel = "countries", path = "countries")
public interface CountryRepository extends Neo4jRepository<Country, String> {}
#RepositoryRestResource(collectionResourceRel = "countryRevisions", path = "country-rev")
public interface CountryRevisionRepository extends Neo4jRepository<CountryRevision, String> {}
#SpringBootApplication
#EnableNeo4jRepositories(basePackageClasses = DemoApplication.class)
#EntityScan(basePackageClasses = DemoApplication.class)
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}
When POSTING to /country-rev, I get the following error:
java.lang.RuntimeException: Field previousRevision not found in class com.example.demo.CountryRevision or any of its superclasses
at org.neo4j.ogm.metadata.ClassInfo.getField(ClassInfo.java:601) ~[neo4j-ogm-core-3.2.1.jar:3.2.1]
at org.neo4j.ogm.metadata.FieldInfo.readProperty(FieldInfo.java:411) ~[neo4j-ogm-core-3.2.1.jar:3.2.1]
What is really strange is that if I modify the "Country" class name to something else, like "Toto", everything works fine.
I debugged the way the OGM is initialized. It looks like depending on the classname, the map containing all OGM ClassInfos will be processed in a different order (in DomainInfo.prepareClass()), which will produce different results.
My question is: is there anything wrong with the previous example, or is this a bug in the OGM?
It's definitely an OGM issue which I reported here:
https://github.com/neo4j/neo4j-ogm/issues/704
Related
We have a concern exposing internal IDs to the outside world. Therefore I'm thinking about using a hashing mechanism (current choice is hashids) to hash our IDs.
I tried to use a #JsonSerializer and #JsonDeserializer mapping on the Entities ID field. But this only takes effect when including the ID in the body, and has no impact on the IDs in the URL paths.
Is there a possibility to do this, e.g. something like an ID Translation SPI?
The only thing I can think of is to create a request filter that would take the request with encoded ID in URL, then decode the ID and redirect to an URL with decoded ID.
What you need is working "right from the box" in Spring Data REST by customizing item resource URIs:
#Configuration
public class RestConfigurer extends RepositoryRestConfigurerAdapter {
#Override
public void configureRepositoryRestConfiguration(RepositoryRestConfiguration config) {
config.withEntityLookup().forRepository(ModelRepo.class, model -> HashIdUtil.encode(model.getId()), ModelRepo::findByEncodedId);
super.configureRepositoryRestConfiguration(config);
}
}
public interface ModelRepo extends JpaRepository<Model, Long> {
default Model findByEncodedId(String encodedId) {
return getById(HashIdUtil.decode(encodedId));
}
Model getById(Long id);
}
public class HashIdUtil {
private static final Hashids HASHIDS = new Hashids("salt", 8);
public static String encode(Long source) {
return HASHIDS.encode(source);
}
public static Long decode(String source) {
return HASHIDS.decode(source)[0];
}
}
Unfortunately, due to the bug (I suppose), PUT/PATCH-ing entities does not work in Spring Boot 2+, unlike the previous version of SB (1.5+) where it works as expected.
See my demo: sdr-hashids-demo
You could try using a converter.
#Component
#AllArgsConstructor
public class HashIdConverter implements Converter<String, Long> {
private final HashidsUtil hashidsUtil;
#Override
public Long convert(#NonNull String source) {
return hashidsUtil.decodeId(source);
}
}
Using it the way I just showed you is a bit unsafe, but it can do the work quite well if you are careful enough
I'm new to OSGI framework and I'm trying to access the 'Derived' Class variable 'publicVariable' from another class 'Derived2' like "Derived.publicVariable" but publicVariable is always shows null. I really appreciate if someone can help me out with this.
Thanks
Manifest file - Derived2
Require-Bundle:com.xxxxxx.Derived1
Java code
abstract class Base {
protected Vector <String> supportedCommands = new Vector <String> ();
protected abstract void initialiseCommands();
}
class Derived extends Base {
private static Derived derivedPlugin = null;
public Derived()
{
derivedPlugin = this;
}
public static Derived getPlugin()
{
return derivedPlugin;
}
public String publicVariable = null;
protected void initialiseCommands()
{
publicVariable = "someData";
System.out.println("Derived" + publicVariable);
}
}
class Derived2 extends Base {
protected void initialiseCommands()
{
supportedCommands.add(Derived.getPlugin().publicVariable);
System.out.println("IMRSAUtilitiesPlugin" +supportedCommands);
}
Also referred below link, which is a similar issue but i'm not using any static variable, it is just a public variable.
how use Singleton object in different class loader....?
The code in the question will not compile. You are trying to access an instance field (publicVariable in class Derived) in a static way, i.e. Derived.publicVariable.
OSGi does not change the semantics of the Java language, and if you cannot even compile your code then OSGi will certainly not be able to run it.
Faced with problem. Some fields in my classes are injected and in debugger i can see something like this:
Problem begins when I am trying to map #Aspect to one of methods defined in SettingService. Like this:
#Aspect
public class SettingsAspect
{
#AfterReturning(pointcut = "execution( * package.SettingsService.method(..))", returning = "result")
public void profilingSettingsAdvice(JoinPoint joinPoint, String result)
{
System.out.println(joinPoint.getArgs());
}
}
My service looks like this:
#Service
#Transactional
public class SettingsService
{
#Cacheable(value = "DefaultSettingsCache", key = "#root.methodName")
public int method()
{
return 1;
}
}
Don't know why, aspect isn't called after method() execution. Mystery is that aspect works ok with other classes/ What does it mean when class is injected with type Blablabla$$EnhancerBySpringCGLIB?
Thank you.
Your advice only matches methods returning a String, but your method returns an int.
I have the following interface
#JsonTypeInfo(use = JsonTypeInfo.Id.CLASS, include = JsonTypeInfo.As.PROPERTY, property = "className")
public interface InfoChartInformation {
public String name();
}
And the following implementation (enum):
public class InfoChartSummary {
public static enum Immobilien implements InfoChartInformation {
CITY, CONSTRUCTION_DATE;
}
public static enum Cars implements InfoChartInformation {
POWER, MILEAGE;
}
}
Then I use all of It in the following entity:
#Entity(noClassnameStored = true)
#Converters(InfoChartInformationMorphiaConverter.class)
public class TestEntity{
#Id
public ObjectId id;
#Embedded
public List<InfoChartInformation> order;
}
Jackson, in order to detect the type on the unmarshalling time, will add to every enum on the list the className.
I thought morphia would do the same, but there's no field className in the List of enum and the unmarshalling cannot be done correctly: java.lang.RuntimeException: java.lang.RuntimeException: java.lang.RuntimeException: java.lang.ClassCastException: java.lang.String cannot be cast to com.mongodb
.DBObject
I guess the correct behavior should be to save all the enum route (package+name), not only the enum name. At least in that way the unmarshalling could be performed. There's a way morphia supports that by default or I need to create my own converter (similar to this) ?
I tried creating a Custom Converter:
public class InfoChartInformationMorphiaConverter extends TypeConverter{
public InfoChartInformationMorphiaConverter() {
super(InfoChartInformation.class);
}
#Override
public Object decode(Class targetClass, Object fromDBObject, MappedField optionalExtraInfo) {
if (fromDBObject == null) {
return null;
}
String clazz = fromDBObject.toString().substring(0, fromDBObject.toString().lastIndexOf("."));
String value = fromDBObject.toString().substring(fromDBObject.toString().lastIndexOf(".") + 1);
try {
return Enum.valueOf((Class)Class.forName(clazz), value);
} catch (ClassNotFoundException e) {
return null;
}
}
#Override
public Object encode(final Object value, final MappedField optionalExtraInfo) {
return value.getClass().getName() + "." + ((InfoChartInformation) value).name();
}
}
Then, I added the converter information to morphia morphia.getMapper().getConverters().addConverter(new InfoChartInformationMorphiaConverter());.
However, when serializing (or marshalling) the object to save it into the database, the custom converter is ignored and the Enum is saved using the default Morphia converter (only the enum name).
If I use in the TestEntity class only an attribute InfoChartInformation; instead of the List<>InfoChartInformation>, my customer converter will work. However I need support for List
Use:
public class InfoChartInformationMorphiaConverter extends TypeConverter implements SimpleValueConverter
It is a marker interface required to make your Convertor work.
i have a question regarding design patterns.
suppose i want to design pig killing factory
so the ways will be
1) catch pig
2)clean pig
3) kill pig
now since these pigs are supplied to me by a truck driver
now if want to design an application how should i proceed
what i have done is
public class killer{
private Pig pig ;
public void catchPig(){ //do something };
public void cleanPig(){ };
public void killPig(){};
}
now iam thing since i know that the steps will be called in catchPig--->cleanPig---->KillPig manner so i should have an abstract class containing these methods and an execute method calling all these 3 methods.
but i can not have instance of abstract class so i am confused how to implement this.
remenber i have to execute this process for all the pigs that comes in truck.
so my question is what design should i select and which design pattern is best to solve such problems .
I would suggest a different approach than what was suggested here before.
I would do something like this:
public abstract class Killer {
protected Pig pig;
protected abstract void catchPig();
protected abstract void cleanPig();
protected abstract void killPig();
public void executeKillPig {
catchPig();
cleanPig();
killPig();
}
}
Each kill will extend Killer class and will have to implement the abstract methods. The executeKillPig() is the same for every sub-class and will always be performed in the order you wanted catch->clean->kill. The abstract methods are protected because they're the inner implementation of the public executeKillPig.
This extends Avi's answer and addresses the comments.
The points of the code:
abstract base class to emphasize IS A relationships
Template pattern to ensure the steps are in the right order
Strategy Pattern - an abstract class is as much a interface (little "i") as much as a Interface (capital "I") is.
Extend the base and not use an interface.
No coupling of concrete classes. Coupling is not an issue of abstract vs interface but rather good design.
public abstract Animal {
public abstract bool Escape(){}
public abstract string SaySomething(){}
}
public Wabbit : Animal {
public override bool Escape() {//wabbit hopping frantically }
public override string SaySomething() { return #"What's Up Doc?"; }
}
public abstract class Killer {
protected Animal food;
protected abstract void Catch(){}
protected abstract void Kill(){}
protected abstract void Clean(){}
protected abstract string Lure(){}
// this method defines the process: the methods and the order of
// those calls. Exactly how to do each individual step is left up to sub classes.
// Even if you define a "PigKiller" interface we need this method
// ** in the base class ** to make sure all Killer's do it right.
// This method is the template (pattern) for subclasses.
protected void FeedTheFamily(Animal somethingTasty) {
food = somethingTasty;
Catch();
Kill();
Clean();
}
}
public class WabbitHunter : Killer {
protected override Catch() { //wabbit catching technique }
protected override Kill() { //wabbit killing technique }
protected override Clean() { //wabbit cleaning technique }
protected override Lure() { return "Come here you wascuhwy wabbit!"; }
}
// client code ********************
public class AHuntingWeWillGo {
Killer hunter;
Animal prey;
public AHuntingWeWillGo (Killer aHunter, Animal aAnimal) {
hunter = aHunter;
prey = aAnimal;
}
public void Hunt() {
if ( !prey.Escape() ) hunter.FeedTheFamily(prey)
}
}
public static void main () {
// look, ma! no coupling. Because we pass in our objects vice
// new them up inside the using classes
Killer ElmerFudd = new WabbitHunter();
Animal BugsBunny = new Wabbit();
AHuntingWeWillGo safari = new AHuntingWeWillGo( ElmerFudd, BugsBunny );
safari.Hunt();
}
The problem you are facing refer to part of OOP called polymorphism
Instead of abstract class i will be using a interface, the difference between interface an abstract class is that interface have only method descriptors, a abstract class can have also method with implementation.
public interface InterfaceOfPigKiller {
void catchPig();
void cleanPig();
void killPig();
}
In the abstract class we implement two of three available methods, because we assume that those operation are common for every future type that will inherit form our class.
public abstract class AbstractPigKiller implements InterfaceOfPigKiller{
private Ping pig;
public void catchPig() {
//the logic of catching pigs.
}
public void cleanPig() {
// the logic of pig cleaning.
}
}
Now we will create two new classes:
AnimalKiller - The person responsible for pig death.
AnimalSaver - The person responsible for pig release.
public class AnimalKiller extends AbstractPigKiller {
public void killPig() {
// The killing operation
}
}
public class AnimalSaver extends AbstractPigKiller {
public void killPing() {
// The operation that will make pig free
}
}
As we have our structure lets see how it will work.
First the method that will execute the sequence:
public void doTheRequiredOperation(InterfaceOfPigKiller killer) {
killer.catchPig();
killer.cleanPig();
killer.killPig();
}
As we see in the parameter we do not use class AnimalKiller or AnimalSever. Instead of that we have the interface. Thank to this operation we can operate on any class that implement used interface.
Example 1:
public void test() {
AnimalKiller aKiller = new AnimalKiller();// We create new instance of class AnimalKiller and assign to variable aKiller with is type of `AnimalKilleraKiller `
AnimalSaver aSaver = new AnimalSaver(); //
doTheRequiredOperation(aKiller);
doTheRequiredOperation(aSaver);
}
Example 2:
public void test() {
InterfaceOfPigKiller aKiller = new AnimalKiller();// We create new instance of class AnimalKiller and assign to variable aKiller with is type of `InterfaceOfPigKiller `
InterfaceOfPigKiller aSaver = new AnimalSaver(); //
doTheRequiredOperation(aKiller);
doTheRequiredOperation(aSaver);
}
The code example 1 and 2 are equally in scope of method doTheRequiredOperation. The difference is that in we assign once type to type and in the second we assign type to interface.
Conclusion
We can not create new object of abstract class or interface but we can assign object to interface or class type.