org.hibernate.InstantiationException：没有实体的默认构造函数：：principal.Cliente

Question

I'm having this error:

Exception in thread "main" org.hibernate.InstantiationException: No default constructor for entity:  : principal.Cliente
   at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:120)
   at org.hibernate.tuple.PojoInstantiator.instantiate(PojoInstantiator.java:136)
   at org.hibernate.tuple.entity.AbstractEntityTuplizer.instantiate(AbstractEntityTuplizer.java:737)
   at org.hibernate.persister.entity.AbstractEntityPersister.instantiate(AbstractEntityPersister.java:4755)
   at org.hibernate.internal.SessionImpl.instantiate(SessionImpl.java:1387)
   at org.hibernate.internal.SessionImpl.instantiate(SessionImpl.java:1375)
   at org.hibernate.loader.plan.exec.process.internal.EntityReferenceInitializerImpl.hydrateEntityState(EntityReferenceInitializerImpl.java:235)
   at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.readRow(AbstractRowReader.java:107)
   at org.hibernate.loader.plan.exec.internal.EntityLoadQueryDetails$EntityLoaderRowReader.readRow(EntityLoadQueryDetails.java:255)
   at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:129)
   at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:138)
   at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:102)
   at org.hibernate.loader.entity.plan.AbstractLoadPlanBasedEntityLoader.load(AbstractLoadPlanBasedEntityLoader.java:186)
   at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:4120)
   at org.hibernate.event.internal.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:502)
   at org.hibernate.event.internal.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:467)
   at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:212)
   at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:274)
   at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:150)
   at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1066)
   at org.hibernate.internal.SessionImpl.access$2000(SessionImpl.java:176)
   at org.hibernate.internal.SessionImpl$IdentifierLoadAccessImpl.load(SessionImpl.java:2540)
   at org.hibernate.internal.SessionImpl.get(SessionImpl.java:951)
   at principal.ClienteDAO.obtenContacto(ClienteDAO.java:83)
   at principal.Main.main(Main.java:43)

Have no idea why im getting that exception

EDIT1 here is principal.Cliente

public class Cliente {
    private String name;

    public Cliente(String name) {
        this.name= name;
    }
}

EDIT 2 removed a bunch of useless code to make it look cleaner

Answer 1

Missing default constructor in principal.Cliente I can say,

public class Cliente{ 
  public Cliente(){}
}

Answer 2

when you are adding more constructors, make sure to keep the default one.

public Cliente(){
   super()
}

Answer 3

The easiest way to get rid of this error in spring boot is to use the @NoArgsConstructor annotation. For this you will need lombok dependency.I always recommend to use lombok in spring boot projects. Then your entity class will be as follows

import lombok.NoArgsConstructor;

    @Entity
    @NoArgsConstructor
    public class Cliente{ 
      
    }

Answer 4

Notice, in spring boot you should have at least 2 constructors for the models you have.

1. Constructor empty

   public Cliente(){}

2. Constructor with all the fields, minus the id.

3. (facultative) Constructor with all the fields, id included.

You should include all of these 3 Constructors in your model. If you remove the first constructor it gives you the error you reported. The 2nd constructor is used by hybernate to generate an instance and save it on the table of the db. The id should be generated automatically. The 3rd constructor it is useful for you for making tests.