title: Spring Boot: Export identifier encountered more than once
body: <p>Following error occures </p>
  
  <pre><code>Caused by: org.hibernate.tool.schema.spi.SchemaManagementException:Export identifier [order_signal] encountered more than once
  </code></pre>
  
  <p>I have the following classes:</p>
  
  <h2>tradingbot.persistence.model.order.TransactionComponent</h2>
  
  <pre><code>@Entity
  @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
  public abstract class TransactionComponent {
      @Id
      @GeneratedValue(strategy = GenerationType.TABLE)
      @Column(name = "id", updatable = false, nullable = false)
      protected Long id;
  
      ...
  }
  </code></pre>
  
  <h2>tradingbot.persistence.model.order.OrderSignal</h2>
  
  <pre><code>@Entity
  @JsonRootName("OrderSignalDAO")
  public class OrderSignal extends TransactionComponent {
      ...
  }
  </code></pre>
  
  <h2>tradingbot.persistence.model.order.TransferSignal</h2>
  
  <pre><code>@Entity(name = "TransferSignal")
  public class TransferSignal extends TransactionComponent {
      ....
  }
  </code></pre>
  
  <p>In class OrderSignal there is no other @Id and there is no getter/setter for id in TransactionComponent as well.</p>
  
  <p>Why does this error occures? What does it mean? How to fix it?</p>