Defines a mechanism to observe produced contract states of type T when they are committed to the ledger.

Users should implement this interface for any states that need to be selectable via the TokenSelection API.

The Corda platform will discover and invoke implementations of this interface for all produced states that match the type specified by getStateType.

Example usage:

• Java:

  
  public class ExampleStateJ implements ContractState {
  public List<PublicKey> participants;
  public SecureHash issuer;
  public String currency;
  public BigDecimal amount;
  
  
  public List<PublicKey> getParticipants() {
  return participants;
  }
  }
  
  public class UtxoLedgerTokenStateObserverJavaExample implements UtxoLedgerTokenStateObserver<ExampleStateJ> {
  
  public Class<ExampleStateJ> getStateType() {
  return ExampleStateJ.class;
  }
  
  public UtxoToken onCommit(@NotNull ExampleStateJ state) {
  return new UtxoToken(
  new UtxoTokenPoolKey(ExampleStateK.class.getName(), state.issuer, state.currency),
  state.amount,
  new UtxoTokenFilterFields()
  );
  }
  }
  

• Kotlin:

  
  data class ExampleStateK(
  override val participants: List<PublicKey>,
  val issuer: SecureHash,
  val currency: String,
  val amount: BigDecimal
  ) : ContractState
  
  class UtxoLedgerTokenStateObserverKotlinExample : UtxoLedgerTokenStateObserver<ExampleStateK> {
  
  override val stateType = ExampleStateK::class.java
  
  override fun onCommit(state: ExampleStateK): UtxoToken {
  return UtxoToken(
  UtxoTokenPoolKey(ExampleStateK::class.java.name, state.issuer, state.currency),
  state.amount,
  UtxoTokenFilterFields()
  )
  }
  }