Implement a ContractStateVaultJsonFactory to create a JSON representation of a state to store alongside the state in the vault. This JSON representation can be used to query states from flows using query.

Classes that implement ContractStateVaultJsonFactory will be executed in a hierarchical way. That means every factory that belongs to a given state or that given state's ancestors will be executed and the end result will be a combined JSON. The combined JSON will be keyed by the state type specified by the factory.

In order to perform a "query by state" query using `UtxoLedgerService.query` for a particular state type, a factory for that given type must be present, even if it's just returning an empty JSON string.

Please note that only one factory can be registered for a state type.

Example usage:

• Kotlin:

  
  class TestUtxoStateVaultJsonFactory: ContractStateVaultJsonFactory<TestUtxoState> {
  
      private data class TestUtxoStatePojo(val testField: String)
  
      override val stateType: Class<TestUtxoState> = TestUtxoState::class.java
  
      override fun append(state: TestUtxoState, jsonMarshallingService: JsonMarshallingService): String {
          return jsonMarshallingService.format(TestUtxoStatePojo(state.testField))
      }
  }
  
  

• Java:

  
  public class TestUtxoStateVaultJsonFactory implements ContractStateVaultJsonFactory<TestUtxoState> {
  
      private class TestUtxoStatePojo {
          private String testField;
  
          TestUtxoStatePojo(String testField) {
              this.testField = testField;
          }
  
          String getTestField() {
              return this.testField;
          }
      }
  
      
      public Class<T> getStateType() {
          return TestUtxoState.class;
      }
  
      
      public String append(TestUtxoState state, JsonMarshallingService jsonMarshallingService) {
          return jsonMarshallingService.format(new TestUtxoStatePojo(state.getTestField()));
      }
  }