public interface StageConfigurer {

  /**
   * get the input schema for this stage, or null if its unknown
   *
   * @return input schema
   */
  @Nullable
  Schema getInputSchema();

  /**
   * set the output schema for this stage, or null if its unknown
   *
   * @param outputSchema output schema for this stage
   */ 	
  void setOutputSchema(@Nullable Schema outputSchema);

  /**
   * set the error schema for this stage, or null if its unknown.
   * If no error schema is set, it will default to the input schema for the stage. Note that since source
   * plugins do not have an input schema, it will default to null for sources.
   *
   * @param errorSchema error schema for this stage
   */
  void setErrorSchema(@Nullable Schema errorSchema);

  /**
   * add errors for this stage to the configurer if pipeline stage is invalid. 
   *
   * @param error {@link InvalidStageExceptionValidationException} when a pipeline stage is invalid for any reason.
   */
  void addStageError(InvalidStageExceptionValidationException error);
}

/**
 * Exception used for invalid stage property.
 */
public class InvalidSchemaFieldExceptionInvalidStagePropertyException extends InvalidStageExceptionValidationException {
  private final String fieldproperty;
  private static final String STAGE_ERROR = "STAGE_ERROR";

  public InvalidSchemaFieldExceptionInvalidStagePropertyException(String message, String fieldproperty) {
    super(message);
    this.fieldproperty = fieldproperty;
  }

  public InvalidSchemaFieldExceptionInvalidStagePropertyException(String message, Throwable cause, String fieldproperty) {
    super(message, cause);
    this.fieldproperty = fieldproperty;
  }

  public String getFieldgetProperty() {
    return fieldproperty;
  }
}

/**
 * AnException errorused thatfor occurredinvalid dueschema to field schema mismatch in a specific pipeline stage.
 */
public class InvalidSchemaFieldErrorInvalidSchemaFieldException extends StageValidationErrorValidationException {
  private final String field;
  private static final String SCHEMA_ERROR = "SCHEMA_ERROR";

  public InvalidSchemaFieldErrorInvalidSchemaFieldException(String stagemessage, InvalidSchemaFieldExceptionString causefield) {
    this(cause.getMessage(), stage, cause.getField())super(message);
    this.field = field;
  }

  public InvalidConfigPropertyErrorInvalidSchemaFieldException(String message, StringThrowable stagecause, String field) {
    super(Type.INVALID_SCHEMA, message, stagecause);
    this.field = field;
  }

  public String getField() {
    return field;
  }

  @Override
  public booleanString equals(Object o) {
    ....
  }

  @Override
  public int hashCode() {
    ...
  getType() {
    return SCHEMA_ERROR;
  }

  @Override
  public String toJson() {
    return "{\"message\" : \"" + getMessage() +
      "\", \"type\" : \"" + getType() +
      "\", \"field\" : \"" + field + "\"}";
  }
}