Write requests that violate hard constraints of your content type model can be aborted when a validator fails. Typical use cases include:

Caution

Blocking writes is not normally useful for text properties, because text values are saved continuously as the user enters data, and a write interceptor might not be able to operate appropriately during the first saves. For blobs or link lists, the impact on the user experience is typically less of a problem. In any case, you need to make sure that the user experience is not impacted negatively.

For implementing immediate validation, you can create an instance of the class ValidatingContentWriteInterceptor as a Spring bean and populate its validators property with a list of PropertyValidator objects. When the validators are configured to report an error issue, an offending write will not be executed (that is, the requested value will not be saved).

A configuration that limits the size of images in the data property of CMPicture content items to 1 Mbyte might look like this (class names are wrapped for layout reasons):

@Bean
ValidatingContentWriteInterceptor
  myValidatingContentWriteInterceptor(MaxBlobSizeValidator myMaxBlobSizeValidator) {

  ValidatingContentWriteInterceptor validatingContentWriteInterceptor =
    new ValidatingContentWriteInterceptor();
  validatingContentWriteInterceptor.setType("CMPicture");
  validatingContentWriteInterceptor.setValidators(
    Collections.singletonList(myMaxBlobSizeValidator)));
  return validatingContentWriteInterceptor;
}

@Bean
MaxBlobSizeValidator myMaxBlobSizeValidator() {
  MaxBlobSizeValidator maxBlobSizeValidator =
    new MaxBlobSizeValidator();
  maxBlobSizeValidator.setProperty("data");
  maxBlobSizeValidator.setMaxSize(1000000);
  return maxBlobSizeValidator;
}

Remember that the validators become active during creation, too, so that an immediate validator might validate initial values set by an earlier write interceptor.