# Validation

## Programmatic

Use the [DataValidatorBuilder](https://github.com/apache/fineract/search?q=%22class+DataValidatorBuilder%22), e.g. like so:

```java
new DataValidatorBuilder().resource("fileUpload")
    .reset().parameter("Content-Length").value(contentLength).notBlank().integerGreaterThanNumber(0)
    .reset().parameter("FormDataContentDisposition").value(fileDetails).notNull()
    .throwValidationErrors();
```

Such code is often encapsulated in [`*Validator`](https://github.com/apache/fineract/search?q=Validator)
classes (if more than a few lines, and/or reused from several places; avoid copy/paste), like so:

```java
public class YourThingValidator {

    public void validate(YourThing thing) {
        new DataValidatorBuilder().resource("yourThing")
        ...
        .throwValidationErrors();
    }
}
```


## Declarative

[FINERACT-1229](https://issues.apache.org/jira/browse/FINERACT-1229) is an open issue about adopting
Bean Validation for _declarative_ instead of _programmatic_ (as above) validation.  Contributions welcome!