FieldValueList & FieldValue throwing null pointer exception when getting value of nullable field

[Sam-Bate-ITV]

I have a table with numerous nullable fields but when using the Java api to get the data from a row I've found that instead of simply getting null instead of a string the code throws an exception.

java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/FieldValue.java

Lines 107 to 121 in 45c5096

	/**
	* Returns this field's value as a {@link String}. This method should only be used if the
	* corresponding field has primitive type ({@link LegacySQLTypeName#BYTES}, {@link
	* LegacySQLTypeName#BOOLEAN}, {@link LegacySQLTypeName#STRING}, {@link LegacySQLTypeName#FLOAT},
	* {@link LegacySQLTypeName#INTEGER}, {@link LegacySQLTypeName#NUMERIC} {@link
	* LegacySQLTypeName#TIMESTAMP}).
	*
	* @throws ClassCastException if the field is not a primitive type
	* @throws NullPointerException if {@link #isNull()} returns {@code true}
	*/
	@SuppressWarnings("unchecked")
	public String getStringValue() {
	checkNotNull(value);
	return (String) value;
	}

As users are likely to want to map all results from a query regardless of whether the field was null or not it would be better if the methods for getting a String or Long handled null gracefully. Or at least provide an alternative method where the caller can provide a default value or null if the fields value is null.

Fortunately as I'm using Kotlin I can work around this for now with an extension function on FieldValueList:

fun FieldValueList.getNullable(name: String): FieldValue? = if (this.get(name).isNull) null else this.get(name)

which in turn means I can simply do row.getNullable("my_nullable_column")?.stringValue when mapping the FieldValueList to an object.

If getStringValue() had on overloaded method that takes an arg that's used as a default I could have done something like:

row.get("my_nullable_column").getStringValue(null)

which would be convenient. Also this could be added without breaking the existing API.

[PhongChuong]

Thank you for the feedback.
I'll discuss this with the team and get back to you soon.

[PhongChuong]

Hi @Sam-Bate-ITV ,
Would it preferable for your use case to:

1. Provide an overloaded getStringValue (from the post) or new method getStringValueOrDefault with similar behavior
2. Provide a knob to turn off the checkNotNull check

[Sam-Bate-ITV]

either would be fine for me as long as it's consistent with other methods that allow a default fallback