Enable default values for text nodes

[ccleve]

When a JsonNode contains an integer or boolean, there's a nice option to specify a default value:

int myInt = myNode.asInt(defaultValue);

This doesn't exist for text nodes. It would be nice to have this:

String myString = myNode.asText("a default value here");

[cowtowncoder]

Sounds reasonable to me.

One question is as to when this should be used: with primitives, value is used if no coercion is found. But with Strings, most other types would convert to String. So should this only use default value if property is missing altogether? Or if it does not have scalar value (i.e. missing property, as well as array/object valued, would use default).

[ccleve]

My thought was that the default value should be returned only when the
value is missing. Otherwise, getText() should behave normally.

On 5/19/2014 6:59 PM, Tatu Saloranta wrote:

Sounds reasonable to me.

One question is as to when this should be used: with primitives, value
is used if no coercion is found. But with Strings, most other types
would convert to String. So should this only use default value if
property is missing altogether? Or if it does not have scalar value
(i.e. missing property, as well as array/object valued, would use
default).

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[cowtowncoder]

Implemented: will return defaultValue for these specific cases:

• For MissingNode (virtual node returned with "path()", and "at(JSONPointer)")
• For 'NullNode`
• For other node types that can contain null value (POJONode, possible StringNode)

but note that it is NOT returned if empty String ("") is available.

[henning-meinhardt]

Hi, bit late to the party but anyway: after upgrading to the latest Jackson databind release I noticed a deprecation warning when using .asText (defaultValue) but don't really understand the explanation given in the java doc:

    /**
     * Method similar to {@link #asText()}, except that it will return
     * <code>defaultValue</code> in cases where null value would be returned;
     * either for missing nodes (trying to access missing property, or element
     * at invalid item for array) or explicit nulls.
     *<p>
     * NOTE: deprecated since 2.17 because {@link #asText()} very rarely returns
     * {@code null} for any node types -- in fact, neither {@link MissingNode}
     * nor {@code NullNode} return {@code null} from {@link #asText()}.
     *
     * @since 2.4
     *
     * @deprecated Since 2.17, to be removed from 3.0
     */
    @Deprecated // @since 2.17
    public String asText(String defaultValue) {

It says that almost no node type did ever return null so the == null comparison was meaningless most of the time. That might be right but doesn't legitimate the deprecation. MissingNode subclass overwrites asText (defaultValue) as follows:

@Override public String asText(String defaultValue) { return defaultValue; }

So the == null check is actually not involved and a MissingNode always returned the specified default value.
So I could use something like this to default a missing node to a meaningful default value:

JsonNode node = ... {} // an empty node {} for example
String value = node.path ("property").asText ("default value");

That returned "default value" for an empty JsonNode.
Now that its deprecated I would have to write more complicated code (or there is a shorter replacement that is unfortunately not mentioned in the deprecation comment):

JsonNode node = ... {} // an empty node {} for example
String value = node.path ("property").getText ();
if (value == null)
    value = "defaultValue";

or

JsonNode node = ... {} // an empty node {} for example
JSonNode propertyNode = node.path ("property");
String value = propertyNode.isMissingNode () ? "defaultValue" : propertyNode.getText();

I have two questions:

1. Is there a simpler workaround for the now missing defaultValue feature?
2. Why did you deprecate asText(defaultValue) but left asInt(defaultValue), asLong(defaultValue) and so on?

Kind regards
Henning

[cowtowncoder]

Follow-up discussion on #4471.