On Fri, Jun 19, 2020 at 10:56 AM nU8K <[email protected]> wrote:
>
> anyway, here's the answer of "What's the difference between "get" and "with"
> function", just check the source code implementation.
Actually I would suggest looking at Javadocs (either from sources), or
if using IDE just look at definition.
There is also `path()` that is distinct from `get()`, as well as
`with()`, but `with()` is meant when changing things: it guarantees
that path you have will exist in `ObjectNode` / `ArrayNode` (fails for
other nodes).
So, you can do, for example:
ObjectNode root = mapper.createObjectNode();
root.with("branch").with("leaf").put("value", 42);
and now ObjectNode structure describes
{
"branch" : {
"leaf" : {
"value" : 42
}
}
}
conversely, `path()` allows traversal through "missing" nodes without
error: for missing nodes, there will
be `MissingNode` instance that never resolves to anything. So you can call
JsonNode root = mapper.readTree(source);
JsonNode maybeValue = root.path("branch").path("leaf").path("value");
assertTrue(maybeValue.isMissingValue());
even if incoming JSON was
{ }
whereas trying to use `get()` would give a NullPointerException (since
`node.get("property") returns `null` if no such property exists).
There is also convenience alternative `at()` which takes `JsonPointer`
for simpler access:
JsonNode maybeValue = root.at("/branch/leaf/value");
I hope this helps,
-+ Tatu +-
>
> ```java
> @Override
> public JsonNode get(String fieldName) {
> return _children.get(fieldName);
> }
>
> @Override
> public ObjectNode with(String propertyName) {
> JsonNode n = _children.get(propertyName);
> if (n != null) {
> if (n instanceof ObjectNode) {
> return (ObjectNode) n;
> }
> throw new UnsupportedOperationException("Property '" + propertyName
> + "' has value that is not of type ObjectNode (but " + n
> .getClass().getName() + ")");
> }
> ObjectNode result = objectNode();
> _children.put(propertyName, result);
> return result;
> }
> ```
>
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