ArrayNode implements Iterable. Iterable has a spliterator() method. You can create a sequential Stream from a Spliterator using
ArrayNode arrayNode = (ArrayNode) json.get("xyz");
StreamSupport.stream(arrayNode.spliterator(), false)
Answer from JB Nizet on Stack OverflowVideos
ArrayNode implements Iterable. Iterable has a spliterator() method. You can create a sequential Stream from a Spliterator using
ArrayNode arrayNode = (ArrayNode) json.get("xyz");
StreamSupport.stream(arrayNode.spliterator(), false)
An ArrayNode class provides random access: you can get size() and an element by index (using get(index)). This is all you need to create a good stream:
Stream<JsonNode> nodes = IntStream.range(0, files.size()).mapToObj(files::get);
Note that this solution is better than using default spliterator (as suggested by other answerers) as it can split well and reports the size properly. Even if you don't care about parallel processing, some operations like toArray() will work more effectively as knowing the size in advance will help to allocate an array of proper size.
Yes, the Jackson manual parser design is quite different from other libraries. In particular, you will notice that JsonNode has most of the functions that you would typically associate with array nodes from other APIs. As such, you do not need to cast to an ArrayNode to use. Here's an example:
JSON:
{
"objects" : ["One", "Two", "Three"]
}
Code:
final String json = "{\"objects\" : [\"One\", \"Two\", \"Three\"]}";
final JsonNode arrNode = new ObjectMapper().readTree(json).get("objects");
if (arrNode.isArray()) {
for (final JsonNode objNode : arrNode) {
System.out.println(objNode);
}
}
Output:
"One"
"Two"
"Three"
Note the use of isArray to verify that the node is actually an array before iterating. The check is not necessary if you are absolutely confident in your data structure, but it's available should you need it (and this is no different from most other JSON libraries).
In Java 8 you can do it like this:
import java.util.*;
import java.util.stream.*;
List<JsonNode> datasets = StreamSupport
.stream(obj.get("datasets").spliterator(), false)
.collect(Collectors.toList())