Filter JsonNode Array in Jackson without Iterating

Question

Json:

{  
   "type":"book",
   "children":[  
      {  
         "key":"123",
         "name":"book1"
      },
      {  
         "key":"456",
         "name":"book2"
         ]
      }
   ]
}

I just want to get the name of the book as string when key = "456".

This is what I have:

JsonNode root = mapper.readTree(investigation.getFilterModel());
JsonNode children = root.path("children");
            if (children.isArray())
            {
                for (final JsonNode objNode : children)
                {
                    if ("456".equalsIgnoreCase(objNode.path("key").textValue()))
                    {
                        String bookName = objNode.path("name").textValue();
                    }
                }
            }

This works for me. I just want to know is there a cleaner way to do it without looping thru the entire children array? As the size of array can be big.

Selections and traversal of this kind are pretty simple when using JsonPath expressions. Have a look into [Jayway JsonPath](https://github.com/json-path/JsonPath) lib or equivalents. — Antot, Oct 05 '18 at 06:08

score 3 · Accepted Answer · answered Oct 05 '18 at 06:42

That kind of query would not be possible with Jackson. You can at most use JsonPointer expression with it when you know the array index where the element is lying:

root.at("/children/1/name");

You can use JsonPath expression $.children[?(@.key==456)].name for your query which is supported in Jayway JsonPath library.

Filter JsonNode Array in Jackson without Iterating

1 Answers1