javajsonjacksonjirajackson2

Jackson -- parse json using xpath or similar


I have some json and it's fairly complex -- (a bit too complex and open-ended to model using something like gson), and I need to extract string values from certain nodes into a list of strings.

The following code works, but due to the way my json works -- it's grabbing lots of extra stuff that I don't want (note: I don't own the json schema)

ObjectMapper mapper = new ObjectMapper();
        JsonNode node = mapper.readTree(json);
        List<JsonNode> keys = node.findValues("key") ;
for(JsonNode key: keys){
         System.out.println(key.toString());
}

The contents of Json is fairly complex (Jira filter export) which looks like this:

{
    "issues": [
    {
        "key":"MIN-123",
        ...
        "fields":{
             "key":"A_Elric"
        }
    }
    ]
}

Assertions: I always want to extract issues[x].key and not any of the subkeys. I would prefer to extract this into a list, but any normal data structure is fine. I'm already using Jackson -- but gson is also an option if there's a sane way of doing so.

Thanks for the assist!


Solution

  • JsonPath is xpath for json, and it has a Java implementation. Here is a working example to get issue keys without subkeys:

    import com.jayway.jsonpath.Configuration;
    import com.jayway.jsonpath.JsonPath;
    import java.nio.file.Files;
    import java.nio.file.Paths;
    import java.util.List;
    
    public class JsonPathTest {
    
        public static String ROOT_ARRAY = "issues";
        public static String KEY = "key";
        // get all KEYs right under ROOT array
        public static String jsonPath = String.format("$.%s[*].%s", ROOT_ARRAY, KEY);
    
        public static void main(String[] args) {
            try {
                String jsonStr = new String(Files.readAllBytes(Paths.get("c:/temp/xx.json")));
                Object jsonObj = Configuration.defaultConfiguration().jsonProvider().parse(jsonStr);
                List<String> keys = JsonPath.parse(jsonObj).read(jsonPath);
                System.out.println(keys);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }