Databases
StackOverflow2013
Postsdbo
POextract map from vertex and return an array of maps via REST-API
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POextract map from vertex and return an array of maps via REST-API
    primarykey
    data
    text
    <p>I am trying to put all properties of a vertex in a map and add additional values to this map. Later, I want to return this map as a JSON response. In general I find the <a href="http://docs.neo4j.org/chunked/stable/gremlin-plugin.html" rel="nofollow">REST-API</a> of neo4j a bit verbose and I need the ID of a vertex among other values. Therefore, I decided to do this directly via a gremlin query.</p> <p>The result should look like:</p> <pre><code>[ {"id": 1, "name": "Name1"}, {"id": 2, "name": "Name2"} ] </code></pre> <p>I managed to do this using the following gremlin script:</p> <pre><code>x = []; g.v( 1 ).out.transform{ m = [:]; m.putAll( it.map() ); m.put( "id", it.id ); x.add( m ) }.iterate(); x </code></pre> <p>However, I ran into issues with this query with neo4j community 1.8.2 and 1.9M05.</p> <p>a) neo4j 1.8.2 returns a JSONArray of Strings instead of a JSONArray of JSONObjects:</p> <pre><code>[ "{id: 1, name: Name1}", "{id: 2, name: Name2}" ] </code></pre> <p>b) neo4j 1.9M5 returns an exception:</p> <pre><code>{ "message":"Invalid list type: map", "exception":"IllegalStateException", "stacktrace": [ "org.neo4j.server.rest.repr.RepresentationFormat.serializeList(RepresentationFormat.java:65)", "org.neo4j.server.rest.repr.ListRepresentation.serialize(ListRepresentation.java:50)", "org.neo4j.server.rest.repr.OutputFormat.assemble(OutputFormat.java:179)", "org.neo4j.server.rest.repr.OutputFormat.formatRepresentation(OutputFormat.java:131)", "org.neo4j.server.rest.repr.OutputFormat.response(OutputFormat.java:117)", "org.neo4j.server.rest.repr.OutputFormat.ok(OutputFormat.java:55)", "org.neo4j.server.rest.web.ExtensionService.invokeGraphDatabaseExtension(ExtensionService.java:122)", "java.lang.reflect.Method.invoke(Method.java:597)" ] } </code></pre> <p>If I modify the gremlin script and change x to a map, it works in both neo4j versions:</p> <pre><code>x = [:]; g.v( 1 ).out.transform{ m = [:]; m.putAll( it.map() ); m.put( "id", it.id ); x.put(it.id, m ); }.iterate(); x </code></pre> <p>returns</p> <pre><code>{ "1" : {"id": 1, "name": "Name1"}, "2" : {"id": 2, "name": "Name2"} } </code></pre> <p>the results, however, is now a JSONObject with JSONObjects in it.</p> <p>Is there a way to solve my problem using gremlin? I just started learning gremlin two days ago.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USPerfectPixel
    1. USPerfectPixel
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. COThis really isn't the answer to your problem as I don't know much about how Neo4j does REST serialization, but here's a tweak to make your Gremlin a bit more Gremliny: x=[];g.v(1).out.transform{m=[id:it.id];m.putAll(it.map());m}.fill(x) This way you get rid of the side-effect in the transform of adding to list and the fill iterates your pipeline for you.
      singulars
      1. POextract map from vertex and return an array of maps via REST-API
      1. USstephen mallette
    2. COThank you for the hint! Still getting used to gremlin.
      singulars
      1. POextract map from vertex and return an array of maps via REST-API
      1. USPerfectPixel
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload