Query using neo4j embedded in java

Question

I have 2 nodes: name and city. and a relationship between these two is (name) [:LIVES_IN]->(city). I am trying to generate a query to find out who are those people living in city X(where X will be coming from a text box).

I am trying this construct this query following Luanne and Micheal Hunger's suggestion:

import java.io.IOException;
import java.util.ArrayList;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.RelationshipType;
import org.neo4j.graphdb.Transaction;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;
import org.neo4j.helpers.collection.IteratorUtil;
import org.neo4j.cypher.javacompat.ExecutionEngine;
import org.neo4j.cypher.javacompat.ExecutionResult;

public class registrationFrame extends javax.swing.JFrame {

    public static final String DB_PATH = "D://data";
    public static GraphDatabaseService graphDb = null;
    Node person;
    Node password;
    Node city;
    String nodeResulta;

    public registrationFrame() {
        initComponents();
    }
    private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {//node and relationship creation code                                         

        try (Transaction tx = graphDb.beginTx();) {
            person = graphDb.createNode();
            person.setProperty("name", jTextField1.getText());
            person.setProperty("password", jPasswordField1.getPassword());
            graphDb.index().forNodes("name").add(person, "name", jTextField1.getText());


            city = graphDb.createNode();
            city.setProperty("city_name", jTextField2.getText());
            graphDb.index().forNodes("city_name").add(city, "city_name", jTextField2.getText());

            person.createRelationshipTo(city, RelTypes.LIVES_IN);

            tx.success();
        }

    }                                        
private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {//query code                                         
        ExecutionEngine engine = new ExecutionEngine(graphDb);
    ExecutionResult result;
    String temp=jTextField2.getText();
    Map<String,Object> params=new HashMap<>();
    //result = engine.execute("START n=node(*) MATCH (x:city)<-[:LIVES_IN]-(y:person) where x.name='"+jTextField2.getText()+"' RETURN y.name;");
    //List<String> columns = result.columns();
    //Iterator<Node> n_column = result.columnAs( "person" );
    try (Transaction ignored = graphDb.beginTx()) {
        //result = engine.execute("START n=node(*) MATCH (x:city)<-[:LIVES_IN]-(y:person) where x.name='"+temp+"' RETURN y");
        // END SNIPPET: execute
        // START SNIPPET: items
        //result = engine.execute("START n=node(*) MATCH (x:city) RETURN x");//this query also returns nothing

        params.put("c_name",temp);
        result=engine.execute("MATCH (city_name:city {city_name:{c_name}})<-[:LIVES_IN]-(person) RETURN person",params);
        System.out.println(result);
        Iterator<Node> n_column = result.columnAs("person");

        for (Node node : IteratorUtil.asIterable(n_column)) {
            // note: we're grabbing the name property from the node,
            // not from the n.name in this case.
            nodeResulta = node + ": " + node.getProperty("name")  + '\n';
            //nodeResult1.add(node.getProperty( "name" ).toString());
        }
        // END SNIPPET: items
    }

        jTextArea1.setText(nodeResulta);// output will show here

    }                       

public static void main(String args[]) {

       java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new registrationFrame().setVisible(true);
                graphDb = new GraphDatabaseFactory().newEmbeddedDatabase(DB_PATH);
                registerShutdownHook(graphDb);
                //System.out.println("Created Social Graph!!");
            }
        });
    }
private static void registerShutdownHook(final GraphDatabaseService graphDb) {
        Runtime.getRuntime().addShutdownHook(new Thread() {
            @Override
            public void run() {
                graphDb.shutdown();
            }
        });
    }

    public static enum RelTypes implements RelationshipType {

        LIVES_IN,
        FRIEND,
        CUISINE,
        LIKES,
        IN
    }

But this query does not give any result as well as any exception.

Is my query formation right? Can any one tell me how can I resolve this? Shall I change my neo4j version because I am following everything as Luanne and Miheal HUnger has asked.

Thank You

Please check carefully- you are returning name but doing a result.columnsAs("n"). Also make sure you execute this query in the browser/shell and verify if it returns anything please. — Luanne
– Luanne, Commented Mar 13, 2014 at 10:33
@Luanne: You are trying most for me. But all turns in vain. I am trying to scratch from the basic. So I have moved to run the query in browser, but it fails to work. I posted a new question in stack overflow on this — sabu
– sabu, Commented Mar 13, 2014 at 14:59
In your code above, only change this line Iterator<Node> n_column = result.columnAs( "n" ); to Iterator<Node> n_column = result.columnAs( "name" ); — Luanne
– Luanne, Commented Mar 13, 2014 at 15:59
@Luanne: I posted the same question again by giving all the details of my code. The result appears same: No result is displayed — sabu
– sabu, Commented Mar 13, 2014 at 18:56
@Luanne: I posted the code what have I written in netbeans as it is. What will you suggest? shall i change my neo4j version. — sabu
– sabu, Commented Mar 14, 2014 at 7:42

Luanne · Accepted Answer · 2014-03-13 10:14:10Z

2

You have not quoted the city value:

start n=node(*) MATCH n-[:LIVES_IN]->city where city.city=dhaka return n.name

should be

start n=node(*) MATCH n-[:LIVES_IN]->city where city.city='dhaka' return n.name

Also, please use parameters:

start n=node(*) MATCH n-[:LIVES_IN]->city where city.city={city} return n.name

http://docs.neo4j.org/chunked/stable/tutorials-cypher-parameters-java.html

EDIT Since you've modified your query, from Michael's comment, try

   Map<String,Object> params=new HashMap<String,Object>();
   params.put("city_name","dhaka");
   result=engine.execute("MATCH (city:City {city:{city_name})<-[:LIVES_IN]-(person) RETURN person",params);

   Iterator<Node> n_column = result.columnAs( "person" );

Create an index on City before that: CREATE INDEX ON :City(city) (http://docs.neo4j.org/chunked/stable/query-schema-index.html)

Please also go through the following learning material:

The online training course: http://www.neo4j.org/learn/online_course

The manual: http://docs.neo4j.org/chunked/stable/

Learn Cypher: http://www.neo4j.org/tracks/cypher_track_start

edited Mar 13, 2014 at 10:14

answered Mar 13, 2014 at 8:35

Luanne

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6 Comments

sabu Over a year ago

Thank you for you kind reply. I change my code as such: result=engine.execute("start n=node(*) MATCH n-[:LIVES_IN]->city where city.city='"+jTextField2.getText()+"' return n.name"); But the following exception arises then: Exception in thread "AWT-EventQueue-0" org.neo4j.cypher.EntityNotFoundException: No column named 'n' was found. Found: ("n.name") ............I just updated my question above accroding to your answer.........

Luanne Over a year ago

Because there is no column n. You're returning n.name

Michael Hunger Over a year ago

Actually as you are using Neo4j 2.0 stay away from using start n=node(*) just create an index for :City(city) and do MATCH (city:City {city:{city_name})<-[:LIVES_IN]-(person) return person.name

sabu Over a year ago

@Luanne: I am a new in neo4j, So I am trying in various ways. I updated my query above by returning only n But it still shows error :NODE[1] has no property with propertyKey="name".

sabu Over a year ago

@Luanne: I am trying to follow your suggestion. But still error arise. I updated my code above.

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