使用嵌入在Java中的neo4j进行查询 [英] Query using neo4j embedded in java
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问题描述
我有2个节点:名称和城市.两者之间的关系是(名称)[:LIVES_IN]->(城市). 我正在尝试生成一个查询，以找出居住在X市(X将来自文本框的人)中的那些人.
我正在尝试按照Luanne和Micheal Hunger的建议构造此查询:
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
}
但是此查询不会给出任何结果以及任何异常.
我的查询格式正确吗?谁能告诉我该如何解决?我应该更改neo4j版本，因为我正在按照Luanne和Miheal HUnger的要求进行操作.
谢谢
解决方案
您尚未引用城市值:
start n=node(*) MATCH n-[:LIVES_IN]->city where city.city=dhaka return n.name
应该是
start n=node(*) MATCH n-[:LIVES_IN]->city where city.city='dhaka' return n.name
另外，请使用参数:
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
编辑 既然您已经修改了查询，请从迈克尔的评论中尝试
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" );
在此之前在City上创建索引: 创建索引:城市(城市) ( http://docs.neo4j.org/chunked/stable/query- schema-index.html )
也请阅读以下学习资料:
在线培训课程: http://www.neo4j.org/learn/online_course
手册: http://docs.neo4j.org/chunked/stable/
了解Cypher: http://www.neo4j.org/tracks/cypher_track_start
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
解决方案
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
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