java - Opening existing embedded neo4j database -
i trying use scala on embedded jave neo4j api. having trouble opening database reading on subsequent occasions. code below should create 2 nodes , edge every time runs, return of them @ begining of each run. so, 0 nodes first time, 2 nodes second time, 4 third time etc.
import org.neo4j.tooling.globalgraphoperations import org.neo4j.graphdb.factory.graphdatabasefactory import org.neo4j.graphdb.relationshiptype object tester extends app{ val db_path = "data/neo4j" object knows extends relationshiptype { override def name(): string = "knows" } val graphdb = new graphdatabasefactory().newembeddeddatabase(db_path) //seems reset whole directory println(graphdb) try { println("begin") val tx = graphdb.begintx() // database operations go here println(globalgraphoperations.at(graphdb).getallnodes.iterator) val nodes = globalgraphoperations.at(graphdb).getallnodes.iterator while (nodes.hasnext()) { println(nodes.next()) } nodes.close() val relt = globalgraphoperations.at(graphdb).getallrelationships.iterator while (relt.hasnext()) { println(relt.next()) } println("success - begin") tx.success() } try { val tx = graphdb.begintx() // database operations go here val firstnode = graphdb.createnode val secondnode = graphdb.createnode val relationship = firstnode.createrelationshipto(secondnode, knows) println(firstnode) println(secondnode) println(relationship) println(relationship.gettype.name) tx.success() println("success") } println("end") try { val tx = graphdb.begintx() // database operations go here println(globalgraphoperations.at(graphdb).getallnodes.iterator) val nodes = globalgraphoperations.at(graphdb).getallnodes.iterator while (nodes.hasnext()) { println(nodes.next()) } nodes.close() val relt = globalgraphoperations.at(graphdb).getallrelationships.iterator while (relt.hasnext()) { println(relt.next()) } println("success - end") tx.success() } graphdb.shutdown() } however, every time seems give empty database , 2 new nodes. what's going on here?
embeddedgraphdatabase [data/neo4j] begin org.neo4j.tooling.globalgraphoperations$1$1@74c49a90 success - begin node[2] node[3] relationship[1] knows success end org.neo4j.tooling.globalgraphoperations$1$1@2ec0df08 node[2] node[3] relationship[1] success - end process finished exit code 0
this happening because not closing transaction. can calling tx.close(). think instantiating tx inside try not how should be. here working version of program:
import org.neo4j.tooling.globalgraphoperations import org.neo4j.graphdb.factory.graphdatabasefactory import org.neo4j.graphdb.relationshiptype object tester extends app{ val db_path = "data/neo4j" object knows extends relationshiptype { override def name(): string = "knows" } val graphdb = new graphdatabasefactory().newembeddeddatabase(db_path) println(graphdb) val tx1 = graphdb.begintx() // database operations go here try { println("will list nodes") println("1 - begin") println("globalgraphoperations.at(graphdb).getallnodes.iterator") val nodes = globalgraphoperations.at(graphdb).getallnodes.iterator while (nodes.hasnext()) { println(nodes.next()) } nodes.close() val relt = globalgraphoperations.at(graphdb).getallrelationships.iterator while (relt.hasnext()) { println(relt.next()) } println("1 - success - begin") tx1.success() } { tx1.close() } val tx2 = graphdb.begintx() // database operations go here try { val firstnode = graphdb.createnode val secondnode = graphdb.createnode val relationship = firstnode.createrelationshipto(secondnode, knows) println(firstnode) println(secondnode) println(relationship) println(relationship.gettype.name) tx2.success() println("2 - success") } { tx2.close() } println("2 - end") val tx3 = graphdb.begintx() // database operations go here try { println(globalgraphoperations.at(graphdb).getallnodes.iterator) val nodes = globalgraphoperations.at(graphdb).getallnodes.iterator while (nodes.hasnext()) { println(nodes.next()) } nodes.close() val relt = globalgraphoperations.at(graphdb).getallrelationships.iterator while (relt.hasnext()) { println(relt.next()) } println("3 - success - end") tx3.success() } { tx3.close() } graphdb.shutdown() } extra
i tried bring program closer "scala-style". also, tried remove boilerplate , repeated code. accomplish i:
- used
javaconvertershandle java collections , iterables handle them in scala - created method
withtransactionautomatic resource management our transaction in scala.
this result:
import org.neo4j.tooling.globalgraphoperations import org.neo4j.graphdb.factory.graphdatabasefactory import org.neo4j.graphdb.relationshiptype import org.neo4j.graphdb.transaction import scala.collection.javaconverters._ object tester extends app{ val db_path = "data/neo4j" object knows extends relationshiptype { override def name(): string = "knows" } def withtransaction (dowithtransaction: transaction => unit) { val temptx = graphdb.begintx() try { dowithtransaction(temptx) } { temptx.close() } } val graphdb = new graphdatabasefactory().newembeddeddatabase(db_path) println(graphdb) withtransaction { tx => println("1 - begin") val nodes = globalgraphoperations.at(graphdb).getallnodes (node <- nodes.asscala) println(node) val relts = globalgraphoperations.at(graphdb).getallrelationships (irelt <- relts.asscala) println(irelt) println("1 - success - begin") tx.success() } withtransaction { tx => val firstnode = graphdb.createnode val secondnode = graphdb.createnode val relationship = firstnode.createrelationshipto(secondnode, knows) println(firstnode) println(secondnode) println(relationship) println(relationship.gettype.name) tx.success() println("2 - success") } println("2 - end") withtransaction { tx => println(globalgraphoperations.at(graphdb).getallnodes.iterator) val nodes = globalgraphoperations.at(graphdb).getallnodes (node <- nodes.asscala) println(node) val relts = globalgraphoperations.at(graphdb).getallrelationships (irelt <- relts.asscala) println(irelt) println("3 - success - end") tx.success() } graphdb.shutdown() }
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