Using neo4j without magic

[szarnyasg]

Thanks for the quick answer! It worked with dependency injection (I based the code on the cineast project).

Thanks to yesterdays release (http://www.springsource.org/node/3547), the instantiation of the Neo4jTemplate class now works correctly. However, I'm unable to start a transaction---both the GraphDatabaseService and the Neo4jTemplate class' beginTx() throw a NullPointerException.
I noticed the postConstruct() method is missing, so I assume Neo4jTemplate's constructor takes care of that automatically.

        GraphDatabaseService gds = new EmbeddedGraphDatabase("testdb");
        try {
            GraphDatabase gd = new DelegatingGraphDatabase(gds);
            template = new Neo4jTemplate(gd);
            
            Transaction tx = gds.beginTx();
            // or
            Transaction tx = template.beginTx();
            try {
                template.save(new Movie("1", "Test Movie")); 
                tx.success();
            } finally {
                tx.finish();
            }
        } finally {
            gds.shutdown();
        }

gds.beginTx() throws:

Exception in thread "main" java.lang.NullPointerException
	at org.springframework.data.neo4j.support.Neo4jTemplate.beginTx(Neo4jTemplate.java:277)
	at org.springframework.data.neo4j.support.mapping.SourceStateTransmitter.copyPropertiesTo(SourceStateTransmitter.java:112)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityConverterImpl.write(Neo4jEntityConverterImpl.java:150)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister$CachedConverter.write(Neo4jEntityPersister.java:177)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister.persist(Neo4jEntityPersister.java:239)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister.persist(Neo4jEntityPersister.java:228)
	at org.springframework.data.neo4j.support.Neo4jTemplate.save(Neo4jTemplate.java:291)
	at neo4jSpringDataTestPackage.Main.main(Main.java:30)

template.beginTx() throws:

Exception in thread "main" java.lang.NullPointerException
	at org.springframework.data.neo4j.support.Neo4jTemplate.beginTx(Neo4jTemplate.java:277)
	at neo4jSpringDataTestPackage.Main.main(Main.java:28)

I resolved the dependencies with Maven, version set to 2.1.0.BUILD-SNAPSHOT.

[MichaelHunger]

Thanks for pointing it out, it will be fixed in the final 2.1.0.RELEASE

see: https://jira.springsource.org/browse/DATAGRAPH-233

Michael

[MichaelHunger]

It's fixed please check.

Michael

[szarnyasg]

Can you please give me a hint about which plugin:goal to use to build the https://github.com/SpringSource/spring-data-neo4j project with mvn? Thanks!

[MichaelHunger]

You mean except mvn clean install with Maven3 ?

[szarnyasg]

Thanks! The build ran successfully with "mvn clean install". I created the following code in the spring-data-neo4j-hello-worlds project:

try {
    GraphDatabaseService graphDatabaseService =  new EmbeddedGraphDatabase("testdb");
    GraphDatabase graphDatabase = new DelegatingGraphDatabase(graphDatabaseService);
    PlatformTransactionManager transactionManager = new JtaTransactionManager(new SpringTransactionManager(graphDatabaseService));
    Neo4jTemplate template = new Neo4jTemplate(graphDatabase, transactionManager);
    Transaction tx = template.beginTx();
    
    // (1)
    Node n = template.createNode();
    n.setProperty("prop", "some value");
    // (2)
    template.save(new Movie("1", "Test Movie"));
    
    tx.success();
    tx.finish();
} catch (Exception e) {
    e.printStackTrace();
}

(1) on its own runs fine, I can query the node from Neoclipse (using Cypher), but (2) throws a NullPointerException:

java.lang.IllegalArgumentException: java.lang.NullPointerException
	at org.springframework.data.neo4j.support.mapping.AbstractConstructorEntityInstantiator.createEntityFromState(AbstractConstructorEntityInstantiator.java:63)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister$CachedInstantiator.createEntityFromState(Neo4jEntityPersister.java:134)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister$CachedInstantiator.createEntityFromState(Neo4jEntityPersister.java:121)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityConverterImpl.read(Neo4jEntityConverterImpl.java:85)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister$CachedConverter.read(Neo4jEntityPersister.java:169)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister.createEntityFromState(Neo4jEntityPersister.java:187)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister.persist(Neo4jEntityPersister.java:240)
	at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister.persist(Neo4jEntityPersister.java:228)
	at org.springframework.data.neo4j.support.Neo4jTemplate.save(Neo4jTemplate.java:296)
	at org.springframework.data.neo4j.examples.hellograph.TestClass.testTemplate(TestClass.java:28)
	at org.springframework.data.neo4j.examples.hellograph.App.main(App.java:24)
Caused by: java.lang.NullPointerException
	at org.springframework.data.neo4j.support.node.NodeEntityInstantiator.setPersistentState(NodeEntityInstantiator.java:46)
	at org.springframework.data.neo4j.support.node.NodeEntityInstantiator.setState(NodeEntityInstantiator.java:42)
	at org.springframework.data.neo4j.support.node.NodeEntityInstantiator.setState(NodeEntityInstantiator.java:31)
	at org.springframework.data.neo4j.support.mapping.AbstractConstructorEntityInstantiator$2.create(AbstractConstructorEntityInstantiator.java:110)
	at org.springframework.data.neo4j.support.mapping.AbstractConstructorEntityInstantiator.createEntityFromState(AbstractConstructorEntityInstantiator.java:56)
	... 10 more

Any ideas why? Thanks in advance.

[MichaelHunger]

Thanks for pointing it out, I'll try to look at it but I'm on vacation till Thursday, so no promises

[MichaelHunger]

fixed in SNAPSHOT

[szarnyasg]

Thanks! The following is working fine:

try {
    GraphDatabaseAPI graphDatabaseService =  new EmbeddedGraphDatabase("testdb");
    GraphDatabase graphDatabase = new DelegatingGraphDatabase(graphDatabaseService);
    PlatformTransactionManager transactionManager = new JtaTransactionManager(new SpringTransactionManager(graphDatabaseService));
    Neo4jTemplate template = new Neo4jTemplate(graphDatabase, transactionManager);
    Transaction tx = template.beginTx();
    
    template.save(new Movie("Node 1", "Test 1"));
    template.save(new Movie("Node 2", "Test 2"));
    
    tx.success();
    tx.finish();

    graphDatabaseAPI.shutdown();
} catch (Exception e) {
    e.printStackTrace();
}

1) Are there any alternatives to the deprecated beginTx()?

Neoclipse doesn't visualize the graph, but a simple Cypher query lists the nodes:

[{"n":{"relation":[],"id":0,"propertyMap":{}}},{"n":{"relation":[],"id":1,"propertyMap":{"moons":0,"b":"Test 1","__type__":"Movie","a":"Node 1"}}},{"n":{"relation":[],"id":2,"propertyMap":{"moons":0,"b":"Test 2","__type__":"Movie","a":"Node 2"}}}]

2) I guess it has to do something with the #0 root node. How can I visualize at least one of the Movie nodes?

[szarnyasg]

I think I found the answer for my questions.

1) Use the GraphDatabaseAPI's beginTx() method:

try {
    GraphDatabaseAPI graphDatabaseAPI =  new EmbeddedGraphDatabase("testdb");
    GraphDatabase graphDatabase = new DelegatingGraphDatabase(graphDatabaseAPI);
    PlatformTransactionManager transactionManager = new JtaTransactionManager(new SpringTransactionManager(graphDatabaseAPI));
    Neo4jTemplate template = new Neo4jTemplate(graphDatabase, transactionManager);
    Transaction tx = graphDatabaseAPI.beginTx();
    
    template.save(new Movie("Node 1", "Test 1"));
    template.save(new Movie("Node 2", "Test 2"));
    
    tx.success();
    tx.finish();
    
    graphDatabaseAPI.shutdown();
} catch (Exception e) {
    e.printStackTrace();
}

2) The graph must contain a connected subgraph in order to be visualized.