Spring Data Neo4j：保存新节点和新关系以及传递持久性

Question

I try to save a new entity who contains another new entity of different type and also a new relationship between them and I failed. Basically I hope to understand Transitive Persistence .

Spring Data Neo4j version : 3.3.2.RELEASE
Neo4j Server : neo4j-community-2.2.3

Here is what I have tested:

SUCCEED : save new entities seperately and then create/save a relationship Entity A, Entity B, Relationship C between A & B

FAILED1 : save new entities seperately, then create several relationship of same type and save Entity A1, A2, Entity B1, B2, Relationship C1, C2. Then A1-C1-B1, A1-C2-B2, A2-C1-B2

Result: I got off course entitie As and Bs but no relationship Cs.

FuncModerate fm1 = new FuncModerate(m, s, "HEAL");
    FuncModerate fm2 = new FuncModerate(m2, s1, "HEAL");
    FuncModerate fm3 = new FuncModerate(m3, s1, "HEAL");

    Set<FuncModerate> fms = new HashSet<FuncModerate>();
    fms.add(fm1);
    fms.add(fm2);
    fms.add(fm3);
    neo4jOps.save(fms); //Exception occurs

Exception Log:

java.lang.NullPointerException
at org.springframework.data.neo4j.support.Neo4jTemplate.getMappingPolicy(Neo4jTemplate.java:549)
at org.springframework.data.neo4j.support.Neo4jTemplate.getMappingPolicy(Neo4jTemplate.java:726)
at org.springframework.data.neo4j.support.Neo4jTemplate.save(Neo4jTemplate.java:354)
at org.ming.controller.Neo4JController.newF(Neo4JController.java:72)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)

FAILED2 : save a new entity A, creat two entities B and set to A, save A again, I got the first entity B saved with the right relationship but then an exception occurs and the second entity B isn't saved.

Entity A:

@NodeEntity
public class Medicine {
    @GraphId Long id;

    @RelatedTo(type = "HEAL")
    private Set<Symptom> symptom;

    ...

 }

Entity B:

@NodeEntity
public class Symptom {
    @GraphId Long nodeId;

    ...

}

Controller:

@RequestMapping(value = "/new", method = RequestMethod.POST)
public void newF() {
    Medicine m = new Medicine("moderate hungry");
    neo4jOps.save(m);
    Symptom s = new Symptom("much confidence");
    Symptom s2 = new Symptom("less angry");
    Set<Symptom> ss = new HashSet<Symptom>();
    ss.add(s);  // got saved
    ss.add(s2); // not got saved
    m.setSymptom(ss);
    neo4jOps.save(m);

    ...

}

Exception Log:

GRAVE: Servlet.service() for servlet [dispatcher] in context with path     [/springlearn] threw exception [Request processing failed; nested     exception is org.neo4j.graphdb.NotFoundException: '__type__' on     http://localhost:7474/db/data/relationship/14] with root cause
org.neo4j.graphdb.NotFoundException: '__type__' on     http://localhost:7474/db/data/relationship/14
    at     org.neo4j.rest.graphdb.entity.RestEntity.getProperty(RestEntity.java:125)
at org.springframework.data.neo4j.support.typerepresentation.AbstractIndexBasedTypeRepresentationStrategy.readAliasFrom(AbstractIndexBasedTypeRepresentationStrategy.java:126)
at org.springframework.data.neo4j.support.mapping.TRSTypeAliasAccessor.readAliasFrom(TRSTypeAliasAccessor.java:36)
at org.springframework.data.neo4j.support.mapping.TRSTypeAliasAccessor.readAliasFrom(TRSTypeAliasAccessor.java:26)
at org.springframework.data.convert.DefaultTypeMapper.readType(DefaultTypeMapper.java:102)
at org.springframework.data.convert.DefaultTypeMapper.getDefaultedTypeToBeUsed(DefaultTypeMapper.java:165)
at org.springframework.data.convert.DefaultTypeMapper.readType(DefaultTypeMapper.java:142)
at org.springframework.data.neo4j.support.mapping.Neo4jEntityConverterImpl.read(Neo4jEntityConverterImpl.java:77)

Answer 1

I solve to problem for Failed 2 Saving Bs to DB should be done before saving A who contains B as a relationship-end node. Then the Annotation RelatedTo from A to B will be created. If B doesnot exist when trying to save A, null exception will be reported.