spring-data-neo4j: 无法创建两个具有相同标签的关系属性

Question

使用 spring-data-neo4j，我无法在具有相同标签的相同 class 中设置两个关系属性。

以下代码可以在我的分支https://github.com/spencerhrob/gs-accessing-data-neo4j/tree/same-name-relationships.

中找到

Person.java:

@NodeEntity
public class Person {

    @GraphId Long id;
    public String name;

    public Person() {}
    public Person(String name) { this.name = name; }

    @RelatedTo(type="MEMBER_OF", direction=Direction.OUTGOING)
    Dojo dojo;

    @RelatedTo(type="MEMBER_OF", direction=Direction.OUTGOING)
    MailingList mailingList;

    public void setDojo(Dojo dojo) {
        this.dojo = dojo;
    }
    public void setMailingList(MailingList mailingList) {
        this.mailingList = mailingList;
    }

    @Override
    public String toString() {
        return "Person [name=" + name + "]";
    }
}

Dojo.java:

@NodeEntity
public class Dojo {

    @GraphId Long id;
    public String name;

    public Dojo() { }
    public Dojo(String name) { this.name = name; }

    @Override
    public String toString() {
        return "Dojo [name=" + name + "]";
    }
}

MailingList.java:

@NodeEntity
public class MailingList {

    @GraphId Long id;
    public String name;

    public MailingList() { }
    public MailingList(String name) { this.name = name; }

    @Override
    public String toString() {
        return "MailingList [name=" + name + "]";
    }

}

Application.java:

@Configuration
@EnableNeo4jRepositories(basePackages = "hello")
public class Application extends Neo4jConfiguration implements CommandLineRunner {

    public Application() {
        setBasePackage("hello");
    }

    @Bean
    GraphDatabaseService graphDatabaseService() {
        return new GraphDatabaseFactory().newEmbeddedDatabase("accessingdataneo4j.db");
    }

    @Autowired
    PersonRepository personRepository;

    @Autowired
    GraphDatabase graphDatabase;

    public void run(String... args) throws Exception {
        Transaction tx = graphDatabase.beginTx();
        try {
            Person linus = new Person("Linus");
            linus.setDojo(new Dojo("Coding Dojo"));
            linus.setMailingList(new MailingList("Kernel Mailing List"));

            personRepository.save(linus);

            tx.success();
        } finally {
            tx.close();
        }
    }

    public static void main(String[] args) throws Exception {
        FileUtils.deleteRecursively(new File("accessingdataneo4j.db"));

        SpringApplication.run(Application.class, args);
    }
}

当我运行这段代码时，我得到以下异常：

java.lang.IllegalStateException: Failed to execute CommandLineRunner at org.springframework.boot.SpringApplication.runCommandLineRunners(SpringApplication.java:680) at org.springframework.boot.SpringApplication.afterRefresh(SpringApplication.java:695) at org.springframework.boot.SpringApplication.run(SpringApplication.java:321) at org.springframework.boot.SpringApplication.run(SpringApplication.java:952) at org.springframework.boot.SpringApplication.run(SpringApplication.java:941) at hello.Application.main(Application.java:56) Caused by: org.springframework.data.mapping.model.MappingException: Setting property mailingList to Dojo [name=null] on Person [name=Linus] at org.springframework.data.neo4j.support.mapping.SourceStateTransmitter.setProperty(SourceStateTransmitter.java:85) at org.springframework.data.neo4j.support.mapping.SourceStateTransmitter.copyEntityStatePropertyValue(SourceStateTransmitter.java:91) at org.springframework.data.neo4j.support.mapping.SourceStateTransmitter.access[=16=]0(SourceStateTransmitter.java:40) at org.springframework.data.neo4j.support.mapping.SourceStateTransmitter.doWithAssociation(SourceStateTransmitter.java:61) at org.springframework.data.mapping.model.BasicPersistentEntity.doWithAssociations(BasicPersistentEntity.java:324) at org.springframework.data.neo4j.support.mapping.SourceStateTransmitter.copyPropertiesFrom(SourceStateTransmitter.java:57) at org.springframework.data.neo4j.support.mapping.Neo4jEntityConverterImpl.loadEntity(Neo4jEntityConverterImpl.java:112) at org.springframework.data.neo4j.support.mapping.Neo4jEntityConverterImpl.read(Neo4jEntityConverterImpl.java:104) at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister$CachedConverter.read(Neo4jEntityPersister.java:170) at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister.createEntityFromState(Neo4jEntityPersister.java:189) at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister.persist(Neo4jEntityPersister.java:244) at org.springframework.data.neo4j.support.mapping.Neo4jEntityPersister.persist(Neo4jEntityPersister.java:231) at org.springframework.data.neo4j.support.Neo4jTemplate.save(Neo4jTemplate.java:356) at org.springframework.data.neo4j.support.Neo4jTemplate.save(Neo4jTemplate.java:350) at org.springframework.data.neo4j.repository.AbstractGraphRepository.save(AbstractGraphRepository.java:91) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.executeMethodOn(RepositoryFactorySupport.java:405) at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.doInvoke(RepositoryFactorySupport.java:390) at org.springframework.data.repository.core.support.RepositoryFactorySupport$QueryExecutorMethodInterceptor.invoke(RepositoryFactorySupport.java:344) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) at org.springframework.transaction.interceptor.TransactionInterceptor.proceedWithInvocation(TransactionInterceptor.java:98) at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:262) at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136) at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207) at com.sun.proxy.$Proxy43.save(Unknown Source) at hello.Application.run(Application.java:44) at org.springframework.boot.SpringApplication.runCommandLineRunners(SpringApplication.java:677) ... 5 common frames omitted Caused by: org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type hello.Dojo to type hello.MailingList at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:291) at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:177) at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:158) at org.springframework.data.mapping.model.BeanWrapper.getPotentiallyConvertedValue(BeanWrapper.java:155) at org.springframework.data.mapping.model.BeanWrapper.setProperty(BeanWrapper.java:75) at org.springframework.data.neo4j.support.mapping.SourceStateTransmitter.setProperty(SourceStateTransmitter.java:83) ... 37 common frames omitted

那里有很多，但真正的错误是 Spring 试图将 Dojo 转换为 MailingList。

同时，如果我用不同的名称命名关系（如在我的分支 https://github.com/spencerhrob/gs-accessing-data-neo4j/tree/different-name-relationships 中），则此代码有效。 Person.java:

@NodeEntity
public class Person {

    @GraphId Long id;
    public String name;

    public Person() {}
    public Person(String name) { this.name = name; }

    @RelatedTo(type="MEMBER_OF_DOJO", direction=Direction.OUTGOING)
    Dojo dojo;

    @RelatedTo(type="MEMBER_OF_LIST", direction=Direction.OUTGOING)
    MailingList mailingList;

    public void setDojo(Dojo dojo) {
        this.dojo = dojo;
    }
    public void setMailingList(MailingList mailingList) {
        this.mailingList = mailingList;
    }

    @Override
    public String toString() {
        return "Person [name=" + name + "]";
    }
}

不对 Application.java（或 Dojo.java 或 MailingList.java）进行任何更改，此代码成功执行。

我对这个例子的理解是 spring-data-neo4j 不允许 class 有两个具有相同标签的属性。在某些情况下，不同的关系需要具有相同的标签——例如，为了符合建模标准。是否可以在spring-data-neo4j中设置多个同名关系？如果是，怎么做？

Answer 1

我找到了这个问题的答案。我一直在寻找 "enforceTargetType" 属性 described in the documentation。

我创建了一个使用此修复程序的存储库分支。它位于 https://github.com/spencerhrob/gs-accessing-data-neo4j/tree/same-name-enforce-target.

Person.java:

@NodeEntity
public class Person {

    @GraphId Long id;
    public String name;

    public Person() {}
    public Person(String name) { this.name = name; }

    @RelatedTo(type="MEMBER_OF", direction=Direction.OUTGOING, enforceTargetType=true)
    Dojo dojo;

    @RelatedTo(type="MEMBER_OF", direction=Direction.OUTGOING, enforceTargetType=true)
    MailingList mailingList;

    public void setDojo(Dojo dojo) {
        this.dojo = dojo;
    }
    public void setMailingList(MailingList mailingList) {
        this.mailingList = mailingList;
    }

    @Override
    public String toString() {
        return "Person [name=" + name + "]";
    }
}

在没有对存储库进行其他更改的情况下，此代码运行时没有任何错误，并且检查创建的 Neo4j 数据库表明它的行为符合预期。

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