在Spring Neo4j starter和OGM SessionFactory中，使用null的uuid不能合并节点的原因是什么？

Question

显然，这是一个常见的例外，但是，这里提出的所有问题似乎都与CSV有关，因此，为什么要问这个问题。

我有一个domain对象，它使用uuid作为惟一id，声明如下

@NodeEntity(label = "TNODE")
public class TestNode {
    @Id @GeneratedValue(strategy = UuidStrategy.class) 
    @Convert(UuidStringConverter.class)
    private UUID uuid;

    private String name; 

    @Relationship(type = "TEST_REL_IS", direction = Relationship.OUTGOING) private TestNodeTarget testTarget;

    public TestNode() {}
    public TestNode(String name, TestNodeTarget target) {
        this.name = name; 
        this.testTarget = target;
    }

    //getters and setters
}

TestNodeTarget如下所示

@NodeEntity(label = "TNODE_TARGET")
public class TestNodeTarget {
    private Long id; 
    private String name;

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

    //getters and setters
}

我用的是Spring Boot 2.0.3.RELEASE和sprng-boot-data-neo4j启动器，它可以拉下neo4j-ogm-core-3.1.0，neo4j-ogm-bolt-driver-3.1.0，neo4j-ogm-api-3.1.0和神秘的neo4j-java-driver-1.5。

我使用Neo4j OGM SessionFactory来构建我自己的通用DAO层，而不是使用Spring来限制

• 所有域的单一存储库(即loadById(classType，id))
• 运行自定义密码查询
• 其他一些我不记得的原因

问题

我能够执行CREATE、READ和DELETE操作。具有以下假设的PUT操作

1. 先前创建的tn:TestNode、t1:TestNodeTarget和t2:TestNodeTarget
2. tn节点与t1节点有关系。
3. 检索tn节点、t1 & t2节点
4. 将tn节点关系从t1更改为t2
5. 调用session.save

例外是

Caused by: org.neo4j.driver.v1.exceptions.ClientException: Cannot merge node using null property value for uuid
    at org.neo4j.driver.internal.util.ErrorUtil.newNeo4jError(ErrorUtil.java:62)
    at org.neo4j.driver.internal.async.inbound.InboundMessageDispatcher.handleFailureMessage(InboundMessageDispatcher.java:137)
    at org.neo4j.driver.internal.messaging.PackStreamMessageFormatV1$Reader.unpackFailureMessage(PackStreamMessageFormatV1.java:432)
    at org.neo4j.driver.internal.messaging.PackStreamMessageFormatV1$Reader.read(PackStreamMessageFormatV1.java:396)
    at org.neo4j.driver.internal.async.inbound.InboundMessageHandler.channelRead0(InboundMessageHandler.java:83)
    at org.neo4j.driver.internal.async.inbound.InboundMessageHandler.channelRead0(InboundMessageHandler.java:35)
    at org.neo4j.driver.internal.shaded.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:310)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:284)
    at org.neo4j.driver.internal.async.inbound.MessageDecoder.channelRead(MessageDecoder.java:40)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:310)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:297)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:413)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
    at org.neo4j.driver.internal.shaded.io.netty.handler.ssl.SslHandler.unwrap(SslHandler.java:1336)
    at org.neo4j.driver.internal.shaded.io.netty.handler.ssl.SslHandler.decodeJdkCompatible(SslHandler.java:1127)
    at org.neo4j.driver.internal.shaded.io.netty.handler.ssl.SslHandler.decode(SslHandler.java:1162)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:489)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:428)
    at org.neo4j.driver.internal.shaded.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:265)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
    at org.neo4j.driver.internal.shaded.io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1359)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
    at org.neo4j.driver.internal.shaded.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
    at org.neo4j.driver.internal.shaded.io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:935)
    at org.neo4j.driver.internal.shaded.io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:134)
    at org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:645)
    at org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:580)
    at org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:497)
    at org.neo4j.driver.internal.shaded.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:459)
    at org.neo4j.driver.internal.shaded.io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
    at org.neo4j.driver.internal.shaded.io.netty.util.concurrent.DefaultThreadFactory$DefaultRunnableDecorator.run(DefaultThreadFactory.java:138)

问题

1. 错误Caused by: org.neo4j.driver.v1.exceptions.ClientException: Cannot merge node using null property value for uuid消息的根本原因是什么？节点uuid值不是null。
2. bolt-driver和neo4j-java-driver是如何相互交流的？我很惊讶地看到neo4j-java-driver。
3. 既然我使用Neo4j OGM来支持Spring的Repository，那么我可以放弃spring-boot-starter-data-neo4j吗？如果是，@Transactional和事务管理会发生什么情况？

Answer 1

TL;DR

使用带有@Id注释的@Id字段不是private Long id字段的替代品(或者是吗？)将id字段添加到类中，异常将消失。

我迫不及待地决定自己调试这个问题，并分享我的发现。

事务

起初，PUT操作毫无例外地工作(没有private Long id字段)，但是没有删除旧的关系，基于这个Github问题，我用@Transactional包装了操作，得到了异常。一些进展。

在ORM上下文中，上面的内容可以很好地工作。换句话说，我可以从@Transactional注释的服务层中对实体进行retrieve，在non-transactional层中进行必要的更改，然后使用使用@Transactional注释的另一个服务层方法对实体进行persist。对于OGM，您必须在同一个事务层进行所有操作。哼！

例外

如上面问题所示，TestNode实体使用UUID，如下所示

@Id @GeneratedValue(strategy = UuidStrategy.class) 
@Convert(UuidStringConverter.class)
private UUID uuid;

我必须更新TestNode类以包括

private Long id; 

在此之后，PUT操作将按预期工作，旧关系将被删除。

混淆

为什么缺少private Long id;只会导致更新过程中的异常？为什么不是当你retrieve，delete，或create实体？