在 Spring Data Neo4j 启动器和 OGM SessionFactory 中无法使用 uuid 的空属性值合并节点的原因是什么？

Question

显然这是一个常见的例外，但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 作为唯一ID，并声明如下

@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

@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
}

我正在使用Spring Boot 2.0.3.RELEASE 和sprng-boot-data-neo4j 启动器，它会拉下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。

我正在使用Neo4j OGM SessionFactory 来构建我自己的通用 DAO 层，而不是限制我使用的 Spring Data Repository

• 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。 PUT 操作具有以下假设

1. 之前创建的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. 致电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 值不为空。
2. bolt-driver 和neo4j-java-driver 如何相互通信？看到neo4j-java-driver，我很惊讶。
3. 既然我使用 Neo4j OGM 来支持 Spring Data 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？

Answer 1

TL;DR

使用带有@Id 注释的UUID 字段不能替代private Long id 字段（或者是吗？）。将id 字段添加到类中，异常消失。

我迫不及待地决定自己调试这个问题并分享我的发现

交易

起初，PUT 操作正常工作（没有private Long id 字段）但未能删除旧关系，基于此Github issue 我将操作包装在@Transactional 中，我得到了异常。一些进展。

在ORM 上下文中，上述内容可以正常工作。换句话说，我可以retrieve 来自@Transactional 注释的服务层的实体，在non-transactional 层中进行必要的更改，然后使用另一种使用@Transactional 注释的服务层方法persist 实体。对于OGM，您必须在同一个事务层中完成所有操作。哼！

异常

如上题所示，TestNode 实体使用UUID 如下

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

我必须更新TestNode 类以包含一个

private Long id; 

在此之后，PUT 操作按预期工作，旧关系被删除。

困惑

为什么缺少private Long id;只会导致更新时出现异常？当你 retrieve、delete 或 create 实体时，为什么不呢？