如何从 Java 获取 JanusGraphManagement

我无法理解如何从使用ConfiguredGraphFactory 创建的图表中获取JanusGraphManagement 实例。

我尝试做这样的事情：

        JanusGraphFactory.Builder config = JanusGraphFactory.build();
        config.set("storage.hostname", storageHostname);
        config.set("storage.port", storagePort);
        config.set("storage.backend", STORAGE_BACKEND);
        config.set("index.search.backend", SEARCH_BACKEND);
        config.set("index.search.hostname", indexHostname);
        config.set("index.search.port", indexPort);
        config.set("graph.graphname", graphName);

        JanusGraph graph = config.open();
        JanusGraphManagement mgmt = graph.openManagement();

但它会产生以下异常：

java.lang.NullPointerException：必须将 Gremlin 服务器配置为使用 JanusGraphManager。

gremlin-server 使用以下配置运行：

host: 0.0.0.0
port: 8182
scriptEvaluationTimeout: 180000
# channelizer: org.apache.tinkerpop.gremlin.server.channel.WebSocketChannelizer
channelizer: org.janusgraph.channelizers.JanusGraphWebSocketChannelizer
graphManager: org.janusgraph.graphdb.management.JanusGraphManager
graphs: {
  #graph: conf/gremlin-server/janusgraph-cql-es-server.properties,
  ConfigurationManagementGraph: conf/gremlin-server/janusgraph-cql-es-server-configured.properties
}
.....

JanusGraph 的一个是这样的：

gremlin.graph=org.janusgraph.core.ConfiguredGraphFactory
graph.graphname=ConfigurationManagementGraph
storage.backend=cql
storage.hostname=127.0.0.1
storage.cql.keyspace=janusgraph
cache.db-cache = true
cache.db-cache-time = 180000
cache.db-cache-size = 0.25
index.search.backend=elasticsearch
index.search.hostname=127.0.0.1
index.search.elasticsearch.client-only=true

我想做的是直接从Java代码定义图形模式，这就是为什么我需要管理实例并且遍历源是不够的

他们似乎真的不希望您从 Java 中执行此操作。检查我的对我构建的示例存储库的初始提交 https://github.com/baughmann/janusgraph-configuredgraphfactory-java-demo/blob/7c4f89882d8c50280a3e78556384dee88e0bdd22/janusgraph-configuredgraphfactory-demo/src/main/kotlin/Main.kt#L29.

一般来说，有很多内部魔法正在发生。您需要创建一个新的嵌入实例ConfigurationManagementGraph以及其他一些事情。获取步骤ConfiguredGraphFactory启动并运行的是：

JanusGraphManager(Settings())
// the configuration file you used for your ConfigurationManagementGraph in your `janusgrpah-server.yaml` file
val mgrConfFile = File("conf/janusgraph-cql-configurationgraph.properties")
// load the configuration
val base = CommonsConfiguration(ConfigurationUtil.loadPropertiesConfig(mgrConfFile))
// modify a fe wthings specific to the ConfigurationManagementGraph
base.set("graph.graphname", "name-of-this-graph-instance")
base.set("graph.unique-instance-id", "some-super-unique-id")
base.set("storage.lock.local-mediator-group", "tmp")
// duplicate the config for some reason?
val local = ModifiableConfiguration(GraphDatabaseConfiguration.ROOT_NS, base, BasicConfiguration.Restriction.NONE)
// build another type of configuration?
val config = GraphDatabaseConfiguration(base, local, instanceId, local)
// create the new ConfigurationManagementGraph instance
return ConfigurationManagementGraph(StandardJanusGraph(config))

不要忘记您仍然需要创建一个先模板配置 https://docs.janusgraph.org/operations/configured-graph-factory/#template-configuration.

现在，您可以使用单例ConfiguredGraphFactory就像文档所说的那样，在应用程序的任何位置。

val myGraph = ConfiguredGraphFactory.open("myGraph")

请记住，您可能不需要这样做。这Client.submit()函数对于大多数事情都很方便。例如：

// connect to the gremlin server
val cluster = Cluster.build("localhost").create()
val client = cluster.connect<Client.ClusteredClient>()
// example: get a list of existing graph names
val existingGraphs = client.submit("ConfiguredGraphFactory.getGraphNames()").all().get()
// check if a graph exists
val exists = existingGraphs.any { it.string == "myGraph" }
// create a new graph with the existing template
// (note: this *cannot* be cast to a JanusGraph, even though that would make this really useful)
val myGraph: TinkerGraph = client.submit("ConfiguredGraphFactory.getGraphNames()").all().get().first().get(TinkerGraph::class.java)

EDIT:

正如 @FlorianHockmann 在 JanusGraph 不和谐服务器上指出的那样，最好not直接从 Java 中使用这些对象。相反，最好使用Client.SessionedClient当你连接时，就像这样

val cluster = Cluster.build("localhost").create()
val session = cluster.connect<Client.SessionedClient>()

由于您已经建立了会话，因此您现在可以在服务器上保存和重复使用变量。正如弗洛里安所说，

client.submit("mgmt = ConfiguredGraphFactory.open('myGraph').openManagement()").all().get()
// afterwards you can use it:
client.submit("// do stuff with mgmt").all().get()

只是别忘了打电话session.close()当你完成时！

看看我做的这个要点作为例子