Question

我必须在java中使用查询gremlin，我不知道该怎么办，因为我试图按照说明进行操作 https://github.com/tinkerpop/gremlin/wiki/Using-Gremlin-through-Java但我没有结果，只有例外。有人帮帮我。

以下是我必须使用的查询示例：

 g.V.filter{it.AffiliatedDepartment != null}.copySplit(_().DepartmentDirector, _().inE.filter{it.label == 'Affiliated_Professor'}.outV.AffiliatedProfessor).fairMerge.

我尝试了两种官方文档建议的方式。编译Gremlin Groovy：

    Pipe pipe = Gremlin.compile("_().filter{it.AffiliatedDepartment != null}.copySplit(_().DepartmentDirector, _().inE.filter{it.label == 'Affiliated_Professor'}.outV.AffiliatedProfessor).fairMerge");
    pipe.setStarts(g.getVertices());

我得到一个java.lang.NoSuchFieldError：asMap

使用JSR 223 GremlinGroovyScriptEngine：

    ScriptEngineManager manager = new ScriptEngineManager();
    ScriptEngine engine = manager.getEngineByName("gremlin-groovy");
    List results = new ArrayList();
    Bindings bindings = engine.createBindings();
    bindings.put("g", g);
    bindings.put("v", g.getVertices()); 
    engine.eval("v.filter{it.AffiliatedDepartment != null}.copySplit(_().DepartmentDirector, _().inE.filter{it.label == 'Affiliated_Professor'}.outV.AffiliatedProfessor).fairMerge", bindings);

我收到带有消息的javax.script.ScriptException：

<p>groovy.lang.MissingMethodException:</p>
<p>No signature of method: com.tinkerpop.blueprints.impls.neo4j.Neo4jVertexIterable.filter() is applicable for argument types:
</div>
<div>
    (Script1$_run_closure1) values: [Script1$_run_closure1@5bcf59f5]
    </p>
    <p>Possible solutions: find(), first(), find(groovy.lang.Closure), sleep(long), with(groovy.lang.Closure) at
        com.tinkerpop.gremlin.groovy.jsr223.GremlinGroovyScriptEngine.eval(GremlinGroovyScriptEngine.java:110) at
        javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:233)</p>
</div>

Answer 1

在ScriptEngine方法中，如果更改此行，它是否有效：

engine.eval("v.filter{it.AffiliatedDepartment != null}.copySplit(_().DepartmentDirector, _().inE.filter{it.label == 'Affiliated_Professor'}.outV.AffiliatedProfessor).fairMerge", bindings);

到

engine.eval("g.V.filter{it.AffiliatedDepartment != null}.copySplit(_().DepartmentDirector, _().inE.filter{it.label == 'Affiliated_Professor'}.outV.AffiliatedProfessor).fairMerge", bindings);

或

engine.eval("v._().filter{it.AffiliatedDepartment != null}.copySplit(_().DepartmentDirector, _().inE.filter{it.label == 'Affiliated_Professor'}.outV.AffiliatedProfessor).fairMerge", bindings);

将v绑定设置为g.getVertices()会将其设置为无法识别filter的Neo4jVertexIterable（因为filter将被视为管道的一部分）。因此，我对这两个建议的理论是评估一个正确形成的管道。

Answer 2

使用2.2版，例外是：

java.lang.NoSuchFieldError：ASMAP。

与版本2.3相反，我得到以下异常：

线程“main”中的异常java.lang.NoSuchMethodError：com.tinkerpop.pipes.util.FluentUtility.prepareFunction（Lcom / tinkerpop / pipes / util / structures / AsMap; Lcom / tinkerpop / pipes / PipeFunction;）Lcom / TinkerPop有关/管/ PipeFunction;

但是，查询在控制台

中工作正常

通过java查询gremlin

2 个答案: