node.js - Gremlin 查询中 Node.js 中的循环 JSON 问题
问题描述
JanusGraph 在 Docker 容器中的 localhost:8182 上运行
我在链接到 Janusgraph Docker 容器的 Docker 容器中运行 gremlin 控制台
我可以对导入的 air-routes.graphml 数据运行成功的遍历
我正在构建一个如下所示的 Node.js/Express 应用程序:
const express = require('express');
const app = express();
const router = express.Router();
const gremlin = require('gremlin');
const traversal = gremlin.process.AnonymousTraversalSource.traversal;
const __ = gremlin.process.statics;
const DriverRemoteConnection = gremlin.driver.DriverRemoteConnection;
const column = gremlin.process.column
const direction = gremlin.process.direction
const p = gremlin.process.P
const textp = gremlin.process.TextP
const pick = gremlin.process.pick
const pop = gremlin.process.pop
const order = gremlin.process.order
const scope = gremlin.process.scope
const t = gremlin.process.t
const g = traversal().withRemote(new DriverRemoteConnection('ws://localhost:8182/gremlin'));
router.get('/home', (req,res) => {
res.send('<h1>Hello World,</h1><p>This is home router</p>');
});
router.get('/query', (req,res) => {
// g.V().has('airport','code','DFW').values().toList()
// .then(DFWdetail => console.log(DFWdetail));
res.send(gremlinQuery());
//res.send("<h1>Airport query</h1><p>g.V().has('airport','code','DFW').values()</p>");
});
router.get('/profile', (req,res) => {
res.send('<h1>Hello World,</h1><p>This is profile router</p>');
});
router.get('/login', (req,res) => {
res.send('<h1>Hello World,</h1><p>This is login router</p>');
});
router.get('/logout', (req,res) => {
res.send('<h1>Hello World,</h1><p>This is logout router</p>');
});
app.use('/', router);
app.listen(process.env.port || 3000);
console.log('Web Server is listening at port '+ (process.env.port || 3000));
function gremlinQuery() {
const info = g.V().has('airport', 'code', 'DFW').values();
console.log(info);
return(info);
}
当我运行这个节点代码时,我得到一个命令行响应:
Web Server is listening at port 3000
GraphTraversal {
graph: Graph {},
traversalStrategies: TraversalStrategies { strategies: [ [RemoteStrategy] ] },
bytecode: Bytecode {
sourceInstructions: [],
stepInstructions: [ [Array], [Array], [Array] ]
},
traversers: null,
sideEffects: null,
_traversalStrategiesPromise: null,
_traversersIteratorIndex: 0
}
TypeError: Converting circular structure to JSON
--> starting at object with constructor 'GraphSON3Reader'
| property '_deserializers' -> object with constructor 'Object'
| property 'g:Traverser' -> object with constructor 'TraverserSerializer'
--- property 'reader' closes the circle
at JSON.stringify (<anonymous>)
at stringify (/home/greg/Development/airlines/node_modules/express/lib/response.js:1123:12)
at ServerResponse.json (/home/greg/Development/airlines/node_modules/express/lib/response.js:260:14)
at ServerResponse.send (/home/greg/Development/airlines/node_modules/express/lib/response.js:158:21)
at /home/greg/Development/airlines/myapp.js:28:9
at Layer.handle [as handle_request] (/home/greg/Development/airlines/node_modules/express/lib/router/layer.js:95:5)
at next (/home/greg/Development/airlines/node_modules/express/lib/router/route.js:137:13)
at Route.dispatch (/home/greg/Development/airlines/node_modules/express/lib/router/route.js:112:3)
at Layer.handle [as handle_request] (/home/greg/Development/airlines/node_modules/express/lib/router/layer.js:95:5)
at /home/greg/Development/airlines/node_modules/express/lib/router/index.js:281:22
我用谷歌搜索了 CircularJSON 并相信它可能与await
但当我尝试它时
function gremlinQuery() {
const info = await g.V().has('airport', 'code', 'DFW').values();
console.log(info);
return(info)
VSCode 声称它是多余的并将其删除
我很困惑。我可以做些什么来构建一个基本的 Node.js/Express 遍历,从航线图数据返回结果?
解决方案
我认为你需要“迭代你的遍历”:
function gremlinQuery() {
const info = await g.V().has('airport', 'code', 'DFW').values().toList();
console.log(info);
return(info)
Basically, a line like g.V().has('airport', 'code', 'DFW').values()
returns a Traversal
object which by itself does nothing because it is a form of Iterator
(or perhaps more explicitly has the behavior of a Java Iterator
). You have to supply some kind of terminating step to get results (in this case I used toList()
).
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