Dgraph 入门教程四《开发环境的搭建》

news2024/12/24 8:52:35

在深入了解Dgraph 之前，我们先了解下开发环境，毕竟让开发人员真正动起手来才是第一步。

Dgraph 支持很多种语言的开发，包括GO，Python，JS，C#和Java等等。出于项目需要，只了解下JS和Java。

1、NodeJS 开发

首先要说一下，js 有两个库，一个gRPC JS Client，一个HTTP JS Client。这里只以http 为例，http也是我们更熟悉的使用方式。

1.1 、demo 下载

链接：https://pan.baidu.com/s/1GCY-dMkHogsVX6mPv3ioqg
提取码：jzvt
下载该链接的nodejs-http

1.2、运行demo

首先用vscode 打开，安装，直接npm install 实现安装。

npm install

修改Dgraph的地址，这给地址一定要改成自己的服务地址

用node 执行上面的js 代码，在demo里面如下执行

node index-promise.js

看到下面信息，表示执行成功

可以用Ratel UI 去查看，可以看到刚才加入的内容

1.3 、讲解

先看下 package.json, node 安装了一个dgraph-js-http的库，正是因为这个库，我们可以用nodejs开发。这个库是开源的，可以去官方下载。

1.3.1、看下完整的demo代码

const dgraph = require("dgraph-js-http");

// Create a client stub.
function newClientStub() {
    return new dgraph.DgraphClientStub("http://10.10.10.215:8080");
}

// Create a client.
function newClient(clientStub) {
    return new dgraph.DgraphClient(clientStub);
}

// Drop All - discard all data and start from a clean slate.
function dropAll(dgraphClient) {
    return dgraphClient.alter({ dropAll: true });
}

// Set schema.
function setSchema(dgraphClient) {
    const schema = `
        name: string @index(exact) .
        age: int .
        married: bool .
        loc: geo .
        dob: datetime .
    `;
    return dgraphClient.alter({ schema: schema });
}

// Create data using JSON.
function createData(dgraphClient) {
    // Create a new transaction.
    const txn = dgraphClient.newTxn();

    // Create data.
    const p = {
        name: "Alice",
        age: 26,
        married: true,
        loc: {
            type: "Point",
            coordinates: [1.1, 2],
        },
        dob: new Date(1980, 1, 1, 23, 0, 0, 0),
        friend: [
            {
                name: "Bob",
                age: 24,
            },
            {
                name: "Charlie",
                age: 29,
            }
        ],
        school: [
            {
                name: "Crown Public School",
            }
        ]
    };

    let assigned;
    let err;

    // Run mutation.
    return txn.mutate({ setJson: p }).then((res) => {
        assigned = res;

        // Commit transaction.
        return txn.commit();
    }).then(() => {
        // Get uid of the outermost object (person named "Alice").
        // Assigned#getUidsMap() returns a map from blank node names to uids.
        // For a json mutation, blank node names "blank-0", "blank-1", ... are used
        // for all the created nodes.
        console.log(`Created person named "Alice" with uid = ${assigned.data.uids["blank-0"]}\n`);

        console.log("All created nodes (map from blank node names to uids):");
        for (let key in assigned.data.uids) {
            if (Object.hasOwnProperty(assigned.data.uids, key)) {
                console.log(`${key}: ${assigned.data.uids[key]}`);
            }
        }
        console.log();
    }).catch((e) => {
        err = e;
    }).then(() => {
        return txn.discard();
    }).then(() => {
        if (err != null) {
            throw err;
        }
    });
}

// Query for data.
function queryData(dgraphClient) {
    // Run query.
    const query = `query all($a: string) {
        all(func: eq(name, $a)) {
            uid
            name
            age
            married
            loc
            dob
            friend {
                name
                age
            }
            school {
                name
            }
        }
    }`;
    console.log(query);
    const vars = { $a: "Alice" };

    return dgraphClient.newTxn().queryWithVars(query, vars).then((res) => {
        const ppl = res.data;

        // Print results.
        console.log(`Number of people named "Alice": ${ppl.all.length}`);
        for (let i = 0; i < ppl.all.length; i++) {
            console.log(ppl.all[i]);
        }
    });
}

function main() {
    const dgraphClientStub = newClientStub();
    const dgraphClient = newClient(dgraphClientStub);
    return dropAll(dgraphClient).then(() => {
        return setSchema(dgraphClient);
    }).then(() => {
        return createData(dgraphClient);
    }).then(() => {
        return queryData(dgraphClient);
    });
}

main().then(() => {
    console.log("\nDONE!");
}).catch((e) => {
    console.log("ERROR: ", e);
});

还有异步代码 ,请查看demo。

1.3.2 、链接服务端

用如下代码

const dgraph = require("dgraph-js-http");

const clientStub = new dgraph.DgraphClientStub(
    // addr: optional, default: "http://localhost:8080"
    "http://localhost:8080",
    // legacyApi: optional, default: false. Set to true when connecting to Dgraph v1.0.x
    false,
);
const dgraphClient = new dgraph.DgraphClient(clientStub);

1.3.3 、操作Schema

用下面的代码去更新Schema

const schema = "name: string @index(exact) .";
await dgraphClient.alter({ schema: schema });

比如在demo中

// Set schema.
function setSchema(dgraphClient) {
    const schema = `
        name: string @index(exact) .
        age: int .
        married: bool .
        loc: geo .
        dob: datetime .
    `;
    return dgraphClient.alter({ schema: schema });
}

1.3.4、操作数据

用mutate 函数操作数据，可以在demo中找到类似代码

// Create data.
const p = {
    name: "Alice",
};

// Run mutation.
await txn.mutate({ setJson: p });

1.3.5、查询数据

可以用变量去拼查询语句。比如变量 $a。

query all($a: string) {
  all(func: eq(name, $a))
  {
    name
  }
}

其他的方式请查看对应的API

2、Java的开发

2.1、demo的下载

链接：https://pan.baidu.com/s/1GCY-dMkHogsVX6mPv3ioqg
提取码：jzvt
下载该链接的DraphJavaSample

注意我们用的是官方的gPRC框架，这个框架不需要安装Idea软件。如果用Spring boot 和Idea软件，只需要参考App.java的内容即可。

2.2、运行demo

首先要装好java 版本，最好是java 9以上的

用vscode 打开，修改ip和端口号

运行

./gradlew run

出现如下代码表示运行成功

2.3、讲解

2.3.1、链接服务端

下面代码演示了链接方法

ManagedChannel channel1 = ManagedChannelBuilder
    .forAddress("localhost", 9080)
    .usePlaintext().build();
DgraphStub stub1 = DgraphGrpc.newStub(channel1);

2.3.2 、操作Schema

增加一个name的Shema

String schema = "name: string @index(exact) .";
Operation operation = Operation.newBuilder()
        .setSchema(schema)
        .setRunInBackground(true)
        .build();
dgraphClient.alter(operation);

2.3.3、操作数据

演示了用一个Person的对象去操作数据

String schema = "name: string @index(exact) .";
Operation operation = Operation.newBuilder()
        .setSchema(schema)
        .setRunInBackground(true)
        .build();
dgraphClient.alter(operation);

2.3.4、查询数据

// Query
String query =
"query all($a: string){\n" +
"  all(func: eq(name, $a)) {\n" +
"    name\n" +
"  }\n" +
"}\n";

Map<String, String> vars = Collections.singletonMap("$a", "Alice");
Response response = dgraphClient.newReadOnlyTransaction().queryWithVars(query, vars);

// Deserialize
People ppl = gson.fromJson(response.getJson().toStringUtf8(), People.class);

// Print results
System.out.printf("people found: %d\n", ppl.all.size());
ppl.all.forEach(person -> System.out.println(person.name));