Flutter书架管理插件shelf_plus的使用

概述

Shelf Plus 是一个用于服务器端开发的质量提升插件，基于 Shelf 平台。它提供了快速启动应用程序的能力，并且与 Shelf 生态系统完全兼容。Shelf Plus 包含了零配置初始化、内置热重载以及强大的路由增强功能。

快速开始

简单示例

import 'package:shelf_plus/shelf_plus.dart';

void main() => shelfRun(init);

Handler init() {
  var app = Router().plus;

  app.get('/', () => 'Hello World!');

  return app.call;
}

路由增强 (Router Plus)

基本用法

var app = Router().plus;

app.use(middleware());

app.get('/text', () => 'I am a text');

app.get('/html/<name>', (Request request, String name) => '<h1>Hello $name</h1>',
    use: typeByExtension('html'));

app.get('/file', () => File('path/to/file.zip'));

app.get('/person', () => Person(name: 'John', age: 42));

处理返回值 (ResponseHandler)

Shelf Plus 提供了一个强大的 ResponseHandler 机制，可以处理多种类型的返回值：

示例代码

import 'dart:io';
import 'package:shelf_plus/shelf_plus.dart';

void main() => shelfRun(init);

Handler init() {
  var app = Router().plus;

  app.get('/text', () => 'a text');
  app.get('/binary', () => File('data.zip').openRead());
  app.get('/json', () => {'name': 'John', 'age': 42});
  app.get('/class', () => Person('Theo'));
  app.get('/list-of-classes', () => [Person('Theo'), Person('Bob')]);
  app.get('/iterables', () => [1, 10, 100].where((n) => n > 9));
  app.get('/handler', () => typeByExtension('html') >> '<h1>Hello</h1>');
  app.get('/file', () => File('thesis.pdf'));
  app.get('/websocket', () => WebSocketSession(
        onOpen: (ws) => ws.send('Hello!'),
        onMessage: (ws, data) => ws.send('You sent me: $data'),
        onClose: (ws) => ws.send('Bye!'),
      ));

  return app.call;
}

class Person {
  final String name;

  Person(this.name);

  Map<String, dynamic> toJson() => {'name': name};
}

中间件 (Middleware)

使用中间件

var app = Router().plus;

app.use(middlewareA); // 应用于所有路由

// 应用于单个路由
app.get('/request1', () => 'response', use: middlewareB);

// 组合中间件
app.get('/request2', () => 'response', use: middlewareB + middlewareC);

在请求处理器中动态应用中间件

app.get('/request/<value>', (Request request, String value) {
  return middleware(value) >> 'response';
});

请求体处理 (Request Body Handling)

解析请求体

app.post('/text', (Request request) async {
  var text = await request.body.asString;
  return 'You send me: $text';
});

app.post('/json', (Request request) async {
  var person = Person.fromJson(await request.body.asJson);
  return 'You send me: ${person.name}';
});

自定义访问器 (Custom Accessors)

extension PersonAccessor on RequestBodyAccessor {
  Future<Person> get asPerson async => Person.fromJson(await asJson);
}

app.post('/person', (Request request) async {
  var person = await request.body.asPerson;
  return 'You send me: ${person.name}';
});

Shelf Run

启动服务器

import 'package:shelf_plus/shelf_plus.dart';

void main() => shelfRun(init);

Handler init() {
  return (Request request) => Response.ok('Hello!');
}

自定义配置

void main() => shelfRun(init, defaultBindPort: 3000);

多线程支持

import 'dart:isolate';
import 'package:shelf_plus/shelf_plus.dart';

void main() {
  const numberOfIsolates = 8;

  for (var i = 0; i < numberOfIsolates - 1; i++) {
    Isolate.spawn(spawnServer, null, debugName: i.toString()); // isolate 0..7
  }
  spawnServer(null); // use main isolate as the 8th isolate
}

void spawnServer(_) => shelfRun(init, defaultShared: true);

Handler init() {
  var app = Router().plus;

  app.get('/', () async {
    await Future.delayed(Duration(milliseconds: 500)); // simulate load
    return 'Hello from isolate: ${Isolate.current.debugName}';
  });

  return app.call;
}

示例

启用 CORS

import 'package:shelf_cors_headers/shelf_cors_headers.dart';
import 'package:shelf_plus/shelf_plus.dart';

void main() => shelfRun(init);

Handler init() {
  final router = Router().plus;

  router.get('/', () => {'data': 'This API is CORS enabled.'});

  return corsHeaders() >> router.call;
}

REST 服务

import 'dart:io';
import 'package:shelf_plus/shelf_plus.dart';
import 'person.dart';

void main() => shelfRun(init);

final data = <Person>[
  Person(firstName: 'John', lastName: 'Doe', age: 42),
  Person(firstName: 'Jane', lastName: 'Doe', age: 43),
];

Handler init() {
  var app = Router().plus;

  app.get('/', () => File('frontend/page.html'));
  app.get('/person', () => data);
  app.get('/person/<id>', (Request request, String id) => data.where((person) => person.id == id));
  app.post('/person', (Request request) async {
    var newPerson = await request.body.as(Person.fromJson);
    data.add(newPerson);
    return {'ok': 'true', 'person': newPerson.toJson()};
  });
  app.put('/person/<id>', (Request request, String id) async {
    data.removeWhere((person) => person.id == id);
    var person = await request.body.as(Person.fromJson);
    person.id = id;
    data.add(person);
    return {'ok': 'true'};
  });
  app.delete('/person/<id>', (Request request, String id) {
    data.removeWhere((person) => person.id == id);
    return {'ok': 'true'};
  });

  return app.call;
}

WebSocket 聊天服务器

import 'dart:io';
import 'package:shelf_plus/shelf_plus.dart';

void main() => shelfRun(init);

Handler init() {
  var app = Router().plus;

  app.get('/', () => File('public/html_client.html'));

  var users = <WebSocketSession>[];

  app.get('/ws', () => WebSocketSession(
        onOpen: (ws) {
          users.add(ws);
          users.where((user) => user != ws).forEach((user) => user.send('A new user joined the chat.'));
        },
        onClose: (ws) {
          users.remove(ws);
          for (var user in users) {
            user.send('A user has left.');
          }
        },
        onMessage: (ws, dynamic data) {
          for (var user in users) {
            user.send(data);
          }
        },
      ));

  return app.call;
}

通过以上内容，您可以快速上手并充分利用 shelf_plus 插件的强大功能来构建高效的服务端应用。