灵活应用中间件机制，可以有效扩展架构的功能。中间件主要的作用有：拦截、重整

  1. 拦截：比如通过中间件判断用户权限，如果没有权限则中止后续执行
  2. 重整：比如通过中间件对前端发来的数据进行验证，并转化为期望的类型

在这里，我们通过一个虚拟的需求，用中间件实现拦截和重整的逻辑：

  1. 需求：前端发送两个参数：a、b，后端计算二者之和，并返回前端
  2. 拦截：中间件判断参数是否为空，如果为空则中止后续执行
  3. 重整：将参数类型强制转换为Integer类型

创建中间件

1. 声明中间件

src/suite-vendor/test-party/modules/test-party/backend/src/config/config.js

  1. 1// middlewares
  2. 2config.middlewares = {
  3. 3  testInterception: {
  4. 4    bean: 'testInterception',
  5. 5    global: false,
  6. 6    dependencies: 'instance',
  7. 7  },
  8. 8  testRestructuring: {
  9. 9    bean: 'testRestructuring',
  10. 10    global: false,
  11. 11    dependencies: 'instance',
  12. 12  },
  13. 13};
名称 说明
bean 用于实现中间件逻辑的Bean组件名称
global 是否为全局中间件，全局中间件会自动加载，局部中间件需要手动指定
dependencies 标明此中间件依赖哪些中间件，从而在那些中间件后面加载。一般要依赖于instance，因为instance提供了多实例的基础逻辑

2. 定义中间件Bean组件

src/suite-vendor/test-party/modules/test-party/backend/src/bean/middleware.interception.js

  1. 1module.exports = ctx => {
  2. 2  class Middleware {
  3. 3    async execute(options, next) {
  4. 4      const { a, b } = ctx.request.body;
  5. 5      if (a === undefined || b === undefined) return ctx.throw(1002); // 1002: 'Incomplete Parameters'
  6. 6      // next
  7. 7      await next();
  8. 8    }
  9. 9  }
  10. 10  return Middleware;
  11. 11};

src/suite-vendor/test-party/modules/test-party/backend/src/bean/middleware.restructuring.js

  1. 1module.exports = ctx => {
  2. 2  class Middleware {
  3. 3    async execute(options, next) {
  4. 4      const { a, b } = ctx.request.body;
  5. 5      ctx.request.body.a = parseInt(a);
  6. 6      ctx.request.body.b = parseInt(b);
  7. 7      // next
  8. 8      await next();
  9. 9    }
  10. 10  }
  11. 11  return Middleware;
  12. 12};

3. 注册中间件Bean组件

src/suite-vendor/test-party/modules/test-party/backend/src/beans.js

  1. 1const middlewareTestInterception = require('./bean/middleware.interception.js');
  2. 2const middlewareTestRestructuring = require('./bean/middleware.restructuring.js');
  3. 3
  4. 4module.exports = app => {
  5. 5  const beans = {
  6. 6    // middleware
  7. 7    'middleware.testInterception': {
  8. 8      mode: 'ctx',
  9. 9      bean: middlewareTestInterception,
  10. 10    },
  11. 11    'middleware.testRestructuring': {
  12. 12      mode: 'ctx',
  13. 13      bean: middlewareTestRestructuring,
  14. 14    },
  15. 15  };
  16. 16  return beans;
  17. 17};

使用中间件

1. 配置API路由

因为testInterception和testRestructuring是局部中间件，因此需要手动在API路由上指定

src/suite-vendor/test-party/modules/test-party/backend/src/routes.js

  1. 1// test/feat/middleware
  2. 2{ method: 'post', path: 'test/feat/middleware/interception', controller: 'testFeatMiddleware', middlewares: 'test,testInterception' },
  3. 3{ method: 'post', path: 'test/feat/middleware/restructuring', controller: 'testFeatMiddleware', middlewares: 'test,testInterception,testRestructuring' },

2. 后端控制器逻辑

src/suite-vendor/test-party/modules/test-party/backend/src/controller/test/feat/middleware.js

  1. 1module.exports = app => {
  2. 2
  3. 3  class TestController extends app.Controller {
  4. 4
  5. 5    async interception() {
  6. 6      const { a, b } = this.ctx.request.body;
  7. 7      const c = parseInt(a) + parseInt(b);
  8. 8      this.ctx.success(c);
  9. 9    }
  10. 10
  11. 11    async restructuring() {
  12. 12      const { a, b } = this.ctx.request.body;
  13. 13      const c = a + b;
  14. 14      this.ctx.success(c);
  15. 15    }
  16. 16
  17. 17  }
  18. 18
  19. 19  return TestController;
  20. 20};

src/suite-vendor/test-party/modules/test-party/backend/src/controllers.js

  1. 1const testFeatMiddleware = require('./controller/test/feat/middleware.js');
  2. 2
  3. 3module.exports = app => {
  4. 4  const controllers = {
  5. 5    testFeatMiddleware,
  6. 6  };
  7. 7  return controllers;
  8. 8};

单元测试

在这里，我们采用单元测试来验证中间件机制是否按预期运作

src/suite-vendor/test-party/modules/test-party/backend/test/controller/test/feat/middleware.test.js

  1. 1const { app, mockUrl, mockInfo, assert } = require('egg-born-mock')(__dirname);
  2. 2
  3. 3describe('test/controller/test/feat/middleware.test.js', () => {
  4. 4
  5. 5  it('action:interception', async () => {
  6. 6    // success
  7. 7    let result = await app.httpRequest()
  8. 8      .post(mockUrl('test/feat/middleware/interception'))
  9. 9      .send({
  10. 10        a: '1',
  11. 11        b: '2',
  12. 12      });
  13. 13    assert.equal(result.body.data, 3);
  14. 14
  15. 15    // fail
  16. 16    result = await app.httpRequest()
  17. 17      .post(mockUrl('test/feat/middleware/interception'))
  18. 18      .send();
  19. 19    assert.equal(result.status, 500);
  20. 20  });
  21. 21
  22. 22  it('action:restructuring', async () => {
  23. 23    // success
  24. 24    const result = await app.httpRequest()
  25. 25      .post(mockUrl('test/feat/middleware/restructuring'))
  26. 26      .send({
  27. 27        a: '1',
  28. 28        b: '2',
  29. 29      });
  30. 30    assert.equal(result.body.data, 3);
  31. 31  });
  32. 32
  33. 33});