Golang 依赖注入

1. 手动实现依赖注入

package mainimport "fmt"type A struct {B *B
}type B struct {Inject string
}func main() {var a Ab := B{Inject: "Golang"}fmt.Println(b.Inject)a.B = &bfmt.Println(a.B.Inject)
}

2.开源的依赖注入框架

依赖反射实现的运行时的依赖注入（facebook/inject、uber/dig）
使用代码生成实现的依赖注入（google/wire）

facebookgo/inject :

facebookgo/inject 实现依赖注入：类A的实例a是需要被注入的对象，类B的实例b是依赖的组件将a、b的依赖关系交给第三方（IOC容器）来控制，调用Provide我们不再需要编写复杂的依赖代码（各种参数，实例的互相传入）。执行完Populate后，我们就可以直接使用实例a，其中需要依赖的组件在运行时由IOC容器来注入。

package mainimport ("fmt""net/http""os""github.com/facebookgo/inject"
)// Our Awesome Application renders a message using two APIs in our fake
// world.
type HomePlanetRenderApp struct {// The tags below indicate to the inject library that these fields are// eligible for injection. They do not specify any options, and will// result in a singleton instance created for each of the APIs.NameAPI   *NameAPI   `inject:""`PlanetAPI *PlanetAPI `inject:""`
}func (a *HomePlanetRenderApp) Render(id uint64) string {return fmt.Sprintf("%s is from the planet %s.",a.NameAPI.Name(id),a.PlanetAPI.Planet(id),)
}// Our fake Name API.
type NameAPI struct {// Here and below in PlanetAPI we add the tag to an interface value.// This value cannot automatically be created (by definition) and// hence must be explicitly provided to the graph.HTTPTransport http.RoundTripper `inject:""`
}func (n *NameAPI) Name(id uint64) string {// in the real world we would use f.HTTPTransport and fetch the namereturn "Spock"
}// Our fake Planet API.
type PlanetAPI struct {HTTPTransport http.RoundTripper `inject:""`
}func (p *PlanetAPI) Planet(id uint64) string {// in the real world we would use f.HTTPTransport and fetch the planetreturn "Vulcan"
}func main() {// Typically an application will have exactly one object graph, and// you will create it and use it within a main function:var g inject.Graph// We provide our graph two "seed" objects, one our empty// HomePlanetRenderApp instance which we're hoping to get filled out,// and second our DefaultTransport to satisfy our HTTPTransport// dependency. We have to provide the DefaultTransport because the// dependency is defined in terms of the http.RoundTripper interface,// and since it is an interface the library cannot create an instance// for it. Instead it will use the given DefaultTransport to satisfy// the dependency since it implements the interface:var a HomePlanetRenderApperr := g.Provide(&inject.Object{Value: &a},&inject.Object{Value: http.DefaultTransport},)if err != nil {fmt.Fprintln(os.Stderr, err)os.Exit(1)}// Here the Populate call is creating instances of NameAPI &// PlanetAPI, and setting the HTTPTransport on both to the// http.DefaultTransport provided above:if err := g.Populate(); err != nil {fmt.Fprintln(os.Stderr, err)os.Exit(1)}// There is a shorthand API for the simple case which combines the// three calls above is available as inject.Populate:////   inject.Populate(&a, http.DefaultTransport)//// The above API shows the underlying API which also allows the use of// named instances for more complex scenarios.fmt.Println(a.Render(42))}

Output:Spock is from the planet Vulcan.

uber/dig：

my.iniapp_name = web# possible values: DEBUG, INFO, WARNING, ERROR, FATAL
log_level = DEBUG[mysql]
ip = 127.0.0.1
port = 3306
user = dj
password = 123456
database = awesome[redis]
ip = 127.0.0.1
port = 6379
db = 0

package mainimport ("fmt""github.com/jessevdk/go-flags""go.uber.org/dig""gopkg.in/ini.v1"
)type Option struct {ConfigFile string `short:"c" long:"config" description:"Name of config file."`
}func InitOption() (*Option, error) {var opt Option_, err := flags.Parse(&opt)return &opt, err
}func InitConf(opt *Option) (*ini.File, error) {cfg, err := ini.Load(opt.ConfigFile)return cfg, err
}func PrintInfo(cfg *ini.File) {fmt.Println("App Name:", cfg.Section("").Key("app_name").String())fmt.Println("Log Level:", cfg.Section("").Key("log_level").String())
}func main() {container := dig.New()container.Provide(InitOption)container.Provide(InitConf)container.Invoke(PrintInfo)
}

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Golang 依赖注入

1. 手动实现依赖注入

2.开源的依赖注入框架

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