golang设计模式
前言
设计模式 Golang实现－《研磨设计模式》读书笔记
https://github.com/senghoo/golang-design-pattern
创建型模式
简单工厂模式(Simple Factory)
go 语言没有构造函数一说，所以一般会定义NewXXX函数来初始化相关类。 NewXXX 函数返回接口时就是简单工厂模式，也就是说Golang的一般推荐做法就是简单工厂。
在这个simplefactory包中只有API 接口和NewAPI函数为包外可见，封装了实现细节。
package simplefactory
import "fmt"
//API is interface
type API interface {
Say(name string) string
}
//NewAPI return Api instance by type
func NewAPI(t int) API {
if t == 1 {
return &hiAPI{}
} else if t == 2 {
return &helloAPI{}
}
return nil
}
//hiAPI is one of API implement
type hiAPI struct{}
//Say hi to name
func (*hiAPI) Say(name string) string {
return fmt.Sprintf("Hi, %s", name)
}
//HelloAPI is another API implement
type helloAPI struct{}
//Say hello to name
func (*helloAPI) Say(name string) string {
return fmt.Sprintf("Hello, %s", name)
}
工厂方法模式(Factory Method)
工厂方法模式使用子类的方式延迟生成对象到子类中实现。
Go中不存在继承，所以使用匿名组合来实现
package factorymethod
//Operator 是被封装的实际类接口
type Operator interface {
SetA(int)
SetB(int)
Result() int
}
//OperatorFactory 是工厂接口
type OperatorFactory interface {
Create() Operator
}
//OperatorBase 是Operator 接口实现的基类，封装公用方法
type OperatorBase struct {
a, b int
}
//SetA 设置 A
func (o *OperatorBase) SetA(a int) {
o.a = a
}
//SetB 设置 B
func (o *OperatorBase) SetB(b int) {
o.b = b
}
//PlusOperatorFactory 是 PlusOperator 的工厂类
type PlusOperatorFactory struct{}
func (PlusOperatorFactory) Create() Operator {
return &PlusOperator{
OperatorBase: &OperatorBase{},
}
}
//PlusOperator Operator 的实际加法实现
type PlusOperator struct {
*OperatorBase
}
//Result 获取结果
func (o PlusOperator) Result() int {
return o.a + o.b
}
//MinusOperatorFactory 是 MinusOperator 的工厂类
type MinusOperatorFactory struct{}
func (MinusOperatorFactory) Create() Operator {
return &MinusOperator{
OperatorBase: &OperatorBase{},
}
}
//MinusOperator Operator 的实际减法实现
type MinusOperator struct {
*OperatorBase
}
//Result 获取结果
func (o MinusOperator) Result() int {
return o.a - o.b
}
factorymethod_test.go
package factorymethod
import "testing"
func compute(factory OperatorFactory, a, b int) int {
op := factory.Create()
op.SetA(a)
op.SetB(b)
return op.Result()
}
func TestOperator(t *testing.T) {
var (
factory OperatorFactory
)
factory = PlusOperatorFactory{}
if compute(factory, 1, 2) != 3 {
t.Fatal("error with factory method pattern")
}
factory = MinusOperatorFactory{}
if compute(factory, 4, 2) != 2 {
t.Fatal("error with factory method pattern")
}
}
抽象工厂模式(Abstract Factory)
抽象工厂模式用于生成产品族的工厂，所生成的对象是有关联的。
如果抽象工厂退化成生成的对象无关联则成为工厂函数模式。
比如本例子中使用RDB和XML存储订单信息，抽象工厂分别能生成相关的主订单信息和订单详情信息。 如果业务逻辑中需要替换使用的时候只需要改动工厂函数相关的类就能替换使用不同的存储方式了。
package abstractfactory
import "fmt"
//OrderMainDAO 为订单主记录
type OrderMainDAO interface {
SaveOrderMain()
}
//OrderDetailDAO 为订单详情纪录
type OrderDetailDAO interface {
SaveOrderDetail()
}
//DAOFactory DAO 抽象模式工厂接口
type DAOFactory interface {
CreateOrderMainDAO() OrderMainDAO
CreateOrderDetailDAO() OrderDetailDAO
}
//RDBMainDAP 为关系型数据库的OrderMainDAO实现
type RDBMainDAO struct{}
//SaveOrderMain ...
func (*RDBMainDAO) SaveOrderMain() {
fmt.Print("rdb main save\n")
}
//RDBDetailDAO 为关系型数据库的OrderDetailDAO实现
type RDBDetailDAO struct{}
// SaveOrderDetail ...
func (*RDBDetailDAO) SaveOrderDetail() {
fmt.Print("rdb detail save\n")
}
//RDBDAOFactory 是RDB 抽象工厂实现
type RDBDAOFactory struct{}
func (*RDBDAOFactory) CreateOrderMainDAO() OrderMainDAO {
return &RDBMainDAO{}
}
func (*RDBDAOFactory) CreateOrderDetailDAO() OrderDetailDAO {
return &RDBDetailDAO{}
}
//XMLMainDAO XML存储
type XMLMainDAO struct{}
//SaveOrderMain ...
func (*XMLMainDAO) SaveOrderMain() {
fmt.Print("xml main save\n")
}
//XMLDetailDAO XML存储
type XMLDetailDAO struct{}
// SaveOrderDetail ...
func (*XMLDetailDAO) SaveOrderDetail() {
fmt.Print("xml detail save")
}
//XMLDAOFactory 是RDB 抽象工厂实现
type XMLDAOFactory struct{}
func (*XMLDAOFactory) CreateOrderMainDAO() OrderMainDAO {
return &XMLMainDAO{}
}
func (*XMLDAOFactory) CreateOrderDetailDAO() OrderDetailDAO {
return &XMLDetailDAO{}
}
测试
package abstractfactory
func getMainAndDetail(factory DAOFactory) {
factory.CreateOrderMainDAO().SaveOrderMain()
factory.CreateOrderDetailDAO().SaveOrderDetail()
}
func ExampleRdbFactory() {
var factory DAOFactory
factory = &RDBDAOFactory{}
getMainAndDetail(factory)
// Output:
// rdb main save
// rdb detail save
}
func ExampleXmlFactory() {
var factory DAOFactory
factory = &XMLDAOFactory{}
getMainAndDetail(factory)
// Output:
// xml main save
// xml detail save
}
创建者模式(Builder)
封装一个复杂对象的构建过程，并可以按步骤构造。
package builder
//Builder 是生成器接口
type Builder interface {
Part1()
Part2()
Part3()
}
type Director struct {
builder Builder
}
// NewDirector ...
func NewDirector(builder Builder) *Director {
return &Director{
builder: builder,
}
}
//Construct Product
func (d *Director) Construct() {
d.builder.Part1()
d.builder.Part2()
d.builder.Part3()
}
type Builder1 struct {
result string
}
func (b *Builder1) Part1() {
b.result += "1"
}
func (b *Builder1) Part2() {
b.result += "2"
}
func (b *Builder1) Part3() {
b.result += "3"
}
func (b *Builder1) GetResult() string {
return b.result
}
type Builder2 struct {
result int
}
func (b *Builder2) Part1() {
b.result += 1
}
func (b *Builder2) Part2() {
b.result += 2
}
func (b *Builder2) Part3() {
b.result += 3
}
func (b *Builder2) GetResult() int {
return b.result
}
测试
package builder
import "testing"
func TestBuilder1(t *testing.T) {
builder := &Builder1{}
director := NewDirector(builder)
director.Construct()
res := builder.GetResult()
if res != "123" {
t.Fatalf("Builder1 fail expect 123 acture %s", res)
}
}
func TestBuilder2(t *testing.T) {
builder := &Builder2{}
director := NewDirector(builder)
director.Construct()
res := builder.GetResult()
if res != 6 {
t.Fatalf("Builder2 fail expect 6 acture %d", res)
}
}
原型模式(Prototype)
通过复制现有的实例来创建新的实例。
原型模式使对象能复制自身，并且暴露到接口中，使客户端面向接口编程时，不知道接口实际对象的情况下生成新的对象。
原型模式配合原型管理器使用，使得客户端在不知道具体类的情况下，通过接口管理器得到新的实例，并且包含部分预设定配置。
package prototype
//Cloneable 是原型对象需要实现的接口
type Cloneable interface {
Clone() Cloneable
}
type PrototypeManager struct {
prototypes map[string]Cloneable
}
func NewPrototypeManager() *PrototypeManager {
return &PrototypeManager{
prototypes: make(map[string]Cloneable),
}
}
func (p *PrototypeManager) Get(name string) Cloneable {
return p.prototypes[name].Clone()
}
func (p *PrototypeManager) Set(name string, prototype Cloneable) {
p.prototypes[name] = prototype
}
测试
package prototype
import "testing"
var manager *PrototypeManager
type Type1 struct {
name string
}
func (t *Type1) Clone() Cloneable {
tc := *t
return &tc
}
type Type2 struct {
name string
}
func (t *Type2) Clone() Cloneable {
tc := *t
return &tc
}
func TestClone(t *testing.T) {
t1 := manager.Get("t1")
t2 := t1.Clone()
if t1 == t2 {
t.Fatal("error! get clone not working")
}
}
func TestCloneFromManager(t *testing.T) {
c := manager.Get("t1").Clone()
t1 := c.(*Type1)
if t1.name != "type1" {
t.Fatal("error")
}
}
func init() {
manager = NewPrototypeManager()
t1 := &Type1{
name: "type1",
}
manager.Set("t1", t1)
}
单例模式(Singleton)
使用懒惰模式的单例模式，使用双重检查加锁保证线程安全
package singleton
import "sync"
// Singleton 是单例模式接口，导出的
// 通过该接口可以避免 GetInstance 返回一个包私有类型的指针
type Singleton interface {
foo()
}
// singleton 是单例模式类，包私有的
type singleton struct{}
func (s singleton) foo() {}
var (
instance *singleton
once sync.Once
)
//GetInstance 用于获取单例模式对象
func GetInstance() Singleton {
once.Do(func() {
instance = &singleton{}
})
return instance
}
测试
package singleton
import (
"sync"
"testing"
)
const parCount = 100
func TestSingleton(t *testing.T) {
ins1 := GetInstance()
ins2 := GetInstance()
if ins1 != ins2 {
t.Fatal("instance is not equal")
}
}
func TestParallelSingleton(t *testing.T) {
start := make(chan struct{})
wg := sync.WaitGroup{}
wg.Add(parCount)
instances := [parCount]Singleton{}
for i := 0; i < parCount; i++ {
go func(index int) {
//协程阻塞，等待channel被关闭才能继续运行
<-start
instances[index] = GetInstance()
wg.Done()
}(i)
}
//关闭channel，所有协程同时开始运行，实现并行(parallel)
close(start)
wg.Wait()
for i := 1; i < parCount; i++ {
if instances[i] != instances[i-1] {
t.Fatal("instance is not equal")
}
}
}
结构型模式
外观模式(Facade)
API 为facade 模块的外观接口，大部分代码使用此接口简化对facade类的访问。
facade模块同时暴露了a和b 两个Module 的NewXXX和interface，其它代码如果需要使用细节功能时可以直接调用。
package facade
import "fmt"
func NewAPI() API {
return &apiImpl{
a: NewAModuleAPI(),
b: NewBModuleAPI(),
}
}
//API is facade interface of facade package
type API interface {
Test() string
}
//facade implement
type apiImpl struct {
a AModuleAPI
b BModuleAPI
}
func (a *apiImpl) Test() string {
aRet := a.a.TestA()
bRet := a.b.TestB()
return fmt.Sprintf("%s\n%s", aRet, bRet)
}
//NewAModuleAPI return new AModuleAPI
func NewAModuleAPI() AModuleAPI {
return &aModuleImpl{}
}
//AModuleAPI ...
type AModuleAPI interface {
TestA() string
}
type aModuleImpl struct{}
func (*aModuleImpl) TestA() string {
return "A module running"
}
//NewBModuleAPI return new BModuleAPI
func NewBModuleAPI() BModuleAPI {
return &bModuleImpl{}
}
//BModuleAPI ...
type BModuleAPI interface {
TestB() string
}
type bModuleImpl struct{}
func (*bModuleImpl) TestB() string {
return "B module running"
}
测试
package facade
import "testing"
var expect = "A module running\nB module running"
// TestFacadeAPI ...
func TestFacadeAPI(t *testing.T) {
api := NewAPI()
ret := api.Test()
if ret != expect {
t.Fatalf("expect %s, return %s", expect, ret)
}
}
适配器模式(Adapter)
适配器模式用于转换一种接口适配另一种接口。
实际使用中Adaptee一般为接口，并且使用工厂函数生成实例。
在Adapter中匿名组合Adaptee接口，所以Adapter类也拥有SpecificRequest实例方法，又因为Go语言中非入侵式接口特征，其实Adapter也适配Adaptee接口。
package adapter
//Target 是适配的目标接口
type Target interface {
Request() string
}
//Adaptee 是被适配的目标接口
type Adaptee interface {
SpecificRequest() string
}
//NewAdaptee 是被适配接口的工厂函数
func NewAdaptee() Adaptee {
return &adapteeImpl{}
}
//AdapteeImpl 是被适配的目标类
type adapteeImpl struct{}
//SpecificRequest 是目标类的一个方法
func (*adapteeImpl) SpecificRequest() string {
return "adaptee method"
}
//NewAdapter 是Adapter的工厂函数
func NewAdapter(adaptee Adaptee) Target {
return &adapter{
Adaptee: adaptee,
}
}
//Adapter 是转换Adaptee为Target接口的适配器
type adapter struct {
Adaptee
}
//Request 实现Target接口
func (a *adapter) Request() string {
return a.SpecificRequest()
}
测试
package adapter
import "testing"
var expect = "adaptee method"
func TestAdapter(t *testing.T) {
adaptee := NewAdaptee()
target := NewAdapter(adaptee)
res := target.Request()
if res != expect {
t.Fatalf("expect: %s, actual: %s", expect, res)
}
}
代理模式(Proxy)
代理模式用于延迟处理操作或者在进行实际操作前后进行其它处理。
代理模式的常见用法有
- 虚代理
- COW代理
- 远程代理
- 保护代理
- Cache 代理
- 防火墙代理
- 同步代理
- 智能指引
等。。。
package proxy
type Subject interface {
Do() string
}
type RealSubject struct{}
func (RealSubject) Do() string {
return "real"
}
type Proxy struct {
real RealSubject
}
func (p Proxy) Do() string {
var res string
// 在调用真实对象之前的工作，检查缓存，判断权限，实例化真实对象等。。
res += "pre:"
// 调用真实对象
res += p.real.Do()
// 调用之后的操作，如缓存结果，对结果进行处理等。。
res += ":after"
return res
}
测试
package proxy
import "testing"
func TestProxy(t *testing.T) {
var sub Subject
sub = &Proxy{}
res := sub.Do()
if res != "pre:real:after" {
t.Fail()
}
}
组合模式(Composite)
组合模式统一对象和对象集，使得使用相同接口使用对象和对象集。
组合模式常用于树状结构，用于统一叶子节点和树节点的访问，并且可以用于应用某一操作到所有子节点。
package composite
import "fmt"
type Component interface {
Parent() Component
SetParent(Component)
Name() string
SetName(string)
AddChild(Component)
Print(string)
}
const (
LeafNode = iota
CompositeNode
)
func NewComponent(kind int, name string) Component {
var c Component
switch kind {
case LeafNode:
c = NewLeaf()
case CompositeNode:
c = NewComposite()
}
c.SetName(name)
return c
}
type component struct {
parent Component
name string
}
func (c *component) Parent() Component {
return c.parent
}
func (c *component) SetParent(parent Component) {
c.parent = parent
}
func (c *component) Name() string {
return c.name
}
func (c *component) SetName(name string) {
c.name = name
}
func (c *component) AddChild(Component) {}
func (c *component) Print(string) {}
type Leaf struct {
component
}
func NewLeaf() *Leaf {
return &Leaf{}
}
func (c *Leaf) Print(pre string) {
fmt.Printf("%s-%s\n", pre, c.Name())
}
type Composite struct {
component
childs []Component
}
func NewComposite() *Composite {
return &Composite{
childs: make([]Component, 0),
}
}
func (c *Composite) AddChild(child Component) {
child.SetParent(c)
c.childs = append(c.childs, child)
}
func (c *Composite) Print(pre string) {
fmt.Printf("%s+%s\n", pre, c.Name())
pre += " "
for _, comp := range c.childs {
comp.Print(pre)
}
}
测试
package composite
func ExampleComposite() {
root := NewComponent(CompositeNode, "root")
c1 := NewComponent(CompositeNode, "c1")
c2 := NewComponent(CompositeNode, "c2")
c3 := NewComponent(CompositeNode, "c3")
l1 := NewComponent(LeafNode, "l1")
l2 := NewComponent(LeafNode, "l2")
l3 := NewComponent(LeafNode, "l3")
root.AddChild(c1)
root.AddChild(c2)
c1.AddChild(c3)
c1.AddChild(l1)
c2.AddChild(l2)
c2.AddChild(l3)
root.Print("")
// Output:
// +root
// +c1
// +c3
// -l1
// +c2
// -l2
// -l3
}
享元模式(Flyweight)
享元模式从对象中剥离出不发生改变且多个实例需要的重复数据，独立出一个享元，使多个对象共享，从而节省内存以及减少对象数量。
package flyweight
import "fmt"
type ImageFlyweightFactory struct {
maps map[string]*ImageFlyweight
}
var imageFactory *ImageFlyweightFactory
func GetImageFlyweightFactory() *ImageFlyweightFactory {
if imageFactory == nil {
imageFactory = &ImageFlyweightFactory{
maps: make(map[string]*ImageFlyweight),
}
}
return imageFactory
}
func (f *ImageFlyweightFactory) Get(filename string) *ImageFlyweight {
image := f.maps[filename]
if image == nil {
image = NewImageFlyweight(filename)
f.maps[filename] = image
}
return image
}
type ImageFlyweight struct {
data string
}
func NewImageFlyweight(filename string) *ImageFlyweight {
// Load image file
data := fmt.Sprintf("image data %s", filename)
return &ImageFlyweight{
data: data,
}
}
func (i *ImageFlyweight) Data() string {
return i.data
}
type ImageViewer struct {
*ImageFlyweight
}
func NewImageViewer(filename string) *ImageViewer {
image := GetImageFlyweightFactory().Get(filename)
return &ImageViewer{
ImageFlyweight: image,
}
}
func (i *ImageViewer) Display() {
fmt.Printf("Display: %s\n", i.Data())
}
测试
package flyweight
import "testing"
func ExampleFlyweight() {
viewer := NewImageViewer("image1.png")
viewer.Display()
// Output:
// Display: image data image1.png
}
func TestFlyweight(t *testing.T) {
viewer1 := NewImageViewer("image1.png")
viewer2 := NewImageViewer("image1.png")
if viewer1.ImageFlyweight != viewer2.ImageFlyweight {
t.Fail()
}
}
装饰模式(Decorator)
装饰模式使用对象组合的方式动态改变或增加对象行为。
Go语言借助于匿名组合和非入侵式接口可以很方便实现装饰模式。
使用匿名组合，在装饰器中不必显式定义转调原对象方法。
package decorator
type Component interface {
Calc() int
}
type ConcreteComponent struct{}
func (*ConcreteComponent) Calc() int {
return 0
}
type MulDecorator struct {
Component
num int
}
func WarpMulDecorator(c Component, num int) Component {
return &MulDecorator{
Component: c,
num: num,
}
}
func (d *MulDecorator) Calc() int {
return d.Component.Calc() * d.num
}
type AddDecorator struct {
Component
num int
}
func WarpAddDecorator(c Component, num int) Component {
return &AddDecorator{
Component: c,
num: num,
}
}
func (d *AddDecorator) Calc() int {
return d.Component.Calc() + d.num
}
测试
package decorator
import "fmt"
func ExampleDecorator() {
var c Component = &ConcreteComponent{}
c = WarpAddDecorator(c, 10)
c = WarpMulDecorator(c, 8)
res := c.Calc()
fmt.Printf("res %d\n", res)
// Output:
// res 80
}
桥接模式(Bridge)
桥接模式分离抽象部分和实现部分。使得两部分独立扩展。
桥接模式类似于策略模式，区别在于策略模式封装一系列算法使得算法可以互相替换。
策略模式使抽象部分和实现部分分离，可以独立变化。
package bridge
import "fmt"
type AbstractMessage interface {
SendMessage(text, to string)
}
type MessageImplementer interface {
Send(text, to string)
}
type MessageSMS struct{}
func ViaSMS() MessageImplementer {
return &MessageSMS{}
}
func (*MessageSMS) Send(text, to string) {
fmt.Printf("send %s to %s via SMS", text, to)
}
type MessageEmail struct{}
func ViaEmail() MessageImplementer {
return &MessageEmail{}
}
func (*MessageEmail) Send(text, to string) {
fmt.Printf("send %s to %s via Email", text, to)
}
type CommonMessage struct {
method MessageImplementer
}
func NewCommonMessage(method MessageImplementer) *CommonMessage {
return &CommonMessage{
method: method,
}
}
func (m *CommonMessage) SendMessage(text, to string) {
m.method.Send(text, to)
}
type UrgencyMessage struct {
method MessageImplementer
}
func NewUrgencyMessage(method MessageImplementer) *UrgencyMessage {
return &UrgencyMessage{
method: method,
}
}
func (m *UrgencyMessage) SendMessage(text, to string) {
m.method.Send(fmt.Sprintf("[Urgency] %s", text), to)
}
测试
package bridge
import "fmt"
type AbstractMessage interface {
SendMessage(text, to string)
}
type MessageImplementer interface {
Send(text, to string)
}
type MessageSMS struct{}
func ViaSMS() MessageImplementer {
return &MessageSMS{}
}
func (*MessageSMS) Send(text, to string) {
fmt.Printf("send %s to %s via SMS", text, to)
}
type MessageEmail struct{}
func ViaEmail() MessageImplementer {
return &MessageEmail{}
}
func (*MessageEmail) Send(text, to string) {
fmt.Printf("send %s to %s via Email", text, to)
}
type CommonMessage struct {
method MessageImplementer
}
func NewCommonMessage(method MessageImplementer) *CommonMessage {
return &CommonMessage{
method: method,
}
}
func (m *CommonMessage) SendMessage(text, to string) {
m.method.Send(text, to)
}
type UrgencyMessage struct {
method MessageImplementer
}
func NewUrgencyMessage(method MessageImplementer) *UrgencyMessage {
return &UrgencyMessage{
method: method,
}
}
func (m *UrgencyMessage) SendMessage(text, to string) {
m.method.Send(fmt.Sprintf("[Urgency] %s", text), to)
}
