简介

建造者模式应用场景是

  • 类中的属性比较多
  • 类中的属性之间有一定的依赖关系，或者是约束关系
  • 存在必选和非必选的属性
  • 希望创建不可变的对象

与工厂模式区别是建造者模式常用于创建参数比较多的对象时候。常见的做法是必填参数直接传递，可选参数通过传递可变的方法进行创建

  1. package main
  3. const (
  4.     defaultMaxTotal = 10
  5.     defaultMaxIdle  = 9
  6.     defalutMinIdle  = 1
  7. )
  9. type ResourcePoolConfig struct {
  10.     name     string
  11.     maxTotal int
  12.     maxIdle  int
  13.     minIdle  int
  14. }
  16. type ResourcePoolConfigBuilder struct {
  17.     name     string
  18.     maxTotal int
  19.     maxIdle  int
  20.     minIdle  int
  21. }
  23. func (b *ResourcePoolConfigBuilder) SetName(name string) error {
  24.     if name == "" {
  25.         return fmt.Errorf("name can not be empty")
  26.     }
  27.     b.name = name
  28.     return nil
  29. }
  31. func (b *ResourcePoolConfigBuilder) SetMinIdle(minIdle int) error {
  32.     if minIdle < 0 {
  33.         return fmt.Errorf("max tatal cannot < 0, input: %d", minIdle)
  34.     }
  35.     b.minIdle = minIdle
  36.     return nil
  37. }
  39. func (b *ResourcePoolConfigBuilder) SetMaxIdle(maxIdle int) error {
  40.     if maxIdle < 0 {
  41.         return fmt.Errorf("max tatal cannot < 0, input: %d", maxIdle)
  42.     }
  43.     b.maxIdle = maxIdle
  44.     return nil
  45. }
  47. func (b *ResourcePoolConfigBuilder) SetMaxTotal(maxTotal int) error {
  48.     if maxTotal < 0 {
  49.         return fmt.Errorf("max tatal cannot <=0, input: %d", maxTotal)
  50.     }
  51.     b.maxTotal = maxTotal
  52.     return nil
  53. }
  55. //Build Build
  56. func (b *ResourcePoolConfigBuilder) Build() (*ResourcePoolConfig, error) {
  57.     if b.name == "" {
  58.         return nil, fmt.Errorf("name can not be empty")
  59.     }
  61.     //设置默认值
  62.     if b.minIdle == 0 {
  63.         b.minIdle = defalutMinIdle
  64.     }
  66.     if b.maxIdle == 0 {
  67.         b.maxIdle = defaultMaxIdle
  68.     }
  70.     if b.maxTotal == 0 {
  71.         b.maxTotal = defaultMaxTotal
  72.     }
  74.     if b.maxTotal < b.maxIdle {
  75.         return nil, fmt.Errorf("max total(%d) cannot < max idle(%d)", b.maxTotal, b.maxIdle)
  76.     }
  78.     if b.minIdle > b.maxIdle {
  79.         return nil, fmt.Errorf("max idle(%d) cannot < min idle(%d)", b.maxIdle, b.minIdle)
  80.     }
  81.     return &ResourcePoolConfig{
  82.         name:     b.name,
  83.         maxTotal: b.maxTotal,
  84.         maxIdle:  b.maxIdle,
  85.         minIdle:  b.minIdle,
  86.     }, nil
  87. }