如何确保我的bean构建正确？

Question

public class Pizza {
  private int size;
  private boolean cheese;
  private boolean pepperoni;
  private boolean bacon;

  private Pizza(Builder builder) {
    size = builder.size;
    cheese = builder.cheese;
    pepperoni = builder.pepperoni;
    bacon = builder.bacon;
  }

  public static class Builder {
    //required
    private final int size;

    //optional
    private boolean cheese = false;
    private boolean pepperoni = false;
    private boolean bacon = false;

    public Builder(int size) {
      this.size = size;
    }

    public Builder cheese(boolean value) {
      cheese = value;
      return this;
    }

    public Builder pepperoni(boolean value) {
      pepperoni = value;
      return this;
    }

    public Builder bacon(boolean value) {
      bacon = value;
      return this;
    }

    public Pizza build() {
      return new Pizza(this);
    }
  }
}

if(builder.size ==null){
    throw new BadPizzaException("Eh, what're ya doin'?"+
             " Pizza Size was not set correctly");
}else{
    size=builder.size;
}

所以这就是我试过的。有更好的方法吗？

Answer 1

确保设置所有变量的一个有趣的模式是使用Step Builder模式，其中第一个设置器只允许设置第二个，第二个设置器只允许设置第三个，以此类推。当您进入最后一步时，您可以构建类，到那时您将知道所有方法都已被调用。

那篇文章的简短摘录：

Panino solePanino = PaninoStepBuilder.newBuilder()
        .paninoCalled("sole panino")
        .breadType("baguette")
        .fish("sole")
        .addVegetable("tomato")
        .addVegetable("lettece")
        .noMoreVegetablesPlease()
        .build();

您必须从panino的名称开始，然后用bread类型跟踪它。