创建型-建造者模式

/**
 * 
 * 建造者模式（应用场景：有必填字段，但参数过多，通过构造器创建会因为参数过多导致可读性差，属性之间有依赖关系，需要在创建对象之前进行前置参数字段校验）
 * name必填无默认值
 * maxTotal非必填默认值为8
 * maxIdle非必填默认值为8
 * minIdle非必填默认值为8
 * 
 * @author jiangwentao
 * @version :ResourcePoolConfig.java v1.0 2022/7/20 17:00 jiangwentao Exp $
 */
public class ResourcePoolConfig {
 
  private String name;
  private int maxTotal;
  private int maxIdle;
  private int minIdle;
 
  private ResourcePoolConfig (Builder builder) {
    this.name = builder.name;
    this.maxTotal = builder.maxTotal;
    this.maxIdle = builder.maxIdle;
    this.minIdle = builder.minIdle;
  }
 
  public String getName() {
    return name;
  }
 
  public int getMaxTotal() {
    return maxTotal;
  }
 
  public int getMaxIdle() {
    return maxIdle;
  }
 
  public int getMinIdle() {
    return minIdle;
  }
 
  @Override
  public String toString() {
    return "ResourcePoolConfig{" +
        "name='" + name + '\'' +
        ", maxTotal=" + maxTotal +
        ", maxIdle=" + maxIdle +
        ", minIdle=" + minIdle +
        '}';
  }
 
  public static class Builder {
 
    private static final int MAX_TOTAL = 8;
    private static final int MAX_IDLE = 8;
    private static final int MIN_IDLE = 0;
 
    private String name;
    private int maxTotal = MAX_TOTAL;
    private int maxIdle = MAX_IDLE;
    private int minIdle = MIN_IDLE;
 
    public ResourcePoolConfig build() {
      if (this.name == null || name == "") {
        throw new IllegalArgumentException("name属性必填");
      }
      if (this.minIdle > this.maxIdle) {
        throw new IllegalArgumentException("配置参数不合法");
      }
      return new ResourcePoolConfig(this);
    }
 
    public Builder name(String name) {
      this.name = name;
      return this;
    }
    public Builder maxTotal(int maxTotal) {
      this.maxTotal = maxTotal;
      return this;
    }
    public Builder maxIdle(int maxIdle) {
      this.maxIdle = maxIdle;
      return this;
    }
    public Builder minIdle(int minIdle) {
      this.minIdle = minIdle;
      return this;
    }
  }
 
 
  //示例
  public static void main(String[] args) {
    ResourcePoolConfig config = new Builder()
        .name("redis")
        .maxIdle(10)
        .minIdle(3)
        .build();
    ResourcePoolConfig mysql = new ResourcePoolConfig.Builder().name("mysql").maxTotal(15).maxIdle(5).minIdle(20).build();
    System.out.println(config);
    System.out.println(mysql);
  }
}