java-类内的吸气剂模式？

我在一个类中有一个字段,只能直接从getter访问.举个例子…

public class CustomerHelper {
  private final Integer customerId;
  private String customerName_ = null;

  public CustomerHelper(Integer customerId) {
    this.customerId = customerId;
  }

  public String getCustomerName() {
    if(customerName_ == null){
      // Get data from database.
      customerName_ = customerDatabase.readCustomerNameFromId(customerId);
      // Maybe do some additional post-processing, like casting to all uppercase.
      customerName_ = customerName_.toUpperCase();
    }
    return customerName_;
  }

  public String getFormattedCustomerInfo() {
    return String.format("%s: %s", customerId, getCustomerName());
  }
}

因此,即使在类本身内,诸如getFormattedCustomerInfo之类的函数也不能通过customerName_访问它.除了提供的getter函数之外,是否有一种方法可以强制类不直接访问字段？

解决方法:

似乎您正在尝试缓存数据库值,并希望防止访问尚未缓存的值.

如果是这样,则变量CustomerName_不应存在于CustomerHelper类中；缓存的值应该更靠近数据库存在.

方法customerDatabase.readCustomerNameFromId(customerId)应该首先查看缓存,如果缓存为空,则调用数据库并缓存结果.

实际上,customerName_成为高速缓存中的值：Map< Integer,String>缓存,其中键是customerId.

标签：private,getter,encapsulation,java
来源： https://codeday.me/bug/20191109/2011259.html