如何进行不同类型的对象状态验证

Question

我需要从一个或两个不同的数据源向调用者提供记录，并且在指定的日期范围或年份范围内。

我的困境是我应该使用重载方法还是具有状态验证逻辑的 Request 对象。

所以要么：

public List<Record> getRecords (Date fromDate, Date toDate, boolean dataSourceARequired, boolean dataSourceBRequired)

public List<Record> getRecords (int fromYear, int toYear, boolean dataSourceARequired, boolean dataSourceBRequired)

或类似这样的内容：

public List<Record> getRecords(Request request)

请求看起来像这样：

public class Request{

private final Date fromDate;
private final Date toDate;
private final int fromYear;
private final int toYear;
private final boolean dataSourceARequired;
private final boolean dataSourceBRequired;



public Request(Date fromDate, Date toDate, boolean dataSourceARequired, boolean dataSourceBRequired){

    if (fromDate == null) {
        throw new IllegalArgumentException("fromDate can't be null");
        }
     if (toDate == null) {
        throw new IllegalArgumentException("toDate can't be null");
        }
    if (!dataSourceARequired && !dataSourceBRequired){
        throw new IllegalStateException ("No data source requested");
        }
     if (fromDate.after(toDate)){
         throw new IllegalStateException ("startDate can't be after    endDate");
        }

     this.fromDate = fromDate;
     this.toDate = toDate;
     this.dataSourceARequired = dataSourceARequired;
     this.dataSourceBRequired = dataSourceBRequired;
     this.fromYear = -1;
     this.toYear = -1;

}


 public Request(int fromYear, int toYear, boolean dataSourceARequired, boolean dataSourceBRequired){

    if (fromYear > toYear) {
        throw new IllegalArgumentException("fromYear can't be greater than toYear");
        }
    if (!dataSourceARequired && !dataSourceBRequired){
        throw new IllegalStateException ("No data source requested");
        }

     this.dataSourceARequired = dataSourceARequired;
     this.dataSourceBRequired = dataSourceBRequired;
     this.fromYear = fromYear;
     this.toYear = toYear;
     this.fromDate = null;
     this.toDate = null;

}

}

或者有别的方法吗？

Answer 1

你不应该使用第二种情况，因为它违反了每个 class 应该有一个 well-defined 责任的规则。在这里，您的 class 负责详细日期范围和年份日期范围。如果您添加更多条件，这个 class 会变得很可怕。

所以你可以使用第一种方法，而且很多人都这样做。

如果您想创建 classes 来封装请求数据，您应该创建一个基础抽象 class 或接口，然后为每种类型创建不同类型的请求子class您可以使用的标准。例如：

public interface Request {
    execute();
}

public class YearRangeRequest implements Request {
    int fromYear;
    int toYear;

    public execute();

... etc

Answer 2

另一种解决方案：使用带有两个构造函数的 DateRange class：

public class DateRange {
    final Date start;
    final Date end;

    public DateRange(Date start, Date end) {
        this.start = start;
        this.end = end;
    }

    public DateRange(int startYear, int endYear) {
        this(yearBegining(startYear), yearBegining(endYear));
    }

    ...
}

如何进行不同类型的对象状态验证

How to do different types of object state validation

java

validation

design-patterns

object-state