将对象列表保存到ORMLite数据库 [英] Save a list of objects to ORMLite database

问题描述

我正在寻找一种使用ORMLite将对象列表保存到数据库的方法并阅读这个问题：存储多个ArrayLists的最佳方法在ORMLite for ApplicationSettings

I am looking for a way to save a list of objects to the database with ORMLite and read upon this question: Best way to store several ArrayLists in ORMLite for ApplicationSettings

并且接受的答案对我有意义：

And the accepted answer makes sense to me:

public class YourClass {
    @GeneratedId
    private int id;

    @ForeignCollectionField
    private Collection<MyString> bunchOfStrings = new ArrayList<MyString>();
}

public class MyString{
     @DatabaseField(canBeNull = true, foreign = true)
     private YourClass yourClass;

     @DatabaseField
     private String text;
}

我唯一不理解的是这行私人收藏< MyString> bunchOfStrings = new ArrayList< MyString>（）。为什么我们将 ForeignCollectionField 保存为 Collection< MyString> 而不是 ArrayList< MyString> ？使用上面的 bunchOfStrings 对象时，我们是否总是需要将其强制转换为 ArrayList< MyString> ？

And the only thing that I don't understand is this line private Collection<MyString> bunchOfStrings = new ArrayList<MyString>(). Why do we save the ForeignCollectionField as Collection<MyString> instead of as ArrayList<MyString>? When working with the bunchOfStrings object above, do we always need to cast it to ArrayList<MyString>?

推荐答案

为什么我们将ForeignCollectionField保存为Collection
而不是ArrayList？

Why do we save the ForeignCollectionField as Collection instead of as ArrayList?

这是设计考虑因素，摘自 doc

That was design consideration, excerpt from doc

The field type of orders must be either ForeignCollection<T> or Collection<T> – no other
collections are supported because they are much heavier with many methods to support

使用上面的bunchOfStrings对象时，我们是否总是需要
将其强制转换为ArrayList

When working with the bunchOfStrings object above, do we always need to cast it to ArrayList

你不必初始化那个字段，Ormlite会这样做。因此，只有可用的方法是Collection或ForeignCollection

You dont have to initialize that field, Ormlite will do that. Hence, only available methods are ones present in Collection or ForeignCollection

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