使用Foreign Collection Field创建表 [英] Create table with Foreign Collection Field

问题描述

我有这个抽象类：

DomainItem

DomainItem

abstract public class DomainItem {

    @DatabaseField(generatedId = true)
    protected long id;

    @ForeignCollectionField(eager = false)
        protected ForeignCollection<ContentItem> contentItens;

    //getters and setters
}

ContentItem：

ContentItem:

abstract public class ContentItem {

    @DatabaseField(generatedId = true)
    protected long id;

    @DatabaseField(foreign = true)
    protected DomainItem domainItem;


    @DatabaseField()
    protected String content;

    //getters and setters
}

这些（没有抽象）：

@DatabaseTable()
public class PhytoterapicItem extends DomainItem{

    public PhytoterapicItem(){

    }

}

PhytoterapicContent

PhytoterapicContent

@DatabaseTable(tableName = "phytoterapiccontent")
public class PhytoterapicContent extends ContentItem {

    @DatabaseField(canBeNull = false)
    private String defaultName;

    @DatabaseField(canBeNull = false)
    private String scientificName;

    //getters and setters
}

在我的DatabaseHelper中我尝试创建表：

In my DatabaseHelper I trying create the tables:

//DatabaseHelper
...
@Override
public void onCreate(SQLiteDatabase db, ConnectionSource connectionSource) {
    try {
        Log.i(TAG, "onCreate");
        TableUtils.createTable(connectionSource, PhytoterapicContent.class);
        Log.i(TAG, "Created table PhytoterapicContent");

        TableUtils.createTable(connectionSource, PhytoterapicItem.class);
        Log.i(TAG, "Created table PhytoterapicItem");
    catch{
       ...
    }

表PhytoterapicContent被建造。但是我得到了以下错误：

The table PhytoterapicContent is created. But I got the follow error:

java.sql.SQLException：外部集合类br.com.project.model.ContentItem for field' contentItens'column-name不包含类br.com.project.model.PhytoterapicItem的外部字段

java.sql.SQLException: Foreign collection class br.com.project.model.ContentItem for field 'contentItens' column-name does not contain a foreign field of class br.com.project.model.PhytoterapicItem

推荐答案

因此异常消息旨在帮助这里。引用删除的类名称：

So the exception message was designed to help here. To quote it with the class names removed:

外地集合类 ContentItem for field contentItens column-name不包含类的外部字段 PhytoterapicItem

Foreign collection class ContentItem for field contentItens column-name does not contain a foreign field of class PhytoterapicItem

看起来就是这样。每当你有 ForeignCollection 时，集合包含的类必须将一个外部字段返回给父类。

That looks to be the case. Whenever you have ForeignCollection, the class contained by the collection must have a foreign field back to the parent class.

在您的情况下， PhytoterapicItem 扩展 DomainItem 类，其中 ForeignCollection of ContentItem 对象。这意味着 ContentItem 必须具有 PhytoterapicItem 类型的外部字段。否则， ORMLite 如何知道表中的哪些 ContentItem 项目与特别是 PhytoterapicItem 。

In your case, PhytoterapicItem extends the DomainItem class which has a ForeignCollection of ContentItem objects. That means that ContentItem must have a foreign field of type PhytoterapicItem. Otherwise, how would ORMLite know which of the ContentItem items in the table are associated with a particular PhytoterapicItem.

帐户和<的例子code>订单 外国馆藏文档中的对象可以帮助您了解架构。每个帐户都有一个订单对象的外国集合。每当您查询帐户时，将执行单独的查询以查找与特定<对应的 Order 对象的集合code>帐户。这意味着每个订单必须有一个外国账户对象。

The example of Account and Order objects in the foreign collection documentation may help you with your schema. Each Account has a foreign collection of Order objects. Whenever you query for an Account a separate query is performed to find the collection of Order objects that correspond to a particular Account. That means that each Order has to have a foreign Account object.

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