Liferay及其中的关系

问题描述

我有一个Portlet，可以添加/更新/删除书籍并添加作者.此外，当您尝试添加图书时，可以选择现有的作者.

I have a portlet, which can add/update/delete books and add authors. Moreover, you can choose existing authors when you try to add book.

现在我需要在作者"表中显示每个作者写了多少本书.我该怎么做?我是liferay的新手，我什至不知道.

And now I need to show how many books were written by each author in "author" table. How can I do it? Im a newbie in liferay and I even have no idea.

这是我的service.xml

It's my service.xml

<entity name="Book" local-service="true" remote-service="true"  cache-enabled="false">

    <column name="bookId" type="long" primary="true" />
    <column name="bookName" type="String" />
    <column name="bookDescription" type="String" />
    <column name="authors" type="Collection" entity="Author" mapping-table="Books_Authors" />
    <finder return-type="Collection" name="bookName">
        <finder-column name="bookName"></finder-column>
    </finder>

</entity>

<entity name="Author" local-service="true" remote-service="true" cache-enabled="false">
    <column name="authorId" type="long" primary="true" />
    <column name="authorName" type="String" />
    <column name="books" type="Collection" entity="Book" mapping-table="Books_Authors" />

</entity>

推荐答案

Service Builder是您的朋友.

Service Builder is your friend.

您只需要在service.xml中的书本实体中添加一个查找器.如果您的实体有一个名为author:

You just need to add a finder in your book entity in service.xml. If your entity has a field named author:

<finder name="Author" return-type="Collection">
    <finder-column name="author" />
</finder>

执行构建服务将生成方法BookUtil.findByAuthor()和BookUtil.countByAuthor().

The execution of build-service will generate the methods BookUtil.findByAuthor() and BookUtil.countByAuthor().

您现在可以在BookLocalServiceImpl中实现相应的方法，调用先前的方法，然后在再次运行build-serivce之后，这些方法在您的Util类中可用.像

You can implement now the corresponding methods in BookLocalServiceImpl, calling the previous, and after another run of build-serivce, they're available in your Util class. Something like

public List<Book> getByAuthor(String author) {
    return getPersistence().findByAuthor(author);
}

public int countByAuthor(String author) {
    return getPersistence().countByAuthor(author);
}

上次致电构建服务后，您可以从BookLocalServiceUtil致电他们.

After the last call to build-service you can call them from your BookLocalServiceUtil.

如果只想计数，请不要检索所有集合.如果记录很多，那是个坏主意.改为调用计数.

If you just want the count, don't retrieve all the collection. If there are many records, it's a bad idea. Invoke the count instead.

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