Getting Data from Multiple tables in Liferay 6.0.6 - liferay-6

Question

i'm trying to get data from multiple tables in liferay 6.0.6 using custom sql, but for now i'm just able to display data from one table.does any one know how to do that.thanks
UPDATE:
i did found this link http://www.liferaysavvy.com/2013/02/getting-data-from-multiple-tables-in.html but for me it's not working because it gives an error BeanLocator is null,and it seems that it's a bug in liferay 6.0.6

Answer 1

The following technique also works with liferay 6.2-ga1.
We will consider we are in the portlet project fooproject.
Let's say you have two tables: article, and author. Here are the entities in your service.xml :
<entity name="Article" local-service="true">
<column name="id_article" type="long" primary="true" />
<column name="id_author" type="long" />
<column name="title" type="String" />
<column name="content" type="String" />
<column name="writing_date" type="Date" />
</entity>
<entity name="Author" local-service="true">
<column name="id_author" type="long" primary="true" />
<column name="full_name" type="String" />
</entity>
At that point run the service builder to generate the persistence and service layers.
You have to use custom SQL queries as described by Liferay's Documentation to fetch info from multiple databases.
Here is the code of your fooproject-portlet/src/main/ressources/default.xml :
<?xml version="1.0"?>
<custom-sql>
<sql file="custom-sql/full_article.xml" />
</custom-sql>
And the custom request in the fooproject-portlet/src/main/ressources/full_article.xml:
<?xml version="1.0"?>
<custom-sql>
<sql
id="com.myCompany.fooproject.service.persistence.ArticleFinder.findByAuthor">
<![CDATA[
SELECT
Author.full_name AS author_name
Article.title AS article_title,
Article.content AS article_content
Article.writing_date AS writing_date
FROM
fooproject_Article AS Article
INNER JOIN
fooproject_Author AS Author
ON Article.id_author=Author.id_author
WHERE
author_name LIKE ?
]]>
</sql>
</custom-sql>
As you can see, we want to fetch author's name, article's title, article's content and article's date.
So let's allow the service builder to generate a bean that can store all these informations. How ? By adding it to the service.xml ! Be careful: the fields of the bean and the fields' name returned by the query must match.
<entity name="ArticleBean">
<column name="author_name" type="String" primary="true" />
<column name="article_title" type="String" primary="true" />
<column name="article_content" type="String" />
<column name="article_date" type="Date" />
</entity>
Note: defining which field is primary here does not really matter as there will never be anything in the ArticleBean table. It is all about not having exceptions thrown by the service builder while generating the Bean.
The finder method must be implemented then. To do so, create the class com.myCompany.fooproject.service.persistence.impl.ArticleFinderImpl. Populate it with the following content:
public class ArticleFinderImpl extends BasePersistenceImpl<Article> {
}
Use the correct import statements and run the service builder. Let's make that class implement the interface generated by the service builder:
public class ArticleFinderImpl extends BasePersistenceImpl<Article> implements ArticleFinder {
}
And populate it with the actual finder implementation:
public class ArticleFinderImpl extends BasePersistenceImpl<Article> implements ArticleFinder {
// Query id according to liferay's query naming convention
public static final String FIND_BY_AUTHOR = ArticleFinder.class.getName() + ".findByAuthor";
public List<Article> findByAuthor(String author) {
Session session = null;
try {
session = openSession();
// Retrieve query
String sql = CustomSQLUtil.get(FIND_BY_AUTHOR);
SQLQuery q = session.createSQLQuery(sql);
q.setCacheable(false);
// Set the expected output type
q.addEntity("StaffBean", StaffBeanImpl.class);
// Binding arguments to query
QueryPos qpos = QueryPos.getInstance(q);
qpos.add(author);
// Fetching all elements and returning them as a list
return (List<StaffBean>) QueryUtil.list(q, getDialect(), QueryUtil.ALL_POS, QueryUtil.ALL_POS);
} catch(Exception e) {
e.printStackTrace();
} finally {
closeSession(session);
}
return null;
}
}
You can then call this method from your ArticleServiceImpl, whether it is to make a local or a remote API.
Note: it is hack. This is not a perfectly clean way to retrieve data, but it is the "less bad" you can do if you want to use Liferay's Service Builder.