Scooter Framework - Active Record Query Interface

Active Record query interface

Why static methods are used

An ActiveRecord instance represents a particular row in a database table. Thus to specify methods which operate on the whole table, it makes sense to use class-level methods which are static methods in a Java class.

Type	DB	Java	Example
static methods	table	Class	//retrieve all posts List posts = Post.findAll(); //retrieve 10 posts containing word Java List posts = Post.where("content like '%Java%'").limit(10).getRecords();
instance methods	row	instance	//reload a record: sync memory data with database data post.reload(); //save a record: store memory data to database post.save();

Type

Java

Example

static
methods

table

Class

//retrieve all posts
List posts = Post.findAll();

//retrieve 10 posts containing word Java
List posts = Post.where("content like '%Java%'").limit(10).getRecords();

instance
methods

row

instance

//reload a record: sync memory data with database data
post.reload();

//save a record: store memory data to database
post.save();

Chainable query methods

Scooter provides the following chainable query interface methods.

where(): specifies where clause in the SQL query
groupBy(): specifies group-by clause in the SQL query
having(): specifies having clause in the SQL query
orderBy(): specifies order-by clause in the SQL query
limit(): specifies number of records for each retrieval
offset(): specifies number of records to skip in a retrieval
page(): specifies the starting page in a pagination
includes(): specifies models to eager loaded. See below for more details.

Record retrieval methods

The following two methods stop the chain and fire query constructed to the database.

public List getRecords(): returns a list of records.
public ActiveRecord getRecord(): returns a specific record.

Notice that plural form of the method is used to return a list of result.

Examples

In the following example, we are going to use the Pet Clinic application as an example. We assume that we are going to use MySQL database.

The Pet Clinic application has the following models:

Owner
Pet
Visit
Type
Vet
Specialty

See the Pet Clinic application page for model details.

Here are some examples. Please notice that the singular form getRecord() returns an ActiveRecord instance, while the plural form getRecords() returns a list of ActiveRecord instances. This is what we have called Convention Over Configuration.

To retrieve a pet named Leo:

ActiveRecord Leo = Pet.where("name='Leo'").getRecord();