PrimaryKey

The PrimaryKey annotation indicates if an entity class's field is a primary key, meaning the value is unique to all other entity instances. It has a single attribute, autoincrement, which denotes if the primary key should automatically increment when a row is inserted, and it's enabled by default. If the annotation is missing from the class hierarchy, Infinitum will look for a field called mId or id to use as the primary key. If such a field is found, autoincrement will be enabled for it by default if it is of type int or long. If the primary key is assigned to a field which is not an int or long and autoincrement is enabled, a ModelConfigurationException will be thrown at runtime. Any field marked as a primary key will inherently be marked as persistent, regardless of any Persistence annotation that might be associated with it.

Currently, Infinitum does not support composite or compound keys. More specifically, only one PrimaryKey annotation may exist per model class. That said, a compound key can effectively be achieved by designating the "primary key" columns as unique using the Unique annotation.

PrimaryKey Example

As was hinted at earlier, Infinitum will search the entire class hierarchy for a PrimaryKey. If class AbstractBase has a field mPk marked as a primary key and class Foo extends AbstractBase, Foo's primary key is mPk. This notion is illustrated in the example below.

public abstract class AbstractBase {

    @PrimaryKey
    protected long mPk;

    public long getPk() {
        return mPk;
    }

    public void setPk(long pk) {
        mPk = pk;
    }

}

public class Foo extends AbstractBase {
    // Foo's primary key is mPk
}