com.datastax.oss.driver.api.mapper.annotations

Annotation Type QueryProvider

@Target(value=METHOD)
 @Retention(value=RUNTIME)
public @interface QueryProvider

Annotates a Dao method that delegates the execution of the query to a user-provided class.

Example:

 @Dao
 public interface SensorDao {
   @QueryProvider(providerClass = FindSliceProvider.class, entityHelpers = SensorReading.class)
   PagingIterable<SensorReading> findSlice(int id, Integer month, Integer day);
 }

 public class FindSliceProvider {
   public FindSliceProvider(
       MapperContext context, EntityHelper<SensorReading> sensorReadingHelper) {
     ...
   }

   public PagingIterable<SensorReading> findSlice(int id, Integer month, Integer day) {
     ... // implement the query logic here
   }
 }
 

Use this for requests that can't be expressed as static query strings, for example if some clauses are added dynamically depending on the values of some parameters.

The parameters and return type are completely free-form, as long as they match those of the provider method.

See Also:

MapperBuilder.withCustomState(Object, Object)

Required Element Summary

Required Elements

Modifier and Type	Required Element and Description
Class<?>	providerClass The class that will execute the query.

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
Class<?>[]	entityHelpers A list of entities for which EntityHelper instances should be injected into the provider class's constructor (in addition to the mapper context).
String	providerMethod The method to invoke on the provider class.

Element Detail

providerClass

public abstract Class<?> providerClass

The class that will execute the query.

The mapper will create an instance of this class for each DAO instance. It must expose a constructor that is accessible from the DAO interface's package, and takes the following parameter types:

• MapperContext.
• zero or more EntityHelpers, as defined by entityHelpers().

It must also expose a method that will be invoked each time the DAO method is called, see providerMethod().

providerMethod

public abstract String providerMethod

The method to invoke on the provider class.

It must be accessible from the DAO interface's package, and have the same parameters and return type as the annotated DAO method.

This is optional; if not provided, it defaults to the name of the annotated DAO method.

Default:

""

entityHelpers

public abstract Class<?>[] entityHelpers

A list of entities for which EntityHelper instances should be injected into the provider class's constructor (in addition to the mapper context).

For example, if entityHelpers = {Product.class, Dimensions.class}, your provider class must expose a constructor that takes the parameter types(MapperContext, EntityHelper<Product>, EntityHelper<Dimensions>).

All provided classes must be annotated with Entity. Otherwise, the mapper will issue a compile-time error.

Default:

{}