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68 lines
2.1 KiB
Plaintext
68 lines
2.1 KiB
Plaintext
[[mapping-streams]]
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== Mapping Streams
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The mapping of `java.util.Stream` is done in a similar way as the mapping of collection types, i.e. by defining mapping
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methods with the required source and target types in a mapper interface.
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The generated code will contain the creation of a `Stream` from the provided `Iterable`/array or will collect the
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provided `Stream` into an `Iterable`/array. If a mapping method or an implicit conversion for the source and target
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element types exists, then this conversion will be done in `Stream#map()`. The following shows an example:
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.Mapper with stream mapping methods
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====
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[source, java, linenums]
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[subs="verbatim,attributes"]
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----
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@Mapper
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public interface CarMapper {
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Set<String> integerStreamToStringSet(Stream<Integer> integers);
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List<CarDto> carsToCarDtos(Stream<Car> cars);
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CarDto carToCarDto(Car car);
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}
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----
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====
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The generated implementation of the `integerStreamToStringSet()` performs the conversion from `Integer` to `String` for
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each element, while the generated `carsToCarDtos()` method invokes the `carToCarDto()` method for each contained
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element as shown in the following:
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.Generated stream mapping methods
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====
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[source, java, linenums]
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[subs="verbatim,attributes"]
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----
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//GENERATED CODE
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@Override
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public Set<String> integerStreamToStringSet(Stream<Integer> integers) {
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if ( integers == null ) {
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return null;
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}
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return integers.map( integer -> String.valueOf( integer ) )
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.collect( Collectors.toCollection( LinkedHashSet<String>::new ) );
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}
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@Override
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public List<CarDto> carsToCarDtos(Stream<Car> cars) {
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if ( cars == null ) {
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return null;
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}
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return cars.map( car -> carToCarDto( car ) )
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.collect( Collectors.toCollection( ArrayList<CarDto>::new ) );
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}
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----
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====
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[WARNING]
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====
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If a mapping from a `Stream` to an `Iterable` or an array is performed, then the passed `Stream` will be consumed
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and it will no longer be possible to consume it.
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====
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The same implementation types as in <<implementation-types-for-collection-mappings>> are used for the creation of the
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collection when doing `Stream` to `Iterable` mapping.
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