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#3112 Document <THROW_EXCEPTION> in the reference guide

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José Carlos Campanero Ortiz 2023-04-13 21:48:13 +02:00 committed by GitHub
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63
documentation/src/main/asciidoc/chapter-8-mapping-values.asciidoc
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@ -65,7 +65,7 @@ public class OrderMapperImpl implements OrderMapper {
----
====
By default an error will be raised by MapStruct in case a constant of the source enum type does not have a corresponding constant with the same name in the target type and also is not mapped to another constant via `@ValueMapping`. This ensures that all constants are mapped in a safe and predictable manner. The generated
mapping method will throw an IllegalStateException if for some reason an unrecognized source value occurs.
mapping method will throw an `IllegalStateException` if for some reason an unrecognized source value occurs.
MapStruct also has a mechanism for mapping any remaining (unspecified) mappings to a default. This can be used only once in a set of value mappings and only applies to the source. It comes in two flavors: `<ANY_REMAINING>` and `<ANY_UNMAPPED>`. They cannot be used at the same time.
@ -75,14 +75,18 @@ MapStruct will *not* attempt such name based mapping for `<ANY_UNMAPPED>` and di
MapStruct is able to handle `null` sources and `null` targets by means of the `<NULL>` keyword.
In addition, the constant value `<THROW_EXCEPTION>` can be used for throwing an exception for particular value mappings. This value is only applicable to `ValueMapping#target()` and not `ValueMapping#source()` since MapStruct can't map from exceptions.
[TIP]
====
Constants for `<ANY_REMAINING>`, `<ANY_UNMAPPED>` and `<NULL>` are available in the `MappingConstants` class.
Constants for `<ANY_REMAINING>`, `<ANY_UNMAPPED>`, `<THROW_EXCEPTION>` and `<NULL>` are available in the `MappingConstants` class.
====
Finally `@InheritInverseConfiguration` and `@InheritConfiguration` can be used in combination with `@ValueMappings`. `<ANY_REMAINING>` and `<ANY_UNMAPPED>` will be ignored in that case.
.Enum mapping method, <NULL> and <ANY_REMAINING>
The following code snippets exemplify the use of the aforementioned constants.
.Enum mapping method, `<NULL>` and `<ANY_REMAINING>`
====
[source, java, linenums]
[subs="verbatim,attributes"]
@ -102,7 +106,7 @@ public interface SpecialOrderMapper {
----
====
.Enum mapping method result, <NULL> and <ANY_REMAINING>
.Enum mapping method result, `<NULL>` and `<ANY_REMAINING>`
====
[source, java, linenums]
[subs="verbatim,attributes"]
@ -137,6 +141,55 @@ public class SpecialOrderMapperImpl implements SpecialOrderMapper {
*Note:* MapStruct would have refrained from mapping the `RETAIL` and `B2B` when `<ANY_UNMAPPED>` was used instead of `<ANY_REMAINING>`.
.Enum mapping method with `<THROW_EXCEPTION>`
====
[source, java, linenums]
[subs="verbatim,attributes"]
----
@Mapper
public interface SpecialOrderMapper {
SpecialOrderMapper INSTANCE = Mappers.getMapper( SpecialOrderMapper.class );
@ValueMappings({
@ValueMapping( source = "STANDARD", target = "DEFAULT" ),
@ValueMapping( source = "C2C", target = MappingConstants.THROW_EXCEPTION )
})
ExternalOrderType orderTypeToExternalOrderType(OrderType orderType);
}
----
====
.Enum mapping method with `<THROW_EXCEPTION>` result
====
[source, java, linenums]
[subs="verbatim,attributes"]
----
// GENERATED CODE
public class SpecialOrderMapperImpl implements SpecialOrderMapper {
@Override
public ExternalOrderType orderTypeToExternalOrderType(OrderType orderType) {
if ( orderType == null ) {
return null;
}
ExternalOrderType externalOrderType;
switch ( orderType ) {
case STANDARD: externalOrderType = ExternalOrderType.DEFAULT;
break;
case C2C: throw new IllegalArgumentException( "Unexpected enum constant: " + orderType );
default: throw new IllegalArgumentException( "Unexpected enum constant: " + orderType );
}
return externalOrderType;
}
}
----
====
[WARNING]
====
The mapping of enum to enum via the `@Mapping` annotation is *DEPRECATED*. It will be removed from future versions of MapStruct. Please adapt existing enum mapping methods to make use of `@ValueMapping` instead.
@ -152,6 +205,7 @@ MapStruct supports enum to a String mapping along the same lines as is described
2. Similarity: `<ANY_UNMAPPED`> stops after handling defined mapping and proceeds to the switch/default clause value.
3. Difference: `<ANY_REMAINING>` will result in an error. It acts on the premise that there is name similarity between enum constants in source and target which does not make sense for a String type.
4. Difference: Given 1. and 3. there will never be unmapped values.
5. Similarity: `THROW_EXCEPTION` can be used for throwing an exception for particular enum values.
*`String` to enum*
@ -159,6 +213,7 @@ MapStruct supports enum to a String mapping along the same lines as is described
2. Similarity: `<ANY_UNMAPPED`> stops after handling defined mapping and proceeds to the switch/default clause value.
3. Similarity: `<ANY_REMAINING>` will create a mapping for each target enum constant and proceed to the switch/default clause value.
4. Difference: A switch/default value needs to be provided to have a determined outcome (enum has a limited set of values, `String` has unlimited options). Failing to specify `<ANY_REMAINING>` or `<ANY_UNMAPPED`> will result in a warning.
5. Similarity: `THROW_EXCEPTION` can be used for throwing an exception for any arbitrary `String` value.
=== Custom name transformation