mapstruct更新现有实体忽略null空值

用JPA在做更新的时候经常要判断不是null的字段进行set很麻烦。

例如：目标实体 A.a1=1,A.a2=2  源实体 B.a1=null,B.a2=1。要实现转换后 A.a1=1,A.a2=1。

1、class上加注解。这个注解参数好像1.3版本以后才开始有的。

@Mapper(nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE)

2、必须用更新现有的Bean的方法。

void updateAFromB(B b, @MappingTarget A a);

mapstruct 1.3.1版文档原文

10.6. Controlling mapping result for 'null' properties in bean mappings (update mapping methods only).

MapStruct offers control over the property to set in an @MappingTarget annotated target bean when the source property equals null or the presence check method results in 'absent'.

By default the target property will be set to null.

However:

1. By specifying nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.SET_TO_DEFAULTon @Mapping, @BeanMapping, @Mapper or @MappingConfig, the mapping result can be altered to return defaultvalues. For List MapStruct generates an ArrayList, for Map a HashMap, for arrays an empty array, for String"" and for primitive / boxed types a representation of false or 0. For all other objects an new instance is created. Please note that a default constructor is required. If not available, use the @Mapping#defaultValue.

2. By specifying nullValuePropertyMappingStrategy = NullValuePropertyMappingStrategy.IGNORE on @Mapping, @BeanMapping, @Mapper or @MappingConfig, the mapping result will be equal to the original value of the @MappingTarget annotated target.

The strategy works in a hierarchical fashion. Setting Mapping#nullValuePropertyMappingStrategy on mapping level will override nullValuePropertyMappingStrategy on mapping method level will override @Mapper#nullValuePropertyMappingStrategy, and @Mapper#nullValuePropertyMappingStrategy will override @MappingConfig#nullValuePropertyMappingStrategy.