The technical principles of the MapStruct Core framework in the Java class library

MapStruct is a Java class library for type mapping between different Java Bean.It can automatically perform these mapping according to the code generated during compilation, and provides simple, type security and maintainable mapping code. The core principle of the MapStruct framework is based on the Annotion Processor.When compiling, the MapStruct scanning marked the interface of the mapping relationship, and then generated the corresponding mapping implementation class based on these interfaces.This method of generating code through the annotation processor can provide better performance and flexibility. MapStruct's use is very simple.First of all, you need to add a MapStruct dependency item in the construction file of the project.Next, create an interface between the two Java Bean that need to be mapping, and use the @Mapper annotation to mark the interface.In the interface, use the @Mapping annotation to specify the mapping relationship between different attributes. For example, assuming that there are two Java Bean, Book and Bookdto, they have the same attribute names and types.We can create an interface called BookMapper to define the mapping relationship between them: @Mapper public interface BookMapper { BookDto bookToBookDto(Book book); } Mapstruct will then generate the corresponding implementation class based on this interface.The generated implementation class will include code to the BookDto attribute mapping. If the attribute name is different, you can use the source and target properties in the @Mapping annotation to clearly specify the mapping relationship between different attributes.You can also use the @Mappings annotation to specify the mapping relationship of multiple attributes. In addition to annotations, MapStruct also provides other functions, such as nested mapping, set mapping and format conversion.By providing a custom converter or using a built -in converter, more complex and customized mapping logic can be achieved. To sum up, MapStruct is a powerful Java mapping framework. It uses an annotation processor to generate mapping code during compilation, providing high -performance, flexible and easy -to -maintain mapping functions.Regardless of the simple or complex mapping relationship, MapStruct can help developers easily conduct the type conversion between Java Bean.