The mapping method of the MapStruct Core framework generates an analysis of the principle (Analysis of MAPPING METHOD Generation Principles in Mapstruct Core Framework)

MapStruct is a Java object mapping framework that simplifies the mapping process between objects by using annotations and code generation.The mapping method of the MapStruct Core framework generates the mechanism that automatically generates the mapping method when compiling. In Mapstruct, we can use @Mapper annotations to mark an interface or abstract class.The annotation will tell MapStruct to generate the implementation code of the mapping method during compilation.The mapping method is a method used to map the attribute value of the source object to the target object. In order to generate a mapping method, MapStruct will automatically scan the class marked by the @Mapper annotation, and generate the corresponding mapping code according to the mapping rules defined in the class.These mapping rules can be specified in various ways, including annotations, naming agreement, and custom configuration. MapStruct uses Java's reflection mechanism to analyze the attributes of the source objects and target objects.It determines the mapping relationship between attributes based on the naming and type information of the attribute.When the naming and type of two attributes are the same, MapStruct automatically generates a simple direct mapping code.If the naming of attributes is different or the type of attributes needs to be converted, we can use @Mapping annotations to specify the mapping rules. In addition to direct attribute mapping, MapStruct also supports some more complex mapping methods, such as set mapping, associated relationship mapping, and custom conversion functions.We can specify the mapping rules under the annotations of these special cases using annotations such as@iTerableMapping,@beanmapping, and @mapping. MapStruct also supports custom conversion functions to process some special mapping logic.We can define ourselves in the mapping interface and use @mapping and @mappings annotations to specify the mapping rules of the conversion function.MapStructs will generate these custom methods with the automatic mapping method into the final mapping implementation class. When using Mapstruct, we need to configure the corresponding plug -in in the project construction tool to generate mapping code during compilation.For example, when using Maven to build a project, we can add MapStruct-Processor dependencies, and configure the plug-in in the pom.xml file to generate code generating operations. To sum up, the mapping method of the MapStruct Core framework is based on the implementation code of the mapping method by using the annotation and code generating method when compiling.It can automatically analyze the attribute mapping relationship between objects according to the given mapping rules and generate corresponding mapping code.This automated mapping method generation mechanism can greatly simplify the mapping process between Java objects and improve development efficiency.