The type conversion principle and implementation of the MapStruct Core framework
MapStruct is an open source Java entity mapping framework, which provides convenient ways to convert between different types.Among them, the type conversion is one of the core functions of MapStruct, which supports seamless transmission and conversion of data.This article will introduce the principles and implementation of the type conversion in the MapStruct Core framework, as well as a programming code and configuration related to it.
1.1 Note processor
In the MapStruct Core framework, the type conversion is implemented through an annotation processor.The annotation processor is a tool for processing specific annotations when compiling, and generating related code according to the annotation.
1.2 maper interface
Each type conversion in MapStruct is completed by a maper interface.The mapper interface contains the method of converting the source type into a target type.
1.3 Configuration file
MapStruct provides a configuration file for details in the configuration type conversion process.Developers can configure different options as needed to meet specific business needs.
2. MapStruct type conversion implementation
2.1 Define the mapper interface
First, a mapper interface is needed, which contains a method that converts the source type into a target type.The name of the method is named based on the source and target types of the conversion.
@Mapper
public interface MyMapper {
MyMapper INSTANCE = Mappers.getMapper(MyMapper.class);
TargetDTO sourceToTarget(SourceDTO source);
}
2.2 Implementing the mapper interface
Next, you need to realize the mapper interface and provide specific type conversion logic.MapStruct generates the code of the implementation class during compilation.
public class MyMapperImpl implements MyMapper {
public TargetDTO sourceToTarget(SourceDTO source) {
// Writing the type conversion logic here
TargetDTO target = new TargetDTO();
target.setTargetProperty(source.getSourceProperty());
return target;
}
}
2.3 Configuration annotation processor
In order to enable the type conversion function of the MapStruct, the annotation processor is configured in the configuration file (such as Maven or Gradle).
Configuration example in Maven:
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.1</version>
<configuration>
<annotationProcessorPaths>
<path>
<groupId>org.mapstruct</groupId>
<artifactId>mapstruct-processor</artifactId>
<version>${mapstruct.version}</version>
</path>
</annotationProcessorPaths>
</configuration>
</plugin>
</plugins>
</build>
2.4 Type conversion
After completing the above steps, you can use the generated mapper interface for the type conversion operation.
SourceDTO source = new SourceDTO();
source.setSourceProperty("Hello, MapStruct!");
TargetDTO target = MyMapper.INSTANCE.sourceToTarget(source);
System.out.println(target.getTargetProperty()); // 输出：Hello, MapStruct!
The above code converts the attribute value of the source type `SourceDto` to the attribute value of the target type` targetdto`, and print out the conversion target attribute value.
3. Summary
The MapStruct Core framework provides a convenient type conversion function, and automatically generates type conversion through the annotation processor.Developers only need to define the mapper interface and specific type conversion logic to easily complete the type conversion operation.Through the right configuration, you can more flexibly meet the needs of different business scenarios.Although the above code is just a simple example, it can help readers have a preliminary understanding of the type conversion principle and implementation of the type conversion principle in the MapStruct Core framework.
