what is org.mapstruct package and how to use it

org.mapstruct is a Java-based code generation library that simplifies the implementation of mappings between Java bean types, commonly used in the context of object-to-object mapping (O2O). It generates mapping code at compile time, reducing the need for handwritten mapping code and providing type-safe mappings.

Here’s a brief overview of org.mapstruct and how to use it:

Mapping Annotations: MapStruct uses annotations to define mappings between source and target types. Some of the commonly used annotations include @Mapper, @Mapping, @Mappings, @InheritInverseConfiguration, and @MappingTarget.
Interface-Based Approach: With MapStruct, you define mapping interfaces containing abstract methods for mapping specific source and target types. The implementation for these mappings is generated automatically at compile time.
Code Generation: MapStruct generates mapping implementations by analyzing your mapping interfaces during the build process. It generates efficient, optimized code based on the specified mappings, resulting in faster runtime performance compared to reflection-based mapping solutions.
Custom Mappings: MapStruct allows you to define custom mappings using methods in the mapping interface. You can also provide custom mapping logic using decorators or helper methods.
Integration with Build Tools: MapStruct seamlessly integrates with popular build tools such as Maven and Gradle. You need to include the MapStruct dependency in your build configuration, and the mapping implementations will be generated automatically during the build process.

Here’s a simple example to illustrate how to use MapStruct:

Suppose you have two Java bean classes, SourceBean and TargetBean, with similar properties. You want to map instances of SourceBean to TargetBean.

// SourceBean.java
public class SourceBean {
    private String name;
    private int age;

    // Getters and setters
}

// TargetBean.java
public class TargetBean {
    private String name;
    private int age;

    // Getters and setters
}

// SourceBean.java

public class SourceBean {

private String name;

private int age;

// Getters and setters

}

// TargetBean.java

public class TargetBean {

private String name;

private int age;

// Getters and setters

}

To define the mapping between these two classes using MapStruct, you create a mapping interface:

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;

@Mapper
public interface BeanMapper {
    @Mapping(source = "name", target = "name")
    @Mapping(source = "age", target = "age")
    TargetBean mapToTargetBean(SourceBean sourceBean);
}

import org.mapstruct.Mapper;

import org.mapstruct.Mapping;

@Mapper

public interface BeanMapper {

@Mapping(source = "name", target = "name")

@Mapping(source = "age", target = "age")

TargetBean mapToTargetBean(SourceBean sourceBean);

}

In this mapping interface:

The @Mapper annotation marks the interface as a mapper interface.
The mapToTargetBean method defines the mapping from SourceBean to TargetBean. The @Mapping annotation specifies the source and target properties to map.

During the build process, MapStruct generates the implementation of the BeanMapper interface, providing efficient mapping code based on the specified mappings. You can then use the generated mapper implementation to perform object mappings in your application.

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what is org.mapstruct package and how to use it