Detailed explanation of the use of common object mapping tools in Java

1. Brief description

Object mapping is an important part of Java development. Especially when processing data conversion, it is necessary to convert data from one structure into data from another structure (such as between DTO and Entity). In this blog, we will understand and parse several commonly used object mapping tools and provide detailed examples.

2. Overview of Object Mapping Tools

Common object mapping tools include:

• MapStruct: A fast tool based on source code generator to realize high-performance object conversion.
• ModelMapper: A tool that automatically maps complete disposal between objects.
• Dozer: A pressure object conversion tool that supports depth conversion and custom rules.
• BeanUtils: Basic tools provided by Spring, suitable for handling simple object mapping.

2.1 MapStruct

MapStruct is an object mapping tool based on source code generation, which is high performance, convenient and implementable. It generates code at compile time and needs to implement mappings in accordance with standardized ways.

• Define DTO and Entity:

public class UserDTO {
    private String name;
    private int age;
    // getter、setter
}

public class UserEntity {
    private String name;
    private int age;
    // getter、setter
}

• Define the mapping controller:

@Mapper
public interface UserMapper {
    UserMapper INSTANCE = ();

    UserDTO entityToDto(UserEntity entity);

    UserEntity dtoToEntity(UserDTO dto);
}

• Using mappers:

public class Main {
    public static void main(String[] args) {
        UserEntity entity = new UserEntity();
        ("John");
        (30);

        UserDTO dto = (entity);
        (()); // John
        (());  // 30
    }
}

2.2 ModelMapper

ModelMapper is an automatic formatting tool suitable for handling complex object mappings.

import ;

public class Main {
    public static void main(String[] args) {
        ModelMapper modelMapper = new ModelMapper();

        UserEntity entity = new UserEntity();
        ("Alice");
        (25);

        UserDTO dto = (entity, );
        (()); // Alice
        (());  // 25
    }
}

2.3 Dozer

Dozer is a stressful Java Bean mapping tool that supports complex scenarios such as depth property conversion.

• Install and configure Dozer:

Add dependencies in Maven:

<dependency>
    <groupId></groupId>
    <artifactId>dozer</artifactId>
    <version>6.5.0</version>
</dependency>

• Use code:

import ;

public class Main {
    public static void main(String[] args) {
        DozerBeanMapper mapper = new DozerBeanMapper();

        UserEntity entity = new UserEntity();
        ("Bob");
        (28);

        UserDTO dto = (entity, );
        (()); // Bob
        (());  // 28
    }
}

2.4 BeanUtils

BeanUtils is a tool provided by Spring Framework to implement simple object mapping, suitable for scenarios with the same attribute name and simple data structure.

• Add dependencies:

If Spring Framework has been introduced, no additional dependencies are required. Otherwise, the following dependencies can be added:

<dependency>
    <groupId></groupId>
    <artifactId>spring-beans</artifactId>
    <version>5.3.26</version>
</dependency>

• Use code:

import ;

public class Main {
    public static void main(String[] args) {
        UserEntity entity = new UserEntity();
        ("Charlie");
        (35);

        UserDTO dto = new UserDTO();
        (entity, dto);

        (()); // Charlie
        (());  // 35
    }
}

Notes:

• BeanUtils does not support deep copying, only one layer of attributes can be copied.
• The attribute name must match exactly, otherwise it will be ignored.
• It is recommended to use MapStruct or ModelMapper for simple scenarios.

3. Summary

In Java development, different object mapping tools are suitable for different scenarios:

• MapStruct: Suitable for high performance and type safety requirements, recommended for complex mapping.
• ModelMapper: Suitable for scenarios with high automation and need to be quickly started, but the performance is slightly inferior.
• Dozer: Supports complex deep mapping, suitable for scenarios where advanced customization is required.
• BeanUtils: Suitable for simple object attribute copy scenarios, but does not support deep copying.

Choosing the right tool requires weighing the specific needs and scenarios of the project. I hope that the analysis and examples of this article can help you better understand and apply these tools!

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