Summary of implementation methods of Java object conversion

Various implementation methods of Java object conversion

In Java development, object conversion is a common requirement. Especially when passing data between different levels, it is often necessary to convert one object to another. While JSON serialization/deserialization is a common approach, it may not be the best choice in some scenarios. This article will summarize several common Java object conversion implementation methods and provide selection suggestions.

Technology/Tools	advantage	shortcoming	Applicable scenarios	Performance evaluation	Learning curve
Manual mapping	High performance, simple and clear	Poor maintainability, redundant code	Simple object conversion, performance key scenarios	⭐⭐⭐⭐⭐	⭐
Builder mode	Good readability, easy to expand	To increase the amount of code, you need to understand the design pattern	There are many object properties, and flexibly configured	⭐⭐⭐⭐	⭐⭐
Tool class auxiliary mapping	Enhance reusability and centralized management	May cause tool expansion and require manual maintenance	Use the same mapping logic in many places	⭐⭐⭐⭐	⭐⭐
MapStruct	Excellent performance, type-safe	Need to learn and configure, additional dependencies	Complex object mapping, high performance requirements	⭐⭐⭐⭐⭐	⭐⭐⭐
Spring BeanUtils	Quick development, easy to use	Low performance and limited flexibility	Rapid prototyping, simple object conversion	⭐⭐⭐	⭐
Dozer Framework	Powerful, supporting complex mapping	Low performance, high learning cost	Flexible mapping configuration, already used by Dozer	⭐⭐	⭐⭐⭐
ModelMapper	Intelligent mapping, easy to use	Medium performance, manual adjustment may be required	Structurally similar objects, quickly implement conversion	⭐⭐⭐	⭐⭐
Reflection mechanism	Highly flexible, no additional dependencies required	Poor performance, high complexity	Special scenarios that require dynamic processing of attributes	⭐	⭐⭐⭐

1. Manual Mapping

Manual mapping is the most direct way to complete object conversion by manually setting each property. This method is simple and clear, and is suitable for objects with fewer attributes.

TargetObject target = new TargetObject();
(());
(());
// ...

2. Builder mode

The Builder pattern provides a streaming API to create objects, enhancing the readability and maintainability of the code.

TargetObject target = ()
    .propertyA(())
    .propertyB(())
    .build();

3. Tool class auxiliary mapping

Encapsulate object transformation logic by creating special tool classes, enhancing code reusability.

public class ObjectMapper {
    public static TargetObject map(SourceObject source) {
        TargetObject target = new TargetObject();
        (());
        (());
        return target;
    }
}

4. Use MapStruct Framework

MapStruct is a code generator that generates type-safe mapping code at compile time, suitable for complex object mapping.

@Mapper
public interface ObjectMapper {
    ObjectMapper INSTANCE = ();
    @Mapping(source = "propertyA", target = "propertyA")
    @Mapping(source = "propertyB", target = "propertyB")
    TargetObject map(SourceObject source);
}

5. Use Spring BeanUtils/CopyProperties

Spring provides BeanUtils tool class, which can quickly copy object attributes, suitable for rapid development scenarios.

TargetObject target = new TargetObject();
(source, target);

6. Using Dozer Framework

Dozer is an open source Java Bean to Java Bean mapper that supports complex mapping requirements.

Mapper mapper = new DozerBeanMapper();
TargetObject target = (source, );

7. Use ModelMapper

ModelMapper is an intelligent object mapping tool suitable for automatic mapping of complex objects.

ModelMapper modelMapper = new ModelMapper();
TargetObject target = (source, );

8. Use reflection mechanism

The Java reflection mechanism can be used to dynamically implement object conversion, which is flexible but has poor performance.

Field[] fields = ().getDeclaredFields();
for (Field field : fields) {
    (true);
    Object value = (source);
    Field targetField = ().getDeclaredField(());
    (true);
    (target, value);
}

Select a suggestion

Simple scene: Manual mapping or Builder mode.
Complex scenes: Use MapStruct or ModelMapper.
Rapid development：Spring BeanUtils。
High performance requirements: Manual mapping or MapStruct.
High flexibility requirements: Reflection mechanism.

Performances are sorted from high to low as follows:

Manual Mapping > MapStruct > ModelMapper > Dozer > BeanUtils > Reflection > JSON Serialization

Maintainability comparison

Maintainability is sorted from high to low as follows:

MapStruct > Manual Mapping > ModelMapper > Dozer > BeanUtils > Reflection > JSON Serialization

Recommendations for use

For simple DTO conversions, manual mapping or Builder mode is recommended.
For complex object mappings, MapStruct is recommended.
For fast development scenarios, Spring BeanUtils can be used.
Try to avoid using JSON serialization/deserialization for object conversion.

Select a suggestion

Small project or simple object: Manual mapping or Spring BeanUtils.
Large project or complex object conversion：MapStruct。
Need to produce results quickly: Spring BeanUtils or ModelMapper.
Highly flexible requirements: Reflection mechanism (used with caution).

Each method has its own applicable scenarios, and developers need to choose the most appropriate implementation method according to specific needs. Hope this article helps you make better choices in your project.

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