Java Object Copy Tools Compared: BeanUtils, BeanCopier, Hutool, MapStruct & Dozer

In daily development we often need to copy or convert objects such as DTO, PO, VO, DO, TO, BO, etc., and the frequency of these operations grows with business complexity.

Common Bean Copy Tools

Apache BeanUtils

Spring BeanUtils

cglib BeanCopier

Hutool BeanUtil

MapStruct

Dozer

1. Apache BeanUtils

Dependency:

<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.3</version>
</dependency>

Typical test code:

@org.junit.Test
public void test() {
    OrderPO orderPO = new OrderPO();
    orderPO.setId(1);
    orderPO.setOrderNumber("orderNumber");
    ArrayList<String> list = new ArrayList<String>() {{
        add("1");
        add("2");
    }};
    orderPO.setProId(list);

    OrderDTO orderDTO = new OrderDTO();
    BeanUtils.copyProperties(orderDTO, orderPO);
}

Result (shallow copy):

OrderPO(id=1, orderNumber=orderNumber, proId=[1, 2])
OrderDTO(id=1, orderNumber=orderNumber, proId=[1, 2])

When the list reference is modified, the target object sees the change, confirming a shallow copy:

list.add("3");
log.info(orderDTO.getProId());

OrderDTO(id=1, orderNumber=orderNumber, proId=[1, 2, 3])

2. Spring BeanUtils

Dependency (already present in most Spring projects):

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-beans</artifactId>
    <version>5.2.2.RELEASE</version>
</dependency>

Usage (parameter order is source, target):

BeanUtils.copyProperties(orderPO, orderDTO);
BeanUtils.copyProperties(orderPO, orderDTO, "orderNumber");

Result with ignored property:

OrderPO(id=1, orderNumber=orderNumber, proId=[1, 2])
OrderDTO(id=1, orderNumber=null, proId=[1, 2])

3. cglib BeanCopier

Dependency:

<dependency>
    <groupId>cglib</groupId>
    <artifactId>cglib</artifactId>
    <version>3.3.0</version>
</dependency>

Usage:

BeanCopier beanCopier = BeanCopier.create(
        orderPO.getClass(),
        orderDTO.getClass(), false);
beanCopier.copy(orderPO, orderDTO, null);

Result (shallow copy, primitive vs wrapper issue):

OrderPO(id=1, orderNumber=orderNumber, proId=[1, 2])
OrderDTO(id=0, orderNumber=orderNumber, proId=[1, 2])

4. Hutool BeanUtil

Dependency:

<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-all</artifactId>
    <version>5.1.0</version>
</dependency>

Usage (also shallow copy):

BeanUtil.copyProperties(orderPO, orderDTO);

Hutool provides many additional utility methods and supports ignore‑properties in the same way as Spring BeanUtils.

5. MapStruct

MapStruct generates mapping code at compile time, avoiding reflection and offering high performance.

Dependencies:

<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct-jdk8</artifactId>
    <version>1.3.0.Final</version>
</dependency>
<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct-processor</artifactId>
    <version>1.3.0.Final</version>
</dependency>

Mapper interface:

@Mapper
public interface ConvertMapper {
    OrderDTO po2Dto(OrderPO orderPO);
}

Usage:

ConvertMapper mapper = Mappers.getMapper(ConvertMapper.class);
OrderDTO orderDTO = mapper.po2Dto(orderPO);

The generated implementation performs deep copy for reference fields, creating new objects instead of sharing references.

6. Dozer

Dozer maps beans recursively and can handle different field names via XML configuration.

Dependency:

<dependency>
    <groupId>net.sf.dozer</groupId>
    <artifactId>dozer</artifactId>
    <version>5.4.0</version>
</dependency>

Usage:

DozerBeanMapper mapper = new DozerBeanMapper();
OrderDTO orderDTO = mapper.map(orderPO, OrderDTO.class);

XML mapping for fields with different names:

<?xml version="1.0" encoding="UTF-8"?>
<mappings xmlns="http://dozer.sourceforge.net"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://dozer.sourceforge.net
          http://dozer.sourceforge.net/schema/beanmapping.xsd">
    <mapping>
        <class-a>com.cn.entity.OrderPO</class-a>
        <class-b>com.cn.entity.OrderDTO</class-b>
        <field>
            <a>name</a>
            <b>value</b>
        </field>
    </mapping>
</mappings>

Result after applying the mapping:

OrderPO(id=1, orderNumber=orderNumber, proId=[1, 2], name=hydra)
OrderDTO(id=1, orderNumber=orderNumber, proId=[1, 2], value=hydra)

Choosing the appropriate tool depends on whether a shallow or deep copy is required, performance considerations, and existing project dependencies.