如何告诉推土机在目标字段中使用LinkedHashSet集合? [英] How to tell Dozer to use LinkedHashSet collection in destination field?

问题描述

在头等舱我有一个字段:

In first class i have field:

private Set<Country> countries;

public Set<Country> getCountries() {
    return countries;
}

public void setCountries(Set<Country> countries) {
    this.countries = countries;
}

将包含LinkedHashSet实现.

which will contain LinkedHashSet implementation.

在第二类中，我具有相同的声明，但是在映射过程中，Dozer在目标类中创建HashSet实现，这破坏了元素的顺序.如何告诉推土机在目标类中使用LinkedHashSet?

In second class i have identical declaration, but during mapping, Dozer creates HashSet implementation in destination class, which destroys the order of elements. How to tell Dozer to use LinkedHashSet in destination class?

推荐答案

推土机映射Set时，它将使用

When Dozer maps a Set, it uses the org.dozer.util.CollectionUtils.createNewSet to create the destination Set instance. You get either a HashSet or TreeSet.

如果元素的顺序与其自然顺序相同，则可以使用

If the order of your elements is the same as their natural order you might use a SortedSet in the destination. If not, then you need to create the destination object yourself and provide the desired Set implementation.

推土机允许使用自定义的创建方法或自定义的

Dozer allows using custom create methods or custom bean factories to instantiate objects beyond using the default constructor so you could use either method:

创建方法

Java代码:

public class MyInstanceCreator {
    public static DestinationObject createDestinationObject() {
        DestinationObject result = new DestinationObject();
        result.setCountries(new LinkedHashSet<Country>());
        return result;
    }
    private MyInstanceCreator() { }
}

映射:

<mapping>
    <class-a create-method="MyInstanceCreator.createDestinationObject">DestinationObject</class-a>
    <class-b>SourceObject</class-b>
    <field>
        <a>countries</a>
        <b>countries</b>
    </field>
</mapping>

豆工厂

Java代码:

public class MyBeanFactory implements BeanFactory {
    public Object createBean(Object source, Class<?> sourceClass, String targetBeanId) {
        DestinationObject result = new DestinationObject();
        result.setCountries(new LinkedHashSet<Country>());
        return result;
    }
}

映射:

<mapping>
    <class-a bean-factory="MyBeanFactory">DestinationObject</class-a>
    <class-b>SourceObject</class-b>
    <field>
        <a>countries</a>
        <b>countries</b>
    </field>
</mapping>

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