如何处理将依赖项注入到丰富的域模型中？

发布于 2024-08-18 07:44:18 字数 243 浏览 10 评论 0原文

在具有丰富域模型的 Web 服务器项目中（应用程序逻辑位于模型中，而不是服务中），如何将依赖项注入到模型对象中？你有什么经历？

你使用某种形式的 AOP 吗？喜欢 Springs @Configurable 注解吗？加载时间或构建时间的偏移？您遇到的问题？

您使用手动注射吗？那么如何处理不同的实例化场景（通过库[如 Hibernate] 创建对象，使用“new”创建对象......）？

或者您是否使用其他方式注入依赖项？

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贪恋 2024-08-25 07:44:18

我们使用 Spring 的 @Configurable（以及常规的 new 运算符），它的作用就像一个魅力。不再有贫血域模型。最后，这是更加面向对象的设计，不是吗：

Person person = new Person(firstname, lastname);
// weird
peopleService.save(person);
// good (save is @Transactional)
person.save();

Mail mail = new Mail(to, subject, body);
// weird
mailService.send(mail);
// good (send is @Transactional)
mail.send();

不过我们还没有进行任何性能比较。到目前为止，我们根本不觉得有必要这样做。

编辑：这就是 person 类的样子：

@Configurable("person")
public class Person {
    private IPersonDAO _personDAO;
    private String _firstname;
    private String _lastname;

    // SNIP: some constructors, getters and setters

    @Transactional(rollbackFor = DataAccessException.class)
    public void save() {
        _personDAO.save(this);
    }

    @Transactional(readOnly = true)
    public List<Role> searchRoles(Company company) void{
        return _personDAO.searchRoles(this, company);
    }

    // it's getting more interesting for more complex methods
    @Transactional(rollbackFor = DataAccessException.class)
    public void resignAllRoles(Company company) {
        for (Role role : searchRoles(company)) {
            role.resign();
        }
    }
}

// the implementation now looks like this
personService.getPerson(id).resignAllRoles(company);

// instead of this
roleService.resignAll(personService.searchRoles(personService.getPerson(id), company));

这就是 Spring 配置：

<context:spring-configured />
<bean id="person" class="org.example.model.Person" lazy-init="true">
  <property name="personDAO" ref="personDAO" />
</bean>

注意：如您所见，周围仍然有服务，例如搜索对象（personService.getPerson(id)），但所有对传递的方法进行操作的方法对象（例如，一个人）被移动到该类本身（即 person.save() 而不是 personService.save(person)）。该方法本身保持不变，并且适用于任何底层数据访问层（纯 JDBC、Hibernate、JPA，...）。它只是搬到了它所属的地方。

We use Spring's @Configurable (along with regular new operator) which works like a charm. No more anemic domain models. Finally, this is much more object oriented design, isn't it:

Person person = new Person(firstname, lastname);
// weird
peopleService.save(person);
// good (save is @Transactional)
person.save();

Mail mail = new Mail(to, subject, body);
// weird
mailService.send(mail);
// good (send is @Transactional)
mail.send();

We haven't done any performance comparison though. So far, we simply haven't felt the need to do so.

EDIT: that's how the person class would look like:

@Configurable("person")
public class Person {
    private IPersonDAO _personDAO;
    private String _firstname;
    private String _lastname;

    // SNIP: some constructors, getters and setters

    @Transactional(rollbackFor = DataAccessException.class)
    public void save() {
        _personDAO.save(this);
    }

    @Transactional(readOnly = true)
    public List<Role> searchRoles(Company company) void{
        return _personDAO.searchRoles(this, company);
    }

    // it's getting more interesting for more complex methods
    @Transactional(rollbackFor = DataAccessException.class)
    public void resignAllRoles(Company company) {
        for (Role role : searchRoles(company)) {
            role.resign();
        }
    }
}

// the implementation now looks like this
personService.getPerson(id).resignAllRoles(company);

// instead of this
roleService.resignAll(personService.searchRoles(personService.getPerson(id), company));

And that's the Spring config:

<context:spring-configured />
<bean id="person" class="org.example.model.Person" lazy-init="true">
  <property name="personDAO" ref="personDAO" />
</bean>

Note: as you see, there are still services around, e.g. to search for objects (personService.getPerson(id)) but all methods that operate on a passed object (e.g. a person) are moved to that class itself (i.e. person.save() instead of personService.save(person)). The method itself stays the same and works with any underlying data access layer (pure JDBC, Hibernate, JPA, ...). It has simply moved where it belongs.

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