Question

我在将xml中的bean引用转换为java config时遇到问题。在XML中我有类似的东西：

<bean id="user" com="User">
    <constructor-arg name="pFirst" value="first" />
    <constructor-arg name="pSecond" value="second" />
    <constructor-arg name="pThird" value="third" />
</bean>

<bean id="department" com="Department">
    <constructor-arg name="pfourth" value="fourth" />
    <constructor-arg name="pFifth" value="fifth" />
    <constructor-arg ref="user" />
</bean>

在java配置中，我现在有了这个：

@Bean
@Autowired
public User user(First first, Second second, Third third)
{
    return new User(first, second, third);
}

@Bean
@Autowired
public Department department(First first, Second second, Third third, Fourth fourth, Fifth fifth)
{
    return new Department(fourth, fifth, user(first, second, third));
}

我不想像对待用户那样将相同的参数传递给部门。在XML中，我可以引用用户bean并在没有其他参数的情况下使用它。我怎么能在java配置文件中这样做。我希望java配置文件看起来如下所示：

@Bean
@Autowired
public User user(First first, Second second, Third third)
{
    return new User(first, second, third);
}

@Bean
@Autowired
public Department department(Fourth fourth, Fifth fifth, User user)
{
    return new Department(fourth, fifth, user);
}

这个使用先前定义的bean作为第三个参数，但我不能得到这样的东西。

我如何将User bean作为构造函数的一部分引用到另一个bean？

Answer 1

@Bean
public User user() {
    return new User("first", "second", "third");
}

@Bean
public Department department() {
    return new Department("fourth", "fifth", user());
}

现在，您可以在容器中的其他类中使用@Autowired并注入您的用户或部门（例如在控制器中）

@Autowired
private User user; // will return the user from the user() java config defined bean

Answer 2

首先，@Bean方法通常不应注释@Autowired;应该应用于包含bean的@Configuration对象上的字段。

@Configuration
public class MyConfig {
    @Autowired First first;
    @Autowired Second second;
    @Autowired Third third;

    @Bean public User user() {
        return new User(first, second, third);
    }

    @Autowired Fourth fourth;
    @Autowired Fifth fifth;

    @Bean public Department department() {
        // call to user() is magically proxied to apply Spring bean scope
        return new Department(fourth, fifth, user());
    }
}

这通常足以让Spring处理适当的依赖项。在存在歧义或其他困难的奇怪情况下，您可以使用嵌套配置类：

@Configuration
public class MyConfig {
    @Autowired First first;
    @Autowired Second second;
    @Autowired Third third;

    @Bean public User user() {
        return new User(first, second, third);
    }

    @Configuration
    public static class MySubConfig {
        @Autowired Fourth fourth;
        @Autowired Fifth fifth;
        @Autowired User user;

        @Bean public Department department() {
            return new Department(fourth, fifth, user);
        }
    }
}

将bean作为构造函数的一部分引用到java config中的不同bean

2 个答案: