Spring的JavaConfig和CustomScopeConfigurer问题

问题描述

我看到一些奇怪的行为，我希望这里有人可以对这个问题有所启发。

I'm seeing some odd behavior, I was hoping someone here can shine some light on the issue.

让我先介绍一下我的设置。首先，一个简单的数据对象

Let me start by describing my setup. First, a simple data object

public class Apple {
    private String name;
    public Apple withName(String name) {
        this.name = name;
        return this;
    }
    public String getName() {
        return name;
    }
}

和测试类..

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes={TestConfig.class})
public class AppleTest {
    @Autowired private Apple apples;

    @Test
    public void simpleTest() {
        System.out.println("OBJ: "+apples);
    }
}

配置如下

@Configuration
public interface ConfigInterface {
    public Apple getApple();
}

使用实施类

@Configuration
@Import(AbstractTestConfig.class)
public class TestConfig implements ConfigInterface {
    public Apple getApple() {
        return new Apple().withName("Granny apples");
    }
}

使用配置依赖...

@Configuration
public class AbstractTestConfig {
    @Autowired ConfigInterface conf;

    @Bean Apple myTestApple() {
        return conf.getApple();
    }
}

所有这一切都很有效。我运行测试，我看到了我期望的输出。但后来我将一个扳手扔进方向盘并修改AbstractTestConfig，如下所示。

All of this works great. I run the test, I see the output I expect. But then I throw a spanner into the wheel and modify AbstractTestConfig to look as follows.

@Configuration
public class AbstractTestConfig {
    @Autowired ConfigInterface conf;

    @Bean Apple myTestApple() {
        return conf.getApple();
    }

    // NEW CODE
    @Bean CustomScopeConfigurer scopeConfigurer() {
        return new CustomScopeConfigurer();
    }
}

突然间 @Autowired 对象 conf 在需要构造 Apple bean时为null。

And all of a sudden the @Autowired object conf is null when it is required to construct the Apple bean.

更奇怪的是，如果我将 CustomScopeConfigurer bean移动到 TestConfig class，然后它可以工作。

Even more odd, if I move the CustomScopeConfigurer bean to the TestConfig class, then it works.

是否有我不了解的范围或 CustomScopeConfigurer 特别是对象？

Is there something I don't know about scopes or the CustomScopeConfigurer object in particular?

推荐答案

从Spring @Bean复制：

Copied from Spring @Bean javadoc:

必须特别考虑返回Spring BeanFactoryPostProcessor（BFPP）类型的@Bean方法。由于BFPP对象必须在容器生命周期的早期实例化，因此它们可能会干扰@Configuration类中@Autowired，@ Value和@PostConstruct等注释的处理。要避免这些生命周期问题，请将BFPP返回@Bean方法标记为静态。例如：

Special consideration must be taken for @Bean methods that return Spring BeanFactoryPostProcessor (BFPP) types. Because BFPP objects must be instantiated very early in the container lifecycle, they can interfere with processing of annotations such as @Autowired, @Value, and @PostConstruct within @Configuration classes. To avoid these lifecycle issues, mark BFPP-returning @Bean methods as static. For example:

@Bean
 public static PropertyPlaceholderConfigurer ppc() {
     // instantiate, configure and return ppc ...
 }

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