[英]Spring's JavaConfig and CustomScopeConfigurer issue
I'm seeing some odd behavior, I was hoping someone here can shine some light on the issue. 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了解。
Let me start by describing my setup. 让我先描述一下我的设置。 First, a simple data object 首先,一个简单的数据对象
public class Apple {
private String name;
public Apple withName(String name) {
this.name = name;
return this;
}
public String getName() {
return name;
}
}
And a test class.. 和一个测试类..
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes={TestConfig.class})
public class AppleTest {
@Autowired private Apple apples;
@Test
public void simpleTest() {
System.out.println("OBJ: "+apples);
}
}
The config is as follows 配置如下
@Configuration
public interface ConfigInterface {
public Apple getApple();
}
With an implementing class 有一个实施类
@Configuration
@Import(AbstractTestConfig.class)
public class TestConfig implements ConfigInterface {
public Apple getApple() {
return new Apple().withName("Granny apples");
}
}
With the config dependency... 使用配置依赖...
@Configuration
public class AbstractTestConfig {
@Autowired ConfigInterface conf;
@Bean Apple myTestApple() {
return conf.getApple();
}
}
All of this works great. 所有这一切都很棒。 I run the test, I see the output I expect. 我运行测试,我看到了我期望的输出。 But then I throw a spanner into the wheel and modify AbstractTestConfig to look as follows. 但后来我将一个扳手扔到方向盘上并修改AbstractTestConfig,如下所示。
@Configuration
public class AbstractTestConfig {
@Autowired ConfigInterface conf;
@Bean Apple myTestApple() {
return conf.getApple();
}
// NEW CODE
@Bean CustomScopeConfigurer scopeConfigurer() {
return new CustomScopeConfigurer();
}
}
And all of a sudden the @Autowired
object conf
is null when it is required to construct the Apple
bean. 当需要构造Apple
bean时,@ @Autowired
对象conf
突然变为null。
Even more odd, if I move the CustomScopeConfigurer
bean to the TestConfig
class, then it works. 更奇怪的是,如果我将CustomScopeConfigurer
bean移动到TestConfig
类,那么它可以工作。
Is there something I don't know about scopes or the CustomScopeConfigurer
object in particular? 是否有我不了解的范围或者特别是CustomScopeConfigurer
对象?
Copied from Spring @Bean javadoc : 从Spring @Bean javadoc复制:
BeanFactoryPostProcessor-returning @Bean methods BeanFactoryPostProcessor-返回@Bean方法
Special consideration must be taken for @Bean methods that return Spring BeanFactoryPostProcessor (BFPP) types. 必须特别考虑返回Spring BeanFactoryPostProcessor(BFPP)类型的@Bean方法。 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. 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。 To avoid these lifecycle issues, mark BFPP-returning @Bean methods as static. 要避免这些生命周期问题,请将BFPP返回@Bean方法标记为静态。 For example: 例如:
@Bean
public static PropertyPlaceholderConfigurer ppc() {
// instantiate, configure and return ppc ...
}
By marking this method as static, it can be invoked without causing instantiation of its declaring @Configuration class, thus avoiding the above-mentioned lifecycle conflicts. 通过将此方法标记为静态,可以调用它而不会导致其声明@Configuration类的实例化,从而避免上述生命周期冲突。 Note however that static @Bean methods will not be enhanced for scoping and AOP semantics as mentioned above. 但请注意,如上所述,静态@Bean方法不会针对作用域和AOP语义进行增强。 This works out in BFPP cases, as they are not typically referenced by other @Bean methods. 这在BFPP案例中有效,因为它们通常不被其他@Bean方法引用。 As a reminder, a WARN-level log message will be issued for any non-static @Bean methods having a return type assignable to BeanFactoryPostProcessor. 作为提醒,将为任何具有可分配给BeanFactoryPostProcessor的返回类型的非静态@Bean方法发出WARN级别的日志消息。
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