注解Conditional按条件注入bean

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根据一定的条件判断是否注入bean

声明两个条件

• Windows环境下注入bean的条件

public class WindowsCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        return context.getEvironment().getProperty("os.name").contains("Windows");
    }
}

• Linux环境下注入bean的条件

public class LinuxCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        return context.getEvironment().getProperty("os.name").contains("Linux");
    }
}

使用条件

@Configuration
public class ConditionConfig {
    @Bean
    @Conditional(WindowsCondition.class)
    public MyService windowMyService() {
        // ...
    }
    
    @Bean
    @Conditional(LinuxCondition.class)
    public MyService linuxMyService() {
        // ...
    }
}

其它衍生的注解

@ConditionalOnMissingBean(xx.class) // 没有xx.class bean时注入
@ConditionalOnBean(xx.class) // 有xx.class bean 时注入
...

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