1.有时候需要根据不同条件生成不同的 bean，这时候就需要用到 @Conditional 注解。常见的一种用法，就是根据操作系统类型，注册不同的 bean。在 BeanConfig 配置类中增加三个 bean。
package io.mieux.config;import io.mieux.bean.Person;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;@Configurationpublic class BeanConfig { @Bean(value = "zhangsan") public Person getPerson() { return new Person("zhangsan", 28);
} @Bean(value = "linux") public Person getLinux() { return new Person("linux", 50);
} @Bean(value = "windows") public Person getWindows() { return new Person("windows", 30);
} @Bean(value = "mac") public Person getMac() { return new Person("mac", 24);
}
}查看当前容器中 Person 类的实例有哪些：
package io.mieux;import io.mieux.bean.Person;import io.mieux.config.BeanConfig;import org.springframework.context.annotation.AnnotationConfigApplicationContext;public class App04 { public static void main(String[] args) {
AnnotationConfigApplicationContext annotationConfigApplicationContext = new AnnotationConfigApplicationContext(BeanConfig.class);
String[] beanNames = annotationConfigApplicationContext.getBeanNamesForType(Person.class); for (String beanName : beanNames) {
System.out.println("beanName: " + beanName);
}
}
}运行效果：
beanName: zhangsan beanName: linux beanName: windows beanName: mac
2.使用 @Conditional 注解来根据操作系统的不同注册不同的 bean。首先需要实现 Condition 接口，创建三个 Condition 接口的实现类 LinuxConditon、MacConditon 和 WindowsConditon，获取运行环境的操作系统类型进行判断。
LinuxConditon：
package io.mieux.condition;import org.springframework.context.annotation.Condition;import org.springframework.context.annotation.ConditionContext;import org.springframework.core.env.Environment;import org.springframework.core.type.AnnotatedTypeMetadata;// 判断是否是 linux 系统public class LinuxConditon implements Condition { public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
Environment environment = context.getEnvironment();
String operatingSystem = environment.getProperty("os.name"); if ("linux".equals(operatingSystem)) {
System.out.println("Operating System: " + environment.getProperty("os.name")); return true;
} return false;
}
}WindowsConditon：
package io.mieux.condition;import org.springframework.context.annotation.Condition;import org.springframework.context.annotation.ConditionContext;import org.springframework.core.env.Environment;import org.springframework.core.type.AnnotatedTypeMetadata;// 判断是否是 windows 系统public class WindowsConditon implements Condition { public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
Environment environment = context.getEnvironment();
String operatingSystem = environment.getProperty("os.name"); if (operatingSystem.contains("Windows")) {
System.out.println("Operating System: " + environment.getProperty("os.name")); return true;
} return false;
}
}MacConditon：
package io.mieux.condition;import org.springframework.context.annotation.Condition;import org.springframework.context.annotation.ConditionContext;import org.springframework.core.env.Environment;import org.springframework.core.type.AnnotatedTypeMetadata;// 判断是否是 mac os 系统public class MacConditon implements Condition { public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
Environment environment = context.getEnvironment();
String operatingSystem = environment.getProperty("os.name"); if ("Mac OS X".equals(operatingSystem)) {
System.out.println("Operating System: " + environment.getProperty("os.name")); return true;
} return false;
}
}在 BeanConfig 配置类中加上 @Conditional 注解。
package io.mieux.config;import io.mieux.bean.Person;import io.mieux.condition.LinuxConditon;import io.mieux.condition.MacConditon;import io.mieux.condition.WindowsConditon;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Conditional;import org.springframework.context.annotation.Configuration;@Configurationpublic class BeanConfig { @Bean(value = "zhangsan") public Person getPerson() { return new Person("zhangsan", 28);
} @Bean(value = "linux") @Conditional(value = {LinuxConditon.class}) public Person getLinux() { return new Person("linux", 50);
} @Bean(value = "windows") @Conditional(value = {WindowsConditon.class}) public Person getWindows() { return new Person("windows", 30);
} @Bean(value = "mac") @Conditional(value = {MacConditon.class}) public Person getMac() { return new Person("mac", 24);
}
}运行效果：
Operating System: Mac OS X beanName: zhangsan beanName: mac
作者：冯先生的笔记
链接：https://www.jianshu.com/p/0d668e86ffc8
來源：简书
简书著作权归作者所有，任何形式的转载都请联系作者获得授权并注明出处。
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