@Conditional
它的作用是按照一定的条件进行判断,满足注解中的条件就给容器注册bean。其他则不注入。这个注解既可以写在方法上也可以写在类上。这个注解被大量的使用在spring Boot中。
实现condition
- 首先定义一个配置类
@Configuration
//定义在类上
@Conditional(WindowCondition.class)
public class MyConfig2 {
@Bean("window")
//定义在方法上
@Conditional(WindowCondition.class)
public Person person01(){
return new Person("王五",50);
}
@Bean("linux")
//定义在方法上
@Conditional(LinuxCondition.class)
public Person person02(){
return new Person("linux",48);
}
}
- 写两个条件也就是condition类,这个类要实现condition接口,并且要重写matches方法
public class LinuxCondition implements Condition {
@Override
public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
Environment environment = conditionContext.getEnvironment();
String property = environment.getProperty("os.name");
if (property.toLowerCase().contains("linux")){
return true;
}
return false;
}
}
public class WindowCondition implements Condition {
@Override
public boolean matches(ConditionContext conditionContext, AnnotatedTypeMetadata annotatedTypeMetadata) {
Environment environment = conditionContext.getEnvironment();
String property = environment.getProperty("os.name");
if (property.toLowerCase().contains("window")){
return true;
}
return false;
}
}
- 测试类
public class App {
public static void main(String[] args) {
//读取注解
ApplicationContext applicationContext1 = new AnnotationConfigApplicationContext(MyConfig.class);
//打印出IOC容器中已经加载的组件
String[] names= applicationContext1.getBeanNamesForType(Person.class);
for (String name:names){
System.out.println(name);
}
}
}