简介
说明
本文用实例介绍Spring的条件注入的用法。
@Component、@Configuration+@Bean都可以与条件注入的注解结合。
@Component+条件注解
Bean
package com.example.config;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.stereotype.Component;
@Component
@ConditionalOnProperty(name = "custom.myComponent.enabled", havingValue = "true")
public class MyComponent {
public MyComponent() {
System.out.println("[MyComponent#MyComponent]");
}
}application.yml
custom:
myComponent:
enabled: true
运行结果：
[MyComponent#MyComponent]
若将application.yml的custom.myComponent.enabled去掉，或者设置为非true值，则不会输出上边的运行结果。
@Configuration+@Bean+条件注解
Bean
package com.example.config;
public class MyComponent {
public MyComponent() {
System.out.println("[MyComponent#MyComponent]");
}
}配置类
package com.example.config;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class MyConfig {
@Bean
@ConditionalOnProperty(name = "custom.myComponent.enabled", havingValue = "true")
public MyComponent getMyComponent() {
return new MyComponent();
}
}application.yml
custom:
myComponent:
enabled: true
运行结果：
[MyComponent#MyComponent]
若将application.yml的custom.myComponent.enabled去掉，或者设置为非true值，则不会输出上边的运行结果。
@Configuration+条件注解+@Bean
Bean
package com.example.config;
public class MyComponent {
public MyComponent() {
System.out.println("[MyComponent#MyComponent]");
}
}配置类
package com.example.config;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
@ConditionalOnProperty(name = "custom.myComponent.enabled", havingValue = "true")
public class MyConfig {
@Bean
public MyComponent getMyComponent() {
return new MyComponent();
}
}application.yml
custom:
myComponent:
enabled: true
运行结果：
[MyComponent#MyComponent]
若将application.yml的custom.myComponent.enabled去掉，或者设置为非true值，则不会输出上边的运行结果。
自定义Condition
自定义的condition的matches方法返回值为true时，才会创建bean。
条件类
//判断当前系统是否是Mac
import org.springframework.context.annotation.Condition;
import org.springframework.context.annotation.ConditionContext;
import org.springframework.core.type.AnnotatedTypeMetadata;
public class MyCondition implements Condition {
@Override
public boolean matches(ConditionContext conditionContext,
AnnotatedTypeMetadata annotatedTypeMetadata) {
return conditionContext.getEnvironment().getProperty("os.name").contains("Mac");
}
}@Configuration
public class Config {
@Conditional(MyCondition.class)
@Bean
public String condition() {
System.err.println("This is mac");
return "";
}
}到此这篇关于Spring示例讲解条件注入方法的文章就介绍到这了,更多相关Spring条件注入内容请搜索编程网以前的文章或继续浏览下面的相关文章希望大家以后多多支持编程网！
