SpringBoot 常用条件注解

注解	条件断类	备注
@ConditionalOnClass	OnClassCondition	如果Classpath 存在匹配到class，就创建
@ConditionalOnMissingClass	OnClassCondition	如果Classpath 不存在匹配到class，就创建
@ConditionalOnBean	OnBeanCondition	如果Spring容器中 存在匹配到Bean，就创建
@ConditionalOnMissingBean	OnBeanCondition	如果Spring容器 存在匹配到Bean，就创建
@ConditionalOnProperty	OnPropertyCondition	如果Spring容器 存在匹配到属性，就创建
@ConditionalOnResource	OnResourceCondition	如果ClassPath下存在匹配到resource，就创建
@ConditionalOnWebApplication	OnWebApplicationCondition	如果应用类型不满足type（ANY、SERVLET、REACTIVE），就创建
@ConditionalOnNotWebApplication	OnWebApplicationCondition	如果应用类型不满足type（ANY、SERVLET、REACTIVE），就创建
@ConditionalOnExpression	OnExpressionCondition	基于SpringEL表达式进行判断，如果true就创建

自定义条件注解

1.编写条件Class继承Condition或者Condition子类SpringBootCondition

public class TestOnCondition extends SpringBootCondition {
    private String defaultValue = "test";

    @Override
    //关键点:实现业务逻辑判断
    public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
        Map<String, Object> map = metadata.getAnnotationAttributes(TestConditional.class.getName());
        String value = String.valueOf(map.get("value"));
        if (defaultValue.equals(value)) {
            return ConditionOutcome.match(ConditionMessage.forCondition(TestConditional.class)
                    .because("match"));
        } else {
            return ConditionOutcome.noMatch(ConditionMessage.forCondition(TestConditional.class)
                    .because("not match"));
        }
    }
}

2.编写自定义注解

@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(TestOnCondition.class)
public @interface TestConditional {
    String value() default "";
}

3.实体类

public class Greeting {
    private final long id;
    private final String content;

    public Greeting(long id, String content) {
        this.id = id;
        this.content = content;
    }

    public long getId() {
        return id;
    }

    public String getContent() {
        return content;
    }
}

测试：

@SpringBootApplication
public class Demo01Application {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(Demo01Application.class, args);
        Object test = context.getBean("greeting");
        System.out.println(test);
    }
    @Bean
    @TestConditional("test")
    public Greeting greeting(){
        return new Greeting(1,"test");
    }

}

结果

把@TestConditional(“test”)改成@TestConditional(“test1”)

结果：