2023-01-31 21:06阅读: 147评论: 0推荐: 0

自定义ConditionalOnXX注解(二)

一、前言

  在之前的文章《自定义ConditionalOnXX注解》中,介绍了Conditional注解的实现原理和实现自定义Conditional注解的基础方法,但是有些场景我们需要用一个ConditionalOnXX注解来实现多条件的与(AND)或(OR)非(NOT)逻辑,本文就是介绍这种复杂场景的应用。

二、自定义注解合并多条件

假设有一个bean MyBean,我们想通过当前操作系统标识来控制其是否注入到Spring容器中。

首先创建windows和mac系统的condition

OnWindowsCondition

/**
* @author Ship
* @version 1.0.0
* @description:
* @date 2023/01/31 10:20
*/
public class OnWindowsCondition implements Condition {
@Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
return SystemUtils.IS_OS_WINDOWS;
}
}

OnMacCondition

/**
* @author Ship
* @version 1.0.0
* @description:
* @date 2023/01/31 10:20
*/
public class OnMacCondition implements Condition {
@Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
return SystemUtils.IS_OS_MAC;
}
}

2.1 与(AND)合并条件

SpringBoot提供了一个抽象类AllNestedConditions,具体用法其类注释写的比较清楚了如下:

/**
* {@link Condition} that will match when all nested class conditions match. Can be used
* to create composite conditions, for example:
*
* <pre class="code">
* static class OnJndiAndProperty extends AllNestedConditions {
*
* OnJndiAndProperty() {
* super(ConfigurationPhase.PARSE_CONFIGURATION);
* }
*
* &#064;ConditionalOnJndi()
* static class OnJndi {
* }
*
* &#064;ConditionalOnProperty("something")
* static class OnProperty {
* }
*
* }
* </pre>
* <p>
* The
* {@link org.springframework.context.annotation.ConfigurationCondition.ConfigurationPhase
* ConfigurationPhase} should be specified according to the conditions that are defined.
* In the example above, all conditions are static and can be evaluated early so
* {@code PARSE_CONFIGURATION} is a right fit.
*
* @author Phillip Webb
* @since 1.3.0
*/
public abstract class AllNestedConditions extends AbstractNestedCondition {
}

只需要新建一个condition类继承AllNestedConditions,重写构造方法并添加条件即可,需要注意的是构造方法里的ConfigurationPhase枚举分为两种情况,具体用哪个取决于Condition注解的使用场景。

ConfigurationPhase.PARSE_CONFIGURATION: 用于控制配置类是否生效

ConfigurationPhase.REGISTER_BEAN: 用于控制Bean是否加载

创建条件类OnWindowsAndMacCondition

package cn.sp.condition.nested;
import cn.sp.condition.OnMacCondition;
import cn.sp.condition.OnWindowsCondition;
import org.springframework.boot.autoconfigure.condition.AllNestedConditions;
import org.springframework.context.annotation.Conditional;
/**
* @author Ship
* @version 1.0.0
* @description: 只有当所有条件都满足时,bean才会被加载
* @date 2023/01/31 10:27
*/
public class OnWindowsAndMacCondition extends AllNestedConditions {
public OnWindowsAndMacCondition() {
super(ConfigurationPhase.REGISTER_BEAN);
}
@Conditional(OnWindowsCondition.class)
static class OnWindows{
}
@Conditional(OnMacCondition.class)
static class OnMac{
}
}

自定义注解@ConditionalOnWindowsAndMac

/**
* @author Ship
* @version 1.0.0
* @description: 条件之是windows且mac系统
* @date 2023/01/31 10:19
*/
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(value = OnWindowsAndMacCondition.class)
public @interface ConditionalOnWindowsAndMac {
}

2.2 或(OR)合并条件

创建条件类OnWindowsOrMacCondition

/**
* @author Ship
* @version 1.0.0
* @description: 只要有一个条件满足时,bean就会被加载
* @date 2023/01/31 10:27
*/
public class OnWindowsOrMacCondition extends AnyNestedCondition {
public OnWindowsOrMacCondition() {
super(ConfigurationPhase.REGISTER_BEAN);
}
@Conditional(OnWindowsCondition.class)
static class OnWindows{
}
@Conditional(OnMacCondition.class)
static class OnMac{
}
}

自定义注解@ConditionalOnWindowsOrMac

/**
* @author Ship
* @version 1.0.0
* @description: 条件之是windows或mac系统
* @date 2023/01/31 10:19
*/
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(value = OnWindowsOrMacCondition.class)
public @interface ConditionalOnWindowsOrMac {
}

2.3 非(NOT)合并条件

创建条件类OnNotWindowsCondition

/**
* @author Ship
* @version 1.0.0
* @description: 只有当所有条件都不满足时,bean才会被加载
* @date 2023/01/31 10:27
*/
public class OnNotWindowsCondition extends NoneNestedConditions {
public OnNotWindowsCondition() {
super(ConfigurationPhase.REGISTER_BEAN);
}
@Conditional(OnWindowsCondition.class)
static class OnWindows {
}
}

自定义注解@ConditionalOnNotWindows

/**
* @author Ship
* @version 1.0.0
* @description: 条件之不是windows系统
* @date 2023/01/31 10:19
*/
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(value = OnNotWindowsCondition.class)
public @interface ConditionalOnNotWindows {
}

三、测试验证

TestConfiguration配置类添加了MyBean的注入方法

@Configuration
public class TestConfiguration {
@ConditionalOnWindowsAndMac
// @ConditionalOnWindowsOrMac
// @ConditionalOnNotWindows
@Bean
public MyBean myBean() {
System.out.println("Initialized bean:myBean...");
return new MyBean();
}
}

@ConditionalOnWindowsAndMac测试

本人机器是Mac系统,启动项目控制台没有任何输出,表明结果正常,毕竟没有既是windows又是mac的系统。

@ConditionalOnWindowsOrMac测试

将myBean()方法打上@ConditionalOnWindowsOrMac注解,启动项目控制台输出如下:

2023-01-31 20:51:25.584 INFO 16669 --- [ main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 967 ms
Initialized bean:myBean...
2023-01-31 20:51:25.955 INFO 16669 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8081 (http) with context path ''
2023-01-31 20:51:25.965 INFO 16669 --- [ main] cn.sp.SpringExtensionApplication : Started SpringExtensionApplication in 2.118 seconds (JVM running for 3.965)

说明MyBean被加载了,条件生效。

@ConditionalOnNotWindows测试

将myBean()方法打上@ConditionalOnNotWindows注解,启动项目控制台也打印出了[Initialized bean:myBean...],说明MyBean被加载了,条件生效。

文章代码已上传至github,点击查看

本文作者:烟味i

本文链接:https://www.cnblogs.com/2YSP/p/17080784.html

版权声明:本作品采用知识共享署名-非商业性使用-禁止演绎 2.5 中国大陆许可协议进行许可。

posted @   烟味i  阅读(147)  评论(0编辑  收藏  举报
点击右上角即可分享
微信分享提示
💬
评论
📌
收藏
💗
关注
👍
推荐
🚀
回顶
收起