@Conditional 是 SpringFramework 的功能， SpringBoot 在它的基礎(chǔ)上定義了 @ConditionalOnClass ， @ConditionalOnProperty 的一系列的注解來(lái)實(shí)現(xiàn)更豐富的內(nèi)容。

import com.example.conditional.MyConditional;import org.springframework.context.annotation.Conditional; import java.lang.annotation.*; @Target({ElementType.TYPE,ElementType.METHOD})@Retention(RetentionPolicy.RUNTIME)@Documented@Conditional(MyConditional.class)public @interface MyConditionalIAnnotation { String key(); String value();}自定義Conditional

import com.example.conditional.interfaceI.MyConditionalIAnnotation;import org.springframework.boot.autoconfigure.condition.ConditionOutcome;import org.springframework.boot.autoconfigure.condition.SpringBootCondition;import org.springframework.context.annotation.ConditionContext;import org.springframework.context.annotation.Conditional;import org.springframework.core.type.AnnotatedTypeMetadata; import java.util.Map; public class MyConditional extends SpringBootCondition { @Override public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) { Map<String, Object> annotationAttributes = metadata.getAnnotationAttributes(MyConditionalIAnnotation.class.getName()); Object key = annotationAttributes.get('key');// Object value = annotationAttributes.get('value'); if(key == null || value == null){ return new ConditionOutcome(false, 'error'); } //獲取environment中的值 String key1 = context.getEnvironment().getProperty(key.toString()); if (value.equals(key1)) { //如果environment中的值與指定的value一致，則返回true return new ConditionOutcome(true, 'ok'); } return new ConditionOutcome(false, 'error'); }}config配置

import com.example.conditional.interfaceI.MyConditionalIAnnotation;import com.example.conditional.service.MyConditionalService;import org.apache.log4j.Logger;import org.springframework.boot.autoconfigure.EnableAutoConfiguration;import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.ComponentScan;import org.springframework.context.annotation.Configuration; @Configurationpublic class MyConditionalConfig { public static Logger logger=Logger.getLogger(MyConditionalService.class); /** * 判斷MyConditional 是否符合條件，是則運(yùn)行MyConditionalService * @return */ @MyConditionalIAnnotation(key = 'com.example.conditional', value = 'lbl') @ConditionalOnClass(MyConditionalService.class) @Bean public MyConditionalService initMyConditionService() { logger.info('MyConditionalService已加載。'); return new MyConditionalService(); }}配置文件：application.propeties

spring.application.name=gatewayserver.port=8084#conditional 動(dòng)態(tài)配置，判斷該值是否等于lbl，是則創(chuàng)建MyConditionalService實(shí)例com.example.conditional=lbl#支持自定義aopspring.aop.auto=trueSpringBootCondition 定義條件化配置1 條件化配置

Spring提供了多種實(shí)現(xiàn)化條件化配置的選擇，如ConditionalOnProperty和ConditionalOnClass等。

用法如下：

@ConditionalOnProperty(prefix = 'pkslow', name = 'service', havingValue = 'larry')

還有：

@ConditionalOnBean（僅僅在當(dāng)前上下文中存在某個(gè)對(duì)象時(shí)，才會(huì)實(shí)例化一個(gè)Bean）@ConditionalOnClass（某個(gè)class位于類路徑上，才會(huì)實(shí)例化一個(gè)Bean）@ConditionalOnExpression（當(dāng)表達(dá)式為true的時(shí)候，才會(huì)實(shí)例化一個(gè)Bean）@ConditionalOnMissingBean（僅僅在當(dāng)前上下文中不存在某個(gè)對(duì)象時(shí)，才會(huì)實(shí)例化一個(gè)Bean）@ConditionalOnMissingClass（某個(gè)class類路徑上不存在的時(shí)候，才會(huì)實(shí)例化一個(gè)Bean）@ConditionalOnNotWebApplication（不是web應(yīng)用）

但有時(shí)候我們需要更靈活的自定義條件配置，這時(shí)可以通過(guò)繼承SpringBootCondition類來(lái)實(shí)現(xiàn)。

自己根據(jù)需求實(shí)現(xiàn)自己的判斷邏輯，我的實(shí)現(xiàn)如下：

public class PkslowCondition extends SpringBootCondition { @Override public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) { BindResult<List<String>> maxBindResult = Binder.get(context.getEnvironment()).bind('pkslow.condition.max', Bindable.listOf(String.class)); BindResult<List<String>> minBindResult = Binder.get(context.getEnvironment()).bind('pkslow.condition.min', Bindable.listOf(String.class)); if ( (maxBindResult.isBound() && !maxBindResult.get().isEmpty()) && (minBindResult.isBound() && !minBindResult.get().isEmpty()) ) { List<String> maxs = maxBindResult.get(); List<String> mins = minBindResult.get(); int max = Integer.parseInt(maxs.get(0)); int min = Integer.parseInt(mins.get(0)); if (max < 1000 && min > 0) { return ConditionOutcome.match(); } } return ConditionOutcome.noMatch('pkslow.condition.max/pkslow.condition.min not matches'); }}

表示需要有配置屬性pkslow.condition.max/pkslow.condition.min才會(huì)生效，并且要求max<1000且min>0。

完成自定義的條件類后，就可以使用它來(lái)限定一個(gè)配置類是否要生效了，使用如下：

@Conditional(PkslowCondition.class)@Configurationpublic class PkslowConfig { @PostConstruct public void postConstruct() { System.out.println('PkslowConfig called'); }}4 總結(jié)

代碼請(qǐng)查看：https://github.com/LarryDpk/pkslow-samples

以上就是如何使用SpringBootCondition更自由地定義條件化配置的詳細(xì)內(nèi)容，更多關(guān)于SpringBootCondition 定義條件化配置的資料請(qǐng)關(guān)注好吧啦網(wǎng)其它相關(guān)文章！