Spring之条件注解

r囧r小猫 2022-04-23 06:08 196阅读 0赞

我们新建一个项目，验证能否通过配置文件能否来控制bean的装配。

项目总体结构

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KafkaConfig，添加@ConditionalOnProperty注解

package com.yj.config;
    
    import java.util.HashMap;
    import java.util.Map;
    import org.apache.kafka.clients.producer.ProducerConfig;
    import org.apache.kafka.common.serialization.StringSerializer;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    import org.springframework.kafka.core.DefaultKafkaProducerFactory;
    import org.springframework.kafka.core.KafkaTemplate;
    import org.springframework.kafka.core.ProducerFactory;
    
    @Configuration
    @ConditionalOnProperty(name = "kafka.enableKafka", havingValue = "1")
    public class KafkaConfig {
    	
    	private static final Logger LOGGER = LoggerFactory.getLogger(KafkaConfig.class);
    	
    	@Value("${kafka.producer.servers:}")
    	private String servers;
    	@Value("${kafka.producer.retries:0}")
    	private int retries;
    
    	public Map<String, Object> producerConfigs() {
    		Map<String, Object> props = new HashMap<>();
    		props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, servers);
    		props.put(ProducerConfig.RETRIES_CONFIG, retries);
    		props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
    		props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG, StringSerializer.class);
    		return props;
    	}
    
    	public ProducerFactory<String, String> producerFactory() {
    		return new DefaultKafkaProducerFactory<>(producerConfigs());
    	}
    
    	@Bean
    	public KafkaTemplate<String, String> kafkaTemplate() {
    		LOGGER.info("==组装KafkaTemplate==");
    		return new KafkaTemplate<String, String>(producerFactory());
    	}
    }

application.properties

server.port=8081
    
    kafka.enableKafka=1
    kafka.producer.servers=127.0.0.1:9092
    kafka.topic.timeData=timeData
    kafka.producer.retries=3

我们将断点打在KafkaConfig的KafkaTemplate这里，观察是否有打印出日志，发现

当db.enableKafka=1时，进入了断点，打印出了日志；

当db.enableKafka=0时，没有进入断点；

即我们通过配置文件中的参数，能控制是否要去装配kafkaTemplate这个bean

SpringBoot中，其他的条件注解还有：

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