SpringBoot之条件注解

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

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：