一般我们在springboot中配置activemq只有以下一行：

spring.activemq.broker-url=tcp://localhost:61616

但如果mq服务器压力过大，可能会导致out of memory，此时就需要进行优化，首先考虑使用mq连接池，避免broker频繁创建连接，减小服务器开销。

1.      引入activemq-pool的pom

首先需要引入activemq-pool：

<dependency>

   <groupId>org.springframework.boot</groupId>

   <artifactId>spring-boot-starter-activemq</artifactId>

</dependency>



<dependency>

   <groupId>org.apache.activemq</groupId>

   <artifactId>activemq-pool</artifactId>

</dependency>

2.      application配置

我们可以在application.yml中加入：

spring:

  activemq:

    broker-url: tcp://localhost:61616

    pool:

      enabled: true

      configuration:

        max-connections: 2

spring.activemq.pool.enabled=true表示打开连接池

spring.activemq.pool.maxConnections=2表示最大连接数为2

但如果我们使用了自定义的mq配置中注入了ActiveMQConnectionFactory，例如：

@Configuration
public class ActivemqComponent {



    @Autowired

    private ActiveMQConnectionFactory connectionFactory;



    

    @Bean(name = "queueListenerFactory")

    public DefaultJmsListenerContainerFactory queueListenerFactory(){

        DefaultJmsListenerContainerFactory factory = new DefaultJmsListenerContainerFactory();

        factory.setConnectionFactory(connectionFactory);

        factory.setPubSubDomain(false);
//        factory.setMessageConverter(new SimpleMessageConverter());

        return factory;

    }

直接启动项目就会出现以下错误：

Field connectionFactory in com.scn7th.mqConfig.ActivemqComponent required a bean of type 'org.apache.activemq.ActiveMQConnectionFactory' that could not be found.

- Bean method 'jmsConnectionFactory' in 'ActiveMQConnectionFactoryConfiguration' not loaded because @ConditionalOnProperty (spring.activemq.pool.enabled=false) found different value in property 'enabled'

- Bean method 'nonXaJmsConnectionFactory' not loaded because @ConditionalOnBean (types: org.springframework.boot.jta.XAConnectionFactoryWrapper; SearchStrategy: all) did not find any beans

其中第二句是关键，也就是说，springboot-activemq-starter中的自定义配置ActiveMQConnectionFactoryConfiguration中注入了ActiveMQConnectionFactory，ActiveMQConnectionFactory在spring.activemq.pool.enabled=false时才会创建，所以我们此时再注入ActiveMQConnectionFactory肯定在spring中找不到。我们可以看到，在ActiveMQConnectionFactoryConfiguration类中定义了PooledConnectionFactory，而它的创建条件正是spring.activemq.pool.enabled=true，所以我们必须使用PooledConnectionFactory来代替ActiveMQConnectionFactory注入到ActiveMqConfig中，需要注意的是，我们注入的PooledConnectionFactory在包org.apache.activemq.pool下，而不是org.apache.activemq.pool.jms下的PooledConnectionFactory，如果引用了错误的类则会报错。

【注】springboot的ActiveMQConnectionFactoryConfiguration.java

package org.springframework.boot.autoconfigure.jms.activemq;



import javax.jms.ConnectionFactory;



import org.apache.activemq.ActiveMQConnectionFactory;

import org.apache.activemq.pool.PooledConnectionFactory;



import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;

import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;

import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;

import org.springframework.boot.context.properties.ConfigurationProperties;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;



@Configuration

@ConditionalOnMissingBean(ConnectionFactory.class)
class ActiveMQConnectionFactoryConfiguration {



   @Bean

   @ConditionalOnProperty(prefix = "spring.activemq.pool", name = "enabled", havingValue = "false", matchIfMissing = true)

   public ActiveMQConnectionFactory jmsConnectionFactory(ActiveMQProperties properties) {

      return new ActiveMQConnectionFactoryFactory(properties)

            .createConnectionFactory(ActiveMQConnectionFactory.class);

   }



   @ConditionalOnClass(PooledConnectionFactory.class)

   static class PooledConnectionFactoryConfiguration {



      @Bean(destroyMethod = "stop")

      @ConditionalOnProperty(prefix = "spring.activemq.pool", name = "enabled", havingValue = "true", matchIfMissing = false)

      @ConfigurationProperties(prefix = "spring.activemq.pool.configuration")

      public PooledConnectionFactory pooledJmsConnectionFactory(

            ActiveMQProperties properties) {

         PooledConnectionFactory pooledConnectionFactory = new PooledConnectionFactory(

               new ActiveMQConnectionFactoryFactory(properties)

                     .createConnectionFactory(ActiveMQConnectionFactory.class));



         ActiveMQProperties.Pool pool = properties.getPool();

         pooledConnectionFactory.setMaxConnections(pool.getMaxConnections());

         pooledConnectionFactory.setIdleTimeout(pool.getIdleTimeout());

         pooledConnectionFactory.setExpiryTimeout(pool.getExpiryTimeout());

         return pooledConnectionFactory;

      }



   }



} 

3.      ActivemqConfig配置修改

@Configuration
public class ActivemqComponent {

    @Autowired
//    private ActiveMQConnectionFactory connectionFactory;

    private PooledConnectionFactory connectionFactory;



    

    @Bean(name = "queueListenerFactory")

    public DefaultJmsListenerContainerFactory queueListenerFactory(){

        DefaultJmsListenerContainerFactory factory = new DefaultJmsListenerContainerFactory();

        factory.setConnectionFactory(connectionFactory);

        factory.setPubSubDomain(false);
//        factory.setMessageConverter(new SimpleMessageConverter());

        return factory;

    }

}   

完成以上三点配置后，就可以成功启动了