上一篇讲到在整合activeMQ如何将queue和topic两种模式共存：spring boot2.0整合activeMQ，实现p2p和topic两者消息模式兼容共存
然后还遗留了一个问题，有读者评论因为配置文件里一句启用连接池导致项目启动报错，只要把那句配置注释掉或者改为false就可以了，这实际上是治标不治本，因毕竟流量大的时候不启用连接池效率会很低：
# 启用连接池
spring.activemq.pool.enabled=true
诚然，如果不想使用连接池，那么快速的办法的确是把这个配置直接干掉，或者改为false，其是默认就是false，但是我们来看一看启用连接池后启动项目提示JmsMessagingTemplate无法注入真正的原因是什么
开启连接池，启动项目会报错，提示JmsMessagingTemplate无法注入、
目前使用springboot最新版本是2.1+，我先直接告诉你解决方法，如果要启用连接池：
- 使用springboot2.0+及以下版本时候，maven配置依赖是：
<dependency>
<groupId>org.apache.activemq</groupId>
<artifactId>activemq-pool</artifactId>
</dependency>
- 使用springboot2.1+时候，maven配置依赖是：
<dependency>
<groupId>org.messaginghub</groupId>
<artifactId>pooled-jms</artifactId>
</dependency>
请按照自己使用的springboot版本更换对应的连接池依赖就可以解决问题。但为什么一样呢？我们来看看springboot的自动配置的部分源码：
- 使用springboot2.0+及以下版本时候：
@Configuration
@ConditionalOnMissingBean(ConnectionFactory.class)
class ActiveMQConnectionFactoryConfiguration {
@Bean
@ConditionalOnProperty(prefix = "spring.activemq.pool", name = "enabled", havingValue = "false", matchIfMissing = true)
public ActiveMQConnectionFactory jmsConnectionFactory(ActiveMQProperties properties,
ObjectProvider<List<ActiveMQConnectionFactoryCustomizer>> factoryCustomizers) {
return new ActiveMQConnectionFactoryFactory(properties,
factoryCustomizers.getIfAvailable())
.createConnectionFactory(ActiveMQConnectionFactory.class);
}
@Configuration
@ConditionalOnClass(PooledConnectionFactory.class)
static class PooledConnectionFactoryConfiguration {
@Bean(destroyMethod = "stop")
@ConditionalOnProperty(prefix = "spring.activemq.pool", name = "enabled", havingValue = "true", matchIfMissing = false)
public PooledConnectionFactory pooledJmsConnectionFactory(
ActiveMQProperties properties,
ObjectProvider<List<ActiveMQConnectionFactoryCustomizer>> factoryCustomizers) {
PooledConnectionFactory pooledConnectionFactory = new PooledConnectionFactory(
new ActiveMQConnectionFactoryFactory(properties,
factoryCustomizers.getIfAvailable()).createConnectionFactory(
ActiveMQConnectionFactory.class));
ActiveMQProperties.Pool pool = properties.getPool();
pooledConnectionFactory.setBlockIfSessionPoolIsFull(pool.isBlockIfFull());
if (pool.getBlockIfFullTimeout() != null) {
pooledConnectionFactory.setBlockIfSessionPoolIsFullTimeout(
pool.getBlockIfFullTimeout().toMillis());
}
pooledConnectionFactory
.setCreateConnectionOnStartup(pool.isCreateConnectionOnStartup());
if (pool.getExpiryTimeout() != null) {
pooledConnectionFactory
.setExpiryTimeout(pool.getExpiryTimeout().toMillis());
}
if (pool.getIdleTimeout() != null) {
pooledConnectionFactory
.setIdleTimeout((int) pool.getIdleTimeout().toMillis());
}
pooledConnectionFactory.setMaxConnections(pool.getMaxConnections());
pooledConnectionFactory.setMaximumActiveSessionPerConnection(
pool.getMaximumActiveSessionPerConnection());
pooledConnectionFactory
.setReconnectOnException(pool.isReconnectOnException());
if (pool.getTimeBetweenExpirationCheck() != null) {
pooledConnectionFactory.setTimeBetweenExpirationCheckMillis(
pool.getTimeBetweenExpirationCheck().toMillis());
}
pooledConnectionFactory
.setUseAnonymousProducers(pool.isUseAnonymousProducers());
return pooledConnectionFactory;
}
}
}
- 使用springboot2.1+时候，maven配置依赖是：
@Configuration
@ConditionalOnMissingBean(ConnectionFactory.class)
class ActiveMQConnectionFactoryConfiguration {
@Configuration
@ConditionalOnClass(CachingConnectionFactory.class)
@ConditionalOnProperty(prefix = "spring.activemq.pool", name = "enabled", havingValue = "false", matchIfMissing = true)
static class SimpleConnectionFactoryConfiguration {
private final JmsProperties jmsProperties;
private final ActiveMQProperties properties;
private final List<ActiveMQConnectionFactoryCustomizer> connectionFactoryCustomizers;
SimpleConnectionFactoryConfiguration(JmsProperties jmsProperties,
ActiveMQProperties properties,
ObjectProvider<ActiveMQConnectionFactoryCustomizer> connectionFactoryCustomizers) {
this.jmsProperties = jmsProperties;
this.properties = properties;
this.connectionFactoryCustomizers = connectionFactoryCustomizers
.orderedStream().collect(Collectors.toList());
}
@Bean
@ConditionalOnProperty(prefix = "spring.jms.cache", name = "enabled", havingValue = "true", matchIfMissing = true)
public CachingConnectionFactory cachingJmsConnectionFactory() {
JmsProperties.Cache cacheProperties = this.jmsProperties.getCache();
CachingConnectionFactory connectionFactory = new CachingConnectionFactory(
createConnectionFactory());
connectionFactory.setCacheConsumers(cacheProperties.isConsumers());
connectionFactory.setCacheProducers(cacheProperties.isProducers());
connectionFactory.setSessionCacheSize(cacheProperties.getSessionCacheSize());
return connectionFactory;
}
@Bean
@ConditionalOnProperty(prefix = "spring.jms.cache", name = "enabled", havingValue = "false")
public ActiveMQConnectionFactory jmsConnectionFactory() {
return createConnectionFactory();
}
private ActiveMQConnectionFactory createConnectionFactory() {
return new ActiveMQConnectionFactoryFactory(this.properties,
this.connectionFactoryCustomizers)
.createConnectionFactory(ActiveMQConnectionFactory.class);
}
}
@Configuration
@ConditionalOnClass({ JmsPoolConnectionFactory.class, PooledObject.class })
static class PooledConnectionFactoryConfiguration {
@Bean(destroyMethod = "stop")
@ConditionalOnProperty(prefix = "spring.activemq.pool", name = "enabled", havingValue = "true", matchIfMissing = false)
public JmsPoolConnectionFactory pooledJmsConnectionFactory(
ActiveMQProperties properties,
ObjectProvider<ActiveMQConnectionFactoryCustomizer> factoryCustomizers) {
ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactoryFactory(
properties,
factoryCustomizers.orderedStream().collect(Collectors.toList()))
.createConnectionFactory(ActiveMQConnectionFactory.class);
return new JmsPoolConnectionFactoryFactory(properties.getPool())
.createPooledConnectionFactory(connectionFactory);
}
}
}
很明显我们看的出来，2.1和2.0以下版本使用连接池时候的连接池对象不一样：
- 2.0+以下版本使用的是PooledConnectionFactory，它存在于org.apache.activemq.pool.PooledConnectionFactory
- 2.1+版本使用的是JmsPoolConnectionFactory，它存在于org.messaginghub.pooled.jms.JmsPoolConnectionFactory
由此我们就明白了为什么更换连接池依赖就ok，因为JmsMessagingTemplate本身依赖连接工厂，启用连接池后就会依赖连接池工厂，因为版本的原因，如果没有正确的引入连接池依赖，那么必定会出现文章一开头说的，项目启动报错：JmsMessagingTemplate无法注入
最后在提醒一下注意源码中的注解：
@ConditionalOnProperty(prefix = "spring.activemq.pool", name = "enabled", havingValue = "true", matchIfMissing = false)
当前缀为：spring.activemq.pool 的配置的属性：enabled的值为：true 的时候就会实例化bean，如果没有正确引入连接池依赖就会报错。