Hibernate4学习（二）配置druid数据连接池

    Hibernate中使用Druid数据库连接池配置如下

<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>
		
		<property name="hibernate.connection.provider_class">
			com.alibaba.druid.support.hibernate.DruidConnectionProvider
		</property>
		<property name="driverClassName">com.mysql.jdbc.Driver</property>
		<property name="url">
				jdbc:mysql://127.0.0.1:3306/lian?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=utf-8&amp;zeroDateTimeBehavior=convertToNull&amp;useSSL=false
		</property>
		<property name="username">root</property>
        <property name="password">root</property>
      	
	    <!-- 配置初始化大小、最小、最大 -->
	    <property name="initialSize">1</property>
	    <property name="minIdle">1</property>
	    <property name="maxActive">20</property>
	 
	    <!-- 配置获取连接等待超时的时间 -->
	    <property name="maxWait">60000</property>
	 
	    <!-- 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒 -->
	    <property name="timeBetweenEvictionRunsMillis">60000</property>
	 
	    <!-- 配置一个连接在池中最小生存的时间，单位是毫秒 -->
	    <property name="minEvictableIdleTimeMillis">300000</property>
	 
	   
	    <!-- 打开PSCache，并且指定每个连接上PSCache的大小 -->
	    <property name="poolPreparedStatements">true</property>
	    <property name="maxPoolPreparedStatementPerConnectionSize">20</property>
	 
	    <!-- 配置监控统计拦截的filters，去掉后监控界面sql无法统计 -->
	    <property name="filters">stat</property>
        <!-- JDBC connection pool (use the built-in) -->
      <!--   <property name="connection.pool_size">5</property> -->
		
        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.internal.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">update</property>
		
        <mapping resource="conf/hibernate/domain/Music.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

     在配置Druid数据库中连接池常常容易犯的一个错误，数据源容易配置错误，使用Hibernate默认的配置

 <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">
        	jdbc:mysql://127.0.0.1:3306/lian?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=utf-8&amp;zeroDateTimeBehavior=convertToNull&amp;useSSL=false
        </property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>

    然后Druid连接池并不能识别上面的配置，会抛出空指针异常，无法创建连接池对象，数据源正确的配置如下

<property name="driverClassName">com.mysql.jdbc.Driver</property>
		<property name="url">
				jdbc:mysql://127.0.0.1:3306/lian?autoReconnect=true&amp;useUnicode=true&amp;characterEncoding=utf-8&amp;zeroDateTimeBehavior=convertToNull&amp;useSSL=false
		</property>
		<property name="username">root</property>
        <property name="password">root</property>

 补充：配置mysql数据库连接url时，需要添加一些参数，在XML文件中参数分隔符"&"符号需要使用转义字符，具体见上。