使用placeholder实现动态配置persistence.xml

项目用到spring data jpa 和 hibernate, 正常情况下会在src/resources下创建META-INF目录, 并在其中创建persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
             xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
            http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">

    <persistence-unit name="myJPA" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <properties>
            <!--配置Hibernate方言 -->
            <property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5Dialect" />
            <!--配置数据库驱动 -->
            <property name="hibernate.connection.driver_class" value="com.mysql.jdbc.Driver" />
            <!--配置数据库用户名 -->
            <property name="hibernate.connection.username" value="root" />
            <!--配置数据库密码 -->
            <property name="hibernate.connection.password" value="root" />
            <!--配置数据库url -->
            <property name="hibernate.connection.url"
                      value="jdbc:mysql://localhost:3306/test?useUnicode=true&amp;characterEncoding=UTF-8" />
            <!--设置外连接抓取树的最大深度 -->
            <property name="hibernate.max_fetch_depth" value="3" />
            <property name="hibernate.jdbc.fetch_size" value="18" />
            <property name="hibernate.jdbc.batch_size" value="10" />
            <!--自动输出schema创建DDL语句 -->
            <property name="hibernate.hbm2ddl.auto" value="update" />
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="true" />
            <property name="javax.persistence.validation.mode" value="none" />
        </properties>
    </persistence-unit>
</persistence>

applicationContext.xml中

<!-- 定义实体管理器工厂 -->
    <bean id="entityManagerFactory"
        class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="persistenceUnitName" value="myJPA" />
    </bean>

但是现在需要在applicationContext.xml中配置 dataSource, 而其中用到了 数据库地址,用户名这些信息, 为了方便, 统一使用 properties 文件保存信息, 并做如下修改

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
             xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
            http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">

    <persistence-unit name="myJPA" transaction-type="RESOURCE_LOCAL"/>
</persistence>

在 src/resources 下创建 config.properties 文件, 并输入配置项

database.driver=com.mysql.jdbc.Driver
database.url=jdbc:mysql://localhost:3306/lottery?autoReconnect=true&useUnicode=true&characterEncoding=UTF-8
database.username=root
database.password=root

applicationContext.xml

<context:property-placeholder location="classpath:config.properties" system-properties-mode="OVERRIDE"/>

    <!--  使用spring 加载jdbc驱动  -->
    <bean id="dataSourceTemplate" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${database.driver}" />
        <property name="url" value="${database.url}" />
        <property name="username" value="${database.username}" />
        <property name="password" value="${database.password}" />
    </bean>

    <!--tomcat jdbc pool数据源配置-->
    <bean id="dataSource" class="org.apache.tomcat.jdbc.pool.DataSource" destroy-method="close">
        <!--  通过引用加载数据库信息  -->
        <property name="dataSource" ref="dataSourceTemplate"/>

        <property name="jmxEnabled" value="true"/>
        <property name="testWhileIdle" value="true"/>
        <property name="testOnBorrow" value="true"/>
        <property name="testOnReturn" value="false"/>
        <property name="validationInterval" value="30000"/>
        <property name="validationQuery" value="SELECT 1"/>
        <property name="timeBetweenEvictionRunsMillis" value="30000"/>
        <property name="initialSize" value="10"/>
        <property name="maxActive" value="40"/>
        <property name="minIdle" value="10"/>
        <property name="maxIdle" value="20"/>
        <property name="maxWait" value="10000"/>
        <property name="minEvictableIdleTimeMillis" value="30000"/>
        <property name="logAbandoned" value="false"/>
        <property name="removeAbandoned" value="true"/>
        <property name="removeAbandonedTimeout" value="60"/>
        <property name="jdbcInterceptors" value="org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer"/>
    </bean>


    <!-- 定义实体管理器工厂 -->
    <bean id="entityManagerFactory"
          class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
        <property name="persistenceUnitName" value="myJPA" />
        <property name="dataSource" ref="dataSource" />
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <property name="showSql" value="true"/>
                <property name="databasePlatform" value="org.hibernate.dialect.MySQL5Dialect"/>
                <property name="generateDdl" value="true" />
                <property name="database" value="MYSQL" />
            </bean>
        </property>
        <property name="persistenceProviderClass" value="org.hibernate.jpa.HibernatePersistenceProvider"/>
        <property name="jpaProperties">
            <props>
                <prop key="hibernate.ejb.naming_strategy">org.hibernate.cfg.ImprovedNamingStrategy</prop>
                <prop key="hibernate.dialect">org.hibernate.dialect.MySQL5Dialect</prop>
                <prop key="hibernate.connection.driver_class">com.mysql.jdbc.Driver</prop>
                <prop key="hibernate.connection.url">${database.url}</prop>
                <prop key="hibernate.connection.username">${database.username}</prop>
                <prop key="hibernate.connection.password">${database.password}</prop>
                <prop key="hibernate.max_fetch_depth">3</prop>
                <prop key="hibernate.jdbc.fetch_size">18</prop>
                <prop key="hibernate.jdbc.batch_size">10</prop>
                <prop key="hibernate.hbm2ddl.auto">update</prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.format_sql">true</prop>
                <prop key="javax.persistence.validation.mode">none</prop>
            </props>
        </property>
    </bean>

dataSourceTemplate 和 dataSource 这么定义是为解决 Tomcat jdbc pool 加载时找不到 Driver 类的错误. http://www.cnblogs.com/ykt8465279130/p/3669355.html