db.properties正确写法

一开始我是这么写的:

applicationContext.xml如下:
<bean class="com.mchange.v2.c3p0.ComboPooledDataSource" id="dataSource">
        <property name="driverClass" value="${driverClass}"/>
        <property name="jdbcUrl" value="${jdbcUrl}"/>
        <property name="user" value="${user}"/>
        <property name="password" value="${password}"/>
    </bean>


db.properties如下:
driverClass=com.mysql.cj.jdbc.Driver
jdbcUrl=jdbc:mysql:///test?useSSL=false
user=root
password=daiwenxiang

尝试了很多遍, 始终报错,但是我把它写死,不用${}来读取 就没有问题,我在另一台机器 用的mysql 5.7 就没有问题 maven驱动用的是5.1.40版本,这台机器用的是mysql8,所有用的mysql驱动是8.0.15

报错信息如下:

Caused by: org.apache.ibatis.exceptions.PersistenceException: 
### Error updating database.  Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:200)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.insert(DefaultSqlSession.java:185)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
    ... 6 more
Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80)
    at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:82)
    at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:68)
    at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:336)
    at org.apache.ibatis.executor.BatchExecutor.doUpdate(BatchExecutor.java:69)
    at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117)
    at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:63)
    at com.sun.proxy.$Proxy14.update(Unknown Source)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:198)
    ... 12 more
Caused by: java.sql.SQLException: Connections could not be acquired from the underlying database!
    at com.mchange.v2.sql.SqlUtils.toSQLException(SqlUtils.java:106)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:529)
    at com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource.getConnection(AbstractPoolBackedDataSource.java:128)
    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)
    ... 25 more
Caused by: com.mchange.v2.resourcepool.CannotAcquireResourceException: A ResourcePool could not acquire a resource from its primary factory or source.
    at com.mchange.v2.resourcepool.BasicResourcePool.awaitAvailable(BasicResourcePool.java:1319)
    at com.mchange.v2.resourcepool.BasicResourcePool.prelimCheckoutResource(BasicResourcePool.java:557)
    at com.mchange.v2.resourcepool.BasicResourcePool.checkoutResource(BasicResourcePool.java:477)
    at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool.checkoutPooledConnection(C3P0PooledConnectionPool.java:525)
    ... 28 more

Process finished with exit code 1

正确的写法是:前面得加上db点,不加就报错

然后读取的时候:如下

这个我研究了半天才发现原因,因为是我mysql 8 版本的,我另一台机器是mysql 5.7 的  用的驱动也不一样,8版本的 driverClass是com.mysql.cj.jdbc.Driver;