修改url：在url后加上?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC"

 <!-- 数据库连接池 -->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
          destroy-method="close">
        <property name="url" value="jdbc:mysql://localhost:3306/user_db?useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC" />
        <property name="username" value="root" />
        <property name="password" value="123456" />
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
    </bean>