mysql-datasource.properties配置文件哪里有错

jdbc.driver=com.mysql.jdbc.Driver
db.url=jdbc:mysql:10.243.40.19:3306:mest
db.usr=root
db.psw=123456

报org.apache.commons.dbcp.SQLNestedException: Cannot create JDBC driver of class 'com.mysql.jdbc.Driver' for connect URL 'jdbc:mysql:10.243.40.19:3306:mest'这个错