當我嘗試使用資料來源訪問mysql時，發生了這樣的異常：
java.sql.SQLException: Access denied for user 'root'@'localhost' (using password: YES)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:965) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3978) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3914) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:871) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1714) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1224) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2199) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2230) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2025) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:778) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:47) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[na:1.8.0_181]
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[na:1.8.0_181]
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[na:1.8.0_181]
at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[na:1.8.0_181]
at com.mysql.jdbc.Util.handleNewInstance(Util.java:425) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:386) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:330) ~[mysql-connector-java-5.1.47.jar:5.1.47]
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1596) ~[druid-1.1.16.jar:1.1.16]
at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1662) ~[druid-1.1.16.jar:1.1.16]
at com.alibaba.druid.pool.DruidDataSource$CreateConnectionThread.run(DruidDataSource.java:2601) ~[druid-1.1.16.jar:1.1.16]
2022-05-27 17:45:02.559 ERROR 31428 --- [eate-1875532039] com.alibaba.druid.pool.DruidDataSource : create connection SQLException, url: jdbc:mysql://localhost:3306/db2022?useUnicode=true&characterEncoding=utf-8&useSSL=false, errorCode 1045, state 28000
原因很低階：application.yml內容：
spring:
datasource:
driver-class-name: com.mysql.jdbc.Driver
url: jdbc:mysql://localhost:3306/db2022?useUnicode=true&characterEncoding=utf-8&useSSL=false
username: root
password: 0123
type: com.alibaba.druid.pool.DruidDataSource改成 application.properties就可以，那是什麼原因呢？
很簡單： 0123這個密碼，被yml解析成非字串了， 加個雙引號就好了，e不easy?password: "0123"