How to Solve JDBC connection error in spring MVC integration

# Error Message:

### Error querying database.  Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
### The error may exist in com/dao/BookMapper.xml
### The error may involve com.dao.BookMapper.queryAllBook
### The error occurred while executing a query
### Cause: org.springframework.jdbc.CannotGetJdbcConnectionException: Failed to obtain JDBC Connection; nested exception is java.sql.SQLException: Connections could not be acquired from the underlying database!
	java.sql.SQLException: Access denied for user 'Charles'@'localhost' (using password: YES)
		at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129)
		at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97)
		at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122)
		at com.mysql.cj.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:835)
		at com.mysql.cj.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:455)
		at com.mysql.cj.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:240)
		at com.mysql.cj.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:207)
		at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:175)
		at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:220)
		at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:206)
		at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:203)
		at com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1138)
		at com.mchange.v2.resourcepool.BasicResourcePool.doAcquireAndDecrementPendingAcquiresWithinLockOnSuccess(BasicResourcePool.java:1125)
		at com.mchange.v2.resourcepool.BasicResourcePool.access$700(BasicResourcePool.java:44)
		at com.mchange.v2.resourcepool.BasicResourcePool$ScatteredAcquireTask.run(BasicResourcePool.java:1870)
		at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:696)

Cause analysis:

    1. check the database.properties file, but there is no error </ OL>
driver = com.mysql.cj.jdbc.Driver
url = jdbc:mysql://localhost:3306/ssm?serverTimezone=UTC
username = root
password = admin
      1. the database used is mysql8.0, and the versions of database driver and database connection pool also match the database version </ OL>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.13</version>
        </dependency>

        <!-- Database connection -->
        <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>c3p0</artifactId>
            <version>0.9.5.2</version>
        </dependency>
        1. related dependencies are also added to the artifacts in project structure

        1. . There is no mistake in the spring Dao configuration file. All reference paths are correct </ OL>
	<context:property-placeholder location="classpath:database.properties"/>

    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="driverClass" value="${driver}"/>
        <property name="jdbcUrl" value="${url}"/>
        <property name="user" value="${username}"/>
        <property name="password" value="${password}"/>

        <property name="maxPoolSize" value="30"/>
        <property name="minPoolSize" value="10"/>

        <property name="autoCommitOnClose" value="false"/>
        <property name="checkoutTimeout" value="10000"/>
        <property name="acquireRetryAttempts" value="2"/>
    </bean>

There is also a prompt when the cursor is placed on the value

online solutions have been tried and have not taken effect

Solution:

Finally, I accidentally tried to explicitly assign the attribute of the database connection pool, and the connection was successful

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