连接url中参数useSSL=true引发的缺少证书异常（使用mysql-connector）

最近在做架构迁移，将基于oracle、ejb、weblogic架构的OA系统迁移至mysql、tomcat环境下。在修改完数据库函数之后，启动测试的时候，遇到一个很诡异的异常，如下：

The last packet successfully received from the server was 6 milliseconds ago. The last packet sent successfully to the server was 6 milliseconds ago. at sun.reflect.GeneratedConstructorAccessor34.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:526) at com.mysql.jdbc.Util.handleNewInstance(Util.java:408) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1137) at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:112) at com.mysql.jdbc.MysqlIO.negotiateSSLConnection(MysqlIO.java:5236) at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1719) at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1287) at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2494) at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2527) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2309) at com.mysql.jdbc.ConnectionImpl.(ConnectionImpl.java:834) at com.mysql.jdbc.JDBC4Connection.(JDBC4Connection.java:46) at sun.reflect.GeneratedConstructorAccessor27.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:526) at com.mysql.jdbc.Util.handleNewInstance(Util.java:408) at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:419) at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:344) at com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:68) at com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:87) at com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1.acquireResource(C3P0PooledConnectionPool.java:83) at com.mchange.v2.resourcepool.BasicResourcePool.assimilateResource(BasicResourcePool.java:884) at com.mchange.v2.resourcepool.BasicResourcePool.acquireUntil(BasicResourcePool.java:601) at com.mchange.v2.resourcepool.BasicResourcePool.access$400(BasicResourcePool.java:31) at com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1079) at com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:354) Caused by: javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at sun.security.ssl.Alerts.getSSLException(Alerts.java:192) at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1904) at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:279) at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:273) at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1446) at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:209) at sun.security.ssl.Handshaker.processLoop(Handshaker.java:913) at sun.security.ssl.Handshaker.process_record(Handshaker.java:849) at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1023) at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1332) at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1359) at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1343) at com.mysql.jdbc.ExportControlled.transformSocketToSSLSocket(ExportControlled.java:97) ... 22 more Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:385) at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:292) at sun.security.validator.Validator.validate(Validator.java:260) at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:326) at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:231) at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:126) at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1428) ... 30 more Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:196) at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:268) at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:380) ... 36 more com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

异常提示缺少证书，也不知道是什么鬼~~。但是，将连接url中的useSSL=true去掉，异常就解决了（当前使用的mysql-connector-java-5.1.32.jar与MySQL 8.0.19数据库，不知道是否和此有关）。