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

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.<init>(ConnectionImpl.java:834)

at com.mysql.jdbc.JDBC4Connection.<init>(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