:javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building

I try to run soapui, I alway got error message as below:

someone give me any advise?

I use ReadyAPI 1.5.0 , java jdk1.8.0_102

ERROR: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

ERROR: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
   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(Unknown Source)
   	at sun.security.ssl.SSLSocketImpl.fatal(Unknown Source)
   	at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
   	at sun.security.ssl.Handshaker.fatalSE(Unknown Source)
   	at sun.security.ssl.ClientHandshaker.serverCertificate(Unknown Source)
   	at sun.security.ssl.ClientHandshaker.processMessage(Unknown Source)
   	at sun.security.ssl.Handshaker.processLoop(Unknown Source)
   	at sun.security.ssl.Handshaker.process_record(Unknown Source)
   	at sun.security.ssl.SSLSocketImpl.readRecord(Unknown Source)
   	at sun.security.ssl.SSLSocketImpl.performInitialHandshake(Unknown Source)
   	at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
   	at sun.security.ssl.SSLSocketImpl.startHandshake(Unknown Source)
   	at org.apache.http.conn.ssl.SSLSocketFactory.createLayeredSocket(SSLSocketFactory.java:552)
   	at org.apache.http.conn.ssl.SSLSocketFactory.createLayeredSocket(SSLSocketFactory.java:433)
   	at org.apache.http.impl.conn.DefaultClientConnectionOperator.updateSecureConnection(DefaultClientConnectionOperator.java:217)
   	at org.apache.http.impl.conn.AbstractPoolEntry.layerProtocol(AbstractPoolEntry.java:243)
   	at org.apache.http.impl.conn.AbstractPooledConnAdapter.layerProtocol(AbstractPooledConnAdapter.java:152)
   	at org.apache.http.impl.client.DefaultRequestDirector.establishRoute(DefaultRequestDirector.java:800)
   	at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:614)
   	at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:445)
   	at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:863)
   	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
   	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:57)
   	at com.eviware.soapui.impl.wsdl.support.http.HttpClientSupport$Helper.execute(HttpClientSupport.java:233)
   	at com.eviware.soapui.impl.wsdl.support.http.HttpClientSupport.execute(HttpClientSupport.java:323)
   	at com.eviware.soapui.impl.wsdl.submit.transports.http.HttpClientRequestTransport.submitRequest(HttpClientRequestTransport.java:295)
   	at com.eviware.soapui.impl.wsdl.submit.transports.http.HttpClientRequestTransport.sendRequest(HttpClientRequestTransport.java:225)
   	at com.eviware.soapui.impl.wsdl.WsdlSubmit.run(WsdlSubmit.java:119)
   	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
   	at java.util.concurrent.FutureTask.run(Unknown Source)
   	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
   	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
   	at java.lang.Thread.run(Unknown Source)
   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(Unknown Source)
   	at sun.security.validator.PKIXValidator.engineValidate(Unknown Source)
   	at sun.security.validator.Validator.validate(Unknown Source)
   	at sun.security.ssl.X509TrustManagerImpl.validate(Unknown Source)
   	at sun.security.ssl.X509TrustManagerImpl.checkTrusted(Unknown Source)
   	at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(Unknown Source)
   	... 29 more
   Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
   	at sun.security.provider.certpath.SunCertPathBuilder.build(Unknown Source)
   	at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(Unknown Source)
   	at java.security.cert.CertPathBuilder.build(Unknown Source)
   	... 35 more