我使用服务器中应用程序中的WS在Salesforce和SAP之间建立连接。连接有效，直到服务器中安装了SSL证书为止。在安装证书后，当我向应用程序发出请求时出现此错误：
System.HttpRequest retrying request in response to handshake failure: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
System.CalloutException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
解决此问题的解决方案是什么？ 在此先感谢。