Key with alias xxx doesn't have a private key with Spring SAML
<p>I'm trying to test this sample application (<a href="https://github.com/deeprot/spring-saml-adfs" rel="nofollow">https://github.com/deeprot/spring-saml-adfs</a>), its a simple Spring SAML Sample application, with my environment, so, I have this error:</p>

<p>SEVERE: Servlet.service() for servlet [default] in context with path [/spring-security-saml2-sample] threw exception
java.lang.RuntimeException: Key with alias XXXX doesn't have a private key</p>

<p>I'm imported the CER file of the IDP system in my KeyStore, but, I dont have a private key for this CER. </p>

<p>Any idea?</p>

<p>The LOG:</p>

<pre><code>[2016-01-22 13:31:04.586] DEBUG [AntPathRequestMatcher] --- Checking match of request : ''; against '/favicon.ico'
[2016-01-22 13:31:04.595] DEBUG [AntPathRequestMatcher] --- Checking match of request : ''; against '/images/**'
[2016-01-22 13:31:04.595] DEBUG [AntPathRequestMatcher] --- Checking match of request : ''; against '/css/**'
[2016-01-22 13:31:04.613] DEBUG [AntPathRequestMatcher] --- Checking match of request : ''; against '/logout.jsp'
[2016-01-22 13:31:04.613] DEBUG [AntPathRequestMatcher] --- Checking match of request : ''; against '/saml/web/**'
[2016-01-22 13:31:04.614] DEBUG [FilterChainProxy] ---  at position 1 of 9 in additional filter chain; firing Filter: 'MetadataGeneratorFilter'
[2016-01-22 13:31:04.615] INFO  [MetadataGeneratorFilter] --- No default metadata configured, generating with default values, please pre-configure metadata for production use
[2016-01-22 13:31:04.615] WARN  [MetadataGeneratorFilter] --- Generated default entity base URL https://localhost:8443/spring-security-saml2-sample based on values in the first server request. Please set property entityBaseURL on MetadataGenerator bean to fixate the value.
[2016-01-22 13:31:04.631] DEBUG [KeyStoreCredentialResolver] --- Building credential from keystore entry for entityID appus, usage type UNSPECIFIED
[2016-01-22 13:31:04.631] DEBUG [KeyStoreCredentialResolver] --- Processing TrustedCertificateEntry from keystore
[2016-01-22 13:31:04.632] DEBUG [EvaluableCredentialCriteriaRegistry] --- Registry located evaluable criteria class org.opensaml.xml.security.credential.criteria.EvaluableEntityIDCredentialCriteria for criteria class org.opensaml.xml.security.criteria.EntityIDCriteria
Jan 22, 2016 1:31:04 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [default] in context with path [/spring-security-saml2-sample] threw exception
java.lang.RuntimeException: Key with alias XXXX doesn't have a private key
    at org.springframework.security.saml.metadata.MetadataGenerator.getServerKeyInfo(MetadataGenerator.java:209)
    at org.springframework.security.saml.metadata.MetadataGenerator.buildSPSSODescriptor(MetadataGenerator.java:329)
    at org.springframework.security.saml.metadata.MetadataGenerator.generateMetadata(MetadataGenerator.java:189)
    at org.springframework.security.saml.metadata.MetadataGeneratorFilter.processMetadataInitialization(MetadataGeneratorFilter.java:127)
    at org.springframework.security.saml.metadata.MetadataGeneratorFilter.doFilter(MetadataGeneratorFilter.java:86)
    at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
</code></pre>