PKIX path building failed when getting data from URL

Question

I am trying to get data as follows (indicated thus by the API):

HttpResponse<String> response = Unirest.get("https://opendata.aemet.es/opendata/api/valores/climatologicos/diarios/datos/fechaini/2017-08-16T00:00:00UTC/fechafin/2017-08-17T23:59:59UTC/estacion/2422/?api_key=eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJqb3NoZXJAY2FydGlmLmVzIiwianRpIjoiZWM3MDkxMzItNTE0ZC00OGZjLTljMjMtYTBiMzVjNTllYzdjIiwiZXhwIjoxNTEwNzMxMzU4LCJpc3MiOiJBRU1FVCIsImlhdCI6MTUwMjk1NTM1OCwidXNlcklkIjoiZWM3MDkxMzItNTE0ZC00OGZjLTljMjMtYTBiMzVjNTllYzdjIiwicm9sZSI6IiJ9.WSVaE3C9TFMMa8x1mUvHpt1-n3Cgy3p7r2DaflSm9VU")
              .header("cache-control", "no-cache")
              .asString();

Nevertheless, when I execute the code, an exception is thrown:

Exception in thread "main" com.mashape.unirest.http.exceptions.UnirestException: 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 com.mashape.unirest.http.HttpClientHelper.request(HttpClientHelper.java:143)
    at com.mashape.unirest.request.BaseRequest.asString(BaseRequest.java:56)
    at eu.cartif.meteo.Weather_Meteo.main(Weather_Meteo.java:38)
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(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.SSLConnectionSocketFactory.createLayeredSocket(SSLConnectionSocketFactory.java:396)
    at org.apache.http.conn.ssl.SSLConnectionSocketFactory.connectSocket(SSLConnectionSocketFactory.java:355)
    at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:142)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:359)
    at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:381)
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:237)
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:111)
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
    at com.mashape.unirest.http.HttpClientHelper.request(HttpClientHelper.java:138)
... 2 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(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)
... 24 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)
... 30 more    

I have also tried to import the certificate by means of the keytool, but I get a message saying "The file keystore does not exist".

May someone support me? Thanks in advance

Answer 1

5 seconds with a browser gave me all this information:

Your connection is not secure

The owner of opendata.aemet.es has configured their web site improperly. To protect your information from being stolen, Firefox has not connected to this web site.

Learn more…

Report errors like this to help Mozilla identify and block malicious sites

opendata.aemet.es uses an invalid security certificate.

The certificate is not trusted because the issuer certificate is unknown.
The server might not be sending the appropriate intermediate certificates.
An additional root certificate may need to be imported.

Error code: SEC_ERROR_UNKNOWN_ISSUER

Answer 2

the version I use unirest is 3.1.02, maven config is :

<dependency>
   <groupId>com.konghq</groupId>
   <artifactId>unirest-java</artifactId>
   <version>3.1.02</version>
   <classifier>standalone</classifier>
</dependency>

and I see kong.unirest.UnirestException: javax.net.ssl.SSLHandshakeException。 when I config Unirest.config().verifySsl(false); it works ,the exception disappear