how to resolve jsoup error: unable to find valid certification path to requested target

Question

I am trying to parse the html of the following URL:

https://www.smuc.ac.kr/mbs/smuc/jsp/board/list.jsp?boardId=6993&id=smuc_040100000000

I'm getting the following error:

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:387)
    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:324)
    at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:229)
    at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:124)
    at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1491)
    ... 15 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
    at sun.security.provider.certpath.SunCertPathBuilder.build(SunCertPathBuilder.java:141)
    at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:126)
    at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:280)
    at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:382)
    ... 21 more

This is my code:

public class MainActivity extends AppCompatActivity {
    private ListView listView;
    private TextView textView;
    public ArrayList<String> arrayList = new ArrayList<String>();
    private ArrayAdapter<String> arrayAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.listView);
        new Insert().execute();
        arrayAdapter = new ArrayAdapter<String>(MainActivity.this, R.layout.list_ok, R.id.text, arrayList );
       }

    class Insert extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... params) {
            try {
               // Connection.Response res = Jsoup.connect("https://www.smuc.ac.kr/mbs/smuc/index.jsp")
               //         .method(Connection.Method.POST)
               //         .execute();
                Document document = Jsoup.connect("https://www.smuc.ac.kr/mbs/smuc/jsp/board/list.jsp?boardId=6993&id=smuc_040100000000").get();
                Elements elements = document.select(".tit");
                arrayList.clear();
                for (Element element : elements) {
                    arrayList.add(element.text());
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
            return null;
        }
        @Override
        protected void onPostExecute(String result){
            listView.setAdapter(arrayAdapter);
        }

    }

}

Answer 1

---

This answer is outdated as JSoup has deprecated and removed the validateTLSCertificates method in version 1.12.1 (https://jsoup.org/news/release-1.12.1).

You can ignore TSL validation, set validateTLSCertificates(false):

Document document = Jsoup.connect("URL").timeout(10000).validateTLSCertificates(false).get();

Since reading the page also takes a while, increase the timeout timeout(10000).