Paypal Integration with struts2

Question

I am trying to integrate paypal. I followed all the steps given in this link: Paypal Integration Wizard .

When I click on the Paypal button I get the error as:

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)

After going though the forums I added this piece of code:

static public void doTrustToCertificates() throws Exception {
    try{
        Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());
        TrustManager[] trustAllCerts = new TrustManager[]{
            new X509TrustManager() {

                @Override
                public X509Certificate[] getAcceptedIssuers() {
                        // TODO Auto-generated method stub
                        return null;
                }

                @Override
                public void checkServerTrusted(X509Certificate[] arg0, String arg1)
                        throws CertificateException {
                        // TODO Auto-generated method stub
                }

                @Override
                public void checkClientTrusted(X509Certificate[] arg0, String arg1)
                        throws CertificateException {
                        // TODO Auto-generated method stub
                        }
                }
        };

        SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, trustAllCerts, new SecureRandom());
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
        HostnameVerifier hv = new HostnameVerifier() {
            public boolean verify(String urlHostName, SSLSession session) {
                if (!urlHostName.equalsIgnoreCase(session.getPeerHost())) {
                    System.out.println("Warning: URL host '" + urlHostName + "' is different to SSLSession host '" + session.getPeerHost() + "'.");
                }
                return true;
            }
        };
        HttpsURLConnection.setDefaultHostnameVerifier(hv);
    } catch(Exception e){
        e.printStackTrace();
    }
}

And Called the method just before calling an URL. Now I get a different exception stating that

java.net.SocketException: Unexpected end of file from server
    at sun.net.www.http.HttpClient.parseHTTPHeader(Unknown Source)
    at sun.net.www.http.HttpClient.parseHTTP(Unknown Source)
    at sun.net.www.http.HttpClient.parseHTTPHeader(Unknown Source)
    at sun.net.www.http.HttpClient.parseHTTP(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
    at com.paypal.actions.PaypalFunctions.httpcall(PaypalFunctions.java:297)
    at com.paypal.actions.PaypalFunctions.setExpressCheckout(PaypalFunctions.java:151)
    at com.paypal.actions.Checkout.doGet(Checkout.java:72)
    at com.paypal.actions.Checkout.doPost(Checkout.java:95)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:646)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    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.ApplicationDispatcher.invoke(ApplicationDispatcher.java:748)

Answer 1

After doing 4-5 days of research I understood that the firewall in the company stopping to access. I tried with my home network and I could able to do it. I will post my version shortly with all the necessary code.