Java在处理SSL时证书无效的问题，以及解决方法

Java内置了对HTTPS和SSL的支持，但是我在写客户端时遇到了一些问题，比如最大的问题就是在连接的服务器没有一个有效的（也就是经过根CA认证的）SSL证书时会报错。Google了一下，说有两种方式：一种是事先把目标证书导入Java的证书管理器里，另一种是强制忽略证书合法性检查。第一种方法不用对代码进行什么更改，只要运行一个命令就行了，但是缺点是每次服务器更换证书都要进行一次导入。
第二种方法需要更改一下代码，优点是可以应用于任何SSL证书，而且不用重复导入，缺点也很明显，降低了系统的安全性。
下面是第二钟方法的实例代码

             try {
                 final SSLContext sslContext = SSLContext.getInstance("TLSv1");
                 sslContext.init(null, new TrustManager[]{new X509TrustManager() {

                         public void checkClientTrusted(X509Certificate[] arg0, String arg1) throws CertificateException {
                         }

                         public void checkServerTrusted(X509Certificate[] arg0, String arg1) throws CertificateException {
                             //这里进行有效性检查，不抛出异常就算检查成功
                         }

                         public X509Certificate[] getAcceptedIssuers() {
                             return null;
                         }
                     }
                         }, null);
                 sleep(100);
                 SSLSocketFactory factory = sslContext.getSocketFactory();
                 final SSLSocket socket = (SSLSocket) factory.createSocket("127.0.0.1", 4433);
                 SSLSession session = socket.getSession();
                 X509Certificate cert = null;
                 try {
                     cert = (X509Certificate) session.getPeerCertificates()[0];
                 } catch (SSLPeerUnverifiedException e) {
                     e.printStackTrace();
                     System.err.println(session.getPeerHost() + " did not present a valid certificate");
                     return;
                 }
                 System.out.println(session.getPeerHost() + " has presented a certificate belonging to" + "[" + cert.getSubjectDN() + "]\n" + "The certificate was issued by: \t" + "[" + cert.getIssuerDN() + "]");
                 PrintWriter pw = new PrintWriter(socket.getOutputStream());
                 pw.println("GET /index.html HTTP/1.0");
                 pw.println("Server: mail.google.com");
                 pw.println("Connection: close");
                 pw.println();
                 pw.flush();
                 BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                 String ln;
                 while ((ln = in.readLine()) != null) {
                     System.err.println(ln);
                 }
             } catch (Exception ex) {
                 Logger.getLogger(ServerLauncher.class.getName()).log(Level.SEVERE, null, ex);
             }