用已有的openssl的pem生成java的证书

1.先用得到的server.pem在openssl环境中生成der证书
   openssl x509 -in server.pem -out clientapp.der -outform DER
2.在java环境中生成java的证书
   keytool -keystore c:\key\mycerts -alias clientapp -import -file c:\key\clientapp.der
3.现在可以用以下方式连接server了
   Socket socket = null;
KeyManagerFactory kmf;
KeyStore ks;
TrustManagerFactory tmf;
SSLContext sslc;

kmf = KeyManagerFactory.getInstance(ALGORITHM);
ks = KeyStore.getInstance("JKS");
ks.load(new FileInputStream(KEYSTORE_FILE), PASSWORD.toCharArray());
kmf.init(ks, PASSWORD.toCharArray());
tmf = TrustManagerFactory.getInstance(ALGORITHM);
tmf.init(ks);
sslc = SSLContext.getInstance("TLS");
sslc.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);

// The process is different from here on the client. Instead of
// getting a ServerSocketFactory, we ask for a SocketFactory from
// the SSL context.
SocketFactory sf = sslc.getSocketFactory();

// Then we get the socket from the factory and treat it
// as if it were a standard (plain) socket.
socket = sf.createSocket(HOST, PORT);