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 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
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package org.apache.http.impl.client;

import java.security.Principal;

import javax.net.ssl.SSLSession;

import org.apache.http.HttpConnection;
import org.apache.http.annotation.Contract;
import org.apache.http.annotation.ThreadingBehavior;
import org.apache.http.auth.AuthScheme;
import org.apache.http.auth.AuthState;
import org.apache.http.auth.Credentials;
import org.apache.http.client.UserTokenHandler;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.conn.ManagedHttpClientConnection;
import org.apache.http.protocol.HttpContext;

Default implementation of UserTokenHandler. This class will use an instance of Principal as a state object for HTTP connections, if it can be obtained from the given execution context. This helps ensure persistent connections created with a particular user identity within a particular security context can be reused by the same user only. 
 DefaultUserTokenHandler will use the user principal of connection based authentication schemes such as NTLM or that of the SSL session with the client authentication turned on. If both are unavailable, null token will be returned. 
Since:
4.0/**
 * Default implementation of {@link UserTokenHandler}. This class will use
 * an instance of {@link Principal} as a state object for HTTP connections,
 * if it can be obtained from the given execution context. This helps ensure
 * persistent connections created with a particular user identity within
 * a particular security context can be reused by the same user only.
 * <p>
 * DefaultUserTokenHandler will use the user principal of connection
 * based authentication schemes such as NTLM or that of the SSL session
 * with the client authentication turned on. If both are unavailable,
 * {@code null} token will be returned.
 *
 * @since 4.0
 */
@Contract(threading = ThreadingBehavior.IMMUTABLE)
public class DefaultUserTokenHandler implements UserTokenHandler {

    public static final DefaultUserTokenHandler INSTANCE = new DefaultUserTokenHandler();

    @Override
    public Object getUserToken(final HttpContext context) {

        final HttpClientContext clientContext = HttpClientContext.adapt(context);

        Principal userPrincipal = null;

        final AuthState targetAuthState = clientContext.getTargetAuthState();
        if (targetAuthState != null) {
            userPrincipal = getAuthPrincipal(targetAuthState);
            if (userPrincipal == null) {
                final AuthState proxyAuthState = clientContext.getProxyAuthState();
                userPrincipal = getAuthPrincipal(proxyAuthState);
            }
        }

        if (userPrincipal == null) {
            final HttpConnection conn = clientContext.getConnection();
            if (conn.isOpen() && conn instanceof ManagedHttpClientConnection) {
                final SSLSession sslsession = ((ManagedHttpClientConnection) conn).getSSLSession();
                if (sslsession != null) {
                    userPrincipal = sslsession.getLocalPrincipal();
                }
            }
        }

        return userPrincipal;
    }

    private static Principal getAuthPrincipal(final AuthState authState) {
        final AuthScheme scheme = authState.getAuthScheme();
        if (scheme != null && scheme.isComplete() && scheme.isConnectionBased()) {
            final Credentials creds = authState.getCredentials();
            if (creds != null) {
                return creds.getUserPrincipal();
            }
        }
        return null;
    }

}