001/**
002 * Copyright 2015 DuraSpace, Inc.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *     http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.fcrepo.mint;
017
018import static org.slf4j.LoggerFactory.getLogger;
019import static org.apache.commons.lang.StringUtils.isBlank;
020
021import org.slf4j.Logger;
022
023import com.codahale.metrics.annotation.Timed;
024import java.io.ByteArrayInputStream;
025import java.io.IOException;
026import java.net.URI;
027import java.util.function.Supplier;
028
029import org.w3c.dom.Document;
030
031import javax.xml.parsers.DocumentBuilder;
032import javax.xml.parsers.DocumentBuilderFactory;
033import javax.xml.parsers.ParserConfigurationException;
034import javax.xml.xpath.XPathException;
035import javax.xml.xpath.XPathExpression;
036import javax.xml.xpath.XPathExpressionException;
037import javax.xml.xpath.XPathFactory;
038
039import org.apache.http.HttpResponse;
040import org.apache.http.client.HttpClient;
041import org.apache.http.client.methods.HttpGet;
042import org.apache.http.client.methods.HttpPost;
043import org.apache.http.client.methods.HttpPut;
044import org.apache.http.client.methods.HttpUriRequest;
045import org.apache.http.impl.client.HttpClientBuilder;
046import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
047import org.apache.http.util.EntityUtils;
048import org.apache.http.auth.AuthScope;
049import org.apache.http.auth.UsernamePasswordCredentials;
050import org.apache.http.client.CredentialsProvider;
051import org.apache.http.impl.client.BasicCredentialsProvider;
052import org.xml.sax.SAXException;
053
054
055/**
056 * PID minter that uses an external REST service to mint PIDs.
057 *
058 * @author escowles
059 * @since 04/28/2014
060 */
061public class HttpPidMinter implements Supplier<String> {
062
063    private static final DocumentBuilderFactory DOCUMENT_BUILDER_FACTORY = DocumentBuilderFactory.newInstance();
064    private static final Logger LOGGER = getLogger(HttpPidMinter.class);
065    protected final String url;
066    protected final String method;
067    protected final String username;
068    protected final String password;
069    private final String regex;
070    private XPathExpression xpath;
071
072    protected HttpClient client;
073    private final PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager();
074
075    /**
076     * Create a new HttpPidMinter.
077     * @param url The URL for the minter service.  This is the only required argument -- all
078     *    other parameters can be blank.
079     * @param method The HTTP method (POST, PUT or GET) used to generate a new PID (POST will
080     *    be used if the method is blank.
081     * @param username If not blank, use this username to connect to the minter service.
082     * @param password If not blank, use this password used to connect to the minter service.
083     * @param regex If not blank, use this regular expression used to remove unwanted text from the
084     *    minter service response.  For example, if the response text is "/foo/bar:baz" and the
085     *    desired identifier is "baz", then the regex would be ".*:".
086     * @param xpath If not blank, use this XPath expression used to extract the desired identifier
087     *    from an XML minter response.
088    **/
089    public HttpPidMinter( final String url, final String method, final String username,
090        final String password, final String regex, final String xpath ) {
091
092        if (isBlank(url)) {
093            throw new IllegalArgumentException("Minter URL must be specified!");
094        }
095
096        this.url = url;
097        this.method = (method == null ? "post" : method);
098        this.username = username;
099        this.password = password;
100        this.regex = regex;
101        if ( !isBlank(xpath) ) {
102            try {
103                this.xpath = XPathFactory.newInstance().newXPath().compile(xpath);
104            } catch ( final XPathException ex ) {
105                LOGGER.warn("Error parsing xpath ({}): {}", xpath, ex );
106                throw new IllegalArgumentException("Error parsing xpath" + xpath, ex);
107            }
108        }
109        this.client = buildClient();
110    }
111
112    /**
113     * Setup authentication in httpclient.
114     * @return the setup of authentication
115    **/
116    protected HttpClient buildClient() {
117        HttpClientBuilder builder = HttpClientBuilder.create().useSystemProperties().setConnectionManager(connManager);
118        if (!isBlank(username) && !isBlank(password)) {
119            final URI uri = URI.create(url);
120            final CredentialsProvider credsProvider = new BasicCredentialsProvider();
121            credsProvider.setCredentials(new AuthScope(uri.getHost(), uri.getPort()),
122                new UsernamePasswordCredentials(username, password));
123            builder = builder.setDefaultCredentialsProvider(credsProvider);
124        }
125        return builder.build();
126    }
127
128    /**
129     * Instantiate a request object based on the method variable.
130    **/
131    private HttpUriRequest minterRequest() {
132        switch (method.toUpperCase()) {
133            case "GET":
134                return new HttpGet(url);
135            case "PUT":
136                return new HttpPut(url);
137            default:
138                return new HttpPost(url);
139        }
140    }
141
142    /**
143     * Remove unwanted text from the minter service response to produce the desired identifier.
144     * Override this method for processing more complex than a simple regex replacement.
145     * @param responseText the response text
146     * @throws IOException if exception occurred
147     * @return the response
148    **/
149    protected String responseToPid( final String responseText ) throws IOException {
150        LOGGER.debug("responseToPid({})", responseText);
151        if ( !isBlank(regex) ) {
152            return responseText.replaceFirst(regex,"");
153        } else if ( xpath != null ) {
154            try {
155                return xpath( responseText, xpath );
156            } catch (ParserConfigurationException | SAXException | XPathExpressionException e) {
157                throw new IOException(e);
158            }
159        } else {
160            return responseText;
161        }
162    }
163
164    /**
165     * Extract the desired identifier value from an XML response using XPath
166    **/
167    private static String xpath( final String xml, final XPathExpression xpath )
168            throws ParserConfigurationException, SAXException, IOException, XPathExpressionException {
169        final DocumentBuilder builder = DOCUMENT_BUILDER_FACTORY.newDocumentBuilder();
170        final Document doc = builder.parse(new ByteArrayInputStream(xml.getBytes()));
171        return xpath.evaluate(doc);
172    }
173
174    /**
175     * Mint a unique identifier using an external HTTP API.
176     * @return The generated identifier.
177     */
178    @Timed
179    @Override
180    public String get() {
181        try {
182            LOGGER.debug("mintPid()");
183            final HttpResponse resp = client.execute( minterRequest() );
184            return responseToPid( EntityUtils.toString(resp.getEntity()) );
185        } catch ( final IOException ex ) {
186            LOGGER.warn("Error minting pid from {}: {}", url, ex);
187            throw new PidMintingException("Error minting pid", ex);
188        } catch ( final Exception ex ) {
189            LOGGER.warn("Error processing minter response", ex);
190            throw new PidMintingException("Error processing minter response", ex);
191        }
192    }
193}