first implementation of the new oai-pmh client

pom.xml

@@ -300,8 +300,11 @@
             <version>2.26.0</version>
             <scope>test</scope>
         </dependency>
-
-
+        <dependency>
+            <groupId>org.apache.httpcomponents</groupId>
+            <artifactId>httpclient</artifactId>
+            <version>4.5.3</version>
+        </dependency>
     </dependencies>
 
     <build>

src/main/java/eu/dnetlib/repo/manager/oaipmh/OAIPMHClient.java

@@ -0,0 +1,134 @@
+package eu.dnetlib.repo.manager.oaipmh;
+
+import org.apache.http.HttpRequest;
+import org.apache.http.HttpResponse;
+import org.apache.http.client.HttpClient;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.client.methods.HttpUriRequest;
+import org.apache.http.client.methods.RequestBuilder;
+import org.apache.http.impl.client.HttpClientBuilder;
+import org.w3c.dom.Document;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+import org.xml.sax.SAXException;
+
+import javax.xml.XMLConstants;
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+import javax.xml.transform.stream.StreamSource;
+import javax.xml.validation.Schema;
+import javax.xml.validation.SchemaFactory;
+import javax.xml.validation.Validator;
+import javax.xml.xpath.XPath;
+import javax.xml.xpath.XPathConstants;
+import javax.xml.xpath.XPathExpressionException;
+import javax.xml.xpath.XPathFactory;
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.util.HashMap;
+import java.util.Map;
+
+public class OAIPMHClient {
+    public void verifyURL(String url) throws OAIPMHException {
+        try {
+            HttpClient client = HttpClientBuilder.create().build();
+            HttpUriRequest request = RequestBuilder.get().setUri(url).
+                    addParameter("verb", "Identify").build();
+
+            HttpResponse response = client.execute(request);
+
+            if (response.getStatusLine().getStatusCode() == 200) {
+                if (!validateResponse(response.getEntity().getContent())) {
+
+                    try {
+                        getSets(url);
+                    } catch (OAIPMHException e) {
+                        throw e;
+                    }
+                    //throw new OAIPMHException("Response is not valid according to OAI-PMH schema");
+                }
+            } else {
+                throw new OAIPMHException("Error getting response from server: '" +  response.getStatusLine().getReasonPhrase());
+            }
+        } catch (IOException e) {
+            throw new OAIPMHException("Error verifying URL ", e);
+        }
+
+    }
+
+    public Map<String, String> getSets(String url) throws OAIPMHException {
+        Map<String, String> result = new HashMap<>();
+
+        try {
+            HttpClient client = HttpClientBuilder.create().build();
+
+            HttpResponse response = client.execute(new HttpGet(url + "?verb=ListSets"));
+
+            if (response.getStatusLine().getStatusCode() != 200) {
+                throw new OAIPMHException("Error getting response from server. Error: '" +  response.getStatusLine().getReasonPhrase());
+            }
+
+            if (!validateResponse(response.getEntity().getContent())) {
+                throw new OAIPMHException("Response is not valid according to OAI-PMH schema");
+            }
+
+            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
+            DocumentBuilder db = dbf.newDocumentBuilder();
+            XPathFactory xpf = XPathFactory.newInstance();
+            XPath xpath = xpf.newXPath();
+
+            String token = null;
+            do {
+                RequestBuilder builder = RequestBuilder.get().setUri(url).addParameter("verb", "ListSets");
+
+                if (token != null)
+                    builder.addParameter("resumptionToken", token);
+
+                HttpUriRequest request = builder.build();
+
+                Document xml = db.parse(client.execute(request).getEntity().getContent());
+                NodeList sets = (NodeList) xpath.evaluate("//*[local-name()='setSpec']", xml, XPathConstants.NODESET);
+
+                for (int i = 0; i < sets.getLength(); i++) {
+                    String setSpec = sets.item(i).getTextContent();
+                    String setName = sets.item(i).getNextSibling().getTextContent();
+
+                    System.out.println(setSpec);
+                    result.put(setSpec, setName);
+                }
+
+                token = ((Node) xpath.evaluate("//*[local-name()='resumptionToken']", xml, XPathConstants.NODE)).getTextContent();
+            } while (token != null && !token.isEmpty());
+        } catch (IOException | ParserConfigurationException | SAXException | XPathExpressionException e) {
+            throw new OAIPMHException("Error getting sets", e);
+        }
+
+        return result;
+    }
+
+    private boolean validateResponse(InputStream response) {
+        try {
+            SchemaFactory factory =
+                    SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
+            Schema schema = factory.newSchema(new StreamSource(new URL("http://www.openarchives.org/OAI/2.0/OAI-PMH.xsd").openStream()));
+            Validator validator = schema.newValidator();
+            validator.validate(new StreamSource(response));
+            return true;
+        } catch(Exception ex) {
+            ex.printStackTrace();
+            return false;
+        }
+    }
+
+    public static void main(String[] args) throws OAIPMHException {
+//        new OAIPMHClient().verifyURL("http://digital.csic.es/dspace-oai/request");
+
+        Map<String, String> sets = new OAIPMHClient().getSets("http://digital.csic.es/dspace-oai/request");
+
+        sets.entrySet().forEach(key -> {
+            System.out.println(sets.get(key));
+        });
+    }
+}

src/main/java/eu/dnetlib/repo/manager/oaipmh/OAIPMHException.java

@@ -0,0 +1,18 @@
+package eu.dnetlib.repo.manager.oaipmh;
+
+public class OAIPMHException extends Exception {
+    public OAIPMHException() {
+    }
+
+    public OAIPMHException(String message) {
+        super(message);
+    }
+
+    public OAIPMHException(String message, Throwable cause) {
+        super(message, cause);
+    }
+
+    public OAIPMHException(Throwable cause) {
+        super(cause);
+    }
+}