[client] News class for getting news from the satellite

1 files changed, 215 insertions, 0 deletions

diff --git a/dozentenmodul/src/main/java/util/News.java b/dozentenmodul/src/main/java/util/News.java
new file mode 100644
index 00000000..239d06e3
--- /dev/null
+++ b/dozentenmodul/src/main/java/util/News.java
@@ -0,0 +1,215 @@
+package util;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.sql.Date;
+
+import javax.swing.JOptionPane;
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+
+import models.SessionData;
+
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+import org.xml.sax.SAXException;
+
+// Class representing the news given by the satellite
+// Makes use of the News-API of the webservice slx-admin:
+// 		http://satellite.ip/slx-admin/api.php?do=news
+//
+// Access the 'headline', 'content' and 'date' by their public getters:
+//		String newsContent = News.getContent();
+
+public class News {
+
+	// Private members representing the news
+	private static String headline = null;
+	private static String content = null;
+	private static Date date = null;
+	 
+	// Public getters
+	public static String getHeadline() {
+		if (headline != null)
+			return headline;
+		else {
+			init();
+			// check if it is still null
+			if (headline != null)
+				return headline;
+			else
+				return null;
+		}
+	}
+	public static String getContent() {
+		if (content != null)
+			return content;
+		else {
+			init();
+			if (content != null)
+				return content;
+			else
+				return null;
+		}
+	}
+	public static Date getDate() {
+		if (date != null)
+			return date;
+		else {
+			init();
+			if (date != null)
+				return date;
+			else
+				return null;
+		}
+	}
+	
+	// Private setters
+	private static void setHeadline(String s) {
+		if (s != null) headline = s;
+	}
+	private static void setContent(String s) {
+		if (s != null) content = s;
+	}
+	private static void setDate(Date d) {
+		if (d != null) date = d;
+	}
+	
+	
+	// Private 'init' function doing the main work.
+	// It is called by getters if their object is null. 
+	//
+	// Follows these steps:
+	// 	- Opens URL as stream
+	// 	- Parse stream as (XML-)Document
+	// 	- Check validity of the news format:
+	//	  	<news>
+	//			<headline>...</headline>
+	//			<content>...</content>
+	//			<date>...</date>
+	//		</news>
+	//
+	//	- Sets private members
+	private static void init(){
+		// Document representing the XML
+		Document doc = null;
+		
+		// URL to news api
+		URL url = null;
+		try {
+			url = new URL("http://" + SessionData.session.getServerAdress() + "/slx-admin/api.php?do=news");
+		} catch (MalformedURLException e2) {
+			e2.printStackTrace();
+			// This shouldn't happen, but in case it does, alert user.
+			JOptionPane.showMessageDialog(null,
+					"News-URL falsch formatiert!",
+					"Fehler", JOptionPane.ERROR_MESSAGE);
+		}
+		
+		// check for argument
+		if (url == null) {
+			// no URL, alert user.
+			JOptionPane.showMessageDialog(null,
+					"Keine News-URL angegben!",
+					"Fehler", JOptionPane.ERROR_MESSAGE);
+			return;
+		}
+				
+		// prepare stream
+		InputStream is = null;
+		try {
+			is = url.openStream();
+		} catch (IOException e1) {
+			e1.printStackTrace();
+			JOptionPane.showMessageDialog(null,
+					"Konnte den News-URL-Stream nicht öffnen!",
+					"Fehler", JOptionPane.ERROR_MESSAGE);
+		}
+		
+		// use java's DocumentBuilder engine to parse the XML
+		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
+		DocumentBuilder builder = null;
+		
+		try {
+			builder = factory.newDocumentBuilder();
+		} catch (ParserConfigurationException e1) {
+			e1.printStackTrace();
+			JOptionPane.showMessageDialog(null,
+					"XML-Parser falsch konfiguriert!",
+					"Fehler", JOptionPane.ERROR_MESSAGE);
+		}
+		
+		// try the parsing
+		try {
+			doc = builder.parse(is);
+		} catch (SAXException e) {
+			e.printStackTrace();
+			JOptionPane.showMessageDialog(null,
+					"Konnte die News-XML nicht parsen!",
+					"Fehler", JOptionPane.ERROR_MESSAGE);
+		} catch (IOException e) {
+			JOptionPane.showMessageDialog(null,
+					"IO-Fehler!",
+					"Fehler", JOptionPane.ERROR_MESSAGE);
+			e.printStackTrace();
+		}
+
+		// now that we have parsed the XML, check if it is valid
+		Element docRoot = doc.getDocumentElement();
+		
+		// first element has to be name "news"
+		if (docRoot.getNodeName().equals("news")) {
+			Node headlineNode = null;
+			Node contentNode = null;
+			Node dateNode = null;
+			
+			// get list of every child
+			NodeList nList = docRoot.getElementsByTagName("*");		
+			
+			// fail if the list is empty
+			if (nList == null) return;
+			
+			// now we go through the list looking for our elements
+			// TODO: get definition of tags externally/through static api?
+			for (int i = 0; i < nList.getLength(); i++) {
+				Node current = nList.item(i);
+				if (current.getNodeType() == Node.ELEMENT_NODE) {
+					if (current.getNodeName().equals("headline") && 
+							current.getFirstChild().getNodeType() == Node.TEXT_NODE) headlineNode = current.getFirstChild();
+					if (current.getNodeName().equals("info") &&
+							current.getFirstChild().getNodeType() == Node.TEXT_NODE) contentNode = current.getFirstChild();
+					if (current.getNodeName().equals("date") &&
+							current.getFirstChild().getNodeType() == Node.TEXT_NODE) dateNode = current.getFirstChild();
+				}
+			}
+			
+			// set what the elements we found
+			if (headlineNode != null) setHeadline(headlineNode.getNodeValue().trim());
+			if (contentNode != null)  setContent(contentNode.getNodeValue().trim());
+			if (dateNode != null) {
+				// for the date we need a bit more stuff
+				Date tmpDate = null;
+				try {
+					tmpDate = new Date(Long.parseLong(dateNode.getNodeValue().trim()));
+				} catch (NumberFormatException nfe) {
+					nfe.printStackTrace();
+					JOptionPane.showMessageDialog(null,
+							"Zeitstempel aus der XML is invalid!",
+							"Fehler", JOptionPane.ERROR_MESSAGE);
+				}
+				// Date creation worked, save it
+				if (tmpDate != null) setDate(tmpDate);
+			}
+		} else {
+			JOptionPane.showMessageDialog(null,
+					"Invalides XML! Kein 'news' Wurzelelement. News wird leer gelassen.",
+					"Fehler", JOptionPane.ERROR_MESSAGE);
+			return;
+		}
+	}	
+}