Der Blog von Benny Neugebauer » Java http://www.bennyn.de Alles über die Informatik & Co. Fri, 18 May 2012 10:09:17 +0000 en hourly 1 http://wordpress.org/?v=3.3.2 HTML5 WebSocket-Server mit Java und Client mit JavaScript http://www.bennyn.de/programmierung/java/html5-websocket-server-mit-java-und-client-mit-javascript.html http://www.bennyn.de/programmierung/java/html5-websocket-server-mit-java-und-client-mit-javascript.html#comments Wed, 16 May 2012 10:57:45 +0000 bennyn http://www.bennyn.de/?p=3686 Zur Demonstration von HTML5-Websockets habe ich mit webbit einen einfachen WebSocket-Server geschrieben, der Nachrichten entgegen nimmt und diese Nachrichten wieder an den jeweiligen angemeldeten Client zurück schickt. Ein solches Beispiel nennt man auch Echo-Server.

Server

Server.java

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import org.webbitserver.WebServer;
import org.webbitserver.WebServers;
import org.webbitserver.handler.StaticFileHandler;
 
public class Server {
 
  public static void main(String[] args) throws Exception {
    WebServer webServer = WebServers.createWebServer(8080);
    webServer.add(new StaticFileHandler("/static-files"));
    webServer.add("/websocket-echo", new WebSocketSampleHandler());
    webServer.start();
  }
}

WebSocketSampleHandler.java

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import org.webbitserver.BaseWebSocketHandler;
import org.webbitserver.WebSocketConnection;
 
public class WebSocketSampleHandler extends BaseWebSocketHandler {
 
  private int connections = 0;
 
  @Override
  public void onOpen(WebSocketConnection connection) {
    this.connections++;
    connection.send("This is the webserver saying Hello! :)<br/>"
            + "Total No. of subscribers: " + this.connections + ".");
  }
 
  @Override
  public void onClose(WebSocketConnection connection) {
    this.connections--;
  }
 
  @Override
  public void onMessage(WebSocketConnection connection, String message) {
    connection.send("The server has received the following message:<br/>"
            + message);
  }
}

Dependencies from pom.xml

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<dependency>
  <groupId>org.webbitserver</groupId>
  <artifactId>webbit</artifactId>
  <version>0.4.6</version>
  <type>jar</type>
</dependency>
<dependency>
  <groupId>org.jboss.netty</groupId>
  <artifactId>netty</artifactId>
  <version>3.2.7.Final</version>
  <type>jar</type>
</dependency>

Client

connect.html

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<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>HTML5 WebSocket-Client</title>
    <script>
      var socket;
 
      function sendMessage(){
        var message = document.getElementById('userInput').value;
        socket.send(message);
      }
 
      function showMessage(text) {
        document.getElementById('message').innerHTML = text;
      }
 
      function subscribeToWebSocket(){
        if('WebSocket' in window){
          socket = new WebSocket('ws://localhost:8080/websocket-echo');
          socket.onopen = function(){
            showMessage('Connected to WebSocket.');
          };
          socket.onmessage = function(msg){
            showMessage(msg.data);
          };
          socket.onerror = function(msg){
            showMessage('Sorry but there was an error.');
          };
          socket.onclose = function(){
            showMessage('Server offline.');
          };
        }else{
          showMessage('Your browser does not support HTML5 WebSockets.');
        }
      }
    </script>
  </head>
  <body onload="javascript:subscribeToWebSocket()">
    <input id="userInput" type="text">
    <button onclick="javascript:sendMessage()">Chat</button>
    <div id="message"></div>
  </body>
</html>

Das Beispiel funktioniert mit allen HTML5 WebSocket-kompatiblen Browser und wurde erfolgreich getestet mit Firefox 12.0 und Google Chrome 20.0.

]]> http://www.bennyn.de/programmierung/java/html5-websocket-server-mit-java-und-client-mit-javascript.html/feed 0 How to get node attributes with Java SAX XML parser http://www.bennyn.de/programmierung/java/how-to-get-node-attributes-with-java-sax-xml-parser.html http://www.bennyn.de/programmierung/java/how-to-get-node-attributes-with-java-sax-xml-parser.html#comments Tue, 08 May 2012 10:19:18 +0000 bennyn http://www.bennyn.de/?p=3572 Code 
import java.io.StringReader;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
 
public class NewMain {
 
  public static void main(String[] args) throws Exception {
    String text = "<person number=\"72\"><name>Benny</name></person>";
 
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = factory.newDocumentBuilder();
    Document document = builder.parse(new InputSource(new StringReader(text)));
    NodeList elementsByTagName = document.getElementsByTagName("person");
    for (int i = 0; i < elementsByTagName.getLength(); i++) {
      Node node = elementsByTagName.item(i);
      Element element = (Element) node;
      String attribute = element.getAttribute("number");
      System.out.println(attribute);
    }
  }
}

Output

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]]> http://www.bennyn.de/programmierung/java/how-to-get-node-attributes-with-java-sax-xml-parser.html/feed 0 How to use Iterator, for and foreach-loop in Java http://www.bennyn.de/programmierung/java/how-to-use-iterator-for-and-foreach-loop-in-java.html http://www.bennyn.de/programmierung/java/how-to-use-iterator-for-and-foreach-loop-in-java.html#comments Mon, 07 May 2012 12:56:07 +0000 bennyn http://www.bennyn.de/?p=3576 Here is a very good example on how to use the Iterator, for and foreach-loop in Java:

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
 
public class JavaApplication {
 
  public static void main(String[] args) throws IOException {
    List<String> names = new ArrayList<>();
    names.add("Benny");
    names.add("Sarah");
    names.add("Daniel");
    names.add("Maria");
 
    // Iterator
    Iterator<String> iterator = names.iterator();
    while (iterator.hasNext()) {
      System.out.println(iterator.next());
    }
 
    // for
    for (int i = 0; i < names.size(); i++) {
      System.out.println(names.get(i));
    }
 
    // foreach
    for (String name : names) {
      System.out.println(name);
    }
  }
}
]]> http://www.bennyn.de/programmierung/java/how-to-use-iterator-for-and-foreach-loop-in-java.html/feed 0 Create GraphML XML files that can be used in the yEd Graph Editor http://www.bennyn.de/programmierung/java/create-graphml-xml-files-that-can-be-used-in-the-yed-graph-editor.html http://www.bennyn.de/programmierung/java/create-graphml-xml-files-that-can-be-used-in-the-yed-graph-editor.html#comments Sun, 06 May 2012 07:51:52 +0000 bennyn http://www.bennyn.de/?p=3628 In my article “Create GraphML XML file with Java” I showed how to write a Graph to a GraphML-compatible XML file. Now I want to show you how you can write a GraphML-compatible file that can be used in the yEd Graph Editor to get visualized later.

Main Class

import com.tinkerpop.blueprints.pgm.Vertex;
import com.tinkerpop.blueprints.pgm.impls.tg.TinkerGraph;
import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;
 
public class Main {
 
  public static void main(String[] args) throws Exception {
    OutputStream out = new FileOutputStream(new File("./test.graphml"));
    TinkerGraph graph = new TinkerGraph();
 
    Vertex source = graph.addVertex("1");
    Vertex target = graph.addVertex("2");
    graph.addEdge("3", source, target, "connection");
 
    YedFileWriter writer = new YedFileWriter(graph);
    writer.outputGraph(out);
  }
}

Specific GraphML-yEd-Writer

import com.tinkerpop.blueprints.pgm.Edge;
import com.tinkerpop.blueprints.pgm.Graph;
import com.tinkerpop.blueprints.pgm.Vertex;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.Iterator;
 
/**
 * YedFileWriter writes a Graph for the yEd Graph Editor to a GraphML OutputStream.
 * 
 * @author Benny Neugebauer (http://www.bennyn.de)
 */
public class YedFileWriter {
 
  private Graph graph = null;
  private String xml = null;
 
  public YedFileWriter(Graph graph) {
    this.graph = graph;
  }
 
  private String getGraphMLHeader() {
    String header = "<?xml version=\"1.0\" ?>";
    header += "\r\n<graphml\r\n  xmlns=\"http://graphml.graphdrawing.org/xmlns\"\r\n  xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"\r\n  xmlns:y=\"http://www.yworks.com/xml/graphml\"\r\n  xmlns:yed=\"http://www.yworks.com/xml/yed/3\"\r\n  xsi:schemaLocation=\"http://graphml.graphdrawing.org/xmlns\r\n  http://www.yworks.com/xml/schema/graphml/1.1/ygraphml.xsd\"\r\n>";
    header += "\r\n  <key for=\"node\" id=\"d5\" attr.name=\"description\" attr.type=\"string\" />";
    header += "\r\n  <key for=\"node\" id=\"d6\" yfiles.type=\"nodegraphics\"/>";
    header += "\r\n  <graph id=\"G\" edgedefault=\"directed\">";
    return header;
  }
 
  private String getGraphMLFooter() {
    String footer = "\r\n  </graph>\r\n</graphml>";
    return footer;
  }
 
  private String getNode(String id) {
    String node = "\r\n    <node id=\"" + id + "\">";
    node += "\r\n      <data key=\"d5\"/>";
    node += "\r\n      <data key=\"d6\">";
    node += "\r\n        <y:ShapeNode>";
    node += "\r\n          <y:NodeLabel>" + id + "</y:NodeLabel>";
    node += "\r\n          <y:Shape type=\"rectangle\"/>";
    node += "\r\n        </y:ShapeNode>";
    node += "\r\n      </data>";
    node += "\r\n    </node>";
    return node;
  }
 
  private String getEdge(Edge edge) {
    Vertex source = edge.getOutVertex();
    Vertex target = edge.getInVertex();
    String edgeId = (String) edge.getId();
    String sourceId = (String) source.getId();
    String targetId = (String) target.getId();
    String label = edge.getLabel();
 
    String edgeXml = "\r\n    <edge id=\"" + edgeId + "\" source=\"" + sourceId + "\" target=\"" + targetId + "\" label=\"" + label + "\">";
    edgeXml += "\r\n    </edge>";
 
    return edgeXml;
  }
 
  private void createGraphXml() {
    xml = getGraphMLHeader();
 
    // Create nodes
    Iterable<Vertex> vertices = graph.getVertices();
    Iterator<Vertex> verticesIterator = vertices.iterator();
    while (verticesIterator.hasNext()) {
      Vertex vertex = verticesIterator.next();
      String id = (String) vertex.getId();
      String node = getNode(id);
      xml += node;
    }
    // Create edges
    Iterable<Edge> edges = graph.getEdges();
    Iterator<Edge> edgesIterator = edges.iterator();
    while (edgesIterator.hasNext()) {
      Edge edge = edgesIterator.next();
      String edgeXml = getEdge(edge);
      xml += edgeXml;
    }
 
    xml += getGraphMLFooter();
  }
 
  public void outputGraph(final OutputStream out) throws IOException {
    createGraphXml();
    System.out.println(xml);
    try (BufferedWriter br = new BufferedWriter(new OutputStreamWriter(out))) {
      br.write(xml);
      br.flush();
    }
    out.flush();
    out.close();
  }
}
]]> http://www.bennyn.de/programmierung/java/create-graphml-xml-files-that-can-be-used-in-the-yed-graph-editor.html/feed 0 Parse some HTML tags with a Java SAX XML parser http://www.bennyn.de/programmierung/java/parse-some-html-tags-with-a-java-sax-xml-parser.html http://www.bennyn.de/programmierung/java/parse-some-html-tags-with-a-java-sax-xml-parser.html#comments Sat, 05 May 2012 09:29:17 +0000 bennyn http://www.bennyn.de/?p=3567 Parsing XML with Java is very simple. If you want to parse some HTML tags, then you just have to add a root element around those tags (to make it a valid XML structure) and then you can use the Java SAX XML parser.

Code

import java.io.StringReader;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
 
public class NewMain {
 
  public static void main(String[] args) throws Exception {
    String html = "<h1>Headline</h1><p><b>Hello World.</b><b>This is a test.</b></p>";
    html = "<root>" + html + "</root>";
 
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    DocumentBuilder builder = factory.newDocumentBuilder();
    Document document = builder.parse(new InputSource(new StringReader(html)));
    NodeList elementsByTagName = document.getElementsByTagName("b");
    for (int i = 0; i < elementsByTagName.getLength(); i++) {
      Node element = elementsByTagName.item(i);
      String text = element.getTextContent();
      System.out.println(text);
    }
  }
}

Result

Hello World.
This is a test.
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