Wednesday, October 1, 2008

JNDI access outside OC4J container

How to connect Standalone Application with DataSource / EJB Beans / any Container Resources ?.
Java Naming and Directory Interface (JNDI)

An application client helps to connect to container resources by referring resources in config xmls. We really not interested in doing all this magic. We know the resource(DataSource/Beans/JMS QUeue/topic) type and the location where it is located.

A JNDI(Java Naming and Directory Interface) name is the reference name specified in container to refer the resource from local and remote.

A J2EE application client is a standalone program launched from the command line or desktop, and typically accesses Enterprise JavaBean programs running on the J2EE application server. In Application client, we have to bundle an application such a way that to access the beans. Please refer for more info J2EE Application Client.

Again this is hectic way of accessing the resources from Application container, then what will I do ?.

yeah, we have the answer for this. Using RMI protocol, we can access any of the Beans/DataSource/Topic/Queue from server.

The following four properties and requesting object executables(classes) in your class path is enough to communicate with server.

java.naming.factory.initial=oracle.j2ee.rmi.RMIInitialContextFactory
java.naming.provider.url=ormi://localhost:23791/
java.naming.security.principal=oc4jadmin
java.naming.security.credentials=welcome1

The above mentioned properties will vary based on what kind of Application server, we are using. Here, I have taken Oracle 10.1.3 Application server OC4J to explain.

we can specify these properties in either of three approaches

1. Programmatically including these attributes

In this Approach, we have to always pass a Hashtable to create a Initialcontext. That HashTable has to store all these properties and values. Most of the time this approach is not suggested, because of the reason we have to modify these values(hard coded values) or we have to pick from external environment and given to Hash table

Hashtable env = new Hashtable();
env.put("java.naming.factory.initial","oracle.j2ee.rmi.RMIInitialContextFactory");
env.put(java.naming.provider.url","ormi://localhost:23791/");
env.put(java.naming.security.principal","oc4jadmin");
env.put(java.naming.security.credentials","welcome1");

2. Specifying in Java Command

Other way is directly specifying in Java command using -D option.

java -Djava.naming.factory.initial=oracle.j2ee.rmi.RMIInitialContextFactory \
-Djava.naming.provider.url=ormi://localhost:23791/ \
-Djava.naming.security.principal=oc4jadmin \
-Djava.naming.security.credentials=welcome1 \ <javaprogram>

3. Specifying in jndi.properties file

Best way of segregating configuration and application is specify these configuration details separately in a proprty file and name it as jndi.properties. This file containing folder has to be included in classpath.

java -cp .;%cp% yourapplication

Note:
This %cp% should load all of your application required classes containing jar files.


I am not able to access some of my beans, what to do ?.

Check java.naming.provider.url is correct or not. If you are accessing beans/topic/queue then you have to specify EJB Application also in this URL. Example, If your EJB Application name is Bank then specify like java.naming.provider.url=ormi://localhost:23791/Bank

Refer Specifying Environment Properties


Weblogic

Weblogic uses t3 protocol to make RMI connection:

java.naming.provider.url=t3://<hostname>:7001
java.naming.factory.initial=weblogic.jndi.WLInitialContextFactory
java.naming.security.principal=weblogic
java.naming.security.credentials=weblogic1

Free/Sample HTTP Server

In this software world, everything has to be built our own or it has to be opensource code which helps us to tune the performance our application. I was in the need of testing my product which makes more than 100 HTTP request per minute. I initially thought of installing freely available any of the HTTP server. But, none of the HTTPServer comes with the flavour of light weight, everything starts minimum of 10 MB and it needs separate installation which will not be started just like that.

Building a HTTP Server:

We have to have little bit of knowledge about the HTTP protocol. This protocol is nothing but built on top of TCP with specific headers, which leads us to important details easily using some kind of getter method.

To build HTTPServer, we have to know the threading concept with socket programming knowledge. Don't worry, I won't ask you to write the HTTPServer code here, I will share with you full code which is ready to use.

No configuration is required for this server. Just add this class in your classpath and create instance of this Class by passing port number.

Here you go with HTTPServer implementation code.

HTTPServer has two inner classes - one is HTTPRequest, HTTPWorker.


import java.io.BufferedInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Enumeration;
import java.util.Properties;

public class HTTPServer implements Runnable {

 public static final String CONTENT_LENGTH = "Content-length";
 public static final String CONTENT_TYPE = "Content-type";
 private static char NEW_LINE = '\n';
 private static final String EOL = "\r\n";
 private static final String SUCCESS_HDR_MESSAGE = "HTTP/1.1 200 OK";
 private static final String SC_NO_CONTENT = 
 "HTTP/1.1 204 No Content" + EOL
   + "Content-Type: text/plain" 
   + EOL + "Cache-Control: private" + EOL
   + EOL;

 private static final String 
 INTERNAL_ERROR = "HTTP/1.1 500 Internal " +
   "Krishna's Server Error"
   + EOL
   + "Content-Type: text/html"
   + EOL
   + EOL
   + "<html><head>BLite Internal Error</head><body>";

 private static int DEFAULT_PORT = 7777;
 private static String SOAP_ACTION = "SOAPAction";

 private int port;

 private boolean isShutdown = false;

 private static HTTPServer httpServer = null;

 public static HTTPServer newInstance(int port) {

  if (null == httpServer) {
   httpServer = new HTTPServer();
   if (port > 0)
    httpServer.port = port;
  }

  return httpServer;
 }

 private HTTPServer() {
  this.port = DEFAULT_PORT;
 }

 public void run() {

  System.out.println(" STARTING HTTP SERVER ");
  System.out.println("HTTP Server Listens on port " + httpServer.port);

  try {
   // ServerSocket
   // ss=ServerSocketFactory.getDefault().createServerSocket(port,1500);
   // ss.setReceiveBufferSize(2048);
   // ss.setReuseAddress(true);
   ServerSocket ss = new ServerSocket(port, 1500);
   long startTime = System.currentTimeMillis();

   while (!isShutdown) {
    try {
     System.out
       .println("SocketTime :"
         + ((startTime = System.currentTimeMillis()) - startTime)
         + "s");
     HTTPWorker httpWorker = new HTTPWorker(ss.accept());
     Thread thread = new Thread(httpWorker);
     thread.start();
     thread = null;
    } catch (Throwable e) {
     System.out.println(e);
    }
   }

  } catch (Throwable e) {
   System.out.println(e);
  }
  // finally
  // {
  // tpe.shutdown();
  // }
 }

 public static String getPropertyIgnoreCase(Properties props, 
   String key) {
  String value = null;

  Enumeration enum0 = props.propertyNames();
  while (enum0.hasMoreElements()) {
   String name = (String) enum0.nextElement();
   if (key.equalsIgnoreCase(name)) {
    value = props.getProperty(name);
    break;
   }
  }

  return value;
 }

 
 public void shutdown() {

  this.isShutdown = true;
 }

 private class HTTPRequest {

  private byte[] request;
  private int headerIndex = 0;
  private Properties headers;
  private byte[] bodyContent;

  public HTTPRequest(byte[] request) {
   this.request = request;
   init();
  }

  private void init() {

   if (request == null)
    return;

   for (int i = 0; i < request.length; i++) {
    if ((NEW_LINE == (char) request[i])
       && (13 == request[i + 1])) {
     headerIndex = i;
     break;
    }
   }

   initHeaders();
   initBodyContent();
  }

  private void initHeaders() {
   String httpMethod;
   String httpVersion;
   String path;
   String headerContent = new String(request, 0, headerIndex);

   String[] availbleHeaders = headerContent.split("\n");

   if (availbleHeaders != null && 
   availbleHeaders.length > 0) {
    String[] typeContainer = availbleHeaders[0].split(" ");

    if (typeContainer != null && 
       typeContainer.length > 2) {
     httpMethod = typeContainer[0];
     path = typeContainer[1];
     httpVersion = typeContainer[2];
    }
   }

   if (availbleHeaders.length > 1) {
    this.headers = new Properties();

    for (int index = 1; index < availbleHeaders.length; index++) {
     String key = availbleHeaders[index].substring(0,
       availbleHeaders[index].indexOf(':'));
     String value = availbleHeaders[index].substring(
       availbleHeaders[index].indexOf(':') + 1,
       availbleHeaders[index].length() - 1);
     this.headers.put(key, value);
    }
   }
  }

  private void initBodyContent() {

   int bodyIndex = headerIndex + 3;
   bodyContent = new byte[request.length - bodyIndex];
   for (int i = (bodyIndex), j = 0; 
   i < request.length; i++, j++) {
    bodyContent[j] = request[i];
   }

  }

  public Properties getHeaders() {
   return headers;
  }

  public byte[] getBodyContent() {
   return bodyContent;
  }

 }

 private class HTTPWorker implements Runnable {

  private String ret = null;
  private BufferedInputStream is;
  private DataOutputStream os;
  private Socket socket = null;
  
  public HTTPWorker(Socket socket) {
   this.socket = socket;
   try {
    this.socket.setTcpNoDelay(true);
    // this.socket.setSoLinger(true, 60);

    is = new BufferedInputStream(socket.getInputStream());
    os = new DataOutputStream(socket.getOutputStream());

   } catch (Exception e) {
   }
  }

  /*
   * (non-Javadoc)
   * 
   * @see java.lang.Runnable#run()
   */
  public void run() {

   try {
    readwrite();
   } catch (Throwable e) {
    System.out.println("\n\n***\n" + ret + "\n****\n\n");
    System.out.println(e);
   }

  }

  private void readwrite() throws Throwable {

   try {
    ret = readHTTPMessage();

    //Here HTTP request string is 
 ready to do your business magic 
 
 
    
    
    StringBuffer strbuffer = new StringBuffer();
    strbuffer.append(SC_NO_CONTENT);
    writebytes(socket, strbuffer.toString());

   } catch (Throwable e) {
    System.out.println(e);
   } finally {

    // Following code has no use, However to make double check
    // whether socket is closed
    if (!socket.isClosed())
     socket.close();
   }
  }

  public String readHTTPMessage() throws IOException {
   String result = null;
   StringBuffer strb = new StringBuffer();
   int bufferSize = 1024; // is.available()==0 ? 1024:is.available();
   int contentLength = 0;
   int headerLength = 0;
   int bodyLength = 0;
   try {
    byte[] buf = new byte[bufferSize];
    int nread = 0;
    while ((nread = is.read(buf)) != -1) {
     if (nread == 0)
      continue;
     strb.append(new String(buf, 0, nread));
     // System.out.println(strb);
     result = strb.toString();

     if (contentLength == 0) {

      // atleast 50 bytes required to identify content length
      if (result.length() < 50)
       continue;

      HTTPRequest request = new HTTPRequest(result.getBytes());
      String contentStr = getPropertyIgnoreCase(request
        .getHeaders(), CONTENT_LENGTH);

      // if length specified
      if (null == contentStr || "".equals(contentStr))
       break;

      contentLength = Integer
        .parseInt("" + contentStr.trim());
      bodyLength = request.getBodyContent().length;
      headerLength = result.length() - bodyLength;
     } else {
      bodyLength = result.length() - headerLength;
     }

     if (bodyLength < contentLength) {
      bufferSize = contentLength - bodyLength;
      buf = new byte[bufferSize];
     } else {

      if (bodyLength >= contentLength 
        || result.endsWith(EOL)) {

       // try{socket.shutdownInput();}catch(Exception e){}
       break;
      }

     }
    }
   } catch (Exception e) {
    System.out.println(e);
   } finally {
    // try{is.close();}catch(Exception e){}

   }
   return result;
  }

  private void writebytes(Socket socket, String data) {
   try {
    //
    os.write(data.getBytes());
    os.flush();
    if (!socket.isClosed())
     is.close();
    if (!socket.isClosed())
     os.close();

   } catch (Throwable e) {
    System.out.println(e);
   }

   try {
    if (!socket.isClosed())
     socket.close();
   } catch (Throwable e) {
    System.out.println("Problem in data writing in channel");
    System.out.println(e);
   }
  }

  @Override
  protected void finalize() throws Throwable {
   // TODO Auto-generated method stub
   super.finalize();
   socket = null;
   ret = null;
  }
 }
}

If you like this blog and posting, please feel free to leave your comments, which will help me to post more useful blogs.. :)

Tuesday, July 8, 2008

URLHandler for ZIP stream

Accessing file from ZIP using URL

In our usual life, we may need to access particular content from ZIP file often and often. We may not be interested in retrieving complete content from ZIP. It would be good idea to have a URL Handler, which will help us to access only the content of ZIP directly and/or seamlessly.

We have a built-in facility of accessing content from JAR file directly. Why should not we form the similar approach to access the content from ZIP ?.

Aim of this post is not only to explain the code which will help us to retrieve the particular content, we do get to know the way how URL handler is going to work.


Agenda:

Name the protocol
Name the Java package
Creating Java files required to enable URLHandler for ZIP protocol
Notifying to JVM by setting in environment
Notifying to JVM by setting as part of Main method

1. Name the Protocol

We have to name the protocol i.e we have to prefix a string which will help us to say what we are trying to do. Here, we will create our own protocol and we will name it as “zip”. Hence the URL format will looks like below
zip:http://www.javafundu.com/baz.zip!/afolder/a.txt
where
!/ - Separator
http://www.javafundu.com/baz.zip - points actual zip file
afolder/a.txt – is the content available in baz.zip

2. Name the Java Package

Java files has to be placed in a package and the naming package should looks like below

<anypackagename>.protocol.<nameoftheprotocol>
Example: com.javafundu.protocol.zip

3. Create Java files URLStreamHandler and URLConnection

Handler, which will instruct JVM to call this Class to open the connection when URL.openConnection().

Handler.java

package com.javafundu.protocol;

import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLStreamHandler;

public class Handler extends URLStreamHandler {

@Override
protected URLConnection openConnection(URL url) throws IOException {
// create new instance of URLConnection
return new ZIPURLConnection(url);
}
}

URLConnection does the actual job of unzipping and returning the subelement. URL argument in openConnection method has the URL http://… , when actual url is “zip:http://…”

ZIPURLConnection.java:

package com.javafundu.protocol;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

public class ZIPURLConnection extends URLConnection {

protected ZIPURLConnection(URL url)throws MalformedURLException {
super(url);
// TODO Auto-generated constructor stub
}

@Override
public void connect() throws IOException {
// TODO Auto-generated method stub

}

/* (non-Javadoc)
* @see java.net.URLConnection#getInputStream()
*/
public InputStream getInputStream() throws IOException {

InputStream result= null;
URL url = this.url;

String spec = url.getFile();

int separator = spec.indexOf('!');
/*
* REMIND: we don't handle nested JAR URLs
*/
if (separator == -1) {
throw new MalformedURLException("no ! found in url spec:" + spec);
}

long startTime = System.currentTimeMillis();

URL zipFileURL = new URL(spec.substring(0, separator++));

String entryName =spec.substring(separator+1);



ZipInputStream zis = new ZipInputStream(zipFileURL.openStream());
ZipEntry entry = null;

// check inputStream is ZIP or not
if ((entry = zis.getNextEntry()) != null) {
do {
// System.out.println(entry.getName());
if(entryName.equals( entry.getName()))
{
result= zis;
break;
}
} while ((entry = zis.getNextEntry()) != null);
} else {
System.out.println("Given path is not referring ZIP file");
}
System.out.println( "Looking for " +entryName + " " +(System.currentTimeMillis() - startTime) + "ms");
return result;
}
}

Now Java implementation is ready for compilation. Bundle your application with these two class files. Assume bundled as jf.jar.

4.Notifying to JVM by setting in environment

Set the environment variable, which specifies the information of Handlers available location.

Java -Djava.protocol.handler.pkgs=”com.javafundu.protocol”

Now, your JVM will understand “zip:” as a URL authority and start works. If you create a URL with zip: , then Java will call com.javafundu.protocol.Handler to parse this URL.

URL url=new URL(“zip:http://www.javafundu.com/baz.zip!/afolder/a.txt ”)

5.Notifying to JVM by setting as part of Main method

Sometime, this is very difficult to set this value in environment variable due to some restriction. Hence, we have alternate approach, which will help us to set and make use of this facility.

System.setProperty("java.protocol.handler.pkgs","com.javafundu.protocol");

We have to set this property at the earliest possible to before creating URL with zip:
If we wants to specify more than one protocol then we have to delimit using symbol. For example

System.setProperty("java.protocol.handler.pkgs","com.javafundu.msaccess.protocolcom.javafundu.protocol");


Resource:
URL (Java 2 Platform SE v1.4.2) |
JarURLConnection (Java 2 Platform SE v1.4.2) |
RFC 2373: IP Version 6 Addressing Architecture

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