NodeJS Web Server for local testing

For my 'day to day' work I usually need to spawn number of web servers to serve files form different locations. Of course those servers need to listen on dedicated ports. The easiest, by far quickest and really simple way to do this is by utilizing NodeJS:

• Install NodeJS by opening http://nodejs.org/ and clicking Install button
• Install Required modules by typing in the console: npm install stdio connect
• Copy modules to home folder: mv node_modules ~/.node_modules
• Create webserver.js:

  var stdio = require('stdio');
  var connect = require('connect');
  
  var ops = stdio.getopt({
      'dirname': {key: "dir", args: 1, description: 'Web Server Folder'},
      'webport': {key: "port", args: 1, description: 'Web Server Port'}
  });
  
  if (ops.help) {
      ops.printHelp();
  }
  
  if (!ops.dirname) {
    ops.dirname = __dirname;
  }
  
  if (!ops.webport) {
    ops.webport = 8080;
  }
  
  console.log("Web Server is listening on port " + ops.webport + " and serving: " + ops.dirname)
  
  connect.createServer(                                                                                      
      connect.static(ops.dirname)                                                                            
  ).listen(ops.webport); 
  

• Create webserver executable:

  #!/bin/bash
  
  BASEDIR=$(dirname $0)
  APPDIR=`pwd`
  
  node $BASEDIR/webserver.js $@ --dirname $APPDIR
  

• Paste webserver and webserver.js into your bin folder (added to your $PATH)
• Start webserver as following:

  
  #from any folder where you have index.html
  webserver
  
  #or if you want to specify port
  webserver -port 8081
  
  #you will see something like
  Web Server is listening on port 8081 and serving: /Users/rkuzmik/Work/DeftJS/IoC-Q-app
  
  

Enjoy!

Cannot agree with Monson-Haefel about J2EE future

This is reply to original article Analysts see Java EE dying in an SOA world. Monson-Haefel is his article compares J2EE with Ruby-on-Rails. Ruby-on-Rails is a Web application framework thus this comparison is just like between a bike and a luxury car. It is wrong by definition. While more and more specs, JSRs and technologies (also come from J2EE) move to J2SE (just take a look at J2SE 6.0) are we going to expect the death to Java?! As Monson-Haefel sad, 'No', so why he is contradicts to himself? Btw, why CORBA is dead? We still use it in our mainframe integration :-) . Does the CORBA look complicated for you? As for me CORBA is most simplest technology ever exists in IT. If CORBA is die-hard for Monson-Haefel then despite of the honor to all his books I've no comments to the rest of the article at all :-) Are all those analysts talking about complexity of the J2EE from the application server implementation point of view? At this point I ready to agree with them. It is pretty hard to build J2EE5 server from scratch. But at the moment we have at least two even OpenSource implementations which work just fine (Glass Fish and JBoss). As for developers it is all about the way of use. Just take those parts form J2EE which are required for you project, then in most cases it will be 10% of all J2SE/J2EE stack. Is it hard to lean how-to use 10% of the complicated thing? It is just enough to read introduction to J2EE and define the needed parts and then follow the table of content to refer to actual information you need. Yep, J2SE/J2EE is a huge stack of technologies, but please look at it as a set of ready to plug and use patterns and then it won't be more complicated then GOF for ya!

SAML Relying Party Implementation

How to implement SAML based SSO Relying Party.

Glossary. SAML - Security Assertion Markup Language is an XML standard for exchanging authentication and authorization data between security domains, that is, between an identity provider and a service provider. SSO - Single sign-on (SSO) is a specialized form of software authentication that enables a user to authenticate once and gain access to the resources of multiple software systems.

Introduction. Recently I have had to implement one part of SSO. My application as a provider of the services acts like a Relying Party in the SAML terms. Relying party is the system, or administrative domain, that relies on information supplied to it by the asserting party. While Asserting party is the system, or administrative domain, that asserts information about a subject. For instance, the asserting party asserts that this user has been authenticated and has given associated attributes. In other words I am in B2B relation with my partners. We want to use SSO all across our services. And of course we want to use modern SAML as assertion contract language.

Finding solution. In order to implement SSO with SAML you have to choose specification to which you conform. There are two of them 1.1 and 2.0. While 2.0 is more feature rich and restrictive, old 1.1 is more wide spread and accepted across business. Specification defines not only the SAML language itself, but also the way it can be used during assertions interchange. There are two possible ways of assertion flow for SSO purpose in 1.1 spec:

• Browser/Artifact Profile - this stand for the case when target service (the service end-user wants to access) asks another party to confirm end-user credentials. Actual assertion flow is more complicated (You can reference to actual specification part 4.1.1 for more details).
• Browser/POST Profile - in this case end-user submits his passport along with the reference to the target service he wants to access.

First case with artifact interchange is not suite for us. I have to initiate outgoing connection to trusted business partner site in order to obtain actual SAML assertion. I have to create request based on artifact supplied me earlier. To involve this kind of dependency is not a good idea for my particular application. I do not want to have a third party system access from inside my firewall. Altough, it is plain HTTP outgoing connection. The second case with all-sufficient SAML assertion I like more. From the top level overview it looks simple as that: End-User (browser) submit me (Relying party) ready to use passport (assertion). I trust this passport based in special trust relationship between me (Relying party) and asserting party who actually issued this passport. The important note here is I do not mention how this trust relationship has been established. This space is for another article I expect to publish in near future. Implementation. It is a good point here to start from utilizing ready to use SAML library. There is open source library called opensaml which can handle most of the SAML related operations. This is quite fresh library from the implementation point of view. And some times I find very strange architectural decisions in it. However, and it is more important for us, it works! So let's take all OpenSAML abstraction into our design and proceed with diagramming. At the first step, according to specification, browser post "Form with Response& Assertion" to our Servlet. Note: It is a little bit unusual here, why we submit response? In general it is clearer to submit requests. At least submit some kind of TransmitAssertionUnit, SAMLAssertionMessage or any other well suited for this particular satiation object name of the underlying abstraction. At the second step we have to construct BrowserProfileRequest object. It encapsulates data submitted for us by Asserting party through user browser in HttpRequest. At the third step we have to create binding profile we have chosen. In our case it is SAMLBrowserProfile. Let's use factory to create an instance and then perform response (actually, as I mentioned early it is request or just a message containing our assertion, but for some reason it is called BrowserProfileResponse) processing. Once we have BrowserProfileResponse object we have all information necessary to perform all other operations. It can be trust relationship validation step (As I mentioned earlier. See the next post for details). It can be some kind of authentications steps in which we create internal object represents authenticated user. And finally, we can redirect user to requested resource. Let's step ahead to actual coding. I want to have my servlet code clear. Thus let's introduce SsoSamlHelper here. This helper takes care of all implementation details. Then actual servlet looks like template method.

package org.ots.sso;

import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.UnrecoverableKeyException;

import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.opensaml.NoSuchProviderException;
import org.opensaml.SAMLAssertion;
import org.opensaml.SAMLBrowserProfile;
import org.opensaml.SAMLBrowserProfileFactory;
import org.opensaml.SAMLException;
import org.opensaml.SAMLSignedObject;
import org.opensaml.UnsupportedProfileException;
import org.opensaml.SAMLBrowserProfile.BrowserProfileRequest;
import org.opensaml.SAMLBrowserProfile.BrowserProfileResponse;

import org.ots.ws.security.KeyStoreHolder;

/**
 * Useful static method to manipulate with SAML objects
 *
 * @version $Id$
 * @author Roman Kuzmik
 */
public class SsoSamlHelper {
    private static final Log log = LogFactory.getLog(SsoSamlHelper.class);

    /**
     * Exctract from HHTP request all SSO SAML related information
     *
     * @param httpRequest
     * @return
     * @throws SsoSamlException
     */
    public static BrowserProfileRequest createRequest(HttpServletRequest httpRequest) throws SsoSamlException{
        log.debug("");

        try {
            SAMLBrowserProfile profile = SAMLBrowserProfileFactory.getInstance();
            BrowserProfileRequest samlRequest = profile.receive(httpRequest);
            return samlRequest;
        } catch (UnsupportedProfileException e) {
            throw new SsoSamlException(e);
        } catch (NoSuchProviderException e) {
            throw new SsoSamlException(e);
        }
    }

    /**
     * Perform SAML assertion reconstruction from the BrowserProfileRequest provided
     *
     * @param samlRequest
     * @return
     * @throws SsoSamlException
     */
    public static BrowserProfileResponse processRequest(BrowserProfileRequest samlRequest) throws SsoSamlException{
        log.debug("");

        try {
            SAMLBrowserProfile profile = SAMLBrowserProfileFactory.getInstance();

            StringBuffer issuerBuffer = new StringBuffer();

            BrowserProfileResponse samlResponse = profile.receive(
                    issuerBuffer,
                    samlRequest,
                    SsoSamlConstants.SAML_SSO_RECEPIENT,
                    /*ReplayCache*/ null,
                    /*SAMLBrowserProfile.ArtifactMapper*/ null,
                    SsoSamlConstants.SAML_MINOR_VERSION
            );
                    
            log.debug("done");
            return samlResponse;
        } catch (UnsupportedProfileException e) {
            throw new SsoSamlException(e);
        } catch (NoSuchProviderException e) {
            throw new SsoSamlException(e);
        } catch (SAMLException e) {
            throw new SsoSamlException(e);
        }  
    }

    /**
     * Give me trust entity key
     *
     * @param assertion
     * @return
     */
    public static String getIssuer(SAMLAssertion assertion){
        return assertion.getIssuer().trim();
    }

    /**
     * WS-S Signature validation
     *
     * @param samlObject
     * @param issuer
     * @param keyStoreHolder
     * @throws SsoSamlException
     */
    public static void verifySignature(SAMLSignedObject samlObject, String issuer, KeyStoreHolder keyStoreHolder) throws SsoSamlException{
        log.debug("");
        try {
            samlObject.verify(keyStoreHolder.getPublicKey(issuer));
        } catch (KeyStoreException e) {
            throw new SsoSamlException(e);
        } catch (NoSuchAlgorithmException e) {
            throw new SsoSamlException(e);
        } catch (UnrecoverableKeyException e) {
            throw new SsoSamlException(e);
        } catch (SAMLException e) {
            throw new SsoSamlException(e);
        }
        log.debug("done");
    }
}

Javadoc provided here should be self explanations. Now we can construct our servlet in three lines of code as follows:

BrowserProfileRequest samlRequest = SsoSamlHelper.createRequest(httpRequest);
BrowserProfileResponse samlResponse = SsoSamlHelper.processRequest(samlRequest);
String issuer = SsoSamlHelper.getIssuer(samlResponse.assertion);
SsoSamlHelper.verifySignature(samlResponse.response, issuer, keyStoreHolder);
String nameIdentifier = samlResponse.authnStatement.getSubject().getNameIdentifier().getName();

//auth user with username==nameIdentifier

//redirect to samlRequest.TARGET

That's it! Servlet out looks as follows:

10:10:27(DEBUG)[ws.security.KeyStoreHolder.initKeyStore():74] 
10:10:27(DEBUG)[ws.security.KeyStoreHolder.initTrustStore():84] 
10:10:27(DEBUG)[sso.SsoSamlServlet.service():42] [START] 
10:10:27(DEBUG)[sso.SsoSamlServlet.service():45] read HTTP request into BrowserProfileRequest 
10:10:27(DEBUG)[sso.SsoSamlHelper.createRequest():40] 
10:10:27(DEBUG)[sso.SsoSamlServlet.service():47] samlRequest.SAMLResponse: base 64 code here 
10:10:27(DEBUG)[sso.SsoSamlServlet.service():48] samlRequest.TARGET:target URL here
10:10:27(DEBUG)[sso.SsoSamlServlet.service():50] process BrowserProfileRequest into BrowserProfileResponse 
10:10:27(DEBUG)[sso.SsoSamlHelper.processRequest():54] 
10:10:28(DEBUG)[sso.SsoSamlHelper.processRequest():70] done 
10:10:28(DEBUG)[sso.SsoSamlServlet.service():54] issuer: 'My partner #1' 
10:10:28(DEBUG)[sso.SsoSamlServlet.service():56] verify response signature 10:10:28(DEBUG)[sso.SsoSamlHelper.verifySignature():86] 
10:10:28(INFO) [security.signature.Reference.verify():742] Verification successful for URI "#cMnRtaOAdFkQmoCoQUdn" 
10:10:28(DEBUG)[sso.SsoSamlHelper.verifySignature():98] done 
10:10:28(DEBUG)[sso.SsoSamlServlet.service():59] perform authentication 10:10:28(DEBUG)[sso.SsoSamlServlet.service():61] nameIdentifier: hemaTest 
10:10:28(DEBUG)[service.handler.SecurityManager.getUserPasswordFromSamlAssertion():39] retrieve runtime properties 
10:10:28(DEBUG)[service.handler.SecurityManager.getUserPasswordFromSamlAssertion():43] companyName:My partner #1 
10:10:28(DEBUG)[service.handler.SecurityManager.getUserPasswordFromSamlAssertion():44] loginId:partnerUser_1 
10:10:28(DEBUG)[sso.SsoSamlServlet.service():69]

Test: SAML Asserting party Implementation. At this point we have to test our code. In order to do it we have to implement Asserting party. This includes "Inter-Site Transfer Service" implementation and all necessary parts for the browser functionality. This is definitely quite enough for the next article.

References. www.opersaml.com - SAML 1.1 and 2.0 implementation SAML 1.1 specifications

Local Managed DNS (Java)

Introduction. As you probably know it is quite often when Web developer goes to change default DNS behavior on his workstation. I mean sometimes it is important to change host name resolution locally and point specific host name to localhost ip address. Suppose you work under 'blahblah.com' web site on your workstation and you have to test this site locally, for example by starting you browser and point it to http://blahblah.com. While this site is already on production you browser resolves 'blahblah.com' to real IP address instead of local one. Of course the simplest way here (and I am sure it is quite wide spread) is to change you local hosts file (/etc/hosts or %SystemRoot%\system32\drivers\etc\hosts) by adding the following entry: 127.0.0.1 blahblah.com It is ok and works quite well not only for browser but also for all IP applications running on you workstation. Today I have a deal with system which has at least three stages: development, staging and production. Thus, sometimes I have to change my hosts file and switch host name-IP mapping for all those configurations. My host now looks like: #this is for dev 12.12.12.10 blahblah.com #this is for staging #12.12.12.11 blahblah.com #this is for production #12.12.12.12 blahblah.com

Problem area. My real hosts file looks much more complicated, because we have more than one server on each stage. Every time when you want to switch environment you go to hosts and comment/uncomment certain lines. Everything works fine until you have to write automated stand alone tool in Java which has to manage this hostname-ip mapping itself. There are a lot of possible targets for such tools. It can be some kind of testing tool, which has to execute several tests on each environment at ones (dev, stage, prod). Or it can be quite complicated tool which has to monitor cluster of web sites (i.e. by execute functional tests against it) where each host has its unique IP address but they all belongs to one host name. It is not very good idea to install this monitoring tool on each node in the cluster. It is better to have dedicated monitoring node which will run its tests in sequence or in parallel, and perform its operations under all nodes in the cluster. There are no any problems in implementing such a tool along if you know all IP addresses of all nodes in the cluster and you tests relay only on this IP addresses. However, in web development host name it is very important. It helps web server which listens on specific IP_address:port to determine certain application requested by particular URL request. And sometimes this web application performs HTTP redirects in order to perform several business operations, which also relay on host name. So at this point we have to implement something like:

Implementation. Do you have any ideas how to implement it? My first idea was to manage hosts file content from my monitoring java application? He-he. Yes, it was not very good idea. There are a lot of other applications can be run on monitoring node and I should not affect them at all. Thus I have to do something inside my JVM to perform host name resolution management. This is a good point let's dig inside it. I have my monitor tool ready, and it uses a lot of network libraries (apache http client, http Unit, CORBA nameservers and so forth). All those libraries use java.net package to perform all network operations. By default this package internally relies on Sun implementation of the IP stack. It means that I have to do something to alter default host name resolution behavior inside java.net package. Let's start. Definitely the entry point is InetAddress class and its

byte[][] lookupAllHostAddr(String name)

method which performs lookup by given hostname, and returns array of IP addresses belong to this hostname. You probably cannot find this method using your javadoc, he-he, and you are right this method is a part of java.net.InetAddressImpl interface which is package level and InetAddress itself doesn't implement it. But internally it uses Inet4AddressImpl class to perform several operation, and this Inet4AddressImpl implements InetAddressImpl interface. lookupAllHostAddr is the native method inside Inet4AddressImpl. Good investigation, but it still won't help us because we still have no idea how to alter name resolution behavior. It is good practice and common way to override default implementation using standard discovery mechanism. You have to place in your META-INF/services/facroty_name_here text file with one line as content with full qualified class name of the factory. This file is used by resource factory configuration.which instantiates this factory class mentioned in file and uses it to produce concrete objects. Common example is XML related libs which uses the following descriptors in META-INF/services:

• com.sun.org.apache.xerces.internal.xni.parser.XMLParserConfiguration
• javax.xml.parsers.DocumentBuilderFactory
• javax.xml.parsers.SAXParserFactory
• javax.xml.validation.SchemaFactory
• org.w3c.dom.DOMImplementationSourceList
• org.xml.sax.driver
• com.sun.org.apache.xml.internal.dtm.DTMManager
• javax.xml.transform.TransformerFactory

Preliminary the same situation we have here in Sun's InetAddress. InetAddress looks at the sun.net.spi.nameservice.provider.X system property in order to decide which name service implementation to use. By default it uses Inet4AddressImpl to create anonymous sun.net.spi.nameservice.NameService object. You have two options here:

1. specify sun.net.spi.nameservice.provider.1=default|dns,sun system property. This will use Sun's DNS name service provider through JNDI.
2. create your own name service and specify sun.net.spi.nameservice.provider.1 system property with you custom value.

Hey! It seems we are about to bring an issue to a close very fast! Let's create our own sun.net.spi.nameservice.NameService, god bless Sun, there are only two methods to override. And then we will be ready to plug it into sun.net.spi.nameservice.provider.X infrastructure. This falls into several steps.

1. create descriptor in META-INF/services/sun.net.spi.nameservice.NameServiceDescriptor and mention our new descriptor class there: org.ots.dns.LocalManagedDnsDescriptor
2. create LocalManagedDnsDescriptor itselfs, it should implements sun.net.spi.nameservice.NameServiceDescriptor and return NameService in createNameService() method
3. create our custom NameService itself: public class LocalManagedDns implements NameService

Now we are going to implement only lookupAllHostAddr which can look as follows:

        if ("blahblah.com".equalsIgnoreCase(hostname)) {
            byte[] ip = Util.textToNumericFormat("12.12.12.10");
            return new byte[][] { ip };
        } else {
            throw new UnknownHostException();
        }

This is quite enough for the first test. If you run this code you will find that it works! However it works only for 'blahblah.com', every other host name lookup will throw UnknownHostException. It is good that we substitute our host name with desired IP address, but we also have to do something with other hostname lookups which are not involved into manipulations. The first idea here is to create sun.net.spi.nameservice.providerS tree, in the way if one provider cannot lookup host then another try to do the lookup itself: sun.net.spi.nameservice.provider.1=dns, LocalManagedDns sun.net.spi.nameservice.provider.2=default sun.net.spi.nameservice.provider.3=dns, sun However, these or any other combination of the properties won't help us, because InetAddress creates only one NameService for its own needs. As I understand this is the first one which is successfully created. For us it means that we have to deal with all host name lookup in our LocalManagedDns. Eh-h-h, it is not very good news. So, let's try to use Sun name service implementation inside our LocalManagedDns. Go to java.net and let's grab something from it. But all interesting classes there are final and package level. Thus, we cannot use them at all. Of course we can try to write our own class in java.net package and extends it from Inet4AddressImpl. But we will get "java.lang.SecurityException: Prohibited package name" at runtime in this case. And as I know there is no way around it, neither java.policy will help us. I could not find any way to use native JVM name service functions from user code. Thanks god, there is java libraries that can take care about DNS functions. It is DnsJava project. It has full DNS server/client functionality, but in our case all we need is to lookup host by name. With DnsJava it can be done in one line of code. Let's create DNSJavaNameService instance inside our LocalManagedDns and delegate all unmatched call to it. Also let's introduce NameStore, it is singleton which will store custom hostname/IP mapping and provide API to manage such a mappings.

package org.ots.dns;

import java.net.UnknownHostException;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import sun.net.spi.nameservice.NameService;

/**
 *
 * @version $Id$
 * @author Roman Kuzmik
 */
public class LocalManagedDns implements NameService {
    private static final Log log = LogFactory.getLog(LocalManagedDns.class);

    NameService defaultDnsImpl = new DNSJavaNameService();

    /**
     * @see sun.net.spi.nameservice.NameService#getHostByAddr(byte[])
     */
    public String getHostByAddr(byte[] ip) throws UnknownHostException {
        log.debug("");

        return defaultDnsImpl.getHostByAddr(ip);
    }

    /**
     * @see sun.net.spi.nameservice.NameService#lookupAllHostAddr(java.lang.String)
     */
    public byte[][] lookupAllHostAddr(String name) throws UnknownHostException {
        log.debug("");

        String ipAddress = NameStore.getInstance().get(name);
        if (!StringUtils.isEmpty(ipAddress)){
            log.debug("\tmatch");
            byte[] ip = Util.textToNumericFormat(ipAddress);
            return new byte[][]{ip};
        } else {
            log.debug("\tmiss");
            return defaultDnsImpl.lookupAllHostAddr(name);
        }
    }

}

Let's design NameStore in way it can handle singleton scope mapping as well as local thread level mapping. In my monitoring tool I have thread pool which executes task in parallel and every task thread has to have its own hostname/IP mapping.

package org.ots.dns;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.lang.StringUtils;

/**
 *
 * @version $Id$
 * @author Roman Kuzmik
 */
public class NameStore {

    protected static NameStore singleton;

    protected Map globalNames;
    protected ThreadLocal localThread;

    protected NameStore(){
        globalNames = Collections.synchronizedMap(new HashMap());
        localThread = new ThreadLocal();
    }

    public static NameStore getInstance(){
        if (singleton == null) {
            synchronized (NameStore.class) {
                if (singleton == null) {
                    singleton = new NameStore();
                }
            }
        }
        return singleton;
    }

    public void put(String hostName, String ipAddress){
        globalNames.put(hostName, ipAddress);
    }
    public void remove(String hostName){
        globalNames.remove(hostName);
    }

    public synchronized void putLocal(String hostName, String ipAddress){
        Map localThreadNames = (Map) localThread.get();
        if (localThreadNames == null){
            localThreadNames = Collections.synchronizedMap(new HashMap());
            localThread.set(localThreadNames);
        }
        localThreadNames.put(hostName, ipAddress);
    }
    public void removeLocal(String hostName){
        Map localThreadNames = (Map) localThread.get();
        if (localThreadNames != null){
            localThreadNames.remove(hostName); 
        }
    }

    public String get(String hostName){
        String ipAddress = null;
        Map localThreadNames = (Map) localThread.get();
        if (localThreadNames != null){
            ipAddress = (String)localThreadNames.get(hostName); 
        }
        if (StringUtils.isEmpty(ipAddress)) {
            return (String)globalNames.get(hostName);
        }
        return ipAddress;
    }

}

At this point we are ready to write simple test:

        hostName = "google.com";
        ipAddress = "127.0.0.1";
        NameStore.getInstance().put(hostName, ipAddress);
        performLookup(hostName);

        hostName = "google.com";
        NameStore.getInstance().remove(hostName);
        performLookup(hostName);

This code should lookup google.com to 127.0.0.1 at a first stage and then lookup the same host to its real IP addresses. First stage works fine, but second fails. It is not because we done something wrong in stage two, it is because InetAddress maintains addressCache. And during second lookup request it simply return cached value. Ups-s-s. We've created our own NameServiceProvider, plugged it into JVM, incorporated JavaDns and all these things do not work because of InetAddress.addressCache ?! Nice:. Let's go back to Java sources again:. searching: found: there is property which can help us! //disable DNS cashe Security.setProperty("networkaddress.cache.ttl", "0"); Now our test code works fine:

        hostName = "google.com";
        ipAddress = "127.0.0.2";
        NameStore.getInstance().put(hostName, ipAddress);
        performLookup(hostName);
      
        hostName = "google.com";
        ipAddress = "127.0.0.3";
        NameStore.getInstance().putLocal(hostName, ipAddress);
        performLookup(hostName);

        new Thread(){

            public void run() {
                String hostName = "google.com";
                try {
                    performLookup(hostName);
                } catch (UnknownHostException e) {
                    e.printStackTrace();
                }
            }
 
        }.start();

Output:

[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsDescriptor.getType():33]
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsDescriptor.getProviderName():41]
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsDescriptor.createNameService():53]
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():34]
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():38]     match
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsTest.performLookup():74] google.com/127.0.0.1
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():34]
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():42]     miss
[java] 19:52:05(DEBUG)[vzb.dns.DNSJavaNameService.lookupAllHostAddr():32] google.com
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsTest.performLookup():74] google.com/64.233.187.99
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsTest.performLookup():74] google.com/72.14.207.99
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsTest.performLookup():74] google.com/64.233.167.99
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():34]
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():38]     match
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsTest.performLookup():74] google.com/127.0.0.2
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():34]
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():38]     match
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsTest.performLookup():74] google.com/127.0.0.3
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():34]
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDns.lookupAllHostAddr():38]     match
[java] 19:52:05(DEBUG)[vzb.dns.LocalManagedDnsTest.performLookup():74] google.com/127.0.0.2

Conclusion. In this article we wrote our custom NameServiceProvider which able to manage its name resolution behavior through it's simple API. It looks like we have our own hosts file inside JVM. See attached LocalManagedDns.zip for the full source code provided along with this article. This is an example code so there is no license required. Please see corresponding license for libraries included into this package.

References. http://java.sun.com/j2se/1.5.0/docs/guide/net/properties.html http://www.xbill.org/dnsjava/

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