Alex Arriaga

alex-arriaga March 30, 2014

How to create a JAR file by using command line

This is only a single post about how to create a JAR file using command line easily. Previously, you need to compile your Java files, if you want to read more about it, please see this post: How to compile Java programs by using command line.

If we need to create a JAR file, we can run next command (if we are in the root of our project):

// Create a JAR file including com and WebContent directories and their contents
jar -cvf web_fragment.jar com/ WebContent/

1 2	// Create a JAR file including com and WebContent directories and their contents jar -cvf web_fragment.jar com/ WebContent/

c: indicates that you want to create a JAR file
v: produces verbose output on stdout while the JAR file is being built. The verbose output tells you the name of each file as it’s added to the JAR file
f: indicates that you want the output to go to a file rather than to stdout
Last list of parameters are folders we want to add. We include com/ and WebContent/ directories and their contents into the JAR file.

alex-arriaga March 10, 2014

How to understand and use Chrome Developer Tools (in spanish)

Web Development No Reply

Hi friends!

Last week someone of the community asked me for how to do debugging of JavaScript in his web applications and web sites, to answer that question I have created a little video (40 minutes, more or less) to give you the big picture about the great tools for developers that are available in Google Chrome. During this video you will see how these tools can improve your skills as front-end developers.

First of all, let me tell you all the official documentation about every single available feature can be found in next link: https://developers.google.com/chrome-developer-tools/

Please, share this video with anyone who could be interested in. And remember, be happy with your code!

alex-arriaga March 10, 2014

Session 2: jQuery for the real world (in spanish)

jQuery, Web Development No Reply

Hi again!

Here is the second session of our jQuery course, please feel free to share it, download it or watch it as many times you want, it is totally free!

In this session following topics are shown:

Validation and use of jQuery from a CDN
Generation of content dinamically
Iterating into Arrays and exploring objects properties
Querying the DOM: find(), children(), next(), prev(), first(), last()
Tips about the best validation of undefined types
Recommendations about how to declare “jquery-generated-variables”

I hope you find this session very useful for your real life as a front-end developer.

Be happy with your code!

alex-arriaga March 4, 2014

Session 1: jQuery for the real world (in spanish)

jQuery, Web Development No Reply

Hi friends!

Today, I would like to share the first session of a new course that I am starting this week, this course includes a lot of the greatest features of jQuery library. During these sessions we are going to learn methods, tricks and advanced code in jQuery that will allow us to obtain a very high level in our jQuery skills. Please, share with your partners, colleagues or anyone who is interested in learning this wonderful library.
And remember, be happy with your code!

Regards.

alex-arriaga January 27, 2014

How to print Attributes enumeration in Java (javax naming directory Attributes)

Enterprise Development, Java EE No Reply

This is only a little piece of code to print all the IDs and values of a javax.naming.directory.Attributes.

If you want to know more about this interface, please see official documentation (http://docs.oracle.com/javase/7/docs/api/javax/naming/directory/Attributes.html), but here, you have a little explanation about it:

This interface represents a collection of attributes.
In a directory, named objects can have associated with them attributes. The Attributes interface represents a collection of attributes. For example, you can request from the directory the attributes associated with an object. Those attributes are returned in an object that implements the Attributes interface.

Attributes in an object that implements the Attributes interface are unordered. The object can have zero or more attributes. Attributes is either case-sensitive or case-insensitive (case-ignore). This property is determined at the time the Attributes object is created. (see BasicAttributes constructor for example). In a case-insensitive Attributes, the case of its attribute identifiers is ignored when searching for an attribute, or adding attributes. In a case-sensitive Attributes, the case is significant.

Note that updates to Attributes (such as adding or removing an attribute) do not affect the corresponding representation in the directory. Updates to the directory can only be effected using operations in the DirContext interface.

public void printAttrs(Attributes attrs)
{
    System.out.println(">> printAttrs()");
    if (attrs == null)
    {
        System.out.println("No attributes");
    }
    else
    {
        // Print every single attribute
        try
        {
            for (NamingEnumeration ae = attrs.getAll(); ae.hasMore();)
            {
                Attribute attr = (Attribute) ae.next();
                System.out.println("Attribute ID: " + attr.getID());

                // Print values of current attribute
                NamingEnumeration e = attr.getAll();
                while(e.hasMore())
                {
                    String value = e.next().toString();
                    System.out.println("Value: " + value);
                }
            }
        } catch (NamingException e) { e.printStackTrace(); }
    }
    System.out.println("<< printAttrs()");
}

public void printAttrs(Attributes attrs)

{

System.out.println(">> printAttrs()");

if (attrs == null)

{

System.out.println("No attributes");

}

else

{

// Print every single attribute

try

{

for (NamingEnumeration ae = attrs.getAll(); ae.hasMore();)

{

Attribute attr = (Attribute) ae.next();

System.out.println("Attribute ID: " + attr.getID());

// Print values of current attribute

NamingEnumeration e = attr.getAll();

while(e.hasMore())

{

String value = e.next().toString();

System.out.println("Value: " + value);

}

} catch (NamingException e) { e.printStackTrace(); }

}

System.out.println("<< printAttrs()");

}

That’s it!

Be happy with your code!

alex-arriaga January 27, 2014

How to get a multi-valued LDAP attribute in JAVA (using a custom query to LDAP)

Enterprise Development, Java EE No Reply

Today, I would like to show you an example of a custom query to an LDAP, this query obtains a multi-valued LDAP attribute.

Situation

Imagine you need to know the associated user ids that are linked to an existing user, so you know the name of the LDAP attribute which is “associatedUserID”, and of course you have access to LDAP using a valid user and password.

1) Create a method to run a query to LDAP:

/*
* An example of a method with a query to get a multi-valued attribute
*/
public boolean isUserAssociatedWithAUser(String userID, String associatedUserID){
	DirContext context = null;
    String dn = "";
    try
		{
    		Hashtable env = new Hashtable();
    		env.put(Context.SECURITY_PRINCIPAL, "your_admin_id");      
			env.put(Context.SECURITY_CREDENTIALS, "password_admin");
	     	DirContext initial = new InitialDirContext(env);
	     	context = (DirContext) initial.lookup("server_url");

    		String ou[] = {"department", "network"};

    		for(int i = 0;i < ou.length;i++)
	  	 	{
	     		String base = "userid=" + userID + ",ou=" + ou[i] + ",o=your_domain.com";	// Your custom LDAP query
	    		String filter = "(objectclass=*)";											// Your filter
	    		SearchControls sc = new SearchControls();  
		  	 	sc.setSearchScope(SearchControls.OBJECT_SCOPE);								// Set scope of your search

		  	 	// The LDAP attribute that you are looking for, in this example "associatedUserID" is multi-valued
		  	 	sc.setReturningAttributes(new String[] {"associatedUserID"});			
	    		try 
	    		{
	    			NamingEnumeration answer = context.search(base, filter, sc);
	    			dn = base;

	    			while (answer.hasMore()) 
	    			{
			     		SearchResult sr = (SearchResult) answer.next(); 
			     		Attributes attrs = sr.getAttributes();
			     		List associatedUserIDs = getAssociatedUserIdsFromAttrs(attrs);

			     		for(int j=0; j<associatedUserIDs.size(); j++)
                        {
			     			Object associatedPortalUserID = associatedUserIDs.get(j);
                        	if(associatedPortalUserID instanceof String)
                        	{
                        		String associatedPortalUserIDStr = (String)associatedPortalUserID;
                        		if(associatedPortalUserIDStr.indexOf(associatedUserID) >= 0)
                    			{
                    				dpLogger.info(userID + " is associated with " + associatedPortalUserIDStr);
                    				return true;
                    			}
                        	}
                        }

			     	}// ends while
	     		}
	    		catch (javax.naming.NameNotFoundException e)
	    		{
	    	  		//Do nothing since the user is not in this ou
	    	  	}
	    		// Found 
	    		if (! dn.equals("")){ break;}
	  	 	}
	  	}
	  	catch (javax.naming.CommunicationException e)
		{
	  		System.out.println("Admin Authentication Exception: Could not communicate with user directory.");
	  		return false;
	  	}
	  	catch(Exception e)
		{
	  		System.out.println("An Error occured while trying to Authenticate Admin.");
	  		return false;
	  	}
	  	finally
		{
	  		if ( context != null )
	  		{
	  			try { context.close(); } catch (Exception e) {}
	  		}
		}

	  	//Check if the user ID was found   
	  	if (dn.equals(""))
	  	{
	  		System.out.println("User not found error");
	  		return false;
	  	}
	return false;
}

* An example of a method with a query to get a multi-valued attribute

public boolean isUserAssociatedWithAUser(String userID, String associatedUserID){

DirContext context = null;

String dn = "";

try

{

Hashtable env = new Hashtable();

env.put(Context.SECURITY_PRINCIPAL, "your_admin_id");

env.put(Context.SECURITY_CREDENTIALS, "password_admin");

DirContext initial = new InitialDirContext(env);

context = (DirContext) initial.lookup("server_url");

String ou[] = {"department", "network"};

for(int i = 0;i < ou.length;i++)

{

String base = "userid=" + userID + ",ou=" + ou[i] + ",o=your_domain.com"; // Your custom LDAP query

String filter = "(objectclass=*)"; // Your filter

SearchControls sc = new SearchControls();

sc.setSearchScope(SearchControls.OBJECT_SCOPE); // Set scope of your search

// The LDAP attribute that you are looking for, in this example "associatedUserID" is multi-valued

sc.setReturningAttributes(new String[] {"associatedUserID"});

try

{

NamingEnumeration answer = context.search(base, filter, sc);

dn = base;

while (answer.hasMore())

{

SearchResult sr = (SearchResult) answer.next();

Attributes attrs = sr.getAttributes();

List associatedUserIDs = getAssociatedUserIdsFromAttrs(attrs);

for(int j=0; j<associatedUserIDs.size(); j++)

{

Object associatedPortalUserID = associatedUserIDs.get(j);

if(associatedPortalUserID instanceof String)

{

String associatedPortalUserIDStr = (String)associatedPortalUserID;

if(associatedPortalUserIDStr.indexOf(associatedUserID) >= 0)

{

dpLogger.info(userID + " is associated with " + associatedPortalUserIDStr);

return true;

}

}// ends while

}

catch (javax.naming.NameNotFoundException e)

{

//Do nothing since the user is not in this ou

}

// Found

if (! dn.equals("")){ break;}

}

catch (javax.naming.CommunicationException e)

{

System.out.println("Admin Authentication Exception: Could not communicate with user directory.");

return false;

}

catch(Exception e)

{

System.out.println("An Error occured while trying to Authenticate Admin.");

return false;

}

finally

{

if ( context != null )

{

try { context.close(); } catch (Exception e) {}

}

//Check if the user ID was found

if (dn.equals(""))

{

System.out.println("User not found error");

return false;

}

return false;

}

2) For explaining purposes, I have split the reading operation (using a Attributes enumeration) in another method:

public List getAssociatedUserIdsFromAttrs(Attributes attrs) {
    List associatedUsers = new ArrayList();

   	if (attrs != null)
    {
    	try
    	{
    		for (NamingEnumeration ae = attrs.getAll(); ae.hasMore();)
    		{
    			Attribute attr = (Attribute) ae.next();
    			System.out.println("Attribute ID:" + attr.getID());

                // Obtaining only the associatedUserID attribute's values
    			if(attr.getID().equals("associatedUserID"))
    			{
    				NamingEnumeration e = attr.getAll();
    				while(e.hasMore())
    				{
    					String value = e.next().toString();
    					System.out.println("Value: " + value);
    					associatedUsers.add(value);
                    }
    			}
            }
    	}catch (NamingException e) { e.printStackTrace(); }
    }
    return associatedUsers;
}

public List getAssociatedUserIdsFromAttrs(Attributes attrs) {

List associatedUsers = new ArrayList();

if (attrs != null)

{

try

{

for (NamingEnumeration ae = attrs.getAll(); ae.hasMore();)

{

Attribute attr = (Attribute) ae.next();

System.out.println("Attribute ID:" + attr.getID());

// Obtaining only the associatedUserID attribute's values

if(attr.getID().equals("associatedUserID"))

{

NamingEnumeration e = attr.getAll();

while(e.hasMore())

{

String value = e.next().toString();

System.out.println("Value: " + value);

associatedUsers.add(value);

}

}catch (NamingException e) { e.printStackTrace(); }

}

return associatedUsers;

}

That’s it!

Be happy with your code!

alex-arriaga January 20, 2014

How to create a List from a JSON object in Java using Jackson Library

Enterprise Development, Java EE No Reply

Today, I would like to share an easy way to parse a JSON string into a List of Java objects in a few lines of code. Imagine the situation where you need to create a List of complex objects from a JSON array in Java, for example if we have this kind of input:

[
	{
		"title":"Title of hotspot #1",
		"x":194,
		"y":180,
		"order":0,
		"url":"http://www.alex-arriaga.com/"
	},
	{
		"title":"Title of hotspot #2",
		"x":23,
		"y":45,
		"order":1,
		"url":"http://www.alex-arriaga.com/about-me/"
	}
]

[

{

"title":"Title of hotspot #1",

"x":194,

"y":180,

"order":0,

"url":"http://www.alex-arriaga.com/"

{

"title":"Title of hotspot #2",

"x":23,

"y":45,

"order":1,

"url":"http://www.alex-arriaga.com/about-me/"

}

]

Now, suppose we have following POJO class (this class will have our fields for doing the mapping from JSON to a Java List):

package com.base22.model;

public class HotSpot{
	private String title;
	private int x;
	private int y;
	private int order;
	private String url;

	public HotSpot(){

	}

	// Create more constructors if you want :)

	public int getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public int getX() {
		return x;
	}

	public void setX(int x) {
		this.x = x;
	}

	public int getY() {
		return y;
	}

	public void setY(int y) {
		this.y = y;
	}

	public int getOrder() {
		return order;
	}

	public void setOrder(int order) {
		this.order = order;
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	@Override
	public String toString(){
		StringBuilder sb = new StringBuilder();
		sb.append("\nHotspot [ID=" + id + "]");
		sb.append("\nUrl: " + url);
		sb.append("\nDescription: " + description);
		sb.append("\nOrder: " + order);

		return sb.toString();
	}

}

package com.base22.model;

public class HotSpot{

private String title;

private int x;

private int y;

private int order;

private String url;

public HotSpot(){

}

// Create more constructors if you want :)

public int getTitle() {

return title;

}

public void setTitle(String title) {

this.title = title;

}

public int getX() {

return x;

}

public void setX(int x) {

this.x = x;

}

public int getY() {

return y;

}

public void setY(int y) {

this.y = y;

}

public int getOrder() {

return order;

}

public void setOrder(int order) {

this.order = order;

}

public String getUrl() {

return url;

}

public void setUrl(String url) {

this.url = url;

}

@Override

public String toString(){

StringBuilder sb = new StringBuilder();

sb.append("\nHotspot [ID=" + id + "]");

sb.append("\nUrl: " + url);

sb.append("\nDescription: " + description);

sb.append("\nOrder: " + order);

return sb.toString();

}

One of the easiest way to reach our goal is by using Jackson library (http://jackson.codehaus.org/), which has a really good mapper. Let me show two single lines to map our JSON input into a Java List.

// This is an example of a JSON input string
String jsonString = "[{\"title\":\"Title of hotspot #1\",\"x\":194,\"y\":180,\"order\":0,\"url\":\"http://www.alex-arriaga.com/\"},{\"title\":\"Title of hotspot #2\",\"x\":23,\"y\":45,\"order\":1,\"url\":\"http://www.alex-arriaga.com/about-me/\"}]";

1 2	// This is an example of a JSON input string String jsonString = "[{\"title\":\"Title of hotspot #1\",\"x\":194,\"y\":180,\"order\":0,\"url\":\"http://www.alex-arriaga.com/\"},{\"title\":\"Title of hotspot #2\",\"x\":23,\"y\":45,\"order\":1,\"url\":\"http://www.alex-arriaga.com/about-me/\"}]";

try{
	ObjectMapper jsonMapper = new ObjectMapper();
	List <HotSpot> hotspots = jsonMapper.readValue(jsonString, new TypeReference<List<HotSpot>>(){});
}catch(Exception e){
	e.printStackTrace();
}

try{

ObjectMapper jsonMapper = new ObjectMapper();

List <HotSpot> hotspots = jsonMapper.readValue(jsonString, new TypeReference<List<HotSpot>>(){});

}catch(Exception e){

e.printStackTrace();

}

Finally, you could iterate among all the objects in your new List.

for(HotSpot hotspot : hotspots){
	System.out.println(hotspot);
}

for(HotSpot hotspot : hotspots){

System.out.println(hotspot);

}

That’s it!

Be happy with your code!

alex-arriaga January 17, 2014

How to set no-cache headers in a Java EE application’s response (using a Spring controller)

Enterprise Development, Java EE No Reply

Sometimes when you do a request to a Java service you will need to add some custom headers in the response, for example, today I was creating a service to get the current logged user data and I realized one client was storing (creating a cache) the response and sometimes the service was not working as expected.

So, in my case I was using Spring MVC to create a custom XML response I wanted to add a no-cache header, for that reason I spent some time to figure out which is the right way to do it, please let me explain how you can do that easily!

1) Following is an example of a Java method that contains Spring and JAXB annotations to create a custom XML and set custom headers in the response:

	@RequestMapping(method ={RequestMethod.GET, RequestMethod.POST}, produces="application/xml")
	public @ResponseBody UserProfileResponse getUserProfileInXML(HttpServletRequest request, HttpServletResponse response) {

		// UserProfileResponse and UserProfileService are MY custom classes, but you can retrieve any class you want!
		UserProfileResponse profileResponse = new UserProfileResponse();
		UserProfileService service = UserProfileService.getInstance();	// A singleton class
		Principal principal = (Principal) request.getUserPrincipal();

		if (principal != null) {
			profileResponse.setUserProfile( service.getUserProfile(principal.getName()) );
		}

		// Setting response's headers
		response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1.
		response.setHeader("Pragma", "no-cache"); // HTTP 1.0.
		response.setDateHeader("Expires", 0); // Proxies.

		return profileResponse;
	}

@RequestMapping(method ={RequestMethod.GET, RequestMethod.POST}, produces="application/xml")

public @ResponseBody UserProfileResponse getUserProfileInXML(HttpServletRequest request, HttpServletResponse response) {

// UserProfileResponse and UserProfileService are MY custom classes, but you can retrieve any class you want!

UserProfileResponse profileResponse = new UserProfileResponse();

UserProfileService service = UserProfileService.getInstance(); // A singleton class

Principal principal = (Principal) request.getUserPrincipal();

if (principal != null) {

profileResponse.setUserProfile( service.getUserProfile(principal.getName()) );

}

// Setting response's headers

response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1.

response.setHeader("Pragma", "no-cache"); // HTTP 1.0.

response.setDateHeader("Expires", 0); // Proxies.

return profileResponse;

}

2) The important lines in previous code are:

// Setting response's headers
response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1.
response.setHeader("Pragma", "no-cache"); // HTTP 1.0.
response.setDateHeader("Expires", 0); // Proxies.

// Setting response's headers

response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1.

response.setHeader("Pragma", "no-cache"); // HTTP 1.0.

response.setDateHeader("Expires", 0); // Proxies.

Because they set custom response’s headers to establish a no-cache configuration.

3) Now, just to test we could do a normal request in a browser and we can see the headers:

As you can see, the headers were set correctly.

That’s it!

Be happy with your code!

alex-arriaga January 7, 2014

Setting UTF-8 encoding in a JSP (changing ISO-8859-1 to UTF-8 on IBM Rational Application Developer)

Enterprise Development, Java EE 2 Replies

Today, I was integrating a custom JSP component into IBM WCM and I noticed some characters were not displaying as expected, after looking into the generated source code in Firefox I realized the used encoding was ISO-8859-1, let me explain what ISO-8859-1 means…

According the W3C the ISO-8859-1 encoding:

ISO-8859-1 is the default character set in most browsers.

The first 128 characters of ISO-8859-1 is the original ASCII character-set (the numbers from 0-9, the uppercase and lowercase English alphabet, and some special characters).

The higher part of ISO-8859-1 (codes from 160-255) contains the characters used in Western European countries and some commonly used special characters.

Entities are used to implement reserved characters or to express characters that cannot easily be entered with the keyboard.

My source code looked like this (in Firefox):

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

1	<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />

And this was the displayed characters (look the “Spanish”, “Portuguese” and “Russian” language labels):

Well, solution for this enconding error is really easy, we only need to:

1) Set the encoding in the JSP file (using your editor or IDE), in my case I was using Rational:

2) Type a directive to indicate we WANT to use UTF-8. At the beginning of your JSP code add following line:

<%@page language="java" contentType="text/html; charset=utf-8" %>

1	<%@page language="java" contentType="text/html; charset=utf-8" %>

That’s it! now all our messages will be ok 🙂

Be happy with your code!

alex-arriaga November 6, 2013

How to know jQuery version using Firebug console

jQuery, Web Development No Reply

This is a little tip for today: sometimes, you don’t have access to know what version of jQuery is loaded in a website or web application, so you can use the Firebug console to know what version is actually loaded. Just, type one of the next lines and you will obtain that data.

Both major version version 1.x and version 2.x have a property called jQuery.fn.jquery, we could check it:

//  It returns something like: "1.9.1"
console.log(jQuery.fn.jquery);

1 2	// It returns something like: "1.9.1" console.log(jQuery.fn.jquery);

// Of course we know jQuery == $, then we can use next shorthand syntax
console.log($.fn.jquery);

1 2	// Of course we know jQuery == $, then we can use next shorthand syntax console.log($.fn.jquery);

Also, we can use an alternative syntax:

// Alternative syntax
console.log(jQuery().jquery);

// or shorthand method
console.log($().jquery);

// Alternative syntax

console.log(jQuery().jquery);

// or shorthand method

console.log($().jquery);

That’s it!

Be happy with your code!

What would you like to know about?

Alex Arriaga

How to create a JAR file by using command line

How to understand and use Chrome Developer Tools (in spanish)

Session 2: jQuery for the real world (in spanish)

Session 1: jQuery for the real world (in spanish)

How to print Attributes enumeration in Java (javax naming directory Attributes)

How to get a multi-valued LDAP attribute in JAVA (using a custom query to LDAP)

Situation

How to create a List from a JSON object in Java using Jackson Library

How to set no-cache headers in a Java EE application’s response (using a Spring controller)

Setting UTF-8 encoding in a JSP (changing ISO-8859-1 to UTF-8 on IBM Rational Application Developer)

How to know jQuery version using Firebug console

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