JavaEE – Alex Arriaga

alex-arriaga July 25, 2018

How to set JAVA_HOME in Mac OS X High Sierra

Enterprise Development, Liferay 3 Replies

This post describes how to configure the JAVA_HOME environment variable required by many enterprise tools, frameworks, and CMSes. For instance, Liferay, Tomcat, etc. will use this variable to work properly.

In case you have changed your default shell (Bash) that comes with OS X out-of-the-box, please read How to set JAVA_HOME in Mac OS X High Sierra with Fish shell

Step 1. Be sure you don’t have the JAVA_HOME already set

Run this command:

echo $JAVA_HOME

1	echo $JAVA_HOME

If the output is empty, then we don’t have the variable correctly set.

Step 2. Find the Java Development Kit directory

If you don’t know where the Java Development Kit (JDK) was installed, just run:

sudo find / -name javac

1	sudo find / -name javac

The output may be similar to this:

/usr/bin/javac
/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/bin/javac
/System/Library/Frameworks/JavaVM.framework/Versions/A/Commands/javac
find: /private/var/db/ConfigurationProfiles/Store: Operation not permitted
find: /private/var/folders/y5/abbasdf/0/SafariFamily: Operation not permitted

/usr/bin/javac

/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/bin/javac

/System/Library/Frameworks/JavaVM.framework/Versions/A/Commands/javac

find: /private/var/db/ConfigurationProfiles/Store: Operation not permitted

find: /private/var/folders/y5/abbasdf/0/SafariFamily: Operation not permitted

Notice the second line, that is our JDK installation directory, so the directory we need to use is this one: /Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/

The path may vary depending on the exact version of Java you have installed

Step 3. Add the JAVA_HOME to the Bash configuration file

Let’s open the file (if don’t exist, just create it):

nano ~/.bash_profile

1	nano ~/.bash_profile

Add the JAVA_HOME variable at the end of ~/.bash_profile

export JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/"

1	export JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/"

Save the file ~/.bash_profile (in nano just press Control + O followed by Control + X to close the file). Finally, let’s review or configuration by typing:

echo $JAVA_HOME

1	echo $JAVA_HOME

This command should now print the correct JAVA_HOME:

/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/

1	/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/

If you don’t see your environment variable, please close all your terminal windows and re-start them so you have a “fresh” start.

Sweet, isn’t it?

See you next time.

Alex Arriaga

alex-arriaga July 25, 2018

How to set JAVA_HOME in Mac OS X High Sierra with Fish shell

Enterprise Development, Java EE, Liferay 1 Reply

This configuration is useful when you decided to change your default shell in OS X, for example in our case we have Fish shell and it will not have the JAVA_HOME set out-of-the-box.

Are you looking for the instructions about how to set the JAVA_HOME for Bash? Visit How to set JAVA_HOME in Mac OS X High Sierra

How can we test if we have configured this environment variable? Easy, just type:

echo $JAVA_HOME

1	echo $JAVA_HOME

If the output is empty, then we don’t have the variable in place.

Step 1. Find and open your configuration file

If you are using Fish shell, chances are you are also using Oh My Fish which provides infrastructure to allow you to install packages to extend and modify the look and feel of your shell. Let’s open the configuration file then:

nano ~/.config/fish/conf.d/omf.fish

1	nano ~/.config/fish/conf.d/omf.fish

The “~/” is a shortcut for accessing the home directory of your user.

Step 2. Locate your Java directory where the Java Development Kit was installed

If you don’t know where the Java Development Kit (JDK) was installed, just run:

sudo find / -name javac

1	sudo find / -name javac

The output may be similar to this:

/usr/bin/javac
/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/bin/javac
/System/Library/Frameworks/JavaVM.framework/Versions/A/Commands/javac
find: /private/var/db/ConfigurationProfiles/Store: Operation not permitted
find: /private/var/folders/y5/abbasdf/0/SafariFamily: Operation not permitted

/usr/bin/javac

/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/bin/javac

/System/Library/Frameworks/JavaVM.framework/Versions/A/Commands/javac

find: /private/var/db/ConfigurationProfiles/Store: Operation not permitted

find: /private/var/folders/y5/abbasdf/0/SafariFamily: Operation not permitted

Notice the second line, that is our JDK installation directory, so the directory we need to use is this one: /Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/

The path may vary depending on the exact version of Java you have installed

Step 3. Add the JAVA_HOME to the Oh My Fish configuration file

Let’s open the file:

nano ~/.config/fish/conf.d/omf.fish

1	nano ~/.config/fish/conf.d/omf.fish

Add the JAVA_HOME variable at the end of ~/.config/fish/conf.d/omf.fish

export JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/"

1	export JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/"

Save the file ~/.config/fish/conf.d/omf.fish (in nano just press Control + O followed by Control + X to close the file). Finally, let’s review or configuration by typing:

echo $JAVA_HOME

1	echo $JAVA_HOME

This command, should now print the correct JAVA_HOME:

/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/

1	/Library/Java/JavaVirtualMachines/jdk1.8.0_171.jdk/Contents/Home/

Sweet, isn’t it?

See you next time.

Alex Arriaga

alex-arriaga July 11, 2014

How to configure session factory to connect to a DB2 datasource with Hibernate

Databases and ORM, Enterprise Development, Hibernate, IBM WebSphere, Java EE 2 Replies

A really brief intro

Hibernate is one of the most incredible Object Relational Mapper (ORM engine) that we have to make scalable and secure Java Enterprise Applications. Today, I going to explain you, how to configure your session factory field by field in order to have a basic connection to a datasource (in this case using IBM DB2 as database engine).

Let’s start

1) You have to create your datasource and that will depend on which application server you are using, in my case I have configured an IBM DB2 datasource into IBM WebSphere Application Server 8.

2) Create a file called hibernate.cfg.xml in YOUR_WEBAPP/WebContent/WEB-INF/ directory.

3) Copy following example and customize accordingly.

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- Database connection settings -->
        <property name="connection.datasource">jdbc/MyAwesomeDatasource</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.DB2Dialect</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>
        <property name="javax.persistence.validation.mode">none</property>
        <mapping class="com.base22.awesomeapp.models.User" />
        <mapping class="com.base22.awesomeapp.models.Page" />
    </session-factory>
</hibernate-configuration>

<?xml version="1.0" encoding="utf-8" ?>

<!DOCTYPE hibernate-configuration PUBLIC

"-//Hibernate/Hibernate Configuration DTD 3.0//EN"

"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

<session-factory>

<property name="connection.datasource">jdbc/MyAwesomeDatasource</property>

<property name="dialect">org.hibernate.dialect.DB2Dialect</property>

<property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

</session-factory>

</hibernate-configuration>

Basic explanation of properties

Property name	Description
connection.datasource	This is the name of the datasource you configure previously, this configuration depends on your specific application server
dialect	A hibernate dialect is a “the variant of a SQL language”. Hibernate can work with many databases engines like: DB2, PostgreSQL, MySQL, Oracle, etc. However, databases have propietary extensions and SQL variations, and of course set or sub-sets of SQL standard implementations, for that reason Hibernate uses “dialect” configuration to know which database you are using and switch to the specific SQL syntax.
cache.provider_class	Cache will allow us to store data in memory to the database, using this we will achieve a reduction in traffic between it and our system and also reduce access time to data.The second level cache is associated with the Session Factory object. This allows that an object -which is cached- can be obtained anywhere in the application by any user at any time as often as necessary and without accessing the database.To operate this level, we must do some settings in Hibernate and also choose a cache implementer. Hibernate supports 4 open-source implementations of cache: EhCache (Easy Hibernate Cache) OSCache (Open Symphony Cache) Swarm Cache JBoss Tree Cache
show_sql	Enables the build-in a function of Hibernate to display all the generated SQL statements to the console.
javax.persistence.validation.mode	Hibernate Validator includes an event listener (part of Hibernate Annotations in the org.hibernate.cfg.beanvalidation.BeanValidationEventListener class). It listens for events like: PreInsertEvent, PreUpdateEvent and PreDeleteEvent, verify all the constraints applied to the entities, and throws an exception when a constraint is violated.

Read more about Hibernate configuration in this link: http://docs.jboss.org/hibernate/orm/4.2/manual/en-US/html/ch01.html#tutorial-firstapp-configuration

And remember, be happy with your code!

alex-arriaga July 11, 2014

How to return different HttpStatus codes using Spring

Enterprise Development, Java EE 1 Reply

Any Java Enterprise Application that manipulates responses will need to return status codes depending on the execution of the code. So, here is one of the easiest ways to return a status code without the classical numbers like 200, 404, 400, etc.

// This method returns HttpStatus.OK (200) in case a wiki page exists, or  HttpStatus.NOT_FOUND (404) otherwise
@RequestMapping(value = "/pages/get/{uuid}", method = RequestMethod.GET, produces=MediaType.APPLICATION_JSON_VALUE)
public ResponseEntity<WikiPage> getWikiPage(@PathVariable("uuid") String uuid, @RequestParam String wikiUuid){
	Boolean exists = wikiPagesService.existsWikiPage(uuid, wikiUuid);
	WikiPage page = null;
	
	if(exists){
		page = wikiPagesService.getWikiPage(uuid, wikiUuid);
		return new ResponseEntity<WikiPage>(page, HttpStatus.OK);
	}else{
			return new ResponseEntity<WikiPage>(page, HttpStatus.NOT_FOUND);
	}
}

// This method returns HttpStatus.OK (200) in case a wiki page exists, or HttpStatus.NOT_FOUND (404) otherwise

@RequestMapping(value = "/pages/get/{uuid}", method = RequestMethod.GET, produces=MediaType.APPLICATION_JSON_VALUE)

public ResponseEntity<WikiPage> getWikiPage(@PathVariable("uuid") String uuid, @RequestParam String wikiUuid){

Boolean exists = wikiPagesService.existsWikiPage(uuid, wikiUuid);

WikiPage page = null;

if(exists){

page = wikiPagesService.getWikiPage(uuid, wikiUuid);

return new ResponseEntity<WikiPage>(page, HttpStatus.OK);

}else{

return new ResponseEntity<WikiPage>(page, HttpStatus.NOT_FOUND);

}

Following is a complete list of status codes in org.springframework.http.HttpStatus enumeration, you can find more information about it in this link: http://docs.spring.io/spring/docs/3.0.x/api/org/springframework/http/HttpStatus.html.

HttStatus value	Code and meaning
ACCEPTED	202 Accepted
ALREADY_REPORTED	208 Already Reported
BAD_GATEWAY	502 Bad Gateway
BAD_REQUEST	400 Bad Request
CONFLICT	409 Conflict
CONTINUE	100 Continue
CREATED	201 Created
DESTINATION_LOCKED	421 Destination Locked
EXPECTATION_FAILED	417 Expectation Failed
FAILED_DEPENDENCY	424 Failed Dependency
FORBIDDEN	403 Forbidden
FOUND	302 Found
GATEWAY_TIMEOUT	504 Gateway Timeout
GONE	410 Gone
HTTP_VERSION_NOT_SUPPORTED	505 HTTP Version Not Supported
IM_USED	226 IM Used
INSUFFICIENT_SPACE_ON_RESOURCE	419 Insufficient Space on Resource
INSUFFICIENT_STORAGE	507 Insufficient Storage
INTERNAL_SERVER_ERROR	500 Internal Server Error
LENGTH_REQUIRED	411 Length Required
LOCKED	423 Locked
LOOP_DETECTED	508 Loop Detected
METHOD_FAILURE	420 Method Failure
METHOD_NOT_ALLOWED	405 Method Not Allowed
MOVED_PERMANENTLY	301 Moved Permanently
MOVED_TEMPORARILY	302 Moved Temporarily
MULTI_STATUS	207 Multi-Status
MULTIPLE_CHOICES	300 Multiple Choices
NO_CONTENT	204 No Content
NON_AUTHORITATIVE_INFORMATION	203 Non-Authoritative Information
NOT_ACCEPTABLE	406 Not Acceptable
NOT_EXTENDED	510 Not Extended
NOT_FOUND	404 Not Found
NOT_IMPLEMENTED	501 Not Implemented
NOT_MODIFIED	304 Not Modified
OK	200 OK
PARTIAL_CONTENT	206 Partial Content
PAYMENT_REQUIRED	402 Payment Required
PRECONDITION_FAILED	412 Precondition failed
PROCESSING	102 Processing
PROXY_AUTHENTICATION_REQUIRED	407 Proxy Authentication Required
REQUEST_ENTITY_TOO_LARGE	413 Request Entity Too Large
REQUEST_TIMEOUT	408 Request Timeout
REQUEST_URI_TOO_LONG	414 Request-URI Too Long
REQUESTED_RANGE_NOT_SATISFIABLE	416 Requested Range Not Satisfiable
RESET_CONTENT	205 Reset Content
SEE_OTHER	303 See Other
SERVICE_UNAVAILABLE	503 Service Unavailable
SWITCHING_PROTOCOLS	101 Switching Protocols
TEMPORARY_REDIRECT	307 Temporary Redirect
UNAUTHORIZED	401 Unauthorized
UNPROCESSABLE_ENTITY	422 Unprocessable Entity
UNSUPPORTED_MEDIA_TYPE	415 Unsupported Media Type
UPGRADE_REQUIRED	426 Upgrade Required
USE_PROXY	305 Use Proxy
VARIANT_ALSO_NEGOTIATES	506 Variant Also Negotiates

alex-arriaga July 11, 2014

How to use array of String as input parameters in a request for a Java application by using Spring annotations

Enterprise Development, Java EE 1 Reply

Hello friend, today I am going to show you how to user a String[] array as an input parameter of a request. This is useful when you want to receive a series of values and then use them for any purpose.

So, let’s get started. Imagine you are creating a controller to read all pages of a CMS given the parent page, but these pages have states as integer values, so you would like to have a method that receives a list of integers (states) and then make a query to the database to get all pages that have the states in the input array.

1) In your controller class you will need to create a method -I would recommend to use Spring annotations-.

@RequestMapping(
	value = "/pages/get-by-parent/{parentUuid}", 	// The {parentUuid} is a PathVariable
	method = RequestMethod.GET, 					// This request is only valid when the request was done by GET method
	produces=MediaType.APPLICATION_JSON_VALUE)		// Result will be returned in JSON 
public ResponseEntity<List<WikiPage>> getWikiPagesList(
			@PathVariable("parentUuid") String parentUuid,	// This matches with the path variable {parentUuid}
			@RequestParam(value="includeStates[]", defaultValue="1,2,3") String[] includeStates // List of states to include
			){
	// Do something here!
}

@RequestMapping(

value = "/pages/get-by-parent/{parentUuid}", // The {parentUuid} is a PathVariable

method = RequestMethod.GET, // This request is only valid when the request was done by GET method

produces=MediaType.APPLICATION_JSON_VALUE) // Result will be returned in JSON

public ResponseEntity<List<WikiPage>> getWikiPagesList(

@PathVariable("parentUuid") String parentUuid, // This matches with the path variable {parentUuid}

@RequestParam(value="includeStates[]", defaultValue="1,2,3") String[] includeStates // List of states to include

){

// Do something here!

}

Please, pay attention to the line, because that is the one that contains an array of String as input.

@RequestParam(value="includeStates[]", defaultValue="1,2,3") String[] includeStates // List of states to include

1	@RequestParam(value="includeStates[]", defaultValue="1,2,3") String[] includeStates // List of states to include

In this case, I am setting some default values: “1,2,3” in order to return pages with states 1, 2 or 3 in case the parameter includeStates[] is not present in the request. Of course, you can personalize this method to receive any other parameters.

I hope you find this tip useful for your development.

See you next time and remember, 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!

What would you like to know about?

Alex Arriaga

Tag Archives:
JavaEE

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Step 1. Be sure you don’t have the JAVA_HOME already set

Step 2. Find the Java Development Kit directory

Step 3. Add the JAVA_HOME to the Bash configuration file

Step 1. Find and open your configuration file

Step 2. Locate your Java directory where the Java Development Kit was installed

Step 3. Add the JAVA_HOME to the Oh My Fish configuration file

A really brief intro

Let’s start

Basic explanation of properties

Situation

Join me, have fun and learn!

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Recent Posts

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Join me, have fun and learn!

Recent Posts

Day quote…

Recent Comments

Categories

Tag Cloud

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Tag Archives:
JavaEE