How to associate a static IP to your AWS EC2 instance using Elastic IP Addresses

Background

When you start up an EC2 instance by default you get a public IP and a public DNS by which you can reach your server from internet. However when you restart your EC2 instance your IP and your public DNS (which is infact your hostname) gets changed and that may not always be way you desire. So in this post we will see how to associate a static IP to your AWS EC2 instance using Elastic IP Addresses.

Elastic IP Addresses

An Elastic IP address is a static IP address designed for dynamic cloud computing. An Elastic IP address is associated with your AWS account. With an Elastic IP address, you can mask the failure of an instance or software by rapidly remapping the address to another instance in your account. 

An Elastic IP address is a public IP address, which is reachable from the Internet. If your instance does not have a public IP address, you can associate an Elastic IP address with your instance to enable communication with the Internet; for example, to connect to your instance from your local computer.

More details - http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/elastic-ip-addresses-eip.html

How to associate a static IP to your AWS EC2 instance using Elastic IP Addresses

If you have an EC2 instance running you can see the current public IP address and your public DNS entry.

And you can reach your EC2 instance using ec2-54-69-69-192.us-west-2.compute.amazonaws.com. (highlighted in image above)For eg I have deployed a webapp I can access it using URL - 

•  http://ec2-54-69-69-192.us-west-2.compute.amazonaws.com:8080/WebDynamo

Please note these URLs are for demo purpose and may not be live when you are reading this. This is just to give you idea about what changes when you assign an elastic IP address.

As I mentioned earlier this will change when you reboot your EC2 instance. Lets see how we can assign an elastic IP.

Go to Elastic IP under Network & Security and select "Allocate New Address" and confirm.

You can see a new entry in the list with your newly assigned elastic IP. Select the entry , go to actions and select "Associate Address"

You can select either your instance your your network interface. I have selected my running EC2 instance. Then click associate.

NOTE : Careful! Note you will get a new public IP and public DNS (you will loose the previous non static one).

You will see the new IP, public DNS and Elastic Ip in EC2 dashboard.

That's it! You can now access your EC2 instance with this new IP and public DNS.  For eg -

• http://ec2-52-24-69-249.us-west-2.compute.amazonaws.com:8080/WebDynamo

Note how the IP has changed and what was before. And this will remain same even when you reboot!

PS : WebDynamo is a sameple webapp (https://github.com/aniket91/WebDynamo) that I have deployed on tomcat on my EC2 instance for demo purpose. Please refer links in Related Links section below for more details.

Related Links

• Launching and connecting to your new EC2 instance of your Amazon web service(OSFG)
• Setup Tomcat on an Amazon EC2 instance to deploy a wep app (OSFG)

Formatting or preety printing XML and JSON in Java

Background

XML as we know is a platform independent format that can be used to communicate between different apps. We have seen couple of things on XML like parsing, handling special characters, java library etc (See links in Related Links section below). In this post we will see how we can format or preety print xml in Java.

To the code... preety printing XML

Following code will do the trick -

    private static String beautifyXml(String unformattedXML) {
        Transformer transformer;
        String formattedXmlString = null;
        try {
            transformer = TransformerFactory.newInstance().newTransformer();
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
            transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
            //initialize StreamResult with File object to save to file
            StreamResult result = new StreamResult(new StringWriter());
            transformer.transform(new StreamSource(new StringReader(unformattedXML)), result);
            formattedXmlString = result.getWriter().toString();
        } catch (TransformerFactoryConfigurationError | TransformerException e) {
            e.printStackTrace();
        }
        return formattedXmlString;
    }

you can test it by simple calling above method with your unformatted xml as input argument. I have created a small web app and have added the functionality of pretty printing xml there. You can see the relevant code (beautifyXml method)-

• https://github.com/aniket91/WebDynamo/blob/master/src/com/osfg/controllers/Beautifier.java

You can clone the webapp itself and see how it works for yourself. It all on github -

• https://github.com/aniket91/WebDynamo

preety printing JSON

You can do similar stuff for Json too -

    public static String beautifyJson(String unformattedStringForm) {
        JsonParser parser = new JsonParser();
        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        
        try {
            String jsonString = unformattedStringForm;
            JsonElement el = parser.parse(jsonString);
            return gson.toJson(el);
        }
        catch(JsonSyntaxException e) {
            e.printStackTrace();
        }
        return null;
    }

Again relevant code can be found in (beautifyJson method) -

• https://github.com/aniket91/WebDynamo/blob/master/src/com/osfg/controllers/Beautifier.java

Related Links

• Escaping special characters of XML in Java (OSFG)
• Parsing XML files in Java using javax.xml.parsers.DocumentBuilder(OSFG) 
• JAXB Tutorial for Java XML binding with annotations (OSFG) 
• Resolving "The markup in the document following the root element must be well-formed" Exception (OSFG)  
• https://github.com/aniket91/WebDynamo

Setup Tomcat on an Amazon EC2 instance to deploy a wep app

Background

Amazon EC2 module is a virtual server in cloud. It's a IaaS (Infrastructure as a service) when you have your own machine (virtual) with an operating system and you can deploy your stuff there. We have already discussed setting up an EC2 instance and connecting to it. If you do not recollect please refer -

• Launching and connecting to your new EC2 instance of your Amazon web service

 In this post we will see how to setup your tomcat and access it remotely. This post assumes you have an EC2 instance up and running and you can SSH to it remotely.

Setup Tomcat on an Amazon EC2 instance to deploy a wep app

Apache Tomcat, often referred to as Tomcat, is an open-source web server developed by the Apache Software Foundation (ASF). Tomcat implements several Java EE specifications including Java Servlet, JavaServer Pages (JSP), Java EL, and WebSocket, and provides a "pure Java" HTTP web server environment in which Java code can run.

There are two ways you can setup tomcat on your machine (EC2 instance) in this case. Either

1. install it through apt-get
2. Download the binary distribution from their official site and use

We are going to take simpler route here and install it via apt-get. First get an update -

• sudo apt-get update

 Next install tomcat7 -

• sudo apt-get install tomcat7

 Post installation you can see the default configuration file located at -

• less /etc/default/tomcat7 

 You can change the configuration parameters here if you wish.

To start,stop and see current tomcat status you can use following commands -

• sudo service tomcat7 start
• sudo service tomcat7 stop
• sudo service tomcat7 status

 Next you can deploy your webapps at /var/lib/tomcat7/webapps

• CATALINA_HOME : /usr/share/tomcat7
• CATALINA_BASE : /var/lib/tomcat7

 Now your tomcat installation is done. Tomcat by default runs on port 8080 that you need to open externally (for inbound traffic). Go to Security Groups and add a custom TCP rule to open port 8080 externally -

 Add the rule and save it. You should not be able to access your tomcat. If it shows you Its up! page you are all set!

I have also deployed a web app. If you have a web app just export it as war and put it in webapps directory

• /var/lib/tomcat7/webapps 

And restart tomcat. Tomcat will automatically extract folder out of it and deploy. If you do not have a webapp and want to test you can checkout -

• https://github.com/aniket91/WebDynamo

Import it in eclipse and export a war out of it. If you want to skip all that you can directly download the war from -

• https://dl.dropboxusercontent.com/u/30440938/WebDynamo.war

and put it in webapps folder. Note this war is compiled with java 8. So make sure you are using Java 8 for your tomcat. You can set it in file -

• /etc/default/tomcat7

Eg. JAVA_HOME=/usr/lib/jvm/java-8-oracle

Once deployed you can hit following URL and see if it works. If it does not you need to check catalina.out logs for any deployment issues.

• http://ec2-52-24-69-249.us-west-2.compute.amazonaws.com:8080/WebDynamo/getEmployeeInfoForm.htm

You should see a page something like above.

Related Links

•  Launching and connecting to your new EC2 instance of your Amazon web service(OSFG) 
• Spring MVC Hello Wold Example(OSFG)

How to delete recently opened files history in ubuntu 14.04

Background

In this post we will see how we can delete recently opened files from Ubuntu's Unity dashboard. Why would I do that you ask? Answer is privacy but then again it largely depends on the usecase. There should not be such a need for a strictly persona computer but if it is shared it is better to delete history when you leave.

How to delete recently opened files history in ubuntu 14.04

Open security and privacy settings from unity dashbaord.

Then go to Files & Applications and select clear usage data and select the period you want to clear data from - 

Click Ok and you are done.

Related Links

• Things to do after installing Ubuntu 14.04 LTS(OSFG)
• How to clear terminal history in Linux(OSFG) 

Programmatically upload files to amazon (AWS) S3

Background

This post will show you how to programmatically upload files to your AWS S3 account using AWS S3 SDK. Lets start by creating access key.

This post hopes you already have a S3 account set up on your AWS console.

Credentials setup

Lets start be creating access key. Following screenshots show you how to create your access key using AWS IAM (Identity and access management).

Once you have create a user you need to give it access to S3. Follow next set of steps for that -

 This will give your new user access to S3.Now you can use these credentials in the code. Before we go to code there is one more step. You need to set up your credential file. It will be in

• ~/.aws/credentials

If its not there create one and add credentials to it as show below from the user you had created from IAM console.

I have used some template here but replace it with your exact access key if and secret key. Lets go on to the code now.

Programmatically upload files to amazon s3

I am using eclipse and ivy dependency management. So your ivy file should look like following -

<ivy-module version="2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:noNamespaceSchemaLocation="http://ant.apache.org/ivy/schemas/ivy.xsd">
    <info
        organisation="osfg"
        module="AwsS3Demo"
        status="integration">
    </info>
    
    <dependencies>
        <dependency org="com.amazonaws" name="aws-java-sdk-s3" rev="1.11.36"/>
    </dependencies>
</ivy-module>

Note the dependency we have used. It for aws s3 only.

Now lets head on to the code -

package com.osfg;

import java.io.File;
import java.io.IOException;

import com.amazonaws.AmazonClientException;
import com.amazonaws.AmazonServiceException;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.model.PutObjectRequest;
import com.amazonaws.services.s3.AmazonS3Client;
import com.amazonaws.auth.profile.ProfileCredentialsProvider;

/**
 * 
 * @author athakur
 *
 */
public class AwsS3Demo {
    
    private static String AWS_BUCKET_NAME = "test-athakur";
    private static String AWS_KEY_NAME = "testData";
    private static String UPLOAD_FILE = "/Users/athakur/Desktop/data.txt";
    
    public static void main(String[] args) throws IOException {
        AmazonS3 s3client = new AmazonS3Client(new ProfileCredentialsProvider());
        try {
            System.out.println("Uploading a new object to S3 from a file\n");
            File file = new File(UPLOAD_FILE);
            s3client.putObject(new PutObjectRequest(
                    AWS_BUCKET_NAME, AWS_KEY_NAME, file));

         } catch (AmazonServiceException ase) {
            System.out.println("Caught an AmazonServiceException, which " +
                    "means your request made it " +
                    "to Amazon S3, but was rejected with an error response" +
                    " for some reason.");
            System.out.println("Error Message:    " + ase.getMessage());
            System.out.println("HTTP Status Code: " + ase.getStatusCode());
            System.out.println("AWS Error Code:   " + ase.getErrorCode());
            System.out.println("Error Type:       " + ase.getErrorType());
            System.out.println("Request ID:       " + ase.getRequestId());
        } catch (AmazonClientException ace) {
            System.out.println("Caught an AmazonClientException, which " +
                    "means the client encountered " +
                    "an internal error while trying to " +
                    "communicate with S3, " +
                    "such as not being able to access the network.");
            System.out.println("Error Message: " + ace.getMessage());
        }
    }

}

Just run the above code and it should upload your file to the AWS bucket. Make sure -

1. Credentials are correct in ~/.aws/credentials file
2. That credential has access to S3 module
3. File is present on your machine
4. bucket name is valid

NOTE : ProfileCredentialsProvider internally uses ~/.aws/credentials file for the credentials to authenticate against AWS S3.

You can also find above code snippet at -

• http://docs.aws.amazon.com/AmazonS3/latest/dev/UploadObjSingleOpJava.html

IF all goes correctly file should get uploaded to the S3 -

Related Links

• Installing and using Apache Ivy as dependency manager(OSFG)
• Launching and connecting to your new EC2 instance of your Amazon web service(OSFG)
• Unprotected private key file error while connecting to AWS via SSH(OSFG)