Quick Tip: How to Work with GitHub and Multiple Accounts


Sometimes you may need to have multiple github accounts (one for office, one for work , one for girl friend, whatever) .

Lets say you have ssh keys already setup and github is set for one account. Now for new account:

  • Create a new ssh key

ssh-keygen -t rsa -C "your-email-address"

     Careful while name the file , dont overwrite the existing one .I named it as ~/.ssh/id_rsa_xxx

  • Add the new key to github account

     This is simple enough. Copy the id_rsa_xxx.pub in github > Settings > SSH Keys

  • Create a new config file in  vi ~.ssh/config

        Add following :

#Default GitHub
Host github.com
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa
Host github-COMPANY
  HostName github.com
  User git
  IdentityFile ~/.ssh/id_rsa_xxxx
 
You are done . Try it out ..
Vola !! Happy coding !!
Advertisements

Ignore transitive dependency in Maven


Maven helps to manage the dependency of JARS . Most of the time it may happen that same JAR file with different versions is being loaded because some other jar files have it as dependency and thus causing the conflicts .

Typical example is have log4j or slf4j jar with different version in spring-xx.jar and junit-xxx.jar . So when you load you classes an conflict may arise and because of incompatible version of same jar file . For e.g.

<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-core</artifactId>
	<version>3.2.1.RELEASE</version>
</dependency>

The above jar uses log4j 1.2.17 (you can check the dependency using mvn dependency:tree).

Consider this log4j jar file is conflicting with some other higher version of log4j which is used by other jar. To resolve this issue we would have to remove the conflicting log4j jar from org.springframework.
it can be done as follows :

<dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-core</artifactId>
	<version>3.2.1.RELEASE</version>
         <exclusions>
                <exclusion>
                    <groupId>log4j</groupId>
                    <artifactId>log4j</artifactId>
                </exclusion>
            </exclusions>
</dependency>

Cheers..

Convert JSON to Map or Map to Json in Java


One of the common uses cases while working with json is to convert it to a java object or convert java object to json. There is an open source library available in java which helps in processing json objects.

Add the Jackson dependency in pom.xml file

<repositories>
	<repository>
		<id>codehaus</id>
		<url>http://repository.codehaus.org/org/codehaus</url>
	</repository>
  </repositories>

  <dependencies>
	<dependency>
		<groupId>org.codehaus.jackson</groupId>
		<artifactId>jackson-mapper-asl</artifactId>
		<version>1.9.12</version>
	</dependency>
  </dependencies>

The Java class :

public static void main(String args[]) {
        ObjectMapper mapper = new ObjectMapper();
        Map m = new HashMap();
        Map personMap = new HashMap<>();
        Map personDetail = new HashMap();
        personDetail.put("firstname", "Bob");
        personDetail.put("lastname", "jackson");
        personDetail.put("age", "12");
        personDetail.put("city", "Berlin");

        personMap.put("person", personDetail);
        //convert Map to json string
        try {
            System.out.println(mapper.writeValueAsString(personMap));
        } catch (IOException e) {
            e.printStackTrace();
        }

        // convert json to Map
        String json = "{\"person\":{\"age\":\"12\",\"lastname\":\"jackson\""
                + ",\"firstname\":\"Bob\",\"city\":\"Berlin\"}}"
        try {
            Map map = mapper.readValue(json, Map.class);
            System.out.println("Map is " + map);
        } catch (Exception e) {
            e.printStackTrace();
        }
 }

Output is

Output: {“person”:{“age”:”12″,”lastname”:”jackson”,”firstname”:”Bob”,”city”:”Berlin”}}

Map is {person={age=12, lastname=jackson, firstname=Bob, city=Berlin}}

ObjectMapper mapper = new ObjectMapper();

Creating an object of ObjectMapper is a expensive operation and as best practice it should be created as a singleton object in a class.

Rails tip #1 – Set a custom layout for a web page


Its may require that you dont want to use application.html layout for some pages . For e.g display different header on page2 which than page 1 and the header is rendered in application.html.erb.

One way is to create a new layout for e,g headerless.html.erb inside a views->layout folder and in the particular controller which serves the request set the new layout .


 class SomeController < ApplicationController

    layout :headless , :only=>[:your_action1,:your_action2]

end

With the layout keyword you can use options such as :only, :except.

Skip maven test while building a project .


Though I would encourage people to skip tests while building a project but sometimes its helpful to go down this path.
Skip Unit Test
To skip the entire unit test, uses argument “-Dmaven.test.skip=true“.

 mvn install -Dmaven.test.skip=true
 mvn package -Dmaven.test.skip=true

Or define skipTests in maven-surefire-plugin.

pom.xml
   <plugin>
	<groupId>org.apache.maven.plugins</groupId>
	<artifactId>maven-surefire-plugin</artifactId>
	<version>2.12.4</version>
	<configuration>
		<skipTests>true</skipTests>
	</configuration>
    </plugin>

Now, build the project again, the entire unit tests will be ignored.