Spring CustomEditor understanding with example



Spring CustomEditorConfigurer Example using spring 4

In this article, I will discuss Spring CustomEditor.
While coding often there is a requirement where you want Text value will automatically convert into a desired Datatype and Vice versa.
Think about Struts ActionForm Or Spring @PathParam , @Formparam
Where parameters value in the request are String but in ActionForm you get it desired Type say Integer, Date etc.

@Path(“employee”)
@RequestParam({age})
Say doX(@Pathparam(“age”)Integer age){….}

In above code snippet age automatically convert String to an integer. But How it is possible?

The Answer is java Bean’s PropertyEditor interface by implementing PropertyEditor you can convert a string to your Custom datatype and Vice versa . To do that you have to implement its two main methods

  public void setAsText(String text) and  public String getAsText().

In Spring We can do it through Spring Built-in Custom editor. Or you can create your Own Editor by extending Java Beans PropertyEditorSupport Class which implements PropertyEditor interface.

Problem statement: In Spring Suppose I want when an employee gives his Address in String format that will automatic convert to Address Class and from Address it will Extract zip-code and State.


To solve this problem, I need to implement a CustomEditor class which will  take the String convert it into Address Object and do the extract operation.
I assume “-“ is the separator  when the employee provides address in String format .

Apart from that, I need to register this custom Editor in Spring application Context so before any bean initialization it should be initialized so that, for any bean where a conversion needed from String to Address Object, this Custom Editor will be invoked by Spring container.

We do this by creating a Custom Register which extends Spring PropertyEditorRegistrar class and register our Custom Editor.


Step 1 : create Address Object and provide the logic to extract zip and state from string provided by Employee

package com.example.aware;

public class Address {

       String adress;
       String pin;
       String state;

       Address() {

       }

       Address(String text) {
              init(text);

       }

       private void init(String text) {
              String[] arr = text.split("-");

              this.setAdress(arr[0]);
              this.setPin(arr[1]);
              this.setState(arr[2]);

       }

       public String getAdress() {
              return adress;
       }

       public void setAdress(String adress) {
              this.adress = adress;
       }

       public String getPin() {
              return pin;
       }

       public void setPin(String pin) {
              this.pin = pin;
       }

       public String getState() {
              return state;
       }

       public void setState(String state) {
              this.state = state;
       }

       @Override
       public String toString() {
              return "Address [adress=" + adress + ", pin=" + pin + ", state="
                           + state + "]";
       }

}


Step 2 : Create an Employee bean

package com.example.aware;

import java.util.Date;

public class Employee {
      

           
           private Integer id;
           private String firstName;
           private String lastName;
           private String designation;
           private Address address;
          
          
          
          
        
           //Setters and Getters
        
           public Integer getId() {
                     return id;
              }





              public void setId(Integer id) {
                     this.id = id;
              }





              public String getFirstName() {
                     return firstName;
              }





              public void setFirstName(String firstName) {
                     this.firstName = firstName;
              }





              public String getLastName() {
                     return lastName;
              }





              public void setLastName(String lastName) {
                     this.lastName = lastName;
              }





              public String getDesignation() {
                     return designation;
              }





              public void setDesignation(String designation) {
                     this.designation = designation;
              }





              public Address getAddress() {
                     return address;
              }





              public void setAddress(Address address) {
                     this.address = address;
              }





              @Override
           public String toString() {
               return "Employee [id=" + id + ", firstName=" + firstName
                       + ", lastName=" + lastName + ", designation=" + designation
                       + ", address=" + address + "]";
           }
      
}




Observe address type is Address not String but from spring bean XML I pass String value that automatically converted to Address Object

Step 3: Create Custom editor which will convert String to Address Object

package com.example.aware;

import java.beans.PropertyEditorSupport;

public class CustomAddressEditor extends PropertyEditorSupport{
      
      
       public void setAsText(String text) {
               setValue(new Address(text.toUpperCase()));
       
       }
      
        
        
}

Look in setAsText I pass Address Object and pass text value as the constructor argument ,setvalue is the method which inherits from PropertyEditorSupport, it set the value to the bean , so here from String to Address conversion is done.

Step 4: Register this bean into Spring Container so it can initialize before any beam. It acts as Bean post processor

package com.example.aware;

import java.util.Date;

import org.springframework.beans.PropertyEditorRegistrar;
import org.springframework.beans.PropertyEditorRegistry;
import org.springframework.beans.propertyeditors.ClassEditor;
import org.springframework.beans.propertyeditors.StringArrayPropertyEditor;

public class CustomAddressEditorRegistrar implements PropertyEditorRegistrar {

       @Override
       public void registerCustomEditors(PropertyEditorRegistry registry) {          
             
             
              registry.registerCustomEditor(Address.class, new CustomAddressEditor());
             
       }

}

Here I register CustomAddressEditor.


Step 5:  Spring Bean XML declaration

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

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

<bean class="org.springframework.beans.factory.config.CustomEditorConfigurer">
    <property name="propertyEditorRegistrars">
        <list>
            <bean class="com.example.aware.CustomAddressEditorRegistrar"/>
        </list>
    </property>
</bean>

<!-- employee bean -->
<bean id="employee" class="com.example.aware.Employee">
    <property name="firstName" value="Shamik"/>
    <property name="lastName" value="Mitra"/>
    <property name="designation" value="Tech Lead"/>
    <property name="address" value="1,NiveditaLane-700003-westbengal"/>
</bean>

</beans>




Step 6 : Test the application

package com.example.aware;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
           
            public static void main(String[] args) {
                        ApplicationContext context = new ClassPathXmlApplicationContext("configFiles/customEditor.xml");
                         
        Employee employee = (Employee) context.getBean("employee");
        
        System.out.println(employee);
      
            }

}



Output :

Employee [id=null, firstName=Shamik, lastName=Mitra, designation=Tech Lead, address=Address [adress=1,NIVEDITALANE, pin=700003, state=WESTBENGAL]]



Please note that in Spring there is many inbuilt CustomEditor try to use them. If your problem statement not matching with any of built-in editor then only create your own custom Editor.

Docker Basics understanding



Docker basics


In DevOps era, Every organization wants to streamline their deployment strategy. To streamline deployments, the center of attraction is IT infrastructure to be precise different kind of servers to maintain application and managed by Operation teams.


Every Organization needs their application should be scalable. But  term scalable may be easy to say but believe me, it is very hard to implement.

What do we mean by scalable?
Suppose a project maintain images, on a normal day, it receives 10,000 requests. The project maintains a load balancer under this balancer project maintains two pools.

Pool A and Pool B.  Pools are acted as Active/Passive mode as Project supports Blue/Green deployment. For a given moment one pool is active.
Furthermore, each pool contains 5 web servers.

Now if Each webserver can take maximum 10000 requests.

So Total request handling capacity of this project is
5*10,000=50,000 requests ,at a given moment.

I can say this project can handle 50,000 requests at a time.

But consider a situation, Let say for Olympics there will be more traffic than a normal day . After all this project is made for hosting Images.

Say in  Olympic this projects got 1,000000 (lakhs) requests, what happens then?
Obviously, servers are gone down as it can maximum handles 50000 requests for a moment so every moment there will 50000 extra requests in a pool and another 100000 comes so next moment it has to serve 150000 requests. So requests in queue increase in exponential order so the system will fall down eventually.
 How to manage such situation?

There are two ways to handle such situation
1.      Vertical scaling: By meaning of Vertical scaling, make your server a  super computer so it can serve many more requests. But Cost of Super computer is Very high ,most of the organization can’t effort it.

2.      Horizontal scaling: Another way is to add many more commodity servers under load balancer so load balancer can distribute requests among them.

Second one look promising right…

But in Current Infrastructure the problem is to add a new server to the pool. To add new servers you need to configure those servers, so you need to a. install OS , b. add necessary software’s,c.  add network configuration, d. add a firewall, update load balancer etc.

Which takes much more times even if you have golden image still it takes time.

So the Solution is Docker.

 Docker is nothing but a slick container. It runs just above host Operating systems and access host m/c hardware but it can spawn multiple containers and each container act as separate m/c and each has separate address spaces, each has separate guest OS with minimum requirement to hosting a software, so If to host a software needs one WebLogic server so a container only contains a Guest OS with WebLogic server.

Docker is faster than a Virtual machine (VM) as Virtual machine contains one or more guest OS which runs on top of host machine OS and in between OS there is a Hypervisor layer which manages guest OS calls or it’s requirements and changes that requirement into host machine specific OS call. Mainly hypervisor responsible for  host OS and Guest OS communication.

Unlike VM, Docker just runs on top of your OS it shares your OS network, hardware everything but Docker container maintains a separate OS which has its own address space and only contains require software to work with. So Docker are very light-weight and easy to spawn, later you can see, by a command you can spawn a container so Horizontal Scale up is very easy







Difference between Docker and VM





Docker Architecture:


 Docker maintains client-server architecture where Docker client talks with Docker daemon via a socket or Restful API. Docker daemon and client can be in the same host or Docker daemon can be hosted on a different machine. If so Docker client has to communicate with Remote Docker daemon via socket.

Docker contains Three main parts
1.       Docker Daemon:  Docker Daemon does most of the work upon  Docker client or Restful API commands/instruction. According to command, it builds an image, spawn a new container, can run a container, update an Image, can push an image etc.
2.       Restful API:  Docker publish Restful API so if you want to control Docker daemon through the program you can call this API and controls Docker daemon.
3.       Docker client: Docker client is a CLI (command Line Interface) where you can fire command then Docker client  talks to Docker daemon visual Rest API or Socket and Docker daemon perform the task for you. You can consider it as Linux terminal which talks to kernel.
 




Docker Architecture – Picture Courtesy:  Docker Site






To understand How docker works you need to know some Docker terms

1.       Docker images: Docker images is nothing but a logical template based on this a new Docker container can spawn.  So according to Image hosting Project states above ,it needs an Image which has an OS say Ubuntu 13.04 with a WebLogic server. So an image can be created with this requirement.
The image can be created locally using Docker file or can be pulled from a global repository (If it exists) which is managed by Docker. we call it Docker Hub or registry.


2.       Docker Hub/Registry: Docker hub contains images which can be pulled to satisfy your requirements. In Docker hub, there can be just OS images and can be Hybrid images such as Solaris with Tomcat. One can push its own image to Docker Hub, to do it you need Docker account.

Docker Hub is a central repository, you can have thought it as a maven Repository. And like GIT you can push your image into it.

3.       Docker Containers: Docker containers is an actual runtime environment spawn from an image. It acts as a separate machine.



Some important commands:

To download an Image from Docker Hub:
In Docker client type
Docker pull <image-name> //that is name of the image

To spawn a container and execute a command:
Docker run -i -t <image-name> <command name>
Docker run -I -t ubuntu13.03 ls

To Push an image in Docker Hub:
Docker push <image-name>

I will discuss more command in next Docker section where I will guide you to set up a Docker container.