How to create a POJO?

Admin 1
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Recently I've started hearing about "POJOs" (Plain Old Java Objects). I googled it, but still don't understand the concept well. Can anyone give me a clear description of a POJO?

Consider a class "Person" with variables "id, name, address, salary" -- how would I create a POJO for this scenario? Is the code below a POJO?

public class Person {
    //variables
    People people = new People();
    private int id;
    private String name;
    private String address;
    private int salary;


    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getAddress() {
        return address;
    }

    public int getSalary() {
        return salary;
    }

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

    public void setName() {
        this.name = name;
    }

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

    public void setSalary() {
        this.salary = salary;
    }
}
pojo java
11 Answers

According to Martin Fowler

The term was coined while Rebecca Parsons, Josh MacKenzie and I were preparing for a talk at a conference in September 2000. In the talk, we were pointing out the many benefits of encoding business logic into regular java objects rather than using Entity Beans. We wondered why people were so against using regular objects in their systems and concluded that it was because simple objects lacked a fancy name. So we gave them one, and it’s caught on very nicely.

Generally, a POJO is not bound to any restriction and any Java object can be called a POJO but there are some directions. A well-defined POJO should follow below directions.

  1. Each variable in a POJO should be declared as private.
  2. Default constructor should be overridden with public accessibility.
  3. Each variable should have its Setter-Getter method with public accessibility.
  4. Generally POJO should override equals(), hashCode() and toString() methods of Object (but it's not mandatory).
  5. Overriding compare() method of Comparable interface used for sorting (Preferable but not mandatory).

And according to Java Language Specification, a POJO should not have to

  1. Extend pre-specified classes
  2. Implement pre-specified interfaces
  3. Contain pre-specified annotations

However, developers and frameworks describe a POJO still requires the use prespecified annotations to implement features like persistence, declarative transaction management etc. So the idea is that if the object was a POJO before any annotations were added would return to POJO status if the annotations are removed then it can still be considered a POJO.

A JavaBean is a special kind of POJO that is Serializable, has a no-argument constructor, and allows access to properties using getter and setter methods that follow a simple naming convention.

Read more on Plain Old Java Object (POJO) Explained.

user_20780930
  1. File-setting-plugins-Browse repositories
  2. Search RoboPOJOGenerator and install, Restart Android studio
  3. Open Project and right click on package select on Generate POJO from JSON
  4. Paste JSON in dialogbox and select option according your requirements
  5. Click on Generate button
Admin1

If a class is not bogged down from a framework or a library, then an object created from that class is recognized as a POJO.

Let's see some examples:

class MyServlet extends HttpServlet{
    //....
}

The sole meaning of MyServlet class is given by the HttpServlet class. Therefore the objects created from the MyServlet are not POJOs.

class MyClass implements Serializable{
    //...
}

The Serializable interface does not give a meaning to the class MyClass. Therefore the objects created from the MyClass are POJOs.

user_123049830
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