Can anyone explain the meaning and usage of POJO or POCO

Question

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What does the term Plain Old Java Object(POJO) exactly mean?

I know those are recent concepts proposed by Mark Fowler. can anyone explain what the purpose of POJO or POCO and their usage?

Solution 1

P lain O ld ( J ava,/ C LR ) O bject

It's just a fancy name for a very basic class structure¹.

[...]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[...]

Solution 2

It stands for Plain Old [Java|CLR] Object, and it means pretty much what it says - a simple object that doesn't require any significant "guts" to make it work. The idea is in contrast with very dependent objects that have a hard time being (or can't be) instantiated and manipulated on their own - they require other services, drivers, provider instances, etc. to also be present.

Here's an example of a c# POCO:

public class Customer
{
    public string Name { get; set; }
}

And here's the hypothetical innards of a hypothetical non-POCO:

public sealed class Customer
{
    //can only be created by a db service layer
    internal Customer(IDbContext databaseContext)
    {
    }

    [EntityMapping("Name")]
    public string Name
    {
        get
        {
            return context.HydrateValue(this, "Name");
        }
        set
        {
            InternalNotifyRevision("Name", value);
        }
    }
}

Solution 3

POCO stands for Plain Old CLR Object and POJO for Plain Old Java Object.