Concept and function of Po Bo vo dto pojo Dao

A large number of professional acronyms in J2EE development are confusing, especially when discussing issues with some experts, they were dizzy by the technical terms in three minutes. Po VO Bo DTO pojo Dao, A lot of things are coming (friends who have heard of Lao Luo's criticism of this phenomenon will smile ).

First of all, I declare that I am not a master. The following summary is my own experience. For more information, see.

Po:
Persistant Object Persistent Object

A po is a record in the database.
The advantage is that a record can be processed as an object, which can be easily converted to other objects.

Bo:
Business Object

The main function is to encapsulate the business logic as an object. This object can include one or more other objects.
For example, a resume includes educational experience, work experience, social relationship, and so on.
We can correspond an educational experience to a po, a work experience to a po, and a social relationship to a po.
Create a bo object to process the resume. Each Bo contains the Po.
In this way, we can process the business logic for Bo.

VO:
Value object Value Object
Viewobject presentation layer object

It mainly corresponds to the Data Objects displayed on the interface. For a Web page, or a SWT or swing interface, use a Vo object to correspond to the value of the entire interface.

Dto:
DaTa transfer object data transmission object
It is mainly used for remote calls and other places where a large number of objects need to be transferred.
For example, if a table has 100 fields, the corresponding Po has 100 attributes.
However, we only need to display 10 fields on the interface,
The client uses Web service to obtain data. It is not necessary to pass the entire Po object to the client,
In this case, we can use DTO with only these 10 attributes to pass the results to the client, so that the server table structure will not be exposed. after the client is reached, if this object is used for display on the corresponding interface, then its identity will be changed to VO

Pojo:
Plain ordinary Java object simple Java object
I personally think that pojo is the most common and variable object. It is an intermediate object and the most common object to deal.

After a pojo is persisted, it is the Po
It is DTO in the process of passing and passing.
Directly used to correspond to the presentation layer is Vo

Dao:
DaTa Access Object Data Access Object
This person is the most familiar with it. It is the most different from the previous O, and there is basically no possibility or need to convert each other.
It is mainly used to encapsulate access to the database. With pojo, pojo can be persistently converted into Po, and PO can be assembled into vo and DTO.

To sum up, I think what is an object? O depends on the specific environment. In different layers and applications, the object identities are different, and the conversion of object identities is natural. Just like you are a husband to your wife and a child to your parents. The original intention of designing these concepts is not to expose people, but to better understand and process various logics, so that everyone can better deal with problems in an object-oriented way.

Do not be overly-designed. You do not have to design objects in code to distinguish them. In a word, the technology serves applications.

Thank you for your correction.

After drawing a picture, I feel that I have not completely expressed my meaning ..... Who can help improve the position of each o in MVC?
# Object-oriented