What is po/Vo/Dao/bo/pojo (explanation of several Java objects)

From: http://blog.csdn.net/hlf48641715/archive/2008/12/25/3605789.aspx

 

Several Java objects (PO, Vo, Dao, Bo, pojo)
I. Po: persistence object of persistant object. It can be regarded as a Java object mapped to a table in the database. The simplest Po is to correspond to a record in a table in the database. A set of PO can be used for multiple records. The PO should not contain any operations on the database.

Ii. VO: Value Object value object. It is usually used for data transmission between business layers. Like Po, it only contains data. However, it should be an abstract business object, which can correspond to a table or not. This is based on the business needs. I personally think it is the same as DTO (data transmission object) and transmitted on the web.

3. Dao: Data Access Object: the data access object used to access the database. It is usually used in combination with Po. Dao contains various database operation methods. It combines Po with other methods to perform database operations.

4. Bo: Business Object business object. It encapsulates Java objects of business logic and performs business operations by calling Dao and combining Po and VO.

5. pojo: plain ordinary Java object is a Java object with no rules. I personally think it and others are not at the same level. Vo and PO should both belong to it.

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, and relationship.
We can map the educational experience to a po, the work experience to a po, and the 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
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
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.