Design mode 2
In order to avoid the shortcomings of design model 1, we introduce the package
Value Object of the Entity Bean value field. Value Object,
In some languages, it is a structural type because they
Very similar to CORBA's structural type.
Value Object Code Snippet for Company
Public Class CompanyStruct IMPLEMENTS
Java.io.serializable {
Public Integer Comid; // Primary Key
Public String COMNAME;
Public String Comdescription;
Public java.sql.timestamp mutationdate;
}
Value Object Code Snippet for Employee
Public Class Employeestruct Implements
Java.io.serializable {
Public Integer Empid; // PRIMARY Key
Public Integer Comid; // Foreign Key
Public String EmpfirstName;
Public String Emplastname;
Public java.sql.timestamp mutationdate;
}
Now, the company and the ENTITY BEAN can use one of the above structural types.
A parameter of ejbcreate (). Since this structure encapsulates all fields of Entity
Value, Entity Bean only needs a getData () and setData () method.
Operate all fields.
Code snippet for an entry bean's create ()
Public Integer Ejbcreate (Companystruct Struct) Throws
CreateException {
this.comid = Struct.comID;
This.comName = struct.comName;
THIS.COMDESCRIPTION = Struct.ComDescription;
THIS.MUTATIONDATE = Struct.MutationDate;
Return NULL;
}
Code snippet for an entry bean's getdata ()
Public companyStruct getdata () {
Companystruct result = new companyStruct ();
Result.comID = this.comid;
Result.comName = this.comName;
Result.comDescription = this.comdescription;
Result.mutationdate = this.mutationDate;
Return Result;
}
Code snippet for an entry bean's setdata ()
Public void setdata (Companystruct Struct) {
This.comName = struct.comName;
THIS.COMDESCRIPTION = Struct.ComDescription;
THIS.MUTATIONDATE = STRUCT.MUTATIONDATE ;;
}
Use a separate GET () and set () method to operate different fields in the design mode 1.
In design mode 2, we avoid this situation and only need a remote call.
Yes. Now, only one transaction operates all the data through a remote call. In this way, we avoid most of the shortcomings of design model 1, in addition to establishing Bean
The relationship is outside the relationship.
Although setData () methods can assign all fields, Borland Appserver
Provides a smart update feature, only the modified field is rewriting
According to the library, if there is no field being modified, the EJBStore () method will be skipped.
The Borland Programmer Development Guide (EJB) has a more detailed description.
Similarly, there is such a repetitive code between Entity Beans and Struct, such as
Field declaration. This means that the modification of any database table structure can cause
Entity Beabn and Struct changes, which makes synchronous Entity and Struct become
Difficult up.
A small improvement can avoid this from a certain extent,
That is to call the setData () method in the ebcreate () method, which can eliminate one
Some redundant code.
Code snippet for an entry bean's create ()
Public Integer Ejbcreate (Companystruct Struct) Throws
CreateException {
this.comid = Struct.comID; // SET The PRIMARY Key
SetData (STRUCT); // This Removes Some Redundant Code
Return NULL;
}
