Datasheet simple java class map

Simple Java class definitions derived from the structure of the data table, 

For example: employee information table, is the employee or department department information table describes information,

In actual development, the mapping between the data tables and simple java classes as follows:

         1, data entity class = design definition table;

         2, members of the attribute table field = class;

         3, a table in a row = instantiated object class;

         4, multi-row table = discipline array of objects;

         5, the foreign key table associated = reference;

 

Suppose the table and a department employee:

A department has more employees;

An employee belongs to a department;

An employee has a leader;

 

The above data table below into the form of a simple Java class,

First, according to the data now to get the following information department:

  1, a complete information department;

  2, complete information within a department of all employees;

  3, corresponding to a leading employee information;

Second, based on the employee to obtain the following information:

   1. An information department where employees;

   2. a leading information corresponding to the employee;

 

The first step: put aside all of the associated field does not look like to write basic components, then configure the associated field by reference relations

Package Mapping_transformation; 

class DEMP 
{ 
    Private  Long DEPTNO;
     Private   String DNAME;
     Private   String LOC;
     public   DEMP ( Long DEPTNO, DNAME String, String LOC) 
    { 
        the this .deptno = DEPTNO;
         the this .dname = DNAME;
         the this .loc = LOC; 
    } 
    // setter, getter, no-argument constructor little 
    public String getInfo () 
    { 
        return "[department] information department number:" + the this .deptno + ", department name:" + the this.dname +"、部门位置："+this.loc ;
    }

}
class Emp
{
    private long empno ;
    private  String ename ;
    private  String job ;
    private double sal ;
    private  double comm ;
    public Emp(long empno ,String ename ,String job , double sal ,double comm)
    {
        this.empno = empno ;
        this.ename = ename ;
        this.job = job ;
        this= .sal SAL;
         the this .comm = COMM; 
    } 
    // setter, getter, no-argument constructor little 
    public String getInfo () 
    { 
        return "[information] Employees Number of employees:" + the this .empno + ", employee name:" + the this .ename + ", employees work:" +
                 the this .job + ", employees' salaries:" + the this .sal + ", a commission employee" + the this .comm; 
    } 

}

 

Step Two: Configure all related fields

package Mapping_transformation;

class Dept
{
    private long deptno ;
    private  String dname ;
    private  String loc ;
    private Emp emps[] ;         //多个雇员信息
    public  Dept(long deptno , String dname ,String loc)
    {
        this.deptno = deptno ;
        this.dname = dname ;
        this.loc = loc ;
    }

    public void setEmps(Emp[] emps) {
        this.emps = emps;
    }
    public Emp [] getEmps () 
    { 
        return  the this .emps; 
    } 
    // setter, getter, no-argument constructor little 
    public String getInfo () 
    { 
        return "[department] information department number:" + the this .deptno + ", department name:" + the this .dname + ", department positions:" + the this .loc; 
    } 

} 
class Emp 
{ 
    Private  Long EMPNO;
     Private   String ename;
     Private   String Job;
     Private  Double SAL;
     Private   Double COMM;
     PrivateThe dept the dept;      // Sector 
    Private Emp MGR;        // leadership belongs to 
    public Emp ( Long empno, ename String, String the Job, Double SAL, Double COMM) 
    { 
        the this .empno = empno;
         the this .ename = ename;
         the this .job = Job;
         the this .sal = SAL;
         the this .comm = COMM; 
    } 
    // the setter, getters, slightly constructor with no arguments 
    public String getInfo () 
    { 
        return "[] employee number employee information:" + the this.empno + ", employee name:" + the this .ename + ", employees work:" +
                 the this .job + ", employees' salaries:" + the this .sal + ", a commission employee" + the this .comm; 
    } 

    public  void setDept (Dept's Dept) {
         the this .dept = Dept; 
    } 

    public  void setMgr (Emp MGR) {
         the this .mgr = MGR; 
    } 

    public Dept's getDept () 
    { 
        return  the this .dept; 
    } 
    public Emp getMgr () 
    { 
        return  the this .mgr; 
    } 

}

 

The third step: the class definition is based on the relationship, is set as an object association

public  class Demo {
     public  static  void main (String [] args) { 
        Dept's Dept = new new Dept's (10, "Finance Department", "Changsha" ); 
        Emp empB = new new Emp (001, "A", "Java Engineer", 800.00,0.0 ); 
        Emp EMPA = new new Emp (002, "B", "manager", 1000.00,0.0 ); 
        Emp-EMPC = new new Emp (003, "C", "BOSS", 1200.00,0.0 ); 

        empA.setDept (the dept); 
        empB.setDept (the dept);       // set the associated employees and departments 
        empC.setDept (the dept); 

        EMPA.       setMgr(empB);       //Provided with leading employee association 
        empB.setMgr (-EMPC); 

        dept.setEmps ( new new Emp [] {EMPA, empB,-EMPC});    // sector employee 
    } 
}

 

Finally: Get data required data

        System.out.println (dept.getInfo () + "\ n-"); // sector information 
        for ( int I = 0; I <dept.getEmps () length;. I ++ ) 
        { 
            System.out.println (Dept. getEmps () [I] .getInfo ());   // employee information 
            IF ! (dept.getEmps () [I] .getMgr () = null ) 
            System.out.println (dept.getEmps () [I] .getMgr () .getInfo ());    // employee's leading information 
            System.out.println (); 
        } 
        System.out.println ( "-------------------- ---------------------- " ); 
        System.out.println (empA.getDept () getInfo ());.      // employees get information department
        System.out.println (empA.getMgr () getInfo ().);       // Employees gain leadership information

 

[Segment Information] department number: 10 , department name: Ministry of Finance, Department Location: Changsha 

[employee information] employee number: 2. Name of employee: B, Employee Work: manager, employee salaries: 1000.0, employee commission 0.0 
[employee information] employees number: 1 employee name: A, employees work: java engineer, employee salaries: 800.0, employee commission 0.0 

[employee information] employees number: 1 employee name: A, employees work: java engineer, employee salaries: 800.0, employees commissions 0.0 
[employee information] employees number: 3 employee name: C, employees work: boss, employees' salaries: 1200.0, employee commission 0.0 

[employee information] employees number: 3 employee name: C, employees work: boss, employee salaries : 1200.0, employee commission 0.0 

------------------------------------------ 
[department information] department number: 10 , department name: Ministry of Finance, Department location: Changsha 
[information] employees number of employees: 1. name of employee: A, employees work: java engineer, employee salaries: 800.0, 0.0 commission employees