當(dāng)我們想要在客戶端到服務(wù)器的一個(gè)傳遞具有多個(gè)屬性的數(shù)據(jù)時(shí)，可使用傳輸對(duì)象模式。傳輸對(duì)象也稱為值對(duì)象。傳輸對(duì)象是一個(gè)具有g(shù)etter/setter方法的簡(jiǎn)單POJO類，并且是可序列化的，因此可以通過網(wǎng)絡(luò)傳輸。它沒有任何行為。服務(wù)器端業(yè)務(wù)類通常從數(shù)據(jù)庫獲取數(shù)據(jù)并填充到POJO類，并將其發(fā)送到客戶端或通過值傳遞它。對(duì)于客戶端，傳輸對(duì)象是只讀的。客戶端可以創(chuàng)建自己的傳輸對(duì)象，并將其傳遞給服務(wù)器，以便一次性更新數(shù)據(jù)庫中的值。以下是這種類型的設(shè)計(jì)模式的實(shí)體。

業(yè)務(wù)對(duì)象 - 業(yè)務(wù)服務(wù)使用數(shù)據(jù)填充傳輸對(duì)象。
傳輸對(duì)象 - 具有僅設(shè)置/獲取屬性的方法的簡(jiǎn)單POJO。
客戶端 - 客戶端請(qǐng)求或發(fā)送傳輸對(duì)象到業(yè)務(wù)對(duì)象。

實(shí)現(xiàn)實(shí)例

在這個(gè)實(shí)現(xiàn)實(shí)例中，將創(chuàng)建一個(gè)StudentBO作為業(yè)務(wù)對(duì)象，Student作為傳輸對(duì)象表示實(shí)體。

TransferObjectPatternDemo是一個(gè)演示類，在這里充當(dāng)客戶端，將使用StudentBO和Student演示傳輸對(duì)象設(shè)計(jì)模式。

服務(wù)定位器模式示例的結(jié)構(gòu)如下圖所示 -

第1步

創(chuàng)建一個(gè)傳輸對(duì)象，其代碼如下所示 -

StudentVO.java

public class StudentVO {
   private String name;
   private int rollNo;

   StudentVO(String name, int rollNo){
      this.name = name;
      this.rollNo = rollNo;
   }

   public String getName() {
      return name;
   }

   public void setName(String name) {
      this.name = name;
   }

   public int getRollNo() {
      return rollNo;
   }

   public void setRollNo(int rollNo) {
      this.rollNo = rollNo;
   }
}

第2步

創(chuàng)建一個(gè)業(yè)務(wù)對(duì)象，其代碼如下所示 -
StudentBO.java

import java.util.ArrayList;
import java.util.List;

public class StudentBO {

   //list is working as a database
   List<StudentVO> students;

   public StudentBO(){
      students = new ArrayList<StudentVO>();
      StudentVO student1 = new StudentVO("Robert",0);
      StudentVO student2 = new StudentVO("John",1);
      students.add(student1);
      students.add(student2);        
   }
   public void deleteStudent(StudentVO student) {
      students.remove(student.getRollNo());
      System.out.println("Student: Roll No " + student.getRollNo() + ", deleted from database");
   }

   //retrive list of students from the database
   public List<StudentVO> getAllStudents() {
      return students;
   }

   public StudentVO getStudent(int rollNo) {
      return students.get(rollNo);
   }

   public void updateStudent(StudentVO student) {
      students.get(student.getRollNo()).setName(student.getName());
      System.out.println("Student: Roll No " + student.getRollNo() +", updated in the database");
   }
}

第3步

使用StudentBO演示傳輸對(duì)象設(shè)計(jì)模式，其代碼如下所示 -
TransferObjectPatternDemo.java

public class TransferObjectPatternDemo {
   public static void main(String[] args) {
      StudentBO studentBusinessObject = new StudentBO();

      //print all students
      for (StudentVO student : studentBusinessObject.getAllStudents()) {
         System.out.println("Student: [RollNo : " + student.getRollNo() + ", Name : " + student.getName() + " ]");
      }

      //update student
      StudentVO student = studentBusinessObject.getAllStudents().get(0);
      student.setName("Michael");
      studentBusinessObject.updateStudent(student);

      //get the student
      student = studentBusinessObject.getStudent(0);
      System.out.println("Student: [RollNo : " + student.getRollNo() + ", Name : " + student.getName() + " ]");
   }
}

第4步

驗(yàn)證輸出，執(zhí)行上面的代碼得到以下結(jié)果 -

Student: [RollNo : 0, Name : Robert ]
Student: [RollNo : 1, Name : John ]
Student: Roll No 0, updated in the database
Student: [RollNo : 0, Name : Michael ]

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