112 lines
3.2 KiB
Markdown
112 lines
3.2 KiB
Markdown
|
---
|
|||
|
|
layout: pattern
|
|||
|
|
title: Data Transfer Object
|
|||
|
|
folder: data-transfer-object
|
|||
|
|
permalink: /patterns/data-transfer-object/
|
|||
|
|
categories: Architectural
|
|||
|
|
tags:
|
|||
|
|
- Performance
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## 目的
|
|||
|
|
|
|||
|
|
次将具有多个属性的数据从客户端传递到服务器，以避免多次调用远程服务器。
|
|||
|
|
|
|||
|
|
## 解释
|
|||
|
|
|
|||
|
|
真实世界例子
|
|||
|
|
|
|||
|
|
> 我们需要从远程数据库中获取有关客户的信息。 我们不使用一次查询一个属性，而是使用DTO一次传送所有相关属性。
|
|||
|
|
|
|||
|
|
通俗的说
|
|||
|
|
|
|||
|
|
> 使用DTO，可以通过单个后端查询获取相关信息。
|
|||
|
|
|
|||
|
|
维基百科说
|
|||
|
|
|
|||
|
|
> 在编程领域，数据传输对象（DTO）是在进程之间承载数据的对象。 使用它的动机是，通常依靠远程接口（例如Web服务）来完成进程之间的通信，在这种情况下，每个调用都是昂贵的操作。
|
|||
|
|
>
|
|||
|
|
> 因为每个（方法）调用的大部分成本与客户端和服务器之间的往返时间有关，所以减少调用数量的一种方法是使用一个对象（DTO）来聚合将要在多次调用间传输的数据，但仅由一个调用提供。
|
|||
|
|
|
|||
|
|
**程序示例**
|
|||
|
|
|
|||
|
|
让我们来介绍我们简单的`CustomerDTO` 类
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
public class CustomerDto {
|
|||
|
|
private final String id;
|
|||
|
|
private final String firstName;
|
|||
|
|
private final String lastName;
|
|||
|
|
|
|||
|
|
public CustomerDto(String id, String firstName, String lastName) {
|
|||
|
|
this.id = id;
|
|||
|
|
this.firstName = firstName;
|
|||
|
|
this.lastName = lastName;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
public String getId() {
|
|||
|
|
return id;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
public String getFirstName() {
|
|||
|
|
return firstName;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
public String getLastName() {
|
|||
|
|
return lastName;
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
`CustomerResource` 类充当客户信息的服务器。
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
public class CustomerResource {
|
|||
|
|
private final List<CustomerDto> customers;
|
|||
|
|
|
|||
|
|
public CustomerResource(List<CustomerDto> customers) {
|
|||
|
|
this.customers = customers;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
public List<CustomerDto> getAllCustomers() {
|
|||
|
|
return customers;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
public void save(CustomerDto customer) {
|
|||
|
|
customers.add(customer);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
public void delete(String customerId) {
|
|||
|
|
customers.removeIf(customer -> customer.getId().equals(customerId));
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
现在拉取客户信息变得简单自从我们有了DTOs。
|
|||
|
|
|
|||
|
|
```java
|
|||
|
|
var allCustomers = customerResource.getAllCustomers();
|
|||
|
|
allCustomers.forEach(customer -> LOGGER.info(customer.getFirstName()));
|
|||
|
|
// Kelly
|
|||
|
|
// Alfonso
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
## 类图
|
|||
|
|
|
|||
|
|
|
|||
|
|
|
|||
|
|
## 适用性
|
|||
|
|
|
|||
|
|
使用数据传输对象模式当
|
|||
|
|
|
|||
|
|
* 客户端请求多种信息。信息都是相关的
|
|||
|
|
* 当你想提高获取资源的性能
|
|||
|
|
* 你想降低远程方法调用的次数
|
|||
|
|
|
|||
|
|
## 鸣谢
|
|||
|
|
|
|||
|
|
* [Design Pattern - Transfer Object Pattern](https://www.tutorialspoint.com/design_pattern/transfer_object_pattern.htm)
|
|||
|
|
* [Data Transfer Object](https://msdn.microsoft.com/en-us/library/ff649585.aspx)
|
|||
|
|
* [J2EE Design Patterns](https://www.amazon.com/gp/product/0596004273/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596004273&linkCode=as2&tag=javadesignpat-20&linkId=f27d2644fbe5026ea448791a8ad09c94)
|
|||
|
|
* [Patterns of Enterprise Application Architecture](https://www.amazon.com/gp/product/0321127420/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0321127420&linkCode=as2&tag=javadesignpat-20&linkId=014237a67c9d46f384b35e10151956bd)
|