2207ea4ce9
* add state and callback pattern * add command and template-method pattern * add iterator pattern * add bridege and DI pattern * fix issue #1600 * add converter,proxy,visitor pattern * add caching,composite,delegation,dirty-flag,interpreter patterns * add dao and producer-consumer * add dto and provate class data pattern * fix #1646 png path problems * fix #1646 composite png path case problem Co-authored-by: Mike <admin@xiaod.info> Co-authored-by: Subhrodip Mohanta <hello@subho.xyz>
112 lines
3.2 KiB
Markdown
112 lines
3.2 KiB
Markdown
---
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layout: pattern
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title: Data Transfer Object
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folder: data-transfer-object
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permalink: /patterns/data-transfer-object/
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categories: Architectural
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tags:
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- Performance
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---
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## 目的
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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。
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## 解释
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真实世界例子
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> 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。
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通俗的说
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> 使用DTO，可以通过单个后端查询获取相关信息。
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维基百科说
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> 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。
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>
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> 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。
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**程序示例**
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让我们来介绍我们简单的`CustomerDTO` 类
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```java
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public class CustomerDto {
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private final String id;
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private final String firstName;
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private final String lastName;
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public CustomerDto(String id, String firstName, String lastName) {
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this.id = id;
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this.firstName = firstName;
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this.lastName = lastName;
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}
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public String getId() {
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return id;
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}
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public String getFirstName() {
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return firstName;
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}
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public String getLastName() {
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return lastName;
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}
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}
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```
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`CustomerResource` 类充当客户信息的服务器。
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```java
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public class CustomerResource {
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private final List<CustomerDto> customers;
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public CustomerResource(List<CustomerDto> customers) {
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this.customers = customers;
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}
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public List<CustomerDto> getAllCustomers() {
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return customers;
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}
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public void save(CustomerDto customer) {
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customers.add(customer);
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}
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public void delete(String customerId) {
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customers.removeIf(customer -> customer.getId().equals(customerId));
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}
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}
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```
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现在拉取客户信息变得简单自从我们有了DTOs。
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```java
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var allCustomers = customerResource.getAllCustomers();
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allCustomers.forEach(customer -> LOGGER.info(customer.getFirstName()));
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// Kelly
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// Alfonso
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```
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## 类图
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## 适用性
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使用数据传输对象模式当
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* 客户端请求多种信息。信息都是相关的
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* 当你想提高获取资源的性能
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* 你想降低远程方法调用的次数
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## 鸣谢
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* [Design Pattern - Transfer Object Pattern](https://www.tutorialspoint.com/design_pattern/transfer_object_pattern.htm)
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* [Data Transfer Object](https://msdn.microsoft.com/en-us/library/ff649585.aspx)
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* [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)
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* [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)
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