f597fc1b07
* Fix languages * Missed change for version number * Add language field for presentation * Revert change in README for double buffer Co-authored-by: Jackie Nim <=>
119 lines
3.5 KiB
Markdown
119 lines
3.5 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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language: en
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tags:
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- Performance
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---
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## Intent
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Pass data with multiple attributes in one shot from client to server, to avoid multiple calls to
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remote server.
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## Explanation
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Real world example
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> We need to fetch information about customers from remote database. Instead of querying the
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> attributes one at a time, we use DTOs to transfer all the relevant attributes in a single shot.
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In plain words
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> Using DTO relevant information can be fetched with a single backend query.
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Wikipedia says
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> In the field of programming a data transfer object (DTO) is an object that carries data between
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> processes. The motivation for its use is that communication between processes is usually done
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> resorting to remote interfaces (e.g. web services), where each call is an expensive operation.
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> Because the majority of the cost of each call is related to the round-trip time between the client
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> and the server, one way of reducing the number of calls is to use an object (the DTO) that
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> aggregates the data that would have been transferred by the several calls, but that is served by
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> one call only.
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**Programmatic Example**
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Let's first introduce our simple `CustomerDTO` class.
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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` class acts as the server for customer information.
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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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Now fetching customer information is easy since we have the 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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## Class diagram
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## Applicability
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Use the Data Transfer Object pattern when:
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* The client is asking for multiple information. And the information is related.
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* When you want to boost the performance to get resources.
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* You want reduced number of remote calls.
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## Credits
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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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