Java Web Services
What is a web service
Service available over web. The main objective of a web service is to serve data to applications in different platforms such as mobile application, desktop or web applications. Web services are for application consumption and they are language independent.
What is an API?
API stands for Application Programming Interface. It is a bridge between applications. It can be referred as an end-point. For example, http://localhost:8080/employees/1. The same URL can be used for different types of HTTP request such as GET, POST, DELETE, PUT etc.
Best practice: End-points are structured in directory structure
What are the types of web services?
SOAP (Simple Object Access Protocol) based web services (API)
- Heavy-weight - SOAP services required to follow some protocol which leads to the consumption of more resources
- Always return the response in XML format, thus requiring XML parser and some other additional resources as well
- These web services use WSDL (Web Service Description Language) files (XML file).
- WSDL files describes the details of web service that include (name, type of operations, datatypes, location etc.)
RESTful Web Services (API)
REST stands for Representationsl State Transfer. These services are not protocol based, they are just designed based on the architechtureal pattern.
Key Characterstics
- Light-weight - RESTful services consume less resources
- These web services can serve data in multiple formats such as XML, JSON (JavaScript Object Notation) etc. JSON provide data in key-value pairs.
Spring Data JPA (Java/Jakarta Persitence API)
Add an additional abstraction by providing various “Java interfaces” such as
- Repository
- CrudRepository
- PagingAndSortingRepository (used to implement pagination)
- JpaRepository
All the above interfaces are referred as Repositories. Implementation classes are provided so there is no need to wrtie the implementation.
API Client
Postman is a popular API client to test end-points. This tool is also available online. Postman facilitates with publishing API documentation which saves time for the API consumers.