Spring - @PostMapping and @GetMapping Annotation

In Spring Boot, @GetMapping and @PostMapping are annotations used to handle HTTP requests in Spring MVC controllers. They help map specific HTTP methods to controller methods when building REST APIs.

• @GetMapping is used to retrieve data from the server.
• @PostMapping is used to send data to the server to create a new resource.

@PostMapping

@PostMapping in Spring MVC is used to handle HTTP POST requests in RESTful web services. It maps a specific URL to a handler method that processes data sent from the client, typically through the request body.

• Used to create or submit data to the server.
• Data is usually received in the request body (e.g., JSON or form data).

Example 1:

import org.springframework.web.bind.annotation.*;

@RestController
public class StudentController {

    @PostMapping("/addStudent")
    public String addStudent(@RequestBody String name) {
        return "Student " + name + " added successfully!";
    }
}

Explanation: the addStudent method is annotated with @PostMapping. It handles HTTP POST requests sent to the /addStudent URL. The student name is passed in the request body and processed by the method.

Example 2: 

import org.springframework.web.bind.annotation.*;

@RestController
public class StudentController {

    @PostMapping("/students/{id}")
    public String updateStudent(@PathVariable int id, @RequestBody Student student) {
        return "Student with ID " + id + " updated successfully!";
    }
}

Explanation: the updateStudent method is annotated with @PostMapping. It handles POST requests sent to the /students/{id} URL. The student ID is received as a path variable, and the updated student object is passed in the request body.

GetMapping annotation

@GetMapping in Spring is used to handle HTTP GET requests in RESTful web services. It maps a specific URL to a controller method that retrieves data from the server.

• Used to retrieve or read data from the server.
• Parameters are usually passed through URL path variables or query parameters.

Examples of @GetMapping annotation

Example 1: 

@GetMapping("/students")
public List<Student> getAllStudents() {
 return studentRepository.findAll();
}

Explanation: getAllStudents method is annotated with @GetMapping annotation. This means that getAllStudents method will be called when an HTTP Get request is received at the /students URL. 

Example 2:

@RestController
public class StudentController {

    @GetMapping("/students/{rollNo}")
    public String getStudent(@PathVariable int rollNo) {
        return "Details of student with Roll No: " + rollNo;
    }
}

Explanation: the getStudent method is annotated with @GetMapping. It handles HTTP GET requests sent to the /students/{rollNo} URL. The roll number is passed as a path variable to fetch the student details.

@PostMapping Vs @GetMapping Annotation