为什么我们在Rest Api中使用标头，它们是如何在Sping Boot 中使用的，以及Spring Boot的类型是什么，如果有人清楚我的概念，我将非常感谢，我搜索了很多，但未能理解。以下是我如何使用

@RestController
@RequestMapping
public class postapi {
    PreparedStatement ps = null;
    @PostMapping("/employee")
    public ResponseEntity<String> insertData(@RequestBody Employee employee,
 //this is my header   @RequestHeader (name = "testName", required = false) String headerPersist){

        try{String query = "insert into employee(emp_id,name,age,dep_id)"+"values(?,?,?,?)";
        Class.forName("com.mysql.cj.jdbc.Driver");
        Connection con = DBUtilities.getConnection();
        ps = con.prepareStatement(query);
        ps.setInt(1,employee.getEmp_id());
        ps.setString(2,employee.getName());
        ps.setInt(3,employee.getAge());
        ps.setInt(4,employee.getDep_id());
        int records_inserted = ps.executeUpdate();
            System.out.println(("Executed"));

        }
        catch (ClassNotFoundException e) {
            System.out.println(("ClassNotFoundException occurs"));
            throw new RuntimeException(e);
        } catch (SQLException e) {
            System.out.println(("you got an error in your sql syntax"));
            throw new RuntimeException(e);
        }
        return new ResponseEntity( HttpStatus.OK);
    }
}