FRQ1 - Methods and Control Structures

• Methods and Control Structures Background
• Hacks

Methods and Control Structures Background

All Web Endpoints are typically backed with Methods and Control Structures. First, there are Methods that manage @RestController endpoint. Additionally, there are the Methods and Control Structures that perform endpoint logic, like fetching data through the JPA. In the 2019 FRQ1 they seem to limit OOP usage in favor of static methods. The implementation below shows these methods as Class methods, not as methods of an Object.

• Tech Talk observers clone: Spring Portfolio Project and open in VSCode. - Tech Talk observers: Download PostMan
• These methods could be endpoints of an API.
• The APCalendar class could be built out to provide interesting facts about Year and Date to support a PBL application
• The class APCalendar shown is described as a Prototype. Why?.

// Prototype Implementation

public class APCalendar {

    /** Returns true if year is a leap year and false otherwise.
     * isLeapYear(2019) returns False
     * isLeapYear(2016) returns True
     */          
    private static boolean isLeapYear(int year) {
        // implementation not shown

        return false;
        }
        
    /** Returns the value representing the day of the week 
     * 0 denotes Sunday, 
     * 1 denotes Monday, ..., 
     * 6 denotes Saturday. 
     * firstDayOfYear(2019) returns 2 for Tuesday.
    */
    private static int firstDayOfYear(int year) {
        // implementation not shown

        return 0;
        }


    /** Returns n, where month, day, and year specify the nth day of the year.
     * This method accounts for whether year is a leap year. 
     * dayOfYear(1, 1, 2019) return 1
     * dayOfYear(3, 1, 2017) returns 60, since 2017 is not a leap year
     * dayOfYear(3, 1, 2016) returns 61, since 2016 is a leap year. 
    */ 
    private static int dayOfYear(int month, int day, int year) {
        // implementation not shown

        return 1;
        }

    /** Returns the number of leap years between year1 and year2, inclusive.
     * Precondition: 0 <= year1 <= year2
    */ 
    public static int numberOfLeapYears(int year1, int year2) {
         // to be implemented in part (a)

        return 0;
        }

    /** Returns the value representing the day of the week for the given date
     * Precondition: The date represented by month, day, year is a valid date.
    */
    public static int dayOfWeek(int month, int day, int year) { 
        // to be implemented in part (b)
        return 0;
        }

    /** Tester method */
    public static void main(String[] args) {
        // Private access modifiers
        System.out.println("isLeapYear: " + APCalendar.isLeapYear(2022));
        System.out.println("firstDayOfYear: " + APCalendar.firstDayOfYear(2022));
        System.out.println("dayOfYear: " + APCalendar.dayOfYear(1, 1, 2022));

        // Public access modifiers
        System.out.println("numberOfLeapYears: " + APCalendar.numberOfLeapYears(2000, 2022));
        System.out.println("dayOfWeek: " + APCalendar.dayOfWeek(1, 1, 2022));
    }

}

Hacks

Completes APIs and methods not completed.

• Implement FRQ1 in Spring project, use Spring Portfolio mvc/calendar for starter code
• Enhance APCalendar.java to provide interesting facts on years, be creative and enhance/finish provided methods. For instance, use a random number or date to complete APCalendar day-of-week method. Or, better see if there is algorithm to figure methods out. Ask your team, pair, crossover, and slack before you ask me.
• Enhance APIs and @RESTController to work with the all POJOs and APCalendar.
• Test APIs with Browser, Curl, or Postman. Illustrate or show tangibles.
• Test and use VSCode Debugger in development. Illustrate or show tangibles.
• Demo and Debugging

REST Serializing and Deserializing Year objects is necessary. There is completed example.

• Read ObjectMapper and Write ObjectMapper. ObjectMapper provides functionality for reading and writing JSON, either to and from basic POJOs (Plain Old Java Objects), or to and from a general-purpose JSON Tree Model (JsonNode).> FYI, in FRQ2 you will see REST Serialization is mostly automatic with JPA
• REST documentation

package com.nighthawk.spring_portfolio.mvc.calendar;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

/** Calendar API
 * Calendar Endpoint: /api/calendar/isLeapYear/2022, Returns: {"year":2020,"isLeapYear":false}
 */
@RestController
@RequestMapping("/api/calendar")
public class CalendarApiController {

    /** GET isLeapYear endpoint
     * ObjectMapper throws exceptions on bad JSON
     *  @throws JsonProcessingException
     *  @throws JsonMappingException
     */
    @GetMapping("/isLeapYear/{year}")
    public ResponseEntity<JsonNode> getIsLeapYear(@PathVariable int year) throws JsonMappingException, JsonProcessingException {
      // Backend Year Object
      Year year_obj = new Year();
      year_obj.setYear(year);  // evaluates Leap Year

      // Turn Year Object into JSON
      ObjectMapper mapper = new ObjectMapper(); 
      JsonNode json = mapper.readTree(year_obj.isLeapYearToString()); // this requires exception handling

      return ResponseEntity.ok(json);  // JSON response, see ExceptionHandlerAdvice for throws
    }

    // add other methods
}

package com.nighthawk.spring_portfolio.mvc.calendar;

/** Simple POJO 
 * Used to Interface with APCalendar
 * The toString method(s) prepares object for JSON serialization
 * Note... this is NOT an entity, just an abstraction
 */
class Year {
   private int year;
   private boolean isLeapYear;

   // zero argument constructor
   public Year() {} 

   /* year getter/setters */
   public int getYear() {
      return year;
   }
   public void setYear(int year) {
      this.year = year;
      this.setIsLeapYear(year);
   }

   /* isLeapYear getter/setters */
   public boolean getIsLeapYear(int year) {
      return APCalendar.isLeapYear(year);
   }
   private void setIsLeapYear(int year) {  // this is private to avoid tampering
      this.isLeapYear = APCalendar.isLeapYear(year);
   }

   /* isLeapYearToString formatted to be mapped to JSON */
   public String isLeapYearToString(){
      return ( "{ \"year\": "  +this.year+  ", " + "\"isLeapYear\": "  +this.isLeapYear+ " }" );
   }	

   /* standard toString placeholder until class is extended */
   public String toString() { 
      return isLeapYearToString(); 
   }

   public static void main(String[] args) {
      Year year = new Year();
      year.setYear(2022);
      System.out.println(year);
   }
}