Spring Boot - API - Guided Exercise: ⚖️ RateMyBurger – Build a Smart Rating Engine (Using @GetMapping + @RequestParam)

[akash-coded]

🧪 Exercise Title: ⚖️ RateMyBurger – Build a Smart Rating Engine (Using @GetMapping + @RequestParam)

---

🎯 Learning Outcomes

By the end of this mission, you will:

✅ Understand how to use @GetMapping to create GET endpoints
✅ Capture query parameters using @RequestParam
✅ Perform conditional logic based on inputs
✅ Return clean responses via HTTP
✅ Build clean controllers using industry-style conventions
✅ Improve API naming, structuring, and parameter handling

---

🎮 THE STORY

You’ve been hired as a backend dev at BurgerByte, a startup that delivers exotic burgers on Mars.

Your task? Build a Burger Rating API that:

• Accepts customer name and rating via query parameters
• Returns a response like "Thanks Sam! You rated SpicyCheezilla 4.5 stars!"
• Adds validation: reject ratings above 5 or below 0
• Handles optional parameters like comment
• Allows filtering reviews by burgerName

---

🛠 SETUP

1. Project Setup

Generate project from [start.spring.io](https://start.spring.io)

• Group: com.burgerbyte
• Artifact: rateburger
• Dependencies: Spring Web
• Language: Java
• Java: 17+
• Unzip & import into Eclipse

---

2. Folder Structure

com.burgerbyte.rateburger
├── controller
│   └── RatingController.java
└── RateburgerApplication.java

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🧩 PHASED MISSION STRUCTURE

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🌟 PHASE 1: Your First Rating Endpoint

🎯 Build a GET endpoint:

URL format:
GET /api/rate?name=Sam&burger=SpicyCheezilla&stars=4.5

📄 RatingController.java

@RestController
@RequestMapping("/api")
public class RatingController {

    @GetMapping("/rate")
    public String rateBurger(
        @RequestParam String name,
        @RequestParam String burger,
        @RequestParam double stars
    ) {
        return "Thanks " + name + "! You rated " + burger + " " + stars + " stars!";
    }
}

✅ Run and test in Postman.
🧠 Challenge to build this without copy-pasting.

---

🔍 PHASE 2: Add Rating Validation

Add logic:

• If stars > 5 or stars < 0, return:
  "⚠️ Invalid rating. Please rate between 0 and 5."

✍️ Write only the conditional block and response.

---

💬 PHASE 3: Accept Optional comment

• Add a new parameter: @RequestParam(required = false) String comment
• If comment exists, append it to the response
• If not, skip it

Example URL:
/api/rate?name=Sam&burger=SpicyCheezilla&stars=4.5&comment=Loved it!

Response:
Thanks Sam! You rated SpicyCheezilla 4.5 stars! Comment: Loved it!

🧪 Challenge: How to write conditional if (comment != null) logic.

---

🗃️ PHASE 4: Maintain Ratings (In-Memory)

Create a simple List<String> inside the controller to store rating responses.

Every time someone rates, add the final response to the list.

Add a new endpoint:

URL: /api/reviews
Output: List of all rating messages

@GetMapping("/reviews")
public List<String> getReviews() {
    return ratings;
}

🧠 Question: Why is List<String> not thread-safe? What could go wrong?

---

🔎 PHASE 5: Add Filtering by Burger Name

Modify /reviews to accept optional param burger.

Example: /api/reviews?burger=SpicyCheezilla

@GetMapping("/reviews")
public List<String> getReviews(@RequestParam(required = false) String burger) {
    if (burger == null) return ratings;

    return ratings.stream()
        .filter(r -> r.toLowerCase().contains(burger.toLowerCase()))
        .toList();
}

✅ Build this filtering logic from scratch.

---

🔁 PHASE 6: Add Ratings Summary (Bonus)

Create a new endpoint:

URL: /api/summary?burger=SpicyCheezilla
Response:
Burger: SpicyCheezilla | Total Reviews: 3 | Avg Stars: 4.3

🧠 You are required to:

• Maintain a Map<String, List<Double>> of burger → ratings
• Return computed average using stream().mapToDouble().average().orElse(0)

---

🎯 API SUMMARY

Endpoint	Params	Purpose
/api/rate	name, burger, stars, comment	Submit a rating
/api/reviews	[burger]	View all or filtered reviews
/api/summary	burger	Show review summary stats

---

🧼 BEST PRACTICES TRAINED

Concept	How It's Used
@GetMapping	Endpoint declaration
@RequestParam	Read query params
Input validation	Stars within range
Optional params	With required = false
In-memory storage	List + Map usage
Stream filtering	Functional data handling
Java naming conventions	camelCase fields, PascalCase classes

---

💡 QUESTIONS TO ANSWER

• Why prefer query params for GET over request body?
• What’s the difference between @RequestParam and @PathVariable?
• What happens if @RequestParam is missing but required?
• What happens if stars is not a number?
• Why shouldn't we store reviews in memory for a real app?

---

🧾 STUDENT DELIVERABLES

• ✅ Full RatingController.java with all endpoints
• ✅ Responses tested via Postman
• ✅ URL + response screenshots
• ✅ One new custom endpoint of their choice (e.g., GET /api/feedback?ratingId=3)

---

🏁 YOU’VE UNLOCKED:

✅ API design using GET
✅ Input reading using @RequestParam
✅ Building filters, optional fields, conditional logic
✅ Building a mini API with real backend logic

[Sdey0907]

**

Task- RateMyBurger_Spring Boot_Sayan Dey_Completed

**

rateburger_SpringBoot.zip

[vbhavana1]

@RestController
@RequestMapping("/api")
public class RatingController {

private final List<String> ratings = new ArrayList<>();
private final Map<String, List<Double>> ratingMap = new HashMap<>();

@GetMapping("/rate")
public String rateBurger(
        @RequestParam String name,
        @RequestParam String burger,
        @RequestParam double stars,
        @RequestParam(required = false) String comment) {

    // Validation
    if (stars < 0 || stars > 5) {
        return "Invalid rating. Please rate between 0 and 5.";
    }

    // Construct message
    StringBuilder message = new StringBuilder("Thanks " + name + "! You rated " + burger + " " + stars + " stars!");
    if (comment != null && !comment.trim().isEmpty()) {
        message.append(" Comment: ").append(comment);
    }

    // Store the review
    String reviewMessage = message.toString();
    ratings.add(reviewMessage);

    // Update rating map
    ratingMap.putIfAbsent(burger, new ArrayList<>());
    ratingMap.get(burger).add(stars);

    return reviewMessage;
}

@GetMapping("/reviews")
public List<String> getReviews(@RequestParam(required = false) String burger) {
    if (burger == null) return ratings;
    return ratings.stream()
            .filter(r -> r.toLowerCase().contains(burger.toLowerCase()))
            .toList();
}

@GetMapping("/summary")
public String getSummary(@RequestParam String burger) {
    List<Double> starList = ratingMap.get(burger);
    if (starList == null || starList.isEmpty()) {
        return "Burger: " + burger + " | Total Reviews: 0 | Avg Stars: 0.0";
    }

    double avg = starList.stream().mapToDouble(Double::doubleValue).average().orElse(0);
    return "Burger: " + burger + " | Total Reviews: " + starList.size() + " | Avg Stars: " + String.format("%.1f", avg);
}

}

[prasetha21-max]

PRASETHA N

package com.burgerbyte.rateburger.controller;

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

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@RestController
@RequestMapping("/api")
public class RatingController {

    private List<String> ratings = new ArrayList<>();
    private Map<String, List<Double>> ratingMap = new HashMap<>();

    @GetMapping("/rate")
    public String rateBurger(
            @RequestParam String name,
            @RequestParam String burger,
            @RequestParam double stars,
            @RequestParam(required = false) String comment) {

        if (stars < 0 || stars > 5) {
            return "Invalid rating. Please rate between 0 and 5.";
        }

        String response = "Thanks " + name + "! You rated " + burger + " " + stars + " stars!";
        if (comment != null && !comment.isEmpty()) {
            response += " Comment: " + comment;
        }

        ratings.add(response);

        String burgerKey = burger.toLowerCase();
        if (!ratingMap.containsKey(burgerKey)) {
            ratingMap.put(burgerKey, new ArrayList<>());
        }
        ratingMap.get(burgerKey).add(stars);

        return response;
    }

    @GetMapping("/reviews")
    public List<String> getReviews(@RequestParam(required = false) String burger) {
        if (burger == null || burger.isEmpty()) {
            return ratings;
        }

        List<String> filtered = new ArrayList<>();
        String burgerKey = burger.toLowerCase();

        for (String rating : ratings) {
            if (rating.toLowerCase().contains(burgerKey)) {
                filtered.add(rating);
            }
        }

        return filtered;
    }

    @GetMapping("/summary")
    public String getSummary(@RequestParam String burger) {
        String burgerKey = burger.toLowerCase();
        List<Double> starList = ratingMap.getOrDefault(burgerKey, new ArrayList<>());

        if (starList.isEmpty()) {
            return "Burger: " + burger + " has no reviews yet.";
        }

        double sum = 0;
        for (Double star : starList) {
            sum += star;
        }

        double avg = sum / starList.size();
        return "Burger: " + burger + " | Total Reviews: " + starList.size() + " | Avg Stars: " + String.format("%.1f", avg);
    }

    @GetMapping("/feedback")
    public String getFeedback(@RequestParam int ratingId) {
        if (ratingId < 0 || ratingId >= ratings.size()) {
            return "Rating not found.";
        }

        return ratings.get(ratingId);
    }
}