Java Rest API with sqlite and simple web frontend

pom.xml

@@ -0,0 +1,49 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" 
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
+                             http://maven.apache.org/maven-v4_0_0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>com.test</groupId>
+  <artifactId>java-project</artifactId>
+  <packaging>jar</packaging>
+  <version>1.0-SNAPSHOT</version>
+  <name>java-project</name>
+  <url>http://maven.apache.org</url>
+
+  <dependencies>
+  
+    <dependency>
+      <groupId>io.javalin</groupId>
+      <artifactId>javalin</artifactId>
+      <version>5.6.3</version>
+    </dependency>
+    
+    <dependency>
+    <groupId>com.fasterxml.jackson.core</groupId>
+    <artifactId>jackson-databind</artifactId>
+    <version>2.15.0</version>
+    </dependency>
+
+    <dependency>
+    <groupId>org.xerial</groupId>
+    <artifactId>sqlite-jdbc</artifactId>
+    <version>3.45.1.0</version>
+    </dependency>
+
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.10.1</version>
+        <configuration>
+          <source>17</source>
+          <target>17</target>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>

src/main/java/com/curlCommand.md

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+CURL COMMAND TUTORIAL
+
+---
+
+### 1.
+
+```bash
+curl http://localhost:7070/total
+```
+
+* **What it does:**
+  Sends an HTTP GET request to your API’s `/total` endpoint.
+* **Purpose:**
+  Fetches the total profit so far from your server.
+* **Response you got:**
+
+  ```json
+  {"totalProfit":12000.0}
+  ```
+
+  This means the total sum of all purchased products recorded so far is ₹12,000.
+
+---
+
+### 2.
+
+```bash
+curl http://localhost:7070/turl -X POST http://localhost:7070/purchase -H "Content-Type: application/json" -d '{"product":"Camera Drone","price":12000}'
+```
+
+* **What you tried to do:**
+  Looks like you tried to send a POST request to `/purchase` to add a new product "Camera Drone" priced at 12000.
+
+* **Why it’s wrong / problematic:**
+  The syntax is incorrect and malformed. You are mixing a GET request to `/turl` with `-X POST http://localhost:7070/purchase`, which doesn’t make sense for `curl`.
+  The command has extra URL (`http://localhost:7070/purchase`) placed incorrectly after `-X POST`, which should only be followed by the HTTP method, not another URL.
+
+* **Correct form:**
+
+  ```bash
+  curl -X POST http://localhost:7070/purchase -H "Content-Type: application/json" -d '{"product":"Camera Drone","price":12000}'
+  ```
+
+* This correctly sends a POST request to `/purchase` endpoint with a JSON body specifying the product and price.
+
+---
+
+
+### Summary of key curl options used:
+
+* `curl [URL]` — by default, sends a GET request to the URL.
+
+* `-X POST` — explicitly sets HTTP method to POST (used to send data).
+
+* `-H "Content-Type: application/json"` — adds HTTP header specifying the request body is JSON.
+
+* `-d '{"product":"Camera Drone","price":12000}'` — the JSON data to send in the body of the POST request.
+
+---
+
+If you want to test adding a new purchase and then check total, this sequence is correct:
+
+```bash
+curl -X POST http://localhost:7070/purchase -H "Content-Type: application/json" -d '{"product":"Camera Drone","price":12000}'
+curl http://localhost:7070/total
+```
+
+This will record the new product and then return the updated total profit.
+
+---
+
+If you want, I can help you build some shell scripts or alias commands to make testing easier! Just say the word.

src/main/java/com/test/App.java

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+package com.test;
+
+//Custom Classes Imported below
+import com.test.PurchaseDAO;
+
+// Import necessary classes
+import java.util.Map;
+import java.util.HashMap;
+import java.util.Scanner;
+
+import io.javalin.Javalin;
+import io.javalin.http.Context;
+import io.javalin.plugin.bundled.CorsPluginConfig;
+
+public class App {
+
+    // Create a Constructor object to hold user and product info
+    Constructor construct = new Constructor("Arul", 24, "India, TN");
+
+    // Counter to track number of products purchased
+    int productIndex = 0;
+
+    // Map to store product name as key and price as value
+    Map<String, Double> purchasedProductDetails = new HashMap<>();
+
+    // Scanner object to read input from console
+    Scanner scanner = new Scanner(System.in);
+
+    PurchaseDAO db = new PurchaseDAO(); // Initializing DB 
+
+    // Method to record a purchase
+    public void recordPurchase(String product, double price) {
+        productIndex++;  // Increment product count
+        construct.setProductName(product);  // Set product name
+        construct.setProductPrice(price);   // Set product price
+        construct.setTotalProductsPurchased(productIndex);  // Update total
+        makeList();  // Add to local Map
+        db.insertPurchase(product, price); // Save to DB
+    }
+
+    // Read user input from console (for CLI use)
+    public void printAndRead() {
+        System.out.println("[+] Enter the Product " + productIndex + " Name:");
+        String productName = scanner.nextLine();
+        System.out.println("[+] Enter price of the Product");
+        Double productPrice = scanner.nextDouble();
+        scanner.nextLine();  // Consume newline
+        recordPurchase(productName, productPrice);
+    }
+
+    // Add product and price to Map
+    public void makeList() {
+        purchasedProductDetails.put(construct.getProductName(), construct.getProductPrice());
+    }
+
+    // Calculate total from DB and print
+    public void calculateTotalProfit() {
+        double sum = db.getTotalProfit(); // ✅ From DB
+        System.out.println("Total profit: ₹" + sum);
+    }
+
+    // 🟢 Start API server
+    public void startApi() {
+        Javalin app = Javalin.create(config -> {
+            // ✅ Enable CORS for frontend origin
+            config.plugins.enableCors(cors -> {
+                cors.add(CorsPluginConfig::anyHost); // Or use allowHost("http://localhost:8080")
+            });
+        }).start(7070);
+
+        // Set JSON response type
+        app.before(ctx -> ctx.contentType("application/json"));
+
+        // 🔸 POST /purchase → Record purchase
+        app.post("/purchase", ctx -> {
+            Map<String, Object> data = ctx.bodyAsClass(Map.class);
+            String product = data.get("product").toString();
+            double price = Double.parseDouble(data.get("price").toString());
+            recordPurchase(product, price);
+            ctx.status(200).result("Recorded: " + product + " for ₹" + price);
+        });
+
+        // 🔹 GET /total → Return total profit
+        app.get("/total", ctx -> {
+            double sum = db.getTotalProfit();
+            ctx.json(Map.of(
+                "totalProfit", sum,
+                "customerName", construct.name,
+                "customerAge", construct.age,
+                "customerRegion", construct.region
+            ));
+        });
+    }
+
+    // 🚀 Main Method
+    public static void main(String[] args) {
+        App app = new App();
+        app.startApi();  // Start server
+
+        // Optional CLI (not needed for frontend, just for manual entry)
+        int flag = 0;
+        while (flag != 1) {
+            System.out.println("Proceed Adding Products? (Y/N)");
+            String userInput = app.scanner.nextLine();
+            if (userInput.equalsIgnoreCase("Y")) {
+                app.printAndRead();
+            } else {
+                app.calculateTotalProfit();
+                flag = 1;
+                app.scanner.close();
+            }
+        }
+    }
+}

src/main/java/com/test/Constructor.java

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+package com.test;
+
+public class Constructor {
+
+    // User info fields
+    String name;
+    int age;
+    String region;
+
+    // Product-related fields (private for encapsulation)
+    private String purchaseProduct;
+    private double productPrice;
+    private double profitOfTheDay;
+    private int totalProductsPurchased;
+
+    // Constructor to initialize user details
+    public Constructor(String name, int age, String region) {
+        this.age = age;
+        this.name = name;
+        this.region = region;
+    }
+
+    // Getter for product name
+    public String getProductName() {
+        return purchaseProduct;
+    }
+
+    // Getter for product price
+    public double getProductPrice() {
+        return productPrice;
+    }
+
+    // Getter for profit of the day (not used yet in App)
+    public double getProfitOfTheDay() {
+        return profitOfTheDay;
+    }
+
+    // Setter for product name
+    public void setProductName(String purchaseProduct) {
+        this.purchaseProduct = purchaseProduct;
+    }
+
+    // Setter for product price
+    public void setProductPrice(double productPrice) {
+        this.productPrice = productPrice;
+    }
+
+    // Setter for profit of the day
+    public void setProfitOfTheDay(double profitOfTheDay) {
+        this.profitOfTheDay = profitOfTheDay;
+    }
+
+    // Setter for total products purchased
+    public void setTotalProductsPurchased(int totalProductsPurchased) {
+        this.totalProductsPurchased = totalProductsPurchased;
+    }
+
+    // Getter for total products purchased
+    public int getTotalProductsPurchased() {
+        return totalProductsPurchased;
+    }
+}

src/main/java/com/test/PurchaseDAO.java

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+package com.test;
+
+import java.sql.*;
+
+public class PurchaseDAO {
+
+private static final String DB_URL = "jdbc:sqlite:purchase.db";
+
+public PurchaseDAO(){
+    try(Connection conn = DriverManager.getConnection(DB_URL);
+        Statement stmt = conn.createStatement())  
+    {
+        String sql = "CREATE TABLE IF NOT EXISTS purchases (" 
+         + "id INTEGER PRIMARY KEY AUTOINCREMENT," 
+         + "product TEXT NOT NULL,"
+         + "price REAL NOT NULL);";
+         stmt.execute(sql);
+
+    }
+    catch(SQLException e){
+        e.printStackTrace();
+    }
+}
+
+public void insertPurchase(String product, double price){
+
+    String sql = "INSERT INTO purchases (product, price) VALUES (?,?)";
+    try (Connection conn = DriverManager.getConnection(DB_URL);
+         PreparedStatement pstmt = conn.prepareStatement(sql)){
+         
+         pstmt.setString(1, product);
+         pstmt.setDouble(2, price);
+         pstmt.executeUpdate();
+    }
+    catch(SQLException e){
+       e.printStackTrace();
+    }
+}
+
+public double getTotalProfit(){
+
+    double total = 0;
+    String sql  = "SELECT SUM(price) FROM purchases";
+    try(Connection conn = DriverManager.getConnection(DB_URL);
+        Statement stmt = conn.createStatement();
+        ResultSet res = stmt.executeQuery(sql)){
+            if(res.next()){
+                total = res.getDouble(1);
+            }
+        }
+    catch(SQLException e){
+       e.printStackTrace();
+    }
+     return total;
+ }
+
+}

src/main/java/com/test/frontend/app.js

@@ -0,0 +1,54 @@
+// Wait until the DOM (HTML page) is fully loaded
+document.addEventListener("DOMContentLoaded", function () {
+  // Grab form elements and buttons
+  const form = document.getElementById("purchaseForm");
+  const resultDiv = document.getElementById("result");
+  const totalBtn = document.getElementById("totalBtn");
+
+  // 🟩 Handle form submission (Add new Purchase)
+  form.addEventListener("submit", function (event) {
+    event.preventDefault(); // Prevent page refresh
+
+    // Get product and price values from form
+    const product = document.getElementById("product").value;
+    const price = parseFloat(document.getElementById("price").value);
+
+    const data = { product: product, price: price };
+
+    // Send POST request to /purchase endpoint
+    fetch("http://localhost:7070/purchase", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(data),
+    })
+      .then(function (response) {
+        return response.text(); // Expecting plain text response
+      })
+      .then(function (data) {
+        resultDiv.innerText = data; // Show server response
+        form.reset(); // Clear form inputs
+      })
+      .catch(function (error) {
+        resultDiv.innerText = "Error: " + error; // Show error if any
+      });
+  });
+
+  // 🟦 Handle "Show Total Profit" button click (GET from /total)
+  totalBtn.addEventListener("click", function () {
+    fetch("http://localhost:7070/total")
+      .then((response) => response.json()) // Expect JSON response
+      .then((data) => {
+        // Format and display returned data
+        const output = `
+Name: ${data.customerName}
+Age: ${data.customerAge}
+Region: ${data.customerRegion}
+Total Profit: ₹${data.totalProfit}
+        `;
+        resultDiv.innerText = output;
+      })
+      .catch((error) => {
+        resultDiv.innerText = "Error: " + error; // Display fetch error
+      });
+  });
+});

src/main/java/com/test/frontend/index.html

@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8" />
+  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+  <title>Purchase Tracker</title>
+
+  <!-- Link CSS -->
+  <link rel="stylesheet" href="styles.css" />
+
+  <!-- Link JS (corrected attribute typo: 'data-jslicence' to 'data-jslicense') -->
+  <script src="app.js" defer data-jslicense="MIT"></script>
+</head>
+
+<body>
+  <div class="container">
+    <h1>Product Purchase Tracker</h1>
+
+    <!-- Purchase form -->
+    <form id="purchaseForm">
+      <label for="product">Product Name:</label>
+      <input type="text" id="product" name="product" required />
+
+      <label for="price">Price (₹):</label>
+      <input type="number" id="price" name="price" step="0.01" required />
+
+      <button type="submit">Add Purchase</button>
+    </form>
+
+    <!-- Button to fetch total -->
+    <button id="totalBtn">Show Total Profit</button>
+
+    <!-- Result will be shown here -->
+    <div id="result"></div>
+  </div>
+</body>
+</html>

src/main/java/com/test/frontend/styles.css

@@ -0,0 +1,28 @@
+body {
+  font-family: sans-serif;
+  background-color: #f4f4f4;
+  padding: 20px;
+}
+
+.container {
+  max-width: 500px;
+  margin: auto;
+  background: white;
+  padding: 20px;
+  border-radius: 8px;
+  box-shadow: 0 0 10px rgba(0, 0, 0, 0.1); /* optional visual polish */
+}
+
+input,
+button {
+  display: block;
+  width: 100%;
+  margin-top: 10px;
+  padding: 8px;
+  font-size: 1rem;
+}
+
+#result {
+  margin-top: 20px;
+  white-space: pre-wrap; /* keep newlines and wrap long lines */
+}

target/classes/com/curlCommand.md

@@ -0,0 +1,72 @@
+CURL COMMAND TUTORIAL
+
+---
+
+### 1.
+
+```bash
+curl http://localhost:7070/total
+```
+
+* **What it does:**
+  Sends an HTTP GET request to your API’s `/total` endpoint.
+* **Purpose:**
+  Fetches the total profit so far from your server.
+* **Response you got:**
+
+  ```json
+  {"totalProfit":12000.0}
+  ```
+
+  This means the total sum of all purchased products recorded so far is ₹12,000.
+
+---
+
+### 2.
+
+```bash
+curl http://localhost:7070/turl -X POST http://localhost:7070/purchase -H "Content-Type: application/json" -d '{"product":"Camera Drone","price":12000}'
+```
+
+* **What you tried to do:**
+  Looks like you tried to send a POST request to `/purchase` to add a new product "Camera Drone" priced at 12000.
+
+* **Why it’s wrong / problematic:**
+  The syntax is incorrect and malformed. You are mixing a GET request to `/turl` with `-X POST http://localhost:7070/purchase`, which doesn’t make sense for `curl`.
+  The command has extra URL (`http://localhost:7070/purchase`) placed incorrectly after `-X POST`, which should only be followed by the HTTP method, not another URL.
+
+* **Correct form:**
+
+  ```bash
+  curl -X POST http://localhost:7070/purchase -H "Content-Type: application/json" -d '{"product":"Camera Drone","price":12000}'
+  ```
+
+* This correctly sends a POST request to `/purchase` endpoint with a JSON body specifying the product and price.
+
+---
+
+
+### Summary of key curl options used:
+
+* `curl [URL]` — by default, sends a GET request to the URL.
+
+* `-X POST` — explicitly sets HTTP method to POST (used to send data).
+
+* `-H "Content-Type: application/json"` — adds HTTP header specifying the request body is JSON.
+
+* `-d '{"product":"Camera Drone","price":12000}'` — the JSON data to send in the body of the POST request.
+
+---
+
+If you want to test adding a new purchase and then check total, this sequence is correct:
+
+```bash
+curl -X POST http://localhost:7070/purchase -H "Content-Type: application/json" -d '{"product":"Camera Drone","price":12000}'
+curl http://localhost:7070/total
+```
+
+This will record the new product and then return the updated total profit.
+
+---
+
+If you want, I can help you build some shell scripts or alias commands to make testing easier! Just say the word.

target/classes/com/test/frontend/app.js

@@ -0,0 +1,54 @@
+// Wait until the DOM (HTML page) is fully loaded
+document.addEventListener("DOMContentLoaded", function () {
+  // Grab form elements and buttons
+  const form = document.getElementById("purchaseForm");
+  const resultDiv = document.getElementById("result");
+  const totalBtn = document.getElementById("totalBtn");
+
+  // 🟩 Handle form submission (Add new Purchase)
+  form.addEventListener("submit", function (event) {
+    event.preventDefault(); // Prevent page refresh
+
+    // Get product and price values from form
+    const product = document.getElementById("product").value;
+    const price = parseFloat(document.getElementById("price").value);
+
+    const data = { product: product, price: price };
+
+    // Send POST request to /purchase endpoint
+    fetch("http://localhost:7070/purchase", {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(data),
+    })
+      .then(function (response) {
+        return response.text(); // Expecting plain text response
+      })
+      .then(function (data) {
+        resultDiv.innerText = data; // Show server response
+        form.reset(); // Clear form inputs
+      })
+      .catch(function (error) {
+        resultDiv.innerText = "Error: " + error; // Show error if any
+      });
+  });
+
+  // 🟦 Handle "Show Total Profit" button click (GET from /total)
+  totalBtn.addEventListener("click", function () {
+    fetch("http://localhost:7070/total")
+      .then((response) => response.json()) // Expect JSON response
+      .then((data) => {
+        // Format and display returned data
+        const output = `
+Name: ${data.customerName}
+Age: ${data.customerAge}
+Region: ${data.customerRegion}
+Total Profit: ₹${data.totalProfit}
+        `;
+        resultDiv.innerText = output;
+      })
+      .catch((error) => {
+        resultDiv.innerText = "Error: " + error; // Display fetch error
+      });
+  });
+});

target/classes/com/test/frontend/index.html

@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8" />
+  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+  <title>Purchase Tracker</title>
+
+  <!-- Link CSS -->
+  <link rel="stylesheet" href="styles.css" />
+
+  <!-- Link JS (corrected attribute typo: 'data-jslicence' to 'data-jslicense') -->
+  <script src="app.js" defer data-jslicense="MIT"></script>
+</head>
+
+<body>
+  <div class="container">
+    <h1>Product Purchase Tracker</h1>
+
+    <!-- Purchase form -->
+    <form id="purchaseForm">
+      <label for="product">Product Name:</label>
+      <input type="text" id="product" name="product" required />
+
+      <label for="price">Price (₹):</label>
+      <input type="number" id="price" name="price" step="0.01" required />
+
+      <button type="submit">Add Purchase</button>
+    </form>
+
+    <!-- Button to fetch total -->
+    <button id="totalBtn">Show Total Profit</button>
+
+    <!-- Result will be shown here -->
+    <div id="result"></div>
+  </div>
+</body>
+</html>

target/classes/com/test/frontend/styles.css

@@ -0,0 +1,28 @@
+body {
+  font-family: sans-serif;
+  background-color: #f4f4f4;
+  padding: 20px;
+}
+
+.container {
+  max-width: 500px;
+  margin: auto;
+  background: white;
+  padding: 20px;
+  border-radius: 8px;
+  box-shadow: 0 0 10px rgba(0, 0, 0, 0.1); /* optional visual polish */
+}
+
+input,
+button {
+  display: block;
+  width: 100%;
+  margin-top: 10px;
+  padding: 8px;
+  font-size: 1rem;
+}
+
+#result {
+  margin-top: 20px;
+  white-space: pre-wrap; /* keep newlines and wrap long lines */
+}

target/maven-status/maven-compiler-plugin/compile/default-compile/createdFiles.lst

@@ -0,0 +1,3 @@
+com/test/PurchaseDAO.class
+com/test/App.class
+com/test/Constructor.class

target/maven-status/maven-compiler-plugin/compile/default-compile/inputFiles.lst

@@ -0,0 +1,3 @@
+/home/arul/apiServerProject/java-project/src/main/java/com/test/App.java
+/home/arul/apiServerProject/java-project/src/main/java/com/test/Constructor.java
+/home/arul/apiServerProject/java-project/src/main/java/com/test/PurchaseDAO.java