Spring Boot simplifies backend development with its embedded servers and auto-configuration. For instance, a basic REST endpoint can be implemented as follows:

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class GymAppLauncher {
    public static void main(String[] args) {
        SpringApplication.run(GymAppLauncher.class, args);
    }

    @GetMapping("/welcome")
    public String showWelcome() {
        return "Welcome to the Gym Management System";
    }
}

This class initializes the application and maps the /welcome endpoint to return a greeting string.

Vue.js enables reactive frontend interfaces. Below is a sample component that displays and updates a message:

<div id="app">
    <h3>{{ greetingText }}</h3>
    <button @click="updateGreeting">Update Text</button>
</div>

<script>
    new Vue({
        el: '#app',
        data: {
            greetingText: 'Initial Greeting'
        },
        methods: {
            updateGreeting() {
                this.greetingText = 'Updated Message';
            }
        }
    });
</script>

Clicking the button triggers an update to the displayed text, showcasing Vue's reactivity.

MyBatis facilitates database operations by separating SQL from Java code. It supports dynamic SQL and caching to enhance performance.

System testing validates functionality and reliability. For example, login testing includes scenarios like valid credentials, incorrect passwords, and empty enputs. A sample test case table is shown below:

Input Data	Expected Outcome	Actual Outcome	Analysis
User: admin, Pass: correct, Code: valid	Login success	Login success	Pass
User: admin, Pass: wrong, Code: valid	Password error	Password error	Pass
User: empty, Pass: correct, Code: valid	Username required	Username required	Pass

User management features, such as adding, editing, and deleting users, are also tested. For adding a user, cases include valid inputs, duplicate usernames, and missing fields.

Testing ensures the system meets design specifications and provides a smooth user experience. All scenarios are evaluated from the user's perspective to identify and resolve issues.

Code examples include authentication logic. Here’s a token generation method:

public String createToken(Long userId, String role) {
    String tokenValue = RandomStringUtils.randomAlphanumeric(32);
    Calendar expiryTime = Calendar.getInstance();
    expiryTime.add(Calendar.HOUR, 1);
    // Store or update token in database
    return tokenValue;
}

An interceptor validates tokens for protected endpoints, returning an error if authentication fails.

The database schema includes tables like member for gym members. An example SQL statement:

CREATE TABLE member (
    id BIGINT AUTO_INCREMENT PRIMARY KEY,
    full_name VARCHAR(100) NOT NULL,
    membership_type VARCHAR(50),
    join_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

This table stores member details with automatic timestamps for record-keeping.