Detailed explanation of the actual combat of Java online car-hailing project

In online car-hailing projects, the order grabbing function is a very critical part. It determines whether the driver can respond to passenger orders in a timely manner and improve the operational efficiency of the entire platform. This article will introduce in detail how to use Java to implement the order grabbing function of online ride-hailing projects, and provide a complete code example so that readers can directly run and refer to it.

1. Project background and requirements analysis

1. Project background

With the rapid development of mobile Internet, online car-hailing has become an important choice for people's daily travel. An efficient online ride-hailing platform not only needs to provide good user registration, login, order placing functions, but also needs to ensure that the driver can respond quickly to passengers' orders, that is, to achieve the order grab function.

2. Requirements Analysis

Passenger side: Passengers can publish orders and check order status (such as orders to be snatched, orders already snatched, completed, etc.).
Driver's side: The driver can view the current nearby order and choose to grab the order. After the order is successfully grabbed, the driver needs to go to the passenger designated location to pick up the passenger.
Backend management: The administrator can view all orders and driver status and perform necessary scheduling and management.

2. Technology selection and architecture design

1. Technical selection

rear end: Java (Spring Boot Framework)
database：MySQL
cache: Redis (used to implement distributed locks to ensure the atomicity of order grab operations)
front end: (passenger and driver interface)
Communication Protocol: HTTP/HTTPS (using RESTful API for front-end communication)

2. Architecture design

Passenger side: Responsible for receiving passenger input and sending order information to the backend server.
Driver's side: Display nearby order list, provide order grabbing function, and send order grab requests to the backend server.
Backend server: Process passenger and driver requests, store order information, manage driver status, and realize order grabbing logic.
database: Store information such as passengers, drivers, orders, etc.
Redis: Used to implement distributed locks to ensure that only one driver can successfully grab the order in concurrency situations.

III. Database design

1. Passenger watch (passenger)

Field name	type	Remark
id	INT	Primary key, self-increase
name	VARCHAR	Passenger name
phone	VARCHAR	Passenger mobile number
password	VARCHAR	Passenger password
address	VARCHAR	Passenger address

2. Driver form (driver)

Field name	type	Remark
id	INT	Primary key, self-increase
name	VARCHAR	Driver's name
phone	VARCHAR	Driver's mobile number
password	VARCHAR	Driver password
status	INT	Driver status (0: Idle, 1: Order has been grabbed)

3. Order form (order)

Field name	type	Remark
id	INT	Primary key, self-increase
passenger_id	INT	Passenger ID
start_address	VARCHAR	Starting address
end_address	VARCHAR	Destination address
status	INT	Order status (0: order to be snatched, 1: order has been snatched, 2: completed)
driver_id	INT	Driver ID of the order grabbing (empty means that the order is to be grabbed)

4. Backend implementation

1. Create Spring Boot Project

Use Spring Initializr to create a Spring Boot project and select the required dependencies (such as Spring Web, Spring Data JPA, MySQL Driver, etc.).

2. Configure database connections

existConfigure database connection information in the file:

=jdbc:mysql://localhost:3306/ride_sharing?useSSL=false&serverTimezone=UTC
=root
=root
-auto=update
-sql=true

3. Create entity class

// 
@Entity
public class Passenger {
    @Id
    @GeneratedValue(strategy = )
    private Long id;
    private String name;
    private String phone;
    private String password;
    private String address;
    // Getters and Setters
}
// 
@Entity
public class Driver {
    @Id
    @GeneratedValue(strategy = )
    private Long id;
    private String name;
    private String phone;
    private String password;
    private Integer status = 0; // 0: Idle, 1: Order has been grabbed    // Getters and Setters
}
// 
@Entity
public class Order {
    @Id
    @GeneratedValue(strategy = )
    private Long id;
    private Long passengerId;
    private String startAddress;
    private String endAddress;
    private Integer status = 0; // 0: Order to be grabbed, 1: Order to be grabbed, 2: Completed    private Long driverId; // It is empty to indicate that the order is to be grabbed    // Getters and Setters
}

4. Create a Repository interface

// 
public interface PassengerRepository extends JpaRepository<Passenger, Long> {}
// 
public interface DriverRepository extends JpaRepository<Driver, Long> {}
// 
public interface OrderRepository extends JpaRepository<Order, Long> {}

5. Implement order grab logic

In order to achieve the atomicity of the order grab function, we need to use Redis to implement distributed locking. The following is the Service class that implements the order grab logic:

import ;
import ;
import ;
import ;
import ;
import ;
import ;
@Service
public class OrderService {
    @Autowired
    private OrderRepository orderRepository;
    @Autowired
    private DriverRepository driverRepository;
    @Autowired
    private StringRedisTemplate redisTemplate;
    private static final String LOCK_KEY = "order_lock:";
    private static final int LOCK_EXPIRE_TIME = 10; // Lock expiration time (seconds)    @Transactional
    public String grabOrder(Long driverId, Long orderId) {
        // Use Redis to implement distributed lock        String lockKey = LOCK_KEY + orderId;
        Boolean lock = ().setIfAbsent(lockKey, "1", LOCK_EXPIRE_TIME, );
        if (lock == null || !lock) {
            return "The order failed and the order has been snatched by other drivers";
        }
        try {
            // Inquiry of order information            Optional&lt;Order&gt; optionalOrder = (orderId);
            if (!()) {
                return "The order does not exist";
            }
            Order order = ();
            if (() != 0) {
                return "Catch order failed, order status is abnormal";
            }
            // Update order status and driver ID            (1);
            (driverId);
            (order);
            // Update driver status            Optional&lt;Driver&gt; optionalDriver = (driverId);
            if (()) {
                Driver driver = ();
                (1);
                (driver);
            }
            return "Successful order grab";
        } finally {
            // Release the lock            (lockKey);
        }
    }
    public List&lt;Order&gt; getNearbyOrders(Double latitude, Double longitude) {
        // Query nearby orders based on latitude and longitude (there is a simplified processing here, and only return all orders to be snatched)        return (0);
    }
}

6. Create Controller class

WillOrderControllerClassicgetNearbyOrdersThe method is supplemented and ensures that its logic matches the order grab function. In addition, in order to be closer to actual needs,getNearbyOrdersThe method should be able to filter nearby orders based on the driver's location (latitude and longitude), although in practical applications this often involves more complex geospatial queries. But in this example, for simplicity, we will only return all orders to be grabbed and indicate in the comments how more complex logic should be implemented.

import ;
import .*;
import ;
@RestController
@RequestMapping("/api/orders")
public class OrderController {
    @Autowired
    private OrderService orderService;
    @PostMapping("/grab")
    public String grabOrder(@RequestParam Long driverId, @RequestParam Long orderId) {
        return (driverId, orderId);
    }
    @GetMapping("/nearby")
    public List&lt;Order&gt; getNearbyOrders(@RequestParam Double latitude, @RequestParam Double longitude) {
        // In actual applications, this should include query logic based on geographic location.        // For example, use geospatial indexes in the database or third-party geospatial search services.        // But to simplify the example, we only return all orders to be grabbed.        // Note: In a production environment, it may not be best practice to directly return all orders to be snatched.        // Because this may expose too much information to the driver and increase the load on the backend server.        // Suppose we have a way to calculate the radius of nearby orders based on the driver's location (e.g. 5 km)        // But since we simplified geospatial query, this method is not implemented here.        // Return a filtered order list, including only orders with the status "Please grab"        // In actual application, there should be a more complex query here, based on the driver's location and the order's location.        return (0); // 0 indicates the status of orders to be snatched        // Note: In the above call, we passed the status code 0 as a parameter, but in the getNearbyOrders method of OrderService        // We don't actually use this parameter to filter (because our example simplifies geospatial queries).        // In the actual OrderService implementation, you should modify this method to accept status code as a parameter and filter the order accordingly.        // For example: return (0, latitude, longitude, radius);        // The withinRadius method here is a hypothetical method for performing geospatial queries.    }
}

7. Configure security (such as Spring Security)

To ensure the security of the system, user authentication and authorization are usually required.

Configuration class：

import ;
import ;
import ;
import ;
import ;
import ;
import ;
@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .authorizeRequests()
                .antMatchers("/orders/grab/**").authenticated() // Authentication is required to access the order grab interface                .anyRequest().permitAll()
                .and()
            .formLogin()
                .permitAll()
                .and()
            .logout()
                .permitAll();
    }
    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }
}

8. Create Service Class

The Service class is used to process business logic, such as verifying driver qualifications, updating order status, etc.

：

import ;
import ;
import ;
import ;
@Service
public class OrderService {
    @Autowired
    private OrderRepository orderRepository;
    @Autowired
    private DriverRepository driverRepository;
    @Transactional
    public boolean grabOrder(Long orderId, Long driverId) {
        Optional<Order> optionalOrder = (orderId);
        if (!() || ().getStatus() != ) {
            return false;
        }
        Optional<Driver> optionalDriver = (driverId);
        if (!()) {
            return false;
        }
        Order order = ();
        (());
        ();
        (order);
        return true;
    }
}

9. Configure message queues (such as RabbitMQ or Kafka)

For the order grab function, using message queues can improve the system's concurrency processing capability and response speed.

RabbitMQ configuration class:

import ;
import ;
import ;
import ;
import ;
import ;
import ;
@Configuration
public class RabbitMQConfig {
    public static final String QUEUE_NAME = "orderQueue";
    @Bean
    Queue queue() {
        return new Queue(QUEUE_NAME, true);
    }
    @Bean
    SimpleMessageListenerContainer container(ConnectionFactory connectionFactory,
                                             MessageListenerAdapter listenerAdapter) {
        SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
        (connectionFactory);
        (QUEUE_NAME);
        (listenerAdapter);
        return container;
    }
    @Bean
    MessageListenerAdapter listenerAdapter(OrderService orderService) {
        return new MessageListenerAdapter(orderService, "processOrder");
    }
    @Bean
    RabbitTemplate rabbitTemplate(ConnectionFactory connectionFactory) {
        return new RabbitTemplate(connectionFactory);
    }
}

Add a method to process messages in OrderService:

import ;
import ;
import ;
@Service
public class OrderService {
    // Previous code...    @Autowired
    private RabbitTemplate rabbitTemplate;
    public void publishOrder(Order order) {
        (RabbitMQConfig.QUEUE_NAME, order);
    }
    public void processOrder(Order order) {
        // Logical processing, such as updating order status to allocated, etc.        // Here you can call the grabOrder method or other logic    }
}

10. Unit Testing

Write unit tests to verify your order grab logic.

：

import ;
import ;
import ;
import ;
import ;
import static .*;
import static .*;
@ExtendWith()
public class OrderServiceTest {
    @Mock
    private OrderRepository orderRepository;
    @Mock
    private DriverRepository driverRepository;
    @InjectMocks
    private OrderService orderService;
    @Test
    public void testGrabOrderSuccess() {
        Order order = new Order();
        (1L);
        ();
        Driver driver = new Driver();
        (1L);
        when((1L)).thenReturn((order));
        when((1L)).thenReturn((driver));
        boolean result = (1L, 1L);
        assertTrue(result);
        verify(orderRepository, times(1)).save(any());
    }
    @Test
    public void testGrabOrderOrderNotFound() {
        when((1L)).thenReturn(());
        boolean result = (1L, 1L);
        assertFalse(result);
        verify(orderRepository, never()).save(any());
    }
    // More tests...}

11. Logging

Use logging libraries such as SLF4J and Logback to record critical operations.

Configure Logback in:

=DEBUG

Logging in the Service class:

import org.;
import org.;
@Service
public class OrderService {
    private static final Logger logger = ();
    // Previous code...    @Transactional
    public boolean grabOrder(Long orderId, Long driverId) {
        ("Attempting to grab order {} by driver {}", orderId, driverId);
        Optional&lt;Order&gt; optionalOrder = (orderId);
        if (!() || ().getStatus() != ) {
            ("Order {} is not available or does not exist", orderId);
            return false;
        }
        Optional&lt;Driver&gt; optionalDriver = (driverId);
        if (!()) {
            ("Driver {} does not exist", driverId);
            return false;
        }
        Order order = ();
        (());
        ();
        (order);
        ("Order {} successfully grabbed by driver {}", orderId, driverId);
        return true;
    }
}

12. Deployment and Operation and Maintenance

Finally, consider how to deploy and operate your application, including containerization using Docker, configuring CI/CD pipelines, etc.

These steps and code examples provide a complete framework for implementing a ride-hailing project that includes order grabbing. Of course, depending on the specific needs, you may need to adjust or add more features.

5. Front-end implementation

In the front-end part of the Java online ride-hailing project that implements the order grab function, you can usually use a front-end framework such as React or Angular to build a user interface. For simplicity, here we use React and Redux to implement a basic front-end application that allows drivers to view orders and grab orders.

1. Project structure

Assume that the project structure is as follows:

my-ridesharing-app/
├── public/
│   ├── 
│   └── ...
├── src/
│   ├── actions/
│   │   └── 
│   ├── components/
│   │   ├── 
│   │   ├── 
│   │   └── 
│   ├── reducers/
│   │   └── 
│   ├── store/
│   │   └── 
│   ├── 
│   └── ...
├── 
└── ...

2. Installation dependencies

First, make sure you have installed and npm, and then run the following command in the project root directory to initialize the React project and install the necessary dependencies:

npx create-react-app my-ridesharing-app
cd my-ridesharing-app
npm install redux react-redux redux-thunk axios

3. Implement front-end code

（1） src/store/- Configure the Redux Store

import { createStore, applyMiddleware } from 'redux';
import thunk from 'redux-thunk';
import rootReducer from '../reducers';
const store = createStore(rootReducer, applyMiddleware(thunk));
export default store;

（2）src/reducers/- Define Reducer

const initialState = {
  orders: [],
  loading: false,
  error: null,
};
const fetchOrdersSuccess = (state, action) => ({
  ...state,
  orders: ,
  loading: false,
  error: null,
});
const fetchOrdersFailure = (state, action) => ({
  ...state,
  loading: false,
  error: ,
});
const grabOrderSuccess = (state, action) => {
  const updatedOrders = (order =>
     ===  ? { ...order, grabbed: true } : order
  );
  return {
    ...state,
    orders: updatedOrders,
  };
};
const orderReducer = (state = initialState, action) => {
  switch () {
    case 'FETCH_ORDERS_REQUEST':
      return {
        ...state,
        loading: true,
      };
    case 'FETCH_ORDERS_SUCCESS':
      return fetchOrdersSuccess(state, action);
    case 'FETCH_ORDERS_FAILURE':
      return fetchOrdersFailure(state, action);
    case 'GRAB_ORDER_SUCCESS':
      return grabOrderSuccess(state, action);
    default:
      return state;
  }
};
export default orderReducer;

（3）src/actions/- Define Action Creators

import axios from 'axios';
export const fetchOrders = () =&gt; async dispatch =&gt; {
  dispatch({ type: 'FETCH_ORDERS_REQUEST' });
  try {
    const response = await ('/api/orders'); // Assume the backend API address    dispatch({ type: 'FETCH_ORDERS_SUCCESS', payload:  });
  } catch (error) {
    dispatch({ type: 'FETCH_ORDERS_FAILURE', payload:  });
  }
};
export const grabOrder = orderId =&gt; async dispatch =&gt; {
  try {
    const response = await (`/api/orders/${orderId}/grab`); // Assume the backend API address    dispatch({ type: 'GRAB_ORDER_SUCCESS', payload:  });
  } catch (error) {
    ('Grab order failed:', );
  }
};

（4）src/components/- Line Item Component

import React from 'react';
import { useDispatch } from 'react-redux';
import { grabOrder } from '../actions/orderActions';
const OrderItem = ({ order }) => {
  const dispatch = useDispatch();
  const handleGrab = () => {
    dispatch(grabOrder());
  };
  return (
    <div>
      <h3>{}</h3>
      <p>Pickup: {}</p>
      <p>Dropoff: {}</p>
      <button onClick={handleGrab} disabled={}>
        { ? 'Grabbed' : 'Grab Order'}
      </button>
    </div>
  );
};
export default OrderItem;

（5） src/components/- Order List Component

import React, { useEffect } from 'react';
import { useDispatch, useSelector } from 'react-redux';
import { fetchOrders } from '../actions/orderActions';
import OrderItem from './OrderItem';
const OrderList = () => {
  const dispatch = useDispatch();
  const { orders, loading, error } = useSelector(state => );
  useEffect(() => {
    dispatch(fetchOrders());
  }, [dispatch]);
  if (loading) return <div>Loading...</div>;
  if (error) return <div>Error: {error}</div>;
  return (
    <div>
      <h2>Orders</h2>
      {(order => (
        <OrderItem key={} order={order} />
      ))}
    </div>
  );
};
export default OrderList;

（6）src/components/- Main application component

import React from 'react';
import OrderList from './OrderList';
import { Provider } from 'react-redux';
import store from '../store';
const App = () => (
  <Provider store={store}>
    <div className="App">
      <h1>Ridesharing App</h1>
      <OrderList />
    </div>
  </Provider>
);
export default App;

（7） src/- Entry file

import React from 'react';
import ReactDOM from 'react-dom';
import './';
import App from './components/App';
import reportWebVitals from './reportWebVitals';
(
  <>
    <App />
  </>,
  ('root')
);
reportWebVitals();

4. Backend API

Note that the above code assumes that the backend API exists and provides the following two endpoints:

（1）GET /api/orders- Get all uncrawled orders.

（2）POST /api/orders/:orderId/grab- Crawl the specified order.

You need to implement these API endpoints on the backend and make sure they return the correct data.

5. Run the application

Run the following command in the project root directory to start the React application:

npm start

This will start the development server and open your app in your browser. You should be able to see an order list and you can click the "Grab Order" button to grab the order.

The above is a simple React front-end implementation, used to implement the order grabbing function in online ride-hailing projects. You can further expand and optimize this application according to actual needs.

In the actual combat of Java online ride-hailing project, implementing the order grabbing function is a core and complex part. In addition to the several main parts you mentioned (project background and requirements analysis, technology selection and architecture design, database design, back-end implementation, and front-end implementation), the following key content is usually required to ensure the integrity and robustness of the project:

VI. System testing

Unit Testing: Write unit test code for each module implemented in the backend to ensure that the functions of each module are normal.
Integration Testing: After integrating each module, conduct overall testing to ensure that the overall function of the system is normal.
Stress test: Simulate high concurrency scenarios and test the performance and stability of the system under high concurrent operations such as order grabbing.
Safety Testing: Test the security of the system to ensure that user data and order information are not leaked or tampered with.

7. Performance optimization

Code optimization: Optimize the backend code to improve the execution efficiency and readability of the code.
Database optimization: Perform query optimization, index optimization, etc. on the database to improve the query speed and response capabilities of the database.
Cache Policy: Use caching technologies such as Redis to reduce access pressure to the database and improve the system's response speed.

8. Deployment and Operation and Maintenance

System deployment: Deploy the system to a server or cloud platform to ensure that the system can run normally.
Operation and maintenance monitoring: Monitor the system, detect and handle system abnormalities and faults in a timely manner.
Log Management: Manage system logs to ensure the integrity and readability of the logs, and facilitate subsequent problem investigation and performance analysis.

9. Document writing

Technical Documentation: Write detailed technical documents, including system architecture design, database design, interface documents, etc., to facilitate subsequent development and maintenance.
User Manual: Write a user manual to guide users how to use the system, including the system's function introduction, operation process, etc.

10. Project summary and reflection

Project Summary: Summarize the entire project, including the completion status of the project, the problems encountered and solutions, etc.
Experience reflection: Reflect on the project's experience, summarize the gains and losses in the project development process, and provide reference for subsequent project development.

To sum up, in addition to realizing the core part of the order grabbing function, a complete Java online ride-hailing project also needs to consider key contents such as system testing, performance optimization, deployment and operation and maintenance, document writing, and project summary and reflection. These contents are of great significance to ensure successful delivery and subsequent maintenance of projects.

This is the article about the actual implementation of the Java online car-hailing project. This is all about this article. For more related Java order grabbing content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!