天生我材必有用，千金散尽还复来。

一、开发环境

二、数据库设计

2.1、数据库（credit_card_db）

CREATE DATABASE IF NOT EXISTS credit_card_db;
USE credit_card_db;

2.2、用户表（Users）

存储用户的基本信息

CREATE TABLE Users (
    user_id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(255) NOT NULL,
    email VARCHAR(255) NOT NULL,
    password VARCHAR(255) NOT NULL
);

2.3、账户表（Accounts）

存储用户的各个账户信息，包括账户类型和名称

CREATE TABLE Accounts (
    account_id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT,
    account_type ENUM('信用卡', '花呗', '京东金条', '京东白条') NOT NULL,
    account_name VARCHAR(255),
    FOREIGN KEY (user_id) REFERENCES Users(user_id)
);

2.4、额度表（Limits）

存储每个账户的额度信息，包括总额度、固定额度和临时额度。

CREATE TABLE Limits (
    limit_id INT AUTO_INCREMENT PRIMARY KEY,
    account_id INT,
    total_limit DECIMAL(15, 2) NOT NULL,
    fixed_limit DECIMAL(15, 2) NOT NULL,
    temporary_limit DECIMAL(15, 2),
    last_updated TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    FOREIGN KEY (account_id) REFERENCES Accounts(account_id)
);

2.5、交易表（Transactions）

记录所有的交易信息，包括消费、还款和分期。

CREATE TABLE Transactions (
    transaction_id INT AUTO_INCREMENT PRIMARY KEY,
    account_id INT,
    amount DECIMAL(15, 2) NOT NULL,
    transaction_type INT NOT NULL,
    transaction_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    status INT NOT NULL,
    FOREIGN KEY (account_id) REFERENCES Accounts(account_id)
);

2.6、账单表（Bills）

记录每个账户的账单信息，包括账单日期、总金额、待还金额和已还金额

CREATE TABLE Bills (
    bill_id INT AUTO_INCREMENT PRIMARY KEY,
    account_id INT,
    bill_date DATE NOT NULL,
    total_amount DECIMAL(15, 2) NOT NULL,
    amount_due DECIMAL(15, 2) NOT NULL,
    amount_paid DECIMAL(15, 2),
    status INT NOT NULL,
    FOREIGN KEY (account_id) REFERENCES Accounts(account_id)
);

2.7、分期表（Installments）

记录分期交易的详细信息，包括每期的金额和状态

CREATE TABLE Installments (
    installment_id INT AUTO_INCREMENT PRIMARY KEY,
    transaction_id INT,
    installment_amount DECIMAL(15, 2) NOT NULL,
    due_date DATE NOT NULL,
    status INT NOT NULL,
    FOREIGN KEY (transaction_id) REFERENCES Transactions(transaction_id)
);

2.8、账户类型表（AccountsType）

CREATE TABLE AccountsType(
    account_type_id INT PRIMARY KEY,
    account_type_name VARCHAR(255)
)

三、Springboot & MybatisPlus

3.1、添加依赖（pom.xml）

<dependencies>
    <!-- Spring Boot Starter Web -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!-- Spring Boot Starter Data JPA -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>

    <!-- MySQL Connector -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>

    <!-- MyBatis Plus -->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.4.2</version>
    </dependency>

    <!-- Lombok (可选，用于简化代码) -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </version>
</dependencies>

3.2、配置数据库连接（application.yml）

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/credit_card_db?useSSL=false&serverTimezone=UTC
    username: root
    password: root
    driver-class-name: com.mysql.cj.jdbc.Driver

mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

3.3、创建实体类

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

import java.math.BigDecimal;
import java.util.Date;

@Data
@TableName("users")
public class User {
    @TableId(type = IdType.AUTO)
    private Long userId;
    private String username;
    private String email;
    private String password;
}

// 其他实体类（Accounts, Limits, Transactions, Bills, Installments）类似创建

3.4、创建Mapper接口

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.apache.ibatis.annotations.Mapper;

@Mapper
public interface UserMapper extends BaseMapper<User> {
}

// 其他Mapper接口（AccountMapper, LimitMapper, TransactionMapper, BillMapper, InstallmentMapper）类似创建

3.5、创建Service接口和实现类

import com.baomidou.mybatisplus.extension.service.IService;

public interface UserService extends IService<User> {
}

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
}

// 其他Service接口和实现类（AccountService, LimitService, TransactionService, BillService, InstallmentService）类似创建

3.6、创建Controller

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/users")
public class UserController {

    @Autowired
    private UserService userService;

    @GetMapping("/{id}")
    public User getUserById(@PathVariable Long id) {
        return userService.getById(id);
    }

    @PostMapping
    public boolean addUser(@RequestBody User user) {
        return userService.save(user);
    }

    // 其他业务接口（AccountController, LimitController, TransactionController, BillController, InstallmentController）类似创建
}

3.7、运行项目

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

TODO：未完待续...

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