实体类设计-山大软院创新实训项目博客

本文链接：https://blog.youkuaiyun.com/ws_bones/article/details/147741335

在软件开发中，实体类（Entities）是对象关系映射（ORM）的核心组成部分。它们定义了应用程序的数据模型，并将这些数据映射到数据库表。在本篇文章中，我们将探讨实体类设计的基本原则，以及如何在项目开发初期确定所需的实体类。这里，我进行了entities的设计，在我们进行项目的开发时，应当去想想这个项目有哪些实体类。

一.Lombok插件的妙用

Lombok 是一个 Java 库，它通过注解耦合（annotation processing）技术自动生成常用的 Java 代码，如构造函数、getter 和 setter 方法、equals()、hashCode() 和 toString() 方法等。Lombok 旨在减少样板代码的编写，让开发者能够专注于业务逻辑的实现。

主要特性

减少样板代码：自动生成常用的方法，减少手动编写的样板代码量。
提高开发效率：通过减少代码量，加快开发速度，提高开发效率。
易于维护：自动生成的方法在 Lombok 升级时可以自动更新，降低维护成本。
兼容性：Lombok 与大多数 IDE 和构建工具兼容，如 IntelliJ IDEA、Eclipse 和 Maven、Gradle 等。
通俗点讲，就是我们在编写实体类时，不用自己去写setter，getter等方法，方便维护。

具体利用

添加 Lombok 依赖：将 Lombok 库添加到项目的依赖中。对于 Maven 项目，可以在 pom.xml 文件中添加 Lombok 的依赖：


<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.2</version> <!-- 请检查最新版本 -->
    <scope>provided</scope> <!-- 或者 compile -->
</dependency>

编写实体类：

import lombok.Getter;
import lombok.Setter;

@Setter
@Getter
public class User {
   private Long id;
   private String name;
   private String email;
   private String password;
}

上面是一个简单的示例，我们只需要编写类的属性，而通过：

@Setter
@Getter

就可以自动生成set&get方法！

二.数据库实体创建

在MYSQL中，依此执行下列语句来创建实体表。

-- 创建用户表
CREATE TABLE users (
    user_id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL,
    password_hash VARCHAR(128) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- 创建故事表
CREATE TABLE stories (
    story_id INT AUTO_INCREMENT PRIMARY KEY,
    title VARCHAR(255) NOT NULL,
    content TEXT NOT NULL,
    difficulty_level ENUM('easy', 'medium', 'hard') NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- 创建故事学习记录表
CREATE TABLE story_learning_records (
    record_id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT NOT NULL,
    story_id INT NOT NULL,
    learning_date DATE NOT NULL,
    completion_status BOOLEAN NOT NULL,
    FOREIGN KEY (user_id) REFERENCES users(user_id),
    FOREIGN KEY (story_id) REFERENCES stories(story_id)
);

-- 创建语音练习记录表
CREATE TABLE voice_practice_records (
    record_id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT NOT NULL,
    practice_date DATE NOT NULL,
    audio_file_path VARCHAR(255) NOT NULL,
    score FLOAT NOT NULL,
    FOREIGN KEY (user_id) REFERENCES users(user_id)
);

-- 创建翻译练习记录表
CREATE TABLE translation_practice_records (
    record_id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT NOT NULL,
    practice_date DATE NOT NULL,
    original_text TEXT NOT NULL,
    translated_text TEXT NOT NULL,
    grammar_feedback TEXT,
    FOREIGN KEY (user_id) REFERENCES users(user_id)
);

-- 创建学习进度表
CREATE TABLE learning_progress (
    progress_id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT NOT NULL,
    last_updated TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    total_stories_read INT DEFAULT 0,
    avg_voice_score FLOAT DEFAULT 0.0,
    avg_grammar_score FLOAT DEFAULT 0.0,
    personalized_suggestions TEXT,
    FOREIGN KEY (user_id) REFERENCES users(user_id)
);

创建成功后，可以运行：

SHOW TABLES;

来检查是否创建成功，创建成功后显示：

三.代码编写

User

package entity;

import jakarta.persistence.*;
import lombok.Getter;
import lombok.Setter;

import java.sql.Timestamp;

@Setter
@Getter
@Entity
@Table(name = "users")
public class User {
    // Getters and Setters
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long userId;

    @Column(nullable = false, length = 50)
    private String username;

    @Column(nullable = false, length = 100)
    private String email;

    @Column(nullable = false, length = 128)
    private String passwordHash;

    @Column(name = "created_at")
    private Timestamp createdAt;

}

Story

package entity;

import jakarta.persistence.*;
import lombok.Getter;
import lombok.Setter;

import java.sql.Timestamp;

@Setter
@Getter
@Entity
@Table(name = "stories")
public class Story {
    // Getters and Setters
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long storyId;

    @Column(nullable = false)
    private String title;

    @Column(nullable = false)
    private String content;

    @Enumerated(EnumType.STRING)
    @Column(nullable = false)
    private DifficultyLevel difficultyLevel;

    @Column(name = "created_at")
    private Timestamp createdAt;

    // 枚举类型
    public enum DifficultyLevel {
        EASY, MEDIUM, HARD
    }
}

LearningProgress

package entity;

import jakarta.persistence.*;
import lombok.Getter;
import lombok.Setter;

import java.sql.Timestamp;

@Setter
@Getter
@Entity
@Table(name = "learning_progress")
public class LearningProgress {
    // Getters and Setters
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long progressId;

    @ManyToOne
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    @Column(name = "last_updated")
    private Timestamp lastUpdated;

    @Column(name = "total_stories_read", nullable = false)
    private int totalStoriesRead;

    @Column(name = "avg_voice_score", nullable = false)
    private float avgVoiceScore;

    @Column(name = "avg_grammar_score", nullable = false)
    private float avgGrammarScore;

    @Column(name = "personalized_suggestions")
    private String personalizedSuggestions;

}

StoryLearningRecord

package entity;


import jakarta.persistence.*;
import lombok.Getter;
import lombok.Setter;

import java.sql.Date;

@Setter
@Getter
@Entity
@Table(name = "story_learning_records")
public class StoryLearningRecord {
    // Getters and Setters
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long recordId;

    @ManyToOne
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    @ManyToOne
    @JoinColumn(name = "story_id", nullable = false)
    private Story story;

    @Column(name = "learning_date", nullable = false)
    private Date learningDate;

    @Column(name = "completion_status", nullable = false)
    private boolean completionStatus;

}

TranslationPracticeRecord

package entity;

import jakarta.persistence.*;
import lombok.Getter;
import lombok.Setter;

import java.sql.Date;

@Setter
@Getter
@Entity
@Table(name = "translation_practice_records")
public class TranslationPracticeRecord {
    // Getters and Setters
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long recordId;

    @ManyToOne
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    @Column(name = "practice_date", nullable = false)
    private Date practiceDate;

    @Column(name = "original_text", nullable = false)
    private String originalText;

    @Column(name = "translated_text", nullable = false)
    private String translatedText;

    @Column(name = "grammar_feedback")
    private String grammarFeedback;

}

VoicePracticeRecord

package entity;

import jakarta.persistence.*;
import lombok.Getter;
import lombok.Setter;

import java.util.Date;

@Setter
@Getter
@Entity
@Table(name = "voice_practice_records")
public class VoicePracticeRecord {
    // Getters and Setters
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long recordId;

    @ManyToOne
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    @Column(name = "practice_date", nullable = false)
    private Date practiceDate;

    @Column(name = "audio_file_path", nullable = false, length = 255)
    private String audioFilePath;

    @Column(name = "score", nullable = false)
    private float score;

}