java大作业聊天系统数据库设计代码

以下是一个简单的聊天系统数据库设计代码，使用Java编写：

import java.sql.*;

public class ChatSystemDatabase {
    private Connection conn;

    public ChatSystemDatabase(String dbUrl, String username, String password) {
        try {
            conn = DriverManager.getConnection(dbUrl, username, password);
        } catch (SQLException e) {
            System.out.println("Error connecting to database: " + e.getMessage());
        }
    }

    public void createTables() {
        try {
            Statement stmt = conn.createStatement();
            String userTable = "CREATE TABLE users (id INT PRIMARY KEY, username VARCHAR(50), password VARCHAR(50))";
            String messageTable = "CREATE TABLE messages (id INT PRIMARY KEY, senderId INT, receiverId INT, content VARCHAR(500), timestamp TIMESTAMP)";
            stmt.executeUpdate(userTable);
            stmt.executeUpdate(messageTable);
            System.out.println("Tables created successfully!");
        } catch (SQLException e) {
            System.out.println("Error creating tables: " + e.getMessage());
        }
    }

    public void addUser(int id, String username, String password) {
        try {
            String query = "INSERT INTO users (id, username, password) VALUES (?, ?, ?)";
            PreparedStatement pstmt = conn.prepareStatement(query);
            pstmt.setInt(1, id);
            pstmt.setString(2, username);
            pstmt.setString(3, password);
            pstmt.executeUpdate();
            System.out.println("User added successfully!");
        } catch (SQLException e) {
            System.out.println("Error adding user: " + e.getMessage());
        }
    }

    public void addMessage(int id, int senderId, int receiverId, String content, Timestamp timestamp) {
        try {
            String query = "INSERT INTO messages (id, senderId, receiverId, content, timestamp) VALUES (?, ?, ?, ?, ?)";
            PreparedStatement pstmt = conn.prepareStatement(query);
            pstmt.setInt(1, id);
            pstmt.setInt(2, senderId);
            pstmt.setInt(3, receiverId);
            pstmt.setString(4, content);
            pstmt.setTimestamp(5, timestamp);
            pstmt.executeUpdate();
            System.out.println("Message added successfully!");
        } catch (SQLException e) {
            System.out.println("Error adding message: " + e.getMessage());
        }
    }

    public void closeConnection() {
        try {
            conn.close();
            System.out.println("Database connection closed successfully!");
        } catch (SQLException e) {
            System.out.println("Error closing database connection: " + e.getMessage());
        }
    }
}

这个数据库设计包括两个表：一个存储用户信息，另一个存储消息信息。用户表包含用户的ID、用户名和密码，消息表包含消息的ID、发送者ID、接收者ID、消息内容和时间戳。

可以使用该类创建一个数据库连接，创建表，添加用户和消息，以及关闭连接。例如：

ChatSystemDatabase db = new ChatSystemDatabase("jdbc:mysql://localhost:3306/chat_system", "root", "password");
db.createTables();
db.addUser(1, "alice", "password");
db.addUser(2, "bob", "password");
db.addMessage(1, 1, 2, "Hello Bob!", new Timestamp(System.currentTimeMillis()));
db.closeConnection();

这将创建一个名为`chat_system`的MySQL数据库，包含用户表和消息表。然后，它将添加两个用户“Alice”和“Bob”，以及一条消息从Alice发送给Bob。最后，它将关闭数据库连接。

请注意，这只是一个简单的示例，并且可能需要根据实际应用程序的要求进行修改。