自定义DAO模式实现对数据库的增删改查

1、创建数据库管理类： 

package com.db.daomodule;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DatabaseManager {
    private static DatabaseManager instance;
    private Connection connection;

    private DatabaseManager() {
        // 私有构造函数，禁止外部直接创建实例
    }

    public static synchronized DatabaseManager getInstance() {
        if (instance == null) {
            instance = new DatabaseManager();
        }
        return instance;
    }

    public Connection getConnection() throws SQLException {
        if (connection == null || connection.isClosed()) {
            // 数据库连接配置
            String url = "jdbc:mysql://localhost:3306/test_data";
            String username = "root";
            String password = "admin";

            connection = DriverManager.getConnection(url, username, password);
        }

        return connection;
    }
}

2、创建WordsInfoDao接口：

package com.db.daomodule;
import java.util.List;
//创建WordsInfoDao接口：
public interface WordsInfoDao {
	
    List<WordsInfo> getAllWords();

    WordsInfo getWordsById(int id);

    void addWords(WordsInfo words);

    void updateWords(WordsInfo words);

    void deleteWords(int id);
}

 3、定义一个WordsInfo类来表示words_info表的数据：

​
public class WordsInfo {
    private int id;
    private String engName;
    private String chiVal;
    private String lastUsedTime;
    private int usedTimes;
    private String createdTime;
    private int priority;

    // getter和setter方法

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getEngName() {
        return engName;
    }

    public void setEngName(String engName) {
        this.engName = engName;
    }

    public String get