Java 開発における一般的なデータベース パフォーマンスの問題と解決策

import java.sql.Connection;
import java.sql.SQLException;
import javax.sql.DataSource;
import com.mchange.v2.c3p0.ComboPooledDataSource;

public class DBUtil {
    private static DataSource ds = null;
    static {
        ds = new ComboPooledDataSource(); // 配置连接池
    }

    public static Connection getConnection() throws SQLException {
        return ds.getConnection(); // 从连接池获取连接
    }
    
    // 其他数据库操作方法...
}

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class CacheUtil {
    private static Map<String, Object> cache = new ConcurrentHashMap<>();

    public static Object getFromCache(String key) {
        return cache.get(key);
    }

    public static void putInCache(String key, Object value) {
        cache.put(key, value);
    }

    // 其他缓存操作方法...
}

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDao {
    public List<User> getUsersByAge(int age) throws SQLException {
        List<User> users = new ArrayList<>();
        Connection conn = DBUtil.getConnection();
        PreparedStatement stmt = conn.prepareStatement("SELECT * FROM user WHERE age=?");
        stmt.setInt(1, age);
        ResultSet rs = stmt.executeQuery();
        
        while (rs.next()) {
            User user = new User();
            // 设置用户属性...
            users.add(user);
        }
        
        rs.close();
        stmt.close();
        conn.close();
        
        return users;
    }
    
    // 其他数据库操作方法...
}