第2篇：数据持久化实战
在上一篇中，我们构建了一个基于内存存储的食谱助手。说实话，内存存储虽然简单，但有个致命问题：程序一重启，数据就全没了。
所以这篇我们要解决数据持久化的问题，将食谱助手从内存存储升级到SQLite数据库。
项目结构重组
先把项目结构整理得更清晰一些。之前我们所有代码都在一个文件里，现在按功能分模块：
mkdir -p recipe-assistant/app recipe-assistant/data
cd recipe-assistant
touch app/__init__.py app/main.py app/models.py
新的目录结构：
recipe-assistant/app/__init__.pymain.py # 主应用入口（包含所有MCP组件）models.py # 数据模型和数据库管理data/recipes.db # SQLite数据库文件bb
重要说明：FastMCP不支持模块化的方式（如include_router），所有的资源、工具和提示词组件都必须定义在同一个FastMCP实例上。因此我们将所有MCP组件都放在main.py中。
数据库设计
创建 app/models.py，定义数据模型和数据库操作：
# app/models.py
from pydantic import BaseModel
from typing import List, Optional, Dict
import sqlite3
import json
import os# 数据模型定义（与第1篇保持一致）
class Ingredient(BaseModel):name: strquantity: strclass Recipe(BaseModel):id: strname: strcuisine: strdescription: stringredients: List[Ingredient]steps: List[str]difficulty: strclass UserPreference(BaseModel):user_id: strfavorite_cuisines: List[str]dietary_restrictions: List[str]cooking_skill: str# 数据库管理类
class DatabaseManager:def __init__(self, db_path="data/recipes.db"):self.db_path = db_pathself.conn = Noneself.initialize_db()def get_connection(self):if self.conn is None:# 确保数据目录存在os.makedirs(os.path.dirname(self.db_path), exist_ok=True)self.conn = sqlite3.connect(self.db_path)self.conn.execute("PRAGMA foreign_keys = ON")self.conn.row_factory = sqlite3.Rowreturn self.conndef initialize_db(self):"""创建数据库表并导入第1篇的示例数据"""conn = self.get_connection()cursor = conn.cursor()# 创建食谱表cursor.execute('''CREATE TABLE IF NOT EXISTS recipes (id TEXT PRIMARY KEY,name TEXT NOT NULL,cuisine TEXT NOT NULL,description TEXT,ingredients TEXT NOT NULL,steps TEXT NOT NULL,difficulty TEXT NOT NULL)''')# 创建用户偏好表cursor.execute('''CREATE TABLE IF NOT EXISTS user_preferences (user_id TEXT PRIMARY KEY,favorite_cuisines TEXT NOT NULL,dietary_restrictions TEXT NOT NULL,cooking_skill TEXT NOT NULL)''')conn.commit()# 导入第1篇的示例数据self.import_data()def import_data(self):"""导入第1篇的示例数据"""conn = self.get_connection()cursor = conn.cursor()# 检查是否已有数据cursor.execute("SELECT COUNT(*) FROM recipes")count = cursor.fetchone()[0]if count == 0:# 第1篇的示例食谱数据recipes = [{"id": "recipe_001","name": "宫保鸡丁","cuisine": "川菜","description": "经典川菜，麻辣鲜香","ingredients": [{"name": "鸡胸肉", "quantity": "300g"},{"name": "花生米", "quantity": "50g"},{"name": "干辣椒", "quantity": "10个"},{"name": "花椒", "quantity": "1茶匙"},{"name": "葱", "quantity": "2根"},{"name": "姜", "quantity": "3片"},{"name": "蒜", "quantity": "3瓣"}],"steps": ["鸡胸肉切丁，用料酒、生抽、淀粉腌制15分钟","热锅凉油，放入花椒和干辣椒爆香","加入鸡丁翻炒至变色","加入葱姜蒜继续翻炒","加入调好的宫保汁炒匀","最后加入花生米炒匀即可"],"difficulty": "中等"},{"id": "recipe_002","name": "番茄炒蛋","cuisine": "家常菜","description": "简单易做的家常菜","ingredients": [{"name": "番茄", "quantity": "2个"},{"name": "鸡蛋", "quantity": "3个"},{"name": "葱", "quantity": "适量"},{"name": "盐", "quantity": "适量"},{"name": "糖", "quantity": "少许"}],"steps": ["番茄切块，鸡蛋打散","热锅倒油，倒入鸡蛋炒熟盛出","锅中再倒少许油，放入番茄翻炒","番茄出汁后加入盐和糖调味","倒入炒好的鸡蛋翻炒均匀","撒上葱花即可"],"difficulty": "简单"}]# 插入食谱数据for recipe in recipes:cursor.execute('''INSERT INTO recipes (id, name, cuisine, description, ingredients, steps, difficulty)VALUES (?, ?, ?, ?, ?, ?, ?)''', (recipe["id"],recipe["name"],recipe["cuisine"],recipe["description"],json.dumps(recipe["ingredients"], ensure_ascii=False),json.dumps(recipe["steps"], ensure_ascii=False),recipe["difficulty"]))# 插入示例用户偏好preferences = {"user_001": {"favorite_cuisines": ["川菜"],"dietary_restrictions": ["少油", "少盐"],"cooking_skill": "初级"},"user_002": {"favorite_cuisines": ["家常菜"],"dietary_restrictions": ["健康"],"cooking_skill": "初级"}}for user_id, prefs in preferences.items():cursor.execute('''INSERT INTO user_preferences (user_id, favorite_cuisines, dietary_restrictions, cooking_skill)VALUES (?, ?, ?, ?)''', (user_id,json.dumps(prefs["favorite_cuisines"], ensure_ascii=False),json.dumps(prefs["dietary_restrictions"], ensure_ascii=False),prefs["cooking_skill"]))conn.commit()print("示例数据导入完成")# 食谱相关操作def get_all_recipes(self):"""获取所有食谱"""conn = self.get_connection()cursor = conn.cursor()cursor.execute("SELECT * FROM recipes")rows = cursor.fetchall()recipes = []for row in rows:recipe = {"id": row["id"],"name": row["name"],"cuisine": row["cuisine"],"description": row["description"],"ingredients": json.loads(row["ingredients"]),"steps": json.loads(row["steps"]),"difficulty": row["difficulty"]}recipes.append(recipe)return recipesdef get_recipe_by_id(self, recipe_id: str):"""根据ID获取食谱"""conn = self.get_connection()cursor = conn.cursor()cursor.execute("SELECT * FROM recipes WHERE id = ?", (recipe_id,))row = cursor.fetchone()if row:return {"id": row["id"],"name": row["name"],"cuisine": row["cuisine"],"description": row["description"],"ingredients": json.loads(row["ingredients"]),"steps": json.loads(row["steps"]),"difficulty": row["difficulty"]}return Nonedef search_recipes_by_ingredient(self, ingredient: str):"""根据食材搜索食谱"""conn = self.get_connection()cursor = conn.cursor()cursor.execute("SELECT * FROM recipes WHERE ingredients LIKE ?", (f'%{ingredient}%',))rows = cursor.fetchall()recipes = []for row in rows:recipe = {"id": row["id"],"name": row["name"],"cuisine": row["cuisine"],"description": row["description"],"ingredients": json.loads(row["ingredients"]),"steps": json.loads(row["steps"]),"difficulty": row["difficulty"]}recipes.append(recipe)return recipes# 用户偏好相关操作def get_user_preferences(self, user_id: str):"""获取用户偏好"""conn = self.get_connection()cursor = conn.cursor()cursor.execute("SELECT * FROM user_preferences WHERE user_id = ?", (user_id,))row = cursor.fetchone()if row:return {"user_id": row["user_id"],"favorite_cuisines": json.loads(row["favorite_cuisines"]),"dietary_restrictions": json.loads(row["dietary_restrictions"]),"cooking_skill": row["cooking_skill"]}return None# 全局数据库实例
db = DatabaseManager()def _get_all_recipes() -> Dict:"""获取所有食谱数据"""try:recipes = db.get_all_recipes()return {"success": True,"recipes": recipes,"count": len(recipes)}except Exception as e:return {"success": False,"error": f"获取食谱数据失败: {str(e)}"}def _get_recipe_by_id(recipe_id: str) -> Dict:"""根据ID获取特定食谱"""try:recipe = db.get_recipe_by_id(recipe_id)if recipe:return {"success": True,"recipe": recipe}else:return {"success": False,"error": f"未找到ID为{recipe_id}的食谱"}except Exception as e:return {"success": False,"error": f"获取食谱失败: {str(e)}"}def _get_user_preferences(user_id: str) -> Dict:"""获取用户偏好数据"""try:preferences = db.get_user_preferences(user_id)if preferences:return {"success": True,"preferences": preferences}else:return {"success": False,"error": f"未找到ID为{user_id}的用户"}except Exception as e:return {"success": False,"error": f"获取用户偏好失败: {str(e)}"}def _search_recipes_by_ingredient(ingredient: str) -> Dict:"""根据食材查询食谱"""try:if not ingredient or not ingredient.strip():return {"success": False,"error": "请提供有效的食材名称"}recipes = db.search_recipes_by_ingredient(ingredient.strip())if recipes:return {"success": True,"message": f"找到了{len(recipes)}个包含{ingredient}的食谱","recipes": recipes}else:return {"success": True,"message": f"抱歉，没有找到包含{ingredient}的食谱","recipes": []}except Exception as e:return {"success": False,"error": f"查询食谱时出错: {str(e)}"}def _recommend_recipes(user_id: str, available_ingredients: List[str] = None) -> Dict:"""根据用户偏好推荐食谱"""try:# 获取用户偏好user_prefs = db.get_user_preferences(user_id)if not user_prefs:return {"success": False,"error": f"未找到ID为{user_id}的用户偏好"}# 获取所有食谱all_recipes = db.get_all_recipes()recommended_recipes = []for recipe in all_recipes:# 根据用户喜好的菜系过滤if recipe["cuisine"] in user_prefs["favorite_cuisines"]:# 如果提供了可用食材，检查是否匹配if available_ingredients:recipe_ingredients = [ing["name"] for ing in recipe["ingredients"]]if any(avail_ing in recipe_ingredients for avail_ing in available_ingredients):recommended_recipes.append(recipe)else:recommended_recipes.append(recipe)return {"success": True,"message": f"为您推荐了{len(recommended_recipes)}道菜","recipes": recommended_recipes[:5] # 限制返回数量}except Exception as e:return {"success": False,"error": f"推荐食谱时出错: {str(e)}"}
这个数据库管理类把之前内存中的操作都移到了SQLite里。
主应用入口
现在创建 app/main.py，将所有MCP组件集中在一个文件中：
# app/main.py
from fastmcp import FastMCP
from typing import Dict, List
from .models import (_get_all_recipes, _get_recipe_by_id, _get_user_preferences,_search_recipes_by_ingredient,_recommend_recipes
)# 创建主应用实例
mcp = FastMCP("RecipeAssistant")# 资源组件
@mcp.resource("recipes://all")
def get_all_recipes() -> Dict:"""获取所有食谱数据Returns:包含所有食谱的字典"""return _get_all_recipes()@mcp.resource("recipes://{recipe_id}")
def get_recipe_by_id(recipe_id: str) -> Dict:"""根据ID获取特定食谱Args:recipe_id: 食谱IDReturns:食谱详细信息"""return _get_recipe_by_id(recipe_id)@mcp.resource("users://{user_id}/preferences")
def get_user_preferences(user_id: str) -> Dict:"""获取用户偏好数据Args:user_id: 用户IDReturns:用户偏好数据"""return _get_user_preferences(user_id)# 工具组件
@mcp.tool()
def search_recipes_by_ingredient(ingredient: str) -> Dict:"""根据食材查询食谱Args:ingredient: 食材名称Returns:包含匹配食谱的字典"""return _search_recipes_by_ingredient(ingredient)@mcp.tool()
def recommend_recipes(user_id: str, available_ingredients: List[str] = None) -> Dict:"""根据用户偏好和可用食材推荐食谱Args:user_id: 用户IDavailable_ingredients: 可用食材列表（可选）Returns:包含推荐食谱的字典"""return _recommend_recipes(user_id, available_ingredients)# 提示词组件
@mcp.prompt()
def generate_recipe_search_response(ingredient: str) -> str:"""生成食谱查询的回复Args:ingredient: 食材名称Returns:格式化的回复文本"""search_result = _search_recipes_by_ingredient(ingredient)if not search_result["success"]:return f"抱歉，查询食谱时出现了问题：{search_result.get('error', '未知错误')}"recipes = search_result["recipes"]if not recipes:return f"抱歉，我没有找到包含{ingredient}的食谱。请尝试其他食材。"# 生成回复文本response = f"我找到了{len(recipes)}个包含{ingredient}的食谱：\n\n"for i, recipe in enumerate(recipes, 1):response += f"{i}. {recipe['name']} - {recipe['description']}\n"response += f" 难度：{recipe['difficulty']}\n"response += f" 主要食材：{', '.join(ing['name'] for ing in recipe['ingredients'][:3])}\n\n"response += f"想了解某个食谱的详细做法，请告诉我食谱的编号。"return response@mcp.prompt()
def generate_recipe_details(recipe_id: str) -> str:"""生成食谱详细信息的回复Args:recipe_id: 食谱IDReturns:格式化的食谱详情"""recipe_result = _get_recipe_by_id(recipe_id)if not recipe_result["success"]:return f"抱歉，无法获取食谱详情：{recipe_result.get('error', '未知错误')}"recipe = recipe_result["recipe"]# 生成详细食谱信息response = f"# {recipe['name']}\n\n"response += f"{recipe['description']}\n\n"response += "## 食材准备\n\n"for ing in recipe["ingredients"]:response += f"- {ing['name']}: {ing['quantity']}\n"response += "\n## 烹饪步骤\n\n"for i, step in enumerate(recipe["steps"], 1):response += f"{i}. {step}\n"response += f"\n难度：{recipe['difficulty']}\n"response += f"菜系：{recipe['cuisine']}\n"return responseif __name__ == "__main__":mcp.run()
测试验证
现在来测试我们升级后的应用。
使用MCP Inspector测试
首先，启动我们的应用：
cd recipe-assistant
python -m app.main
在另一个终端启动MCP Inspector测试，可以按照我们之前的方式进行测试：
npx @modelcontextprotocol/inspector stdio python -m app.main
下一篇预告：我们将通过实际代码对比，学习如何将一个FastMCP工具改写成原生SDK版本，直观理解两者的差异和使用场景。