from flask import Flask, jsonify from flaskext.mysql import MySQL from flask import make_response app = Flask(__name__) app.config['MYSQL_DATABASE_USER'] = 'fsxu_1' app.config['MYSQL_DATABASE_PASSWORD'] = '123456' app.config['MYSQL_DATABASE_DB'] = 'fsxu_json' app.config['MYSQL_DATABASE_HOST'] = 'localhost' mysql = MySQL() mysql.init_app(app) @app.route('/api/get_data', methods=['GET']) def get_data(): conn = mysql.connect() cursor = conn.cursor() # 查询nodes表和edges表的全部数据 cursor.execute("SELECT * FROM nodes") nodes_data = cursor.fetchall() cursor.execute("SELECT * FROM edges") edges_data = cursor.fetchall() cursor.close() conn.close() # 格式化查询结果 nodes = [] for row in nodes_data: node = { 'id': row[0], 'label': row[1], 'info': row[2], 'type': row[3] } nodes.append(node) edges = [] for row in edges_data: edge = { 'from': row[0], 'to': row[1], 'label': row[2], 'arrows': row[3] } edges.append(edge) # 创建JSON格式的响应 response = make_response(jsonify({'nodes': nodes, 'edges': edges})) # 添加头信息禁止缓存 response.headers['Cache-Control'] = 'no-cache, no-store, must-revalidate' response.headers['Pragma'] = 'no-cache' response.headers['Expires'] = '0' return response if __name__ == '__main__': app.run() 该代码有什么问题，为什么web页面没有相关知识图谱的展示

根据提供的代码，存在几个可能导致知识图谱没有展示的问题：

1. MySQL 配置问题：请确保你的 MySQL 服务器已正确配置，并且包含名为 'fsxu_json' 的数据库以及名为 'nodes' 和 'edges' 的表。确保提供的用户名和密码正确，并且具有对数据库和表的适当权限。

2. MySQL Python 连接库问题：代码中使用了 `flaskext.mysql` 库来连接 MySQL，但是这个库已经过时了。可以考虑使用更常见的 `flask-mysql` 库，或者使用 `pymysql` 库进行连接。确保这些库已正确安装，并根据需要进行相应的引入和配置。

3. 节点和边的数据格式问题：请确保数据库中的节点表和边表中的列与代码中的数据格式一致。检查列名、顺序和数据类型是否匹配。

4. vis.js 配置问题：代码中使用了 vis.js 库来可视化知识图谱，但是在提供的代码中并没有看到相关的前端 HTML 和 JavaScript 部分。请确保你已正确引入并配置 vis.js 库，并在前端页面中使用相关的 HTML 和 JavaScript 代码来展示图谱。

5. 路由配置问题：请确保你的 Flask 应用已正确配置路由，使 `/api/get_data` 能够正确映射到 `get_data` 函数。

通过检查上述问题，你可以逐一排除可能导致知识图谱无法展示的原因，并进行相应的修复。如果问题仍然存在，请提供更多详细信息，以便更好地帮助你解决问题。

相关问题

from flask.globals import app_ctx

As an AI language model, I don't have access to the specific Flask application that you're working on. However, I can explain what the `app_ctx` object is in Flask.

The `app_ctx` object is a context object that is used to store application-level information in Flask. It is a global object that is created when the Flask application is initialized and it is destroyed when the application is shut down. The `app_ctx` object is used to store information that is shared across multiple requests, such as database connections, configuration settings, and other resources that are needed by the application.

To access the `app_ctx` object in Flask, you can use the `current_app.app_context()` method. This method returns a context object that provides access to the `app_ctx` object. Once you have the `app_ctx` object, you can access any application-level information that has been stored in it.

For example, to access a database connection that has been stored in the `app_ctx` object, you could use code like this:

from flask import current_app

with current_app.app_context():
    db_conn = current_app.config['DB_CONN']
    # Use the database connection here

In this code, the `current_app.config['DB_CONN']` line retrieves the database connection from the `app_ctx` object, which has been stored there as part of the application's configuration settings. The `with current_app.app_context():` line ensures that the `app_ctx` object is available for use within the code block.

from flask import current_app ImportError: cannot import name 'current_app'

This error message indicates that there is an issue with importing the `current_app` object from the `flask` module. This object is used to access the current Flask application instance, and is typically used in a context where the application instance is not available through other means.

There are a few possible reasons why you might encounter this error:

1. You may be importing `current_app` from the wrong module. Make sure that you are importing it from the `flask` module and not another module with a similar name.

2. You may be importing `current_app` before the Flask application has been created. `current_app` is only available when a Flask application context is active, so if you try to import it outside of a request or application context, you will get this error. Make sure that you are importing `current_app` from within a Flask view function, or from within a function that is called within a Flask view function.

3. There may be a circular import issue in your application. Flask applications can be prone to circular import issues if you're not careful about how you structure your code. If you're importing `current_app` from a module that also imports something from the module where your Flask application instance is created, you may run into this error. Try restructuring your code to avoid circular imports.

To resolve this error, you should check your code for the above issues and make sure that you are importing `current_app` correctly and in the right context. You may also want to review the Flask documentation on application context and request context to better understand how they work.