Tutorial by Examples: d

The ClassLoader needs to provide a ProtectionDomain identifying the source of the code: public class PluginClassLoader extends ClassLoader { private final ClassProvider provider; private final ProtectionDomain pd; public PluginClassLoader(ClassProvider provider) { this...

Applications running in non-development environments often require database updates. After using the Add-Migration command to create your database patches there's the need to run the updates on other environments, and then the test environment as well. Challenges commonly faced are: no Visual S...

To get random data from certain collection refer to $sample aggregation. db.emplyees.aggregate({ $sample: { size:1 } }) where size stands for number of items to select.

Let say you want to build your API to comply jsonapi.org specification and the result should look like: { "article": { "id": "305", "type": "articles", "attributes": { "title": "Asking Alexandria&q...

from pymongo import MongoClient uri = "mongodb://localhost:27017/" client = MongoClient(uri) db = client['test_db'] # or # db = client.test_db # collection = db['test_collection'] # or collection = db.test_collection collection.save({"hello":"world"...

import cv2 import numpy as np import urllib stream=urllib.urlopen('http://96.10.1.168/mjpg/video.mjpg') bytes='' while True: bytes+=stream.read(1024) a = bytes.find('\xff\xd8') # JPEG start b = bytes.find('\xff\xd9') # JPEG end if a!=-1 and b!=-1: jpg = bytes[a:b+...

"Fat Model, Skinny Controller" is a very good first step, but it doesn't scale well once your codebase starts to grow. Let's think on the Single Responsibility of models. What is the single responsibility of models? Is it to hold business logic? Is it to hold non-response-related logic? ...

In your Maven project, add the following to your pom.xml file. The following versions are for Cassandra 3.x. <dependency> <groupId>com.datastax.cassandra</groupId> <artifactId>cassandra-driver-core</artifactId> <version>3.1.0</ve...

Connecting to Cassandra is very similar to connecting to other datasources. With Cassandra, credentials are not required. String cassandraIPAddress = "127.0.0.1"; String cassandraKeyspace = "myKeyspace"; String username = "foo"; String password = "bar"; ...

Nested serializers by default don't support create and update. To support this without duplicating DRF create/update logic, it is important to remove the nested data from validated_data before delegating to super: # an ordinary serializer class UserProfileSerializer(serializers.ModelSerializer): ...

std::vector<int> primes = {2, 3, 5, 7, 11, 13}; for(auto prime : primes) { std::cout << prime << std::endl; }

The only way if your components does not have a parent-child relationship (or are related but too further such as a grand grand grand son) is to have some kind of a signal that one component subscribes to, and the other writes into. Those are the 2 basic operations of any event system: subscribe/li...

This fetches the value of NOW() in local time, in India Standard Time, and then again in UTC. SELECT NOW(); SET time_zone='Asia/Kolkata'; SELECT NOW(); SET time_zone='UTC'; SELECT NOW();

If you have a stored DATE or DATETIME (in a column somewhere) it was stored with respect to some time zone, but in MySQL the time zone is not stored with the value. So, if you want to convert it to another time zone, you can, but you must know the original time zone. Using CONVERT_TZ() does the con...

This is really easy. All TIMESTAMP values are stored in universal time, and always converted to the present time_zone setting whenever they are rendered. SET SESSION time_zone='America/Los_Angeles'; SELECT timestamp_sold FROM sales WHERE state_sold = 'CA' Why is this? TIMESTAMP values are...

SELECT NOW(3) does the trick.

CREATE TABLE times ( dt DATETIME(3), ts TIMESTAMP(3) ); makes a table with millisecond-precision date / time fields. INSERT INTO times VALUES (NOW(3), NOW(3)); inserts a row containing NOW() values with millisecond precision into the table. INSERT INTO times VALUES ('2015-01...

%f is the fractional precision format specifier for the DATE_FORMAT() function. SELECT DATE_FORMAT(NOW(3), '%Y-%m-%d %H:%i:%s.%f') displays a value like 2016-11-19 09:52:53.248000 with fractional microseconds. Because we used NOW(3), the final three digits in the fraction are 0.

Here's an example of a React component with a "managed" input field. Whenever the value of the input field changes, an event handler is called which updates the state of the component with the new value of the input field. The call to setState in the event handler will trigger a call to ...

ActionScript 2.0: _root.createTextField("message", 0, 5, 5, 300, 50); var tf:TextFormat = new TextFormat(); tf.color = 0xFF0000; tf.size = 32; tf.bold = true; message.setTextFormat(tf); message.text = "Hello World!"; First function creates a TextField named "mess...