Friday, October 28, 2022

Java - Always Name Your Thread Pools - Naming threads and thread-pools of ExecutorService - set name of thread

You could supply a ThreadFactory to newSingleThreadScheduledExecutor(ThreadFactory threadFactory).

The factory will be responsibe for creating threads, and will be able to name them.
ExecutorService is a JDK API that makes asynchronous task execution easier.

ExecutorService offers a pool of threads and an easy-to-use API for assigning tasks.

The ExecutorService gives the name of the threads in the thread pool.

This shot discusses how we can assign custom names to the threads of the thread pool of the ExecutorService.
BasicThreadFactory

An ExecutorService employs a ThreadFactory to create its threads to execute tasks.

In many circumstances, users do not need to worry about a ThreadFactory because the ExecutorService's default one will suffice.

A custom ThreadFactory must be constructed with particular needs, such as thread naming.
import java.util.TimerTask;
import java.util.concurrent.*;

public class Main {
    public static void main(String[] args) {
        // instant thread execution
        ExecutorService executorService = Executors.newFixedThreadPool(3, namedThreadFactory("test-thread"));
        for (int i=0; i < 5; i++) {
            executorService.submit(() -> System.out.println(Thread.currentThread().getName()));
        }
        executorService.shutdown();

        // scheduled thread execution


        ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor(namedThreadFactory("scheduled-thread"));
        TimerTask repeatedTask = new TimerTask() {
            @Override
            public void run() {
                try {
                    System.out.println(Thread.currentThread().getName());
                }
                finally {
                    executor.shutdownNow();
                }
            }
        };
        executor.schedule(repeatedTask, 1L, TimeUnit.MINUTES);
    }

    static ThreadFactory namedThreadFactory(String name) {
        return new YourThreadFactory(name);
    }
}

class YourThreadFactory implements ThreadFactory {
    private String name = "[No Name]";

    YourThreadFactory(String name) {
        this.name = name;
    }

    public Thread newThread(Runnable r) {
        return new Thread(r, name);
    }
}

How to convert result table to JSON Array or JSON Object or JSON String in MySQL

I'd like to convert result table to JSON Array of Object in MySQL using preferably only plain MySQL commands. For example with query

SELECT name, phone FROM person;

| name | phone |
| Jack | 12345 |
| John | 23455 |


the expected JSON output would be as below as per my requirement:

[
  {
    "name": "Jack",
    "phone": 12345
  },
  {
    "name": "John",
    "phone": 23455
  }
]
The maximum value for group_concat_max_len is 18446744073709551615.

To set the variable forever use

SET GLOBAL group_concat_max_len=4294967295;
Example 1:
SELECT i.id,
JSON_OBJECT('id', ig.id, "name", ig.name) AS 'group_json'
FROM item i 
LEFT JOIN item_group ig ON i.item_group_id=ig.id 
ORDER BY i.id DESC LIMIT 10;


Example 2 (Group Concat):
SELECT ig.item_sales_rate_id,
GROUP_CONCAT(DISTICT JSON_OBJECT('id', ig.id, "status", ig.status)) AS 'group_json'
FROM item_sales_rate i 
LEFT JOIN item_sales_uom ig ON i.id=ig.item_sales_rate_id 
WHERE ig.item_sales_rate_id IS NOT NULL 
GROUP BY ig.item_sales_rate_id ORDER BY i.id ASC LIMIT 10;

MySQL casting from decimal to string - mysql cast to varchar - mysql convert decimal to string char varchar

MySQL - casting from decimal to string

select CAST(ROUND(345345345345345345345353453453453454.4345345,6) AS CHAR(65)) AS 'big_number';

don't try to cast to varchar, there is a bug at MySQL end

Wednesday, October 26, 2022

Grails on Groovy - join tables using createAlias with additional condition along with sql on condition for additional filter of data

We frequently use createAlias to create alias between entity. It actually create connection based on foreign key and primary key between two entities. Below is a example how we create alias between entities:
Table1.createCriteria().list {
    createAlias("scores", "scores")
}
Which will produce SQL like below where we can see that foreign key of table1 create a link with table2_child based on primary key id as following:
select ... from table1 this_ inner join table2_child scores1_ on (this_.id=scores1_.table1_id)
But if we need more on add to filter when joining them, yeah, we can do that. We can add extra conditions to on part of that SQL. To do so, first need to create a AliasBuiilder.groovy file like below:
package com.gradle_app

import org.hibernate.criterion.Criterion
import org.hibernate.sql.JoinType

abstract class AliasBuilder {
    static final Object synk0 = new Object()
    static Long number = 0L

    static void fixCriteriaBuilderProps(criteriaBuilder) {
        if (!criteriaBuilder.properties.containsKey("aliases")) {
            criteriaBuilder.metaClass.aliases = [:]
            criteriaBuilder.metaClass.data = [:]
        }
        criteriaBuilder = null
    }

    static String createAlias0(criteriaBuilder, String field, String aliasPath = field, JoinType joinType = JoinType.INNER_JOIN, Criterion customCriterion = null) {
        aliasPath = aliasPath ? aliasPath : field
        joinType = joinType ? joinType : JoinType.INNER_JOIN

        fixCriteriaBuilderProps(criteriaBuilder)

        def subCriteria = criteriaBuilder.criteria.subcriteriaList.find { it.path == aliasPath }

        if(subCriteria) {
            try {
                return subCriteria.alias
            }
            finally {
                criteriaBuilder = field = aliasPath = joinType = subCriteria = null
            }
        }
        else {
            String alias = "${field}_custom_name_${nextSerialNumber()}".toLowerCase()
            criteriaBuilder.createAlias(aliasPath, alias, joinType, customCriterion)
            String other = alias.substring(0, criteriaBuilder.sessionFactory.dialect.getMaxAliasLength()) + (criteriaBuilder.properties.aliases.size() + 1) + "_"
            criteriaBuilder.properties.aliases[alias] = other
            criteriaBuilder.properties.data[aliasPath] = alias
            try {
                return alias
            }
            finally {
                criteriaBuilder = field = aliasPath = joinType = subCriteria = alias = other = null
            }
        }
    }

    static String nextSerialNumber() {
        Long serial = null
        try {
            synchronized (synk0) {
                number = serial = number + 1L
                if (number == Long.MAX_VALUE) {
                    number = 1L
                }
            }
            return serial.toString()
        }
        finally {
            serial
        }
    }
}
And another CustomCriteria.groovy file like this:

package com.gradle_app

import org.hibernate.Criteria
import org.hibernate.HibernateException
import org.hibernate.criterion.CriteriaQuery
import org.hibernate.criterion.Criterion
import org.hibernate.engine.spi.TypedValue
import org.hibernate.internal.util.StringHelper

class CustomCriteria implements Criterion {
    private static final TypedValue[] NO_VALUES = new TypedValue[0]

    public String toSqlString(Criteria criteria, CriteriaQuery criteriaQuery) throws HibernateException {
        String alias = criteriaQuery.getSQLAlias(criteria)
        return "${alias}.status='1'"
    }

    public TypedValue[] getTypedValues(Criteria criteria, CriteriaQuery criteriaQuery) throws HibernateException {
        return NO_VALUES
    }
}
And you can use the above custom condition using as below example:

void checkCustomCriteria() {
	List list = Table1.createCriteria().list {
		//setResultTransformer(Criteria.DISTINCT_ROOT_ENTITY)
		resultTransformer(CriteriaSpecification.ALIAS_TO_ENTITY_MAP)
		String scores = AliasBuilder.createAlias0(delegate, "scores", "scores", JoinType.LEFT_OUTER_JOIN, new CustomCriteria())
		"projections" {
			"groupProperty" "id", "id"
			addProjectionToList(Projections.sqlProjection(
					"GROUP_CONCAT(${delegate.aliases[scores]}.id) as scores",
					["scores"] as String[],
					[StringType.INSTANCE] as Type[]
			), "scores")
		}
	}
	list.each { dataRow->
		println("Data row=${dataRow}")
	}
}
Which will generate below SQL with additional condition on statement ( scores1_.status='1' )

select ... from table1 this_ inner join table2_child scores1_ on this_.id=scores1_.table1_id and ( scores1_.score.status='1' ) where this_.id<>?

Monday, October 24, 2022

Laravel Blade @include .html files | Laravel Blade Highlight Change Tags when use AngularJS along with Laravel

I am going to use AngularJS along with Laravel, and I wanted to change Laravel tags to [[ ]], it can achived by below codes:

Blade::setContentTags('[[', ']]'); // for variables and all things Blade

Blade::setEscapedContentTags('[[[', ']]]'); // for escaped data
But my solution is to have Angular and Blade works very simple, I create a another xxx.php every time instead of xxx.blade.php. I need some Angular and name this partial just '.php' and not '.blade.php'.

Lets say I have a user create form named "create.blade.php" inside "views/user" directory using below content:

@extends('layouts.user')
@section('content')
    <form>
        <h2>Create User</h2>
        @include('user.createBody');
    </form>
@endsection

Now I will create an php file named "createBody.php" inside "views/user" directory and put some html there:

<div class="row">
    <h1>User Name={{userName}}</h1>
    <div class="col-lg-4 col-sm-6">
        <label>Name</label>
        <input type="text" class="form-control" ng-model="userName">
    </div>
    <div class="col-lg-4 col-sm-6">
        <label>ID</label>
        <input type="text" class="form-control">
    </div>
</div>

So here we can use {{ }} tags both in Laravel and AngularJS

Tuesday, October 4, 2022

How to use static content / resource files in app root directory in grails

In Grails latest version like 4 and 5, it provides static assets management mechanism more standard way. We can use different files under the corresponding folders.
All the images will go under the images directory, js files go under the javascripts directory and CSS goes under the stylesheets directory. These files will be accessed by the URL path start with "/assets/".
Now, what if you don't want to use this structure or need to use the root path for some static file content.
For this, grails provide another option to manage static resources. So, what you can do is create the /resources/public directory under /src/main/ and use static resources there.
For example, if you had a file under /src/main/resources/public/images/example.jpg path then you can access that file using https://example.com/static/images/example.jpg.
This means, your file can be accessed with "/static/" URL by default. If you want to access the file in the app root directory, setup the following configuration under application.groovy

grails.resources.pattern = '/**'
Now, for the above example the file can be accessed with https://example.com/images/example.jpg URL and if the file is in /public/ directory that file can be accessed with root path https://example.com/file.js