Study Notes on LOCRIAN_V Blog

Studying for the System Architect Software Exam

Tue, 18 Jun 2024 12:51:35 +0800

These notes are organized around the core knowledge points of the exam syllabus, with code examples and memory mnemonics — good for a final sprint review. (The exam is China’s “Soft Exam” — Computer Technology and Software Professional Qualification — System Architect level.)

1. Laws, Regulations, and Standardization

1.1 Copyright

Category	Content
Not protected	Government documents, laws and regulations, current-affairs news
Protected	Speeches, authored books, software code
When it vests	Automatically arises from the day software development is completed
Protection term	50 years (attribution, modification, and integrity rights are protected permanently)

Copyright ownership rules:

Learning ElasticSearch

Sat, 18 May 2024 12:51:05 +0800

1. Fundamentals

1.1 Origin: Lucene

Lucene: Apache’s open-source Java full-text search engine library.
Advantages: easy to extend, high performance (pure Java, embeddable).
Drawbacks: complex to use — you must handle low-level details like index creation and query parsing, with no distributed support.
Elasticsearch is built on Lucene, providing a distributed, easy-to-use RESTful API.

1.2 The tech stack (ELK)

Elasticsearch: the storage, search, and analytics engine.
Logstash: a server-side data processing pipeline that collects and transforms data before sending it to ES.
Kibana: a visualization platform for building charts and dashboards and managing ES.
Beats: lightweight data shippers that send to Logstash or ES.

1.3 Installing with Docker

Elasticsearch (single node):

Learning AWS

Thu, 18 Apr 2024 12:48:03 +0800

Compiled for the Solutions Architect certification, from a Java backend perspective. Core idea: what pain point each service solves, when to choose it, and how to distinguish it from similar services.

1. Storage

1.1 Comparison of the three storage types

Type	Representative service	Access unit	Typical scenario
Block storage	EBS, EC2 Instance Store	Block	Databases, OS disks
File storage	EFS, FSx	Files / directory tree	Multi-instance sharing, NFS/SMB mounts
Object storage	S3	Object (Object + Key)	Static assets, backups, data lakes

Block storage  → like a local hard drive; the OS sees a raw device it formats and mounts itself
File storage   → like a NAS; multiple machines can mount the same directory at once
Object storage → like HTTP PUT/GET key-value; no directory concept, simulated with prefixes

1.2 Amazon S3

Quick reference of core features:

Learning Spring Cloud

Mon, 18 Mar 2024 12:46:51 +0800

1. Service Decomposition and Remote Calls

1.1 Why decompose into services?

As business grows, a monolith faces slow deployment, poor scalability, a frozen tech stack, and more. Microservices split it into small, independently deployable and scalable services, each responsible for a single business domain.

Decomposition principles:

Single responsibility: each service does one thing
High cohesion, low coupling: tight within a service, loose between services
Data independence: each service owns an independent database

Client → Gateway (auth) → business microservice A → microservice B (OpenFeign)
                ↓
           Nacos (service discovery)

1.3 RestTemplate — the raw inter-service call

RestTemplate is the HTTP client Spring provides for inter-service calls, but its code is verbose and it doesn’t support load balancing — a transitional solution before OpenFeign.

Learning the SSM Framework

Sun, 18 Feb 2024 12:40:44 +0800

1. The Spring IoC Container

1.1 Container architecture

BeanFactory (top-level interface)
    └── ApplicationContext (the commonly used interface, extends BF)
            ├── ClassPathXmlApplicationContext (XML config)
            ├── FileSystemXmlApplicationContext (filesystem-path XML)
            └── AnnotationConfigApplicationContext (annotation config)

Core differences between BeanFactory and ApplicationContext:

Feature	BeanFactory	ApplicationContext
Bean init timing	Lazy (on the first getBean)	Eager (at container startup)
Features	Basic IoC	IoC + event publishing + i18n + AOP, etc.
Use case	Extremely resource-constrained embedded	99% of business scenarios

Why doesn’t ApplicationContext have close()?
The ApplicationContext interface itself doesn’t define close(), to keep the interface general (not all containers can/need to be closed, e.g. web containers). But its implementation AbstractApplicationContext implements Closeable, so you can cast and call it, or receive it via the ConfigurableApplicationContext interface.

Learning MyBatis-Plus

Tue, 16 Jan 2024 15:38:37 +0800

1. Introduction

MyBatis-Plus (MP for short) is an enhancement tool for MyBatis. It only enhances MyBatis without changing it, built to simplify development and improve efficiency.

Core features:

Non-intrusive: adding MP has no effect on an existing MyBatis project — smooth as silk.
Low overhead: basic CRUD is auto-injected at startup, with essentially no performance loss.
Powerful CRUD operations: built-in generic Mapper and generic Service; with just a little configuration you get most single-table CRUD.
Supports Lambda-style calls: write query conditions safely and efficiently via lambda expressions, preventing mistyped field names.
Built-in code generator: generate Mapper, Service, Controller, etc. with minimal configuration.
Built-in pagination plugin: physical pagination based on MyBatis; developers don’t need to worry about the details — just configure and use.

Official site: https://baomidou.com/