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The innodb_force_recovery option starts MySQL in a recovery mode that lets the InnoDB storage engine run on a corrupted database, so we can dump the data before we rebuild the damaged tables. When innodb_force_recovery is not working, the cause is either a problem in the option file or corruption that …
The jpackage is a command-line tool introduced in Java 14 and helps create native installable packages (.exe, .msi, .dmg, .pkg, .deb, .rpm) for Windows, macOS, and Linux. Jpackage bundles Java applications along with a Java runtime (JRE) image, ensuring that end users do not need to install Java separately.
Database integrity refers to the accuracy, consistency, and reliability of the data stored within a database. It ensures that data remains uncorrupted, and adheres to defined rules. In SQL databases, integrity is supported through constraints like primary keys, foreign keys, unique constraints, and check constraints, alongside physical and logical data …
Declare a typed array of objects with an interface or type alias, then add, find, filter, sort, group and update its objects without surprises.
TypeScript has no Vector class. Model each vector as a tuple such as [x: number, y: number, z: number], store them in an array, and do vector math with typed functions.
Generate PDF from HTML template in Java with OpenHTMLtoPDF 1.1.97, Thymeleaf or FreeMarker, plus jsoup for broken HTML, page numbers, fonts and safety.
Since version 3.4, Spring Boot will provide native support for structured logging in the most common and popular formats, such as JSON and XML.
Creating REST APIs is a better approach for building one-time token-based authentication combined with Jwt tokens in Spring Security.
Read a file line by line in Python with a for loop, readlines(), readline(), generators, islice() and mmap. Handle large files, encodings and line numbers.
orphanRemoval = true deletes a child entity as soon as it leaves its parent’s association. See the SQL Hibernate 7 runs, how it differs from CascadeType.REMOVE, and the common mistakes.
Save a parent and its child entities with one persist() call in Hibernate 7. See cascade PERSIST and MERGE, the helper method that sets both sides, managed and detached parents, getReference(), and the real SQL and errors.
This short Logback tutorial lists examples for configuring logback.xml to log messages to both the console and/or file appenders. 1. Logback Dependencies To include Logback, include the latest version of logback-classic dependency, which transitively includes all the necessary dependencies, including SLF4J. Spring Boot comes with SLF4J and Logback as the …
1. Problem When writing tests that depend on H2 database in a Spring boot application, we may encounter the CommandAcceptanceException: Error executing DDL. The root cause exception will be org.h2.jdbc.JdbcSQLSyntaxErrorException in the logs. The exception stack trace will look something like this: If you are trying to run unit tests …
Learn to configure log4j2.yaml file to output the log statements to the console, rolling files, etc. Also, learn to configure log4j2 appenders, levels, and patterns.
Learn to make HTTP GET requests (sync and async) using Spring Boot WebClient, pass URI and query params, handle responses, and handle errors.
Learn to compare Java objects without getters or equals() using EqualsBuilder.reflectionEquals(), excluded fields, recursive mode and AssertJ.
In Spring Security, a One-Time Token (OTT) is a server-side generated string that can be used only once for user login authentication purpose.
Spring AI pgvector example: run PostgreSQL with pgvector in Docker, configure PgVectorStore, load and search documents, and fix the dimension errors.
Build a Spring AI RAG chatbot that lets users upload PDF files and ask questions about each file, with Tika, a vector store and a safe metadata filter.
Spring AI tool calling with Ollama: describe Java methods with @Tool, pass them to ChatClient, and handle errors, loops and tools that change data safely.
Learn to download, install, and run an LLM model using Ollama. Also learn to configure Spring AI Ollama module to access the model’s chat API.
Spring AI tutorial: a learning path of articles in reading order, from the first ChatClient call to RAG, tools, agents, testing and other model providers.
Spring AI text to SQL: turn a question into a SELECT with a ChatClient, check it, run it read-only, explain the rows and fix the model’s common SQL errors.
For creating an ETL pipeline for Spring AI data ingestion microservice, Spring cloud functions are an excellent choice for serverless providers.
Spring AI ETL pipeline example: read Markdown and PDF files, add metadata, split with TokenTextSplitter and load a vector store without duplicates.
Spring AI vector store example: load documents into SimpleVectorStore, search by meaning with filters, then move the same code to ChromaDB in Docker.
Spring AI embedding model example with Ollama: turn text into a 768-number vector and compare a question with policy sentences by cosine similarity.
Spring AI speech to text with OpenAI whisper-1: TranscriptionModel, language and prompt options, a voice-note endpoint, and answering it with ChatClient.
Spring AI text to speech with OpenAI: TextToSpeechModel, voices, speed and tone per request, streaming audio, and the traps of length and cost.
Spring AI prompt template examples: system prompt and user template from files, few-shot examples as message pairs, and measured results on a small model.
Serialize object to String in Java with ObjectOutputStream and Base64 or with Jackson JSON, read it back, and avoid the deserialization security risk.
Learn to read or write the records in a JSON file using Spring Batch JsonItemReader and JsonFileItemWriter implementations.
Learn to read and write XML files using StaxEventItemReader and StaxEventItemWriter classes in a Spring Batch application.
Learn to read all the rows from an Excel (.xls or .xlsx) file using Spring Batch and save them in a database in a Spring Boot application.
In LangChain4j, the AiServices helps in working with strongly typed objects and tasks such as extracting and parsing the structured output in JSON or XML format.
Executors.newVirtualThreadPerTaskExecutor() runs each task in a new virtual thread. Learn close(), invokeAll, Semaphore limits, thread names and errors.
This Spring Boot tutorial aims at Langchain4j Chat APIs to get started with and run a few examples to give you a high-level understanding.
In Lucene, ByteBuffersDirectory is for pure in-memory access for demos, and MMapDirectory uses memory-mapped files stored in the filesystem.
Spring AI structured output examples: entity() for records, lists and maps, native JSON schema output with Ollama, and the validation advisor.
Spring AI image generation with ImageModel and OpenAI gpt-image-1-mini: ImagePrompt, size and quality options, Base64 output and a banner endpoint.
Spring AI getting started guide: install Ollama, create a Spring Boot 4 project, write a ChatClient endpoint, run it locally and fix the common errors.
Learn to write SQL queries with ‘LIKE’ keyword in a Spring Boot JPA application and execute with JdbcClient, JdbcTemplate or JpaRepository template methods.
Learn to create a REST API controller using @RestController in a Spring Boot application, and add method validation, error handling and unit tests.
Learn to Spring Data JPA module and work with JpaRepository interface for performing the CRUD operations in underlying databases in a Spring Boot application.
The build error NoSuchFieldError: Class com.sun.tools.javac.tree.JCTree$JCImport does not have member field ‘qualid’ means an old Lombok (1.18.28 or older) is compiling on JDK 21 or newer. Upgrade Lombok to 1.18.48 in Maven, Gradle or the IDE and rebuild.
Learn to filter a map by keys and values with Java streams, plus Predicate helpers, removeIf(), order-preserving toMap() and null-safe collecting.
Java Stream contains, containsAny and containsAll checks with anyMatch() and a Set, with empty-input rules, single-use streams and collection alternatives.
Learn to filter nested collections with Java streams using flatMap(), mapMulti() and anyMatch(), trim inner lists without mutation and handle null lists.
Learn Java Stream mapMulti() with examples, the type witness it needs, when it beats flatMap() and when it does not, primitive variants and a real case.
Get the first and last day of week, month or year in Java with TemporalAdjusters, WeekFields for locales, YearMonth and quarter boundaries.
HowToDoInJava provides tutorials and how-to guides on Java and related technologies.
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