How to Configure MyBatis with Spring Boot
Learn to configure MyBatis with Spring Boot 3 and configure @Mapper and DataSource. Also, learn mapper scanning with @MapperScan with example.
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Lokesh Gupta
Website: https://howtodoinjava.com
Github: https://github.com/lokeshgupta1981/
Twitter: @HowToDoInJAVA
My Articles:
Spring Boot HTTP Interface using @HttpExchange
Learn to use the Spring @HttpExchange to create and configure a declarative HTTP client interface (blocking/non-blocking) with examples.
Spring ProblemDetail and ErrorResponse
Starting since Spring 6 and Spring Boot 3, the Spring Framework supports the “Problem Details for HTTP APIs” specification, RFC 7807. This Spring tutorial will guide you through this new enhancement in detail. 1. Problem Details Specification [RFC 7807] This RFC defines simple JSON and XML document formats that can …
Getting Started with JHipster and Spring Boot
This JHipster tutorial will familiarize you with this popular code generation platform and work with front-end and backend generated code.
TypeScript Remove Item from Array: splice, filter, pop
Remove items from a TypeScript array by position or by value, in place or on a copy, with the common bugs (-1 index, splice in a loop, delete) shown and fixed.
TypeScript Add Element to Array: push, unshift, splice
Add items to the end, start or any index of a TypeScript array, or to a new array with spread, concat() and toSpliced(), with the compiler errors explained.
TypeScript Date: Current Date, Add Days, Compare, Format
Get the current date in TypeScript, create dates, add days and months, compare and format them, and avoid the time zone and JSON pitfalls of the Date object.
Java ArrayDeque Tutorial: Stack, Queue and Deque Examples
Java ArrayDeque tutorial with stack and queue examples, both-end methods, Java 21 reversed(), iteration, an undo history and ArrayDeque vs LinkedList.
JMH Java Microbenchmark Harness: Setup, Blackhole, Pitfalls
Learn the JMH Java Microbenchmark Harness with the Maven archetype, the Java 23+ processor fix, @State, @Param, Blackhole, real results and pitfalls.
Spring @Lookup Method Injection
Spring lookup method injection is the container’s ability to override methods on container-managed beans and return another container-managed bean.
Spring: Injecting Prototype Bean into Singleton Bean
Spring context supports singleton and prototype bean scopes along with four other scopes specific to the web context. The singleton is the default bean scope. A common problem arises when we want to inject a prototype-scoped bean into a singleton-scoped bean. In this case, as the singleton bean is initialized …
Springdoc OpenAPI: Swagger UI for Spring Boot REST APIs
Springdoc OpenAPI generates the OpenAPI 3 document and the Swagger UI page for a Spring Boot REST API from one starter dependency. Default URLs, springdoc.* properties, Swagger annotations, groups, security scheme and how to switch the docs off in production.
Java Keywords List: Reserved and Contextual Keywords (Java 25)
The full list of Java keywords as of Java 25, with 51 reserved and 17 contextual keywords grouped by category, literals, version history and rules.
Java I/O: Files, Streams, NIO and Serialization
Java IO tutorial for Java 25 covering Path and Files, byte and character streams, NIO channels, how IO works in the OS, and every file task by topic.
Java SynchronousQueue: Direct Handoff Between Threads
Java SynchronousQueue explained with put(), take(), offer() and poll() examples, a producer-consumer handoff, thread pool use and the alternatives.
Spring Framework Tutorials
Spring helps write high-performing, easily testable, and reusable code and promotes programming best practices by applying dependency injection (DI).
Spring MVC
Spring WebMVC (or Spring MVC) contains Spring’s model-view-controller (MVC) and REST Web Services implementation for web applications.
Spring Batch Tutorial
Spring batch is a lightweight, comprehensive framework designed for the development of robust batch processing applications. Learn with examples.
Java Queue Interface: Methods, Implementations and Examples
Java Queue interface guide with the six methods, how to choose ArrayDeque, PriorityQueue or a BlockingQueue, iteration, BFS and thread-safe queues.
JUnit XML Report: Surefire and Open Test Reporting Formats
Read and configure the JUnit XML report from Maven Surefire and Gradle, enable Open Test Reporting XML in JUnit 6, show display names and publish in CI.
What’s New in Spring 6 and Spring Boot 3
Learn about the new features and changes introduced in Spring 6 and Spring boot 3 such as baseline upgrade to Java 17 and removing all deprecated classes, methods and properties.
Java String & Regex Tutorials
Java String methods grouped by task with Java 25 examples, from equals() and compareTo() to strip(), split() and replaceAll(), with pitfalls and FAQs.
Find a File in a Directory and Subdirectories in Java
Find a file in a directory and its subdirectories in Java with Files.find(), Files.walk() and walkFileTree(), with depth limits and globs.
Java Stream groupingBy(): Group, Count and Sum a List
Java stream groupingBy() examples that group a list by one or more fields and count, sum, average or sort each group with downstream collectors.
Read a File from AWS S3 using S3Client
Learn to read a text file stored in AWS S3 bucket. We will learn to read a public file or non-public file using the access/secret keys.
Log4j2 Dynamic ThresholdFilter Example
Learn to configure log4j2 DynamicThresholdFilter and how to match thresholds and write the filtered messages using various combinations.
Log4j2 – Filter Messages using MarkerFilter
Learn to filter the logging messages or events using the Log4j2 MarkerFilter, create instances, and configure them in log4j2.xml.
Convert a Map to a List, Array or Set in Java
Convert a map to a list, array or set in Java using keySet(), values() and entrySet(), with streams, toArray(), ordering rules and lists of records.
Stream Has Already Been Operated Upon or Closed: Causes and Fix
Fix the IllegalStateException stream has already been operated upon or closed in Java. See why streams are single-use and three ways to reuse the data.
How to Handle InterruptedException in Java (with Examples)
How to handle InterruptedException in Java correctly. Propagate it or restore the interrupt flag, avoid common mistakes, and cancel executor tasks.
Semaphore vs ReentrantLock in Java: Key Differences
Semaphore vs ReentrantLock in Java compared with a table and code for ownership, reentrancy, IllegalMonitorStateException, conditions and when to use each.
Flatten a List of Lists in Java: flatMap, Loops and Libraries
Learn to flatten a list of lists in Java with flatMap(), addAll() loops, mapMulti(), recursion for deep nesting, Guava and Eclipse Collections.
Developer Interview Preparation Questions and Guides
Choose Java, Spring, SQL, coding and best-practice interview guides for your role, then practice explaining answers with examples and project decisions.
Convert List to Map in Java: toMap(), Duplicate Keys and Order
Convert List to Map in Java with Collectors.toMap() and groupingBy(), fix the duplicate key IllegalStateException with a merge function, keep order.
Java Stream With Index: Iterate Over a Stream With Indices
Learn to iterate over a stream with indices in Java using IntStream.range(), a record, a Java 24 gatherer, AtomicInteger, Guava and StreamEx.
Spring Boot Filter: with Order and URL Pattern Examples
In this Spring boot tutorial, we will learn to create, order and register servlet filters in different ways including Filter interface, @WebFilter annotation and inbuilt filter bean classes. 1. Introduction In a web application, we must implement the javax.servlet.Filter interface (jakarta.servlet.Filter in Spring Boot 3) to create filters that can …
Build Tools: Maven & Gradle
Maven is a build tool based on POM and is generally used for Java projects to automatically download the project dependencies in build time.
Remove or Update List Elements Using Streams in Java
Learn to remove or update list elements using streams in Java with filter() and map(), or in place with removeIf() and replaceAll(), using records.
Running JUnit Tests with Maven
Learn to run JUnit tests using Maven Surefire Plugin. We will learn to run a single test, run only selected tests or run all the tests in the project.
Arrays.asList() vs new ArrayList() in Java: Key Differences
Arrays.asList() vs new ArrayList() in Java explained with examples, covering fixed size, the shared array, List.of(), primitive arrays and conversions.
Convert an Object to Map in Java: Jackson, Gson and Reflection
Convert an object to Map in Java with Jackson 3 convertValue(), JavaPropsMapper flat keys, Gson and reflection, plus nulls, records and Map back to object.
Java 8 date/time type not supported by default: Jackson Fix
Fix the Jackson error “Java 8 date/time type not supported by default” for LocalDate, LocalDateTime and Instant by registering JavaTimeModule, with the Spring Boot and Jackson 3 cases and the output format settings.
Filter a Map by a List of Keys in Java: Lookup vs Stream
Learn to filter a map by a list of keys in Java with get() lookups, streams and retainAll(), keep the key order and report the keys that are missing.
TypeScript Tutorial: All Articles Grouped by Topic
All TypeScript tutorials on howtodoinjava.com, grouped by topic: basics, types, operators, arrays, collections, functions, interfaces and classes.
JavaScript Check if Variable is a Number (and NaN Traps)
Number.isFinite() is the reliable way to check if a variable is a number in JavaScript. Learn why typeof and the global isNaN() let bad values through, how to validate numeric strings from forms, and how to write a TypeScript type guard.
IllegalMonitorStateException in Java: Causes and Fixes
IllegalMonitorStateException in Java explained, with every cause from wait() and notify() outside synchronized to ReentrantLock unlock() and the fixes.
Round a Double to 2 Decimal Places in Java (or N Places)
Learn how to round a double to 2 decimal places in Java with BigDecimal, Math.round(), String.format() and DecimalFormat, plus rounding modes and pitfalls.
Invert a Map in Java: Swap Keys and Values, Even With Duplicates
Invert a map in Java by swapping keys and values with a loop or Collectors.toMap(), handle duplicate values with groupingBy(), and use Guava BiMap.
Java printf() and String.format(): Format Specifier Guide
Java printf examples for %s, %d, %.2f, width, flags, dates and locales, plus String.format(), formatted() and fixes for common format exceptions.
Spring Boot Actuator /Info Endpoint Example
Learn about Spring Boot Actuator and adding custom static and dynamic information to the /info endpoint using properties and InfoContributor.