In Java, we can use the Files.walk() API to traverse all files from a folder and its subfolders. Table of contents: 1. Traverse all files from a folder in Java 2. Traverse all files from a folder and its subfolders in Java 3. List all file name from a folder in Java 4. Find a […]
This article shows how to pretty print JSON with JSON.simple. Table of contents: 1. Setup JSON.simple 2. Default Compact Print JSON 3. Pretty Print JSON with JSON.simple 4. Write Pretty Print JSON to a File 5. Download Source Code 6. References P.S Tested with json-simple 4.0.1 1. Setup JSON.simple pom.xml <dependency> <groupId>com.github.cliftonlabs</groupId> <artifactId>json-simple</artifactId> <version>4.0.1</version> </dependency> […]
In GSON, we can use the transient keyword, ExclusionStrategy, and @Expose to exclude fields during the JSON serialization or deserialization process. Table of contents: 1. Setup Google Gson 2. Using the "transient" Keyword 3. Using the "ExclusionStrategy" 4. Using the "ExclusionStrategy" and custom annotation 5. Using the @Expose annotation 6. Download Source Code 7. References […]
Gson does not directly support Java 8’s date-time APIs like LocalDate, LocalDateTime, and ZonedDateTime. However, we can create a custom JSON serializer to support Java 8 date-time types. This article shows how to use Gson to handle the LocalDate type. Table of contents: 1. Setup Google Gson 2. Default, Gson does not support Java 8 […]
When the JSON field name doesn’t exactly match the Java object field names, we can use @SerializedName to change the JSON’s matching field name in Gson. Table of contents: 1. Setup Google Gson 2. JSON Unrecognized Field 3. Custom field name with @SerializedName 4. Download Source Code 5. References P.S Tested with Gson 2.10.1 1. […]
This article shows how to use Gson to write a Java object to a JSON file and read that JSON file back into a Java object. Table of contents: 1. Download Google Gson 2. A Java Object 3. Write Java object to JSON file using Gson 4. Read JSON from a file using Gson 5. […]
This article shows how to create a Jackson custom serializer and deserializer to parse JSON data that contains a LocalDate type. The Jackson custom serializer or deserializer is useful when we want to process a specific format that is not the default. Table of contents: 1. Setup Jackson 2. Jackson Custom Serializer for LocalDate 3. […]
When the JSON field name doesn’t exactly match the Java field names, we can use @JsonProperty to change the name of a JSON field in Jackson. Table of contents: 1. Setup Jackson 2. JSON Unrecognized field 3. Custom field name with @JsonProperty 4. Download Source Code 5. References P.S Tested with Jackson 2.17.0 1. Setup […]
Moshi does not have built-in adapters to process types like Java 8 date time APIs java.time.* or JSR-310; we need to manually provide a custom adapter to handle the Java 8 date time type. This article shows how to use Moshi to convert the Java 8 Localdate type to JSON data. Table of contents: 1. […]
This article shows how to use Moshi’s JsonAdaptor indent method to enable the pretty print JSON. Table of contents: 1. Download Moshi 2. Compact print JSON (Default) 3. Pretty print JSON using Moshi 4. Download Source Code 5. References P.S Tested with Moshi 1.15.1 1. Download Moshi Declare moshi in the pom.xml. pom.xml <dependency> <groupId>com.squareup.moshi</groupId> […]
Moshi does not have built-in adapters to process types like java.math.BigDecimal; we need to manually provide a custom adapter to handle the BigDecimal type. Table of contents: 1. Download Moshi 2. BigDecimal requires explicit JsonAdapter 3. Make Moshi supports BigDecimal 3.1 Define BigDecimal Adapter 3.2 Register the Adapter with Moshi 4. Download Source Code 5. […]
This article shows how to write JSON to a file using Moshi. Table of contents: 1. Download Moshi 2. Write JSON to a file using Moshi 3. Read JSON from a file using Moshi 4. Download Source Code 6. References P.S Tested with Moshi 1.15.1 1. Download Moshi Declare moshi in the pom.xml. pom.xml <dependency> […]
This article shows how to parse JSON using Moshi. Table of contents: 1. Download Moshi 2. Parse JSON using Moshi 3. Parse JSON Array using Moshi 4. Convert Java Object to JSON String 5. Download Source Code 6. References P.S Tested with Moshi 1.15.1 1. Download Moshi Declare moshi in the pom.xml, and it will […]
This article shows how to use Jackson and Lombok together. Table of contents: 1. Download Jackson and Lombok 2. Model with Lombok annotations 3. Parse JSON using Jackson 5. Download Source Code 6. References P.S Tested with Jackson 2.17.0 and Lombok 1.18.32 1. Download Jackson and Lombok Declares jackson-databind and lombok at pom.xml. pom.xml <dependency> […]
This article shows how to map a subset of a JSON file using Jackson. Table of contents: 1. Download Jackson 2. Map a subset of a JSON file 3. Define Java Classes that reflect JSON structure 4. Ignoring Unneeded Fields with Jackson 5. Testing the subset of JSON using Jackson 6. Download Source Code 7. […]
This article shows you write JSON to a file with Jackson. Table of contents: 1. Download Jackson 2. Define a Java Object 3. Write JSON to a File 4. Download Source Code 5. References P.S Tested with Jackson 2.17.0 1. Download Jackson Declare jackson-databind in the pom.xml. pom.xml <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.17.0</version> </dependency> 2. Define […]
This article will show you how to convert Java objects to JSON with Jackson. Table of contents: 1. Setup Jackson 2. Jackson quick examples 3. Convert Java Object to JSON using Jackson 4. Convert JSON to Java object using Jackson 5. Write Java object to JSON file 6. Read from JSON file to Java object […]
In Jackson, we can use @JsonIgnore to ignore a single field, @JsonIgnoreProperties to ignore multiple fields and @JsonIgnoreType to ignore a specified type during JSON serialization and deserialization. Table of contents: 1. Setup Jackson 2. Jackson @JsonIgnore – Ignores a field 3. Jackson @JsonIgnoreProperties – Ignores multiple fields 4. Jackson @JsonIgnoreType – Ignores a specified […]
When we compile our Java programs, each generated .class file carries a major version that indicates which Java version was used during compilation. For example, if we compile our code using Java 21 (major version 65), and then run the class file on an environment with an older Java version, we will encounter the error: […]
This article shows different ways to run a CommandLineRunner bean conditionally in a Spring Boot application. Table of contents: 1. Using @ConditionalOnProperty 2. Using Environment 3. Using Spring Profiles 4. Check the Presence of Other Beans 4.1 Using @ConditionalOnBean 4.2 Using @ConditionalOnMissingBean 5. Download Source Code 6. References P.S. Tested with Spring Boot 3.1.2 1. […]
This article tells what is CommandLineRunner and different ways of implementing it or use it in Spring Boot. Table of contents: 1. What is CommandLineRunner? 2. Implementing CommandLineRunner 3. @Bean CommandLineRunner 4. Download Source Code 5. References P.S. Tested with Spring Boot 3.1.2 1. What is CommandLineRunner? The CommandLineRunner is an interface in Spring Boot. […]
This article shows how Jackson can support the Java 8 date time APIs or JSR-310. Table of contents: 1. Download Jackson 2. Jackson does not support Java 8 date time APIs 3. Make Jackson support Java 8 date time APIs or JSR310 3.1 jackson-datatype-jsr310 3.1 Register JavaTimeModule() 4. Download Source Code 5. References P.S Tested […]
Spring Boot 3.1 introduced @ServiceConnection to enable the Spring Boot’s auto-configuration to use the service connection details to connect to a remote service (Testcontainers). Tables of contents: 1. Testing with @DynamicPropertySource 2. Spring Boot 3.1 and @ServiceConnection 3. Download Source Code 4. References 1. Testing with @DynamicPropertySource The following example uses @DynamicPropertySource to register the […]
In Spring Boot, we can use @DynamicPropertySource to dynamically register or override property values in the ApplicationContext for integration tests. Tables of contents: 1. Testing with ApplicationContextInitializer 2. Testing with @DynamicPropertySource 3. Testing with Spring Boot 3.1 and @ServiceConnection 4. Download Source Code 5. References P.S. The @DynamicPropertySource feature is available from Spring Framework 5.2.5 […]
We open a Terminal and use the one-liner command sudo nginx -s stop && sudo nginx to restart the Nginx on macOS. Restart the Nginx service. Terminal sudo nginx -s stop && sudo nginx Reload the Nginx configuration file. Terminal sudo nginx -s reload Table of Contents 1. Restart the Nginx on macOS 2. Reload […]
In Spring Boot, we can use the @ConditionalOnProperty annotation to conditionally register the beans based on the property value in the application.properties or application.yml file. This article will use the @ConditionalOnProperty annotation to simulate a toggle feature to turn features on or off at runtime without any code changes. Technologies used: Spring Boot 3.1.2 Java […]
This article shows how to do Spring Data JPA paging and sorting using the PagingAndSortingRepository interface. Technologies used: Spring Boot 3.1.2 Spring Data JPA H2 in-memory database Java 17 Maven 3 JUnit 5 Spring Integration Tests with TestRestTemplate Unit Tests with Mocking (Mockito) Table of contents: 1. Extends PagingAndSortingRepository 2. Extends JpaRepository 3. Pageable and […]
This article shows how to use the -U (uppercase U) option to change the user agent in wget command. Terminal wget -U {user-agent} {location} Change user agent in wget The below command changes the wget user agent to Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7). Terminal wget -U "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7)" […]
The IntelliJ cannot find the mysql-connector-java dependency and hits error "unknown was not found"? pom.xml <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> Terminal mysql:mysql-connector-java:jar:unknown was not found in https://repo.maven.apache.org/maven2 during a previous attempt. This failure was cached in the local repository and resolution is not reattempted until the update interval of central has elapsed or updates are […]
This article shows how to delete .DS_Store files from the current directory and all its subdirectories on macOS. 1. Delete “.DS_Store” files The below command will delete .DS_Store files from the current directory and all its subdirectories without asking for confirmation. Terminal find . -name ".DS_Store" -type f -delete The command breakdown: find . – […]
The official Docker mariadb image will run all *.sh and *.sql scripts in its /docker-entrypoint-initdb.d directory automatically when it starts. Table of contents: 1. Create an init.sql 2. Run an init script for Docker MariaDB 3. Access the MariaDB running container 4. References Technologies used: Docker 24.0.5 Official Docker mariadb image (latest tag) 1. Create […]
This article shows how to use Docker to run MariaDB as a container. Tables of contents: 1. Run MariaDB as a container 2. Specify the MariaDB version 3. Access the running MariaDB container 4. MariaDB Persistent Storage with Volume 5. Access the MariaDB container log 6. Stop the MariaDB Container 7. Start the MariaDB Container […]
This article shows how to use @DataJpaTest to test the Spring Data JPA application. Technologies used: Spring Boot 3.1.2 Spring Data JPA (Hibernate 6 is the default JPA implementation) H2 in-memory database Maven Java 17 JUnit 5 Table of contents: 1. Project Directory 2. Spring Data JPA – Entity and Repository 3. @DataJpaTest 3.1 Disable […]
The official Docker postgres image will run all *.sh and *.sql scripts in its /docker-entrypoint-initdb.d directory automatically when it starts. Table of contents: 1. Create an init.sql 2. Copy init.sql to container 3. Start the Postgres container 4. Access the Postgres container 5. References Technologies used: Docker 24.0.5 Official Docker postgres image (latest) 1. Create […]
Learn how to run PostgreSQL as a Docker container using Docker Compose. This guide is perfect for developers who want a clean, isolated database environment for local development and testing.
We migrated the project to Spring Boot 3, and the JPA entity class hits package javax.persistence does not exist. java: package javax.persistence does not exist import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; P.S. Tested with Spring Boot 3.1.2 Solution Spring Boot 3 migrated all Java EE APIs javax.* to their equivalent Jakarta EE variant […]
This article shows how to use @PropertySource annotation to load custom properties files in Spring Boot. Table of contents: 1. Load default properties file 2. Load custom properties files 3. Load multiple custom properties files 4. Download Source Code 5. References P.S. Tested with Spring Boot 3.1.2 1. Load default properties file Spring default loads […]
This article shows how to generate the Maven Wrapper files in a Maven project: mvnw (For Linux or macOS) mvnw.cmd (For Windows) .mvn/wrapper/maven-wrapper.jar .mvn/wrapper/maven-wrapper.properties Table of contents 1. What is Maven Wrapper 2. Generate the mvnw and mvnw.cmd 2.1 Ensure Maven installed 2.2 Navigate to the Maven project 2.3 Generate Maven Wrapper files 2.4 Build […]
This article shows how to test the Spring Boot REST endpoints using TestRestTemplate and Testcontainers (PostgreSQL container). Technologies used : Spring Boot 3.1.2 (Spring Web MVC, Spring Data JPA and Spring Test) Testcontainers 1.19.0 PostgreSQL 15, Alpine Linux base image postgres:15-alpine Java 17 JUnt 5 Tables of contents: 1. Project Structure 2. Project Dependencies 3. […]
Uploads a file and hits the following Nginx error page. Table of Contents 1. Reason 2. Fix the 413 Request Entity Too Large 2.1 Find the Nginx configuration file 2.2 Adjust the client_max_body_size 2.3 Reload Nginx 3. client_max_body_size default limit References 1. Reason The 413 Request Entity Too Large error in Nginx means the request […]