Author: anis kchaou

🔑 Hibernate / JPA Annotations Cheat Sheet AnnotationPurpose@EntityMarks a class as a persistent entity (mapped to a table).@Table(name = "...")Customizes the table name.@IdMarks the primary key field.@GeneratedValue(strategy = ...)Specifies primary key generation strategy. Common for Postgres: GenerationType.IDENTITY or GenerationType.SEQUENCE.@ColumnCustomizes a column (name, nullable, length, unique, etc.).@ManyToOneDefines a many-to-one relationship (foreign key).@OneToManyDefines a one-to-many relationship…

🚀 Common Spring Data JPA Annotations @Entity → Marks a class as a JPA entity (maps to a table). @Table → Specifies the table name in the database. @Id → Marks a field as the primary key. @GeneratedValue → Defines how the primary key is generated (IDENTITY, SEQUENCE, etc.). @Column → Customizes column mapping…

WebClient is the non-blocking, reactive HTTP client in Spring WebFlux, introduced as a replacement for RestTemplate (though RestTemplate is still supported for blocking I/O). 1. Add Dependency If you’re using Maven, add: <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-webflux</artifactId> </dependency> For Gradle: implementation 'org.springframework.boot:spring-boot-starter-webflux' implementation 'org.springframework.boot:spring-boot-starter-webflux' 2. Create a WebClient Bean You can configure…

1. What is Liquibase? Liquibase is a database version control tool. It allows you to manage schema changes (like creating tables, adding columns, indexes, etc.) across environments in a consistent way. With Spring Boot, it integrates seamlessly. 2. Add Dependencies In your pom.xml (Maven project): <dependencies> <!-- Spring Boot Starter Data JPA --> <dependency>…

📌 Common Spring Data MongoDB Annotations @DocumentMarks a class as a MongoDB document (like an @Entity in JPA).collection attribute can specify the collection name.@Document(collection = "users") public class User { ... } @IdMarks the primary identifier field (usually _id in MongoDB).@Id private String id; @FieldMaps a Java field to a specific MongoDB field name.@Field("user_name")…

🔹 What is Spring Data Redis? Spring Data Redis provides easy integration with Redis, an in-memory key-value store. It abstracts the low-level Redis API and gives you repositories, templates, pub/sub messaging, and caching support. 🔹 Maven Dependency Add this to your pom.xml: <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> <dependency> <groupId>io.lettuce</groupId> <artifactId>lettuce-core</artifactId> <!-- Lettuce is the default…

Feign is a declarative REST client in Spring Cloud that makes writing web service clients easier. Instead of writing boilerplate RestTemplate or WebClient code, you define an interface and annotate it — Spring generates the implementation for you at runtime. Here’s a step-by-step example of using Feign Client in Spring Boot: 1. Add dependencies…

1. Add Dependencies If you’re using Maven, add the following to your pom.xml: <dependencies> <!-- Spring Boot Starter Web --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!-- GraphQL Starter --> <dependency> <groupId>com.graphql-java</groupId> <artifactId>graphql-spring-boot-starter</artifactId> <version>5.0.2</version> </dependency> <!-- GraphQL Tools (schema parsing) --> <dependency> <groupId>com.graphql-java-kickstart</groupId> <artifactId>graphql-java-tools</artifactId> <version>11.0.0</version> </dependency> <!-- Optional: GraphiQL UI --> <dependency> <groupId>com.graphql-java-kickstart</groupId> <artifactId>graphiql-spring-boot-starter</artifactId> <version>11.1.0</version> </dependency>…

1. Setup your Spring Boot project You can generate a Spring Boot project via Spring Initializr with the following dependencies: Spring Web (optional for testing REST endpoints) gRPC (we’ll add via Maven) Protobuf (for compiling .proto files) Lombok (optional, for boilerplate reduction) Your pom.xml should include: <dependencies> <!-- Spring Boot Starter --> <dependency> <groupId>org.springframework.boot</groupId>…

In Spring Boot, RestTemplate is used to make synchronous HTTP requests to other services (GET, POST, PUT, DELETE). Although Spring recommends using WebClient for reactive applications, RestTemplate is still widely used in many projects. Here's a clear example: 1. Add Dependencies If you are using Maven, make sure you have Spring Web dependency: <dependency>…