Category: Spring

To pass a List (or any Collection) into a Spring Data JPA repository query, you can use the IN clause in JPQL or native SQL, and Spring will automatically bind the list elements. ✅ Example 1: Using @Query with JPQL @Query(“SELECT p FROM Product p WHERE p.id IN :ids”) List<Product> findByIds(@Param(“ids”) List<Long> ids); You can…

A Spring Data Repository typically returns entities or List of Object arrays List<Object[]> – for custom queries, not collections like HashMap<K, V> directly. You can structure a custom query or a method that returns a Map in your Service or in additional method, but it’s not automatic — you have to be explicit about it….

Spring Boot decides which format (JSON, XML, Protobuf, etc.) to use when handling a request based on the configuration for content negotiation. 1. Content Negotiation in Spring Boot Spring Boot decides how to serialize and deserialize request/response bodies using HttpMessageConverters. These converters are automatically registered based on the libraries in the classpath. 2. How Does…

The N+1 query problem is a common issue that occurs when using JPA repositories in Spring Boot. It happens when you have a one-to-many or many-to-one relationship between entities, and you’re fetching the parent entity with its children. This results in a separate database query for each child, leading to inefficient performance. Optimizing N+1 Query…

Here are minimal examples of different Database Integrations in Spring Boot that you could choose from in your applications. 1. JdbcTemplate (Plain JDBC) JdbcTemplate is a lower-level approach that directly executes SQL queries. import org.springframework.jdbc.core.JdbcTemplate; import org.springframework.jdbc.core.RowMapper; import org.springframework.stereotype.Repository; import java.sql.ResultSet; import java.sql.SQLException; import java.util.List; @Repository public class UserJdbcRepository { private final JdbcTemplate jdbcTemplate; public…

You can use Spring Data JPA’s @ Modifying and @ Query annotations to achieve Update a field of a Table using Sping Repository Modifying Query. Spring Repository Here is an example: import org.springframework.data.jpa.repository.Modifying; import org.springframework.data.jpa.repository.Query; import org.springframework.data.repository.CrudRepository; import org.springframework.transaction.annotation.Transactional; public interface UserRequestRepository extends CrudRepository<UserRequest, Long> { @Modifying @Query(“UPDATE UserRequest u SET u.fieldCount = 0”) void…

How to check for presence of specific header in every request with spring boot and if it is not – return 401? You can achieve this by implementing a custom HandlerInterceptor in Spring Boot. Here’s an example: import org.springframework.stereotype.Component; import org.springframework.web.servlet.HandlerInterceptor; import org.springframework.web.servlet.ModelAndView; import jakarta.servlet.http.HttpServletRequest; import jakarta.servlet.http.HttpServletResponse; //import javax.servlet.http.HttpServletRequest; //import javax.servlet.http.HttpServletResponse; import java.util.Arrays; @Component public…

The error java.io.IOException: Stream Closed indicates that the InputStream passed to the InputStreamResource has already been closed before it is read by the Spring framework to create the response. Use Case The use case where you may need to encounter this error is file download from Spring Boot App. Writing down bytes loaded in memory…

Implementing checkpoint or partial commits within a database transaction in a Spring Boot service can be tricky since Spring transactions are designed to be atomic: they either fully commit or fully roll back. However, you can achieve a similar effect by managing transactions explicitly in your service layer and leveraging Spring’s PlatformTransactionManager or nested transactions…