Grasshopper ----------> Master ( D 2 ): August 2021

The purpose of this blogpost is to explain main components and layers of a simple spring boot application and how to develop them.

Please find the source code for above application.

Rest Controller

This is sample post method.
Request body can be validated with @Validate annotation.
HTTP status code for success scenario can be mentioned with @ResponseStatus annotation.
URI is /sb/transactions.
We can use ResponseStatusException for other HTTP status code based on each scenario.

Service Implementation

Logging can be initialized by lombok @Slf4j annotation .
Constructor with argument can be created with lombok @RequiredArgsConstructor annotation .
We can map DTO to domain object and wise versa using transactionMapper .
Using transactionRepository we can persist the domain object in database through JPA/JDBC .

JPA Repository/Backend Layer

Most of the commonly used CRUD operations based on domain entity and primary key can be found from JpaRepository .
For the native query, we have used a custom method.

Native query can be found in the same domain entity class Transaction .
The name of the native query should be : (Entity class name) . ( Domain Repository method name) - @NamedNativeQuery(name = "Transaction.findStatistics",
@SqlResultSetMapping(name = "Mapping.StatisticsDto" : This will map sql result set to DTO.
Please note that constructor of DTO have to create manually since order of argument data type should match with @SqlResultSetMapping columns.

public StatisticsDto(BigDecimal sum, BigDecimal avg, BigDecimal max, BigDecimal min,Long count)

Spring Boot Application : Where Every things Begins

Data Mapper

We can use multiple mapper classes like DateMapper.class .
componentModel = "spring" should be mentioned, then only mapstruct can be used within spring.
DateMapper useful when we deserialize JSON to java object and wise versa since parser can identify Java 8 Date Time package.

Mockito with Spring Boot