I have a 4 table. I created a join query

Question

I have a 4 table. I created a join query

with some specific field for the tables . I want to call the query in spring boot within single dto. How I can do that ?
I am using jdbc template but it's not the good way my senior says.

0

24.11.2023

4 ответов

32 просмотра

venkat

Certainly! To call a join query in Spring Boot with JDBC template and map the results to a single DTO: 1. Create a DTO: Define a DTO class with fields matching the query result. 2. Write a Join Query: Use JDBC template to execute the join query across your tables. 3. Map Results to DTO: Manually map the result set to your DTO object. However, if your senior suggests a better way, consider using Spring Data JPA: 1. Create a DTO: Define a DTO class. 2. Write a Repository Interface: Use Spring Data JPA's @Query to write a custom query in your repository interface, mapping directly to your DTO. 3. Invoke Query in Service: In your service, call the repository method to execute the query and return the mapped DTO. This way, Spring Data JPA simplifies the process by handling the mapping for you.

0

24.11.2023

venkat

Certainly! Let's go through a more detailed example using Spring Data JPA for clarity. Assume you have two entities: Author and Book, and you want to retrieve a list of books with their authors. First, create DTOs for the result: public class BookDTO { private String title; private String authorName; public BookDTO(String title, String authorName) { this.title = title; this.authorName = authorName; } // getters and setters } Now, create a repository interface for your entities: import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.Query; import org.springframework.data.repository.query.Param; import java.util.List; public interface BookRepository extends JpaRepository<Book, Long> { @Query("SELECT new com.example.BookDTO(b.title, a.authorName) FROM Book b JOIN b.author a WHERE b.genre = :genre") List<BookDTO> findBooksByGenre(@Param("genre") String genre); } In this example, Book has a ManyToOne relationship with Author. The query selects BookDTO instances directly, mapping the title from the book and the author's name. Finally, use this repository in a service: import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; import java.util.List; @Service public class BookService { @Autowired private BookRepository bookRepository; public List<BookDTO> getBooksByGenre(String genre) { return bookRepository.findBooksByGenre(genre); } } Now, when you call getBooksByGenre in your service, it executes the custom query defined in the repository and returns a list of BookDTO objects, neatly mapping the results to your desired DTO structure.

0

24.11.2023

M

venkat
Certainly! Let's go through a more detailed exampl...

how do you send codes like this on telegram?

0

24.11.2023

venkat · Accepted Answer

If you want to fetch data from multiple tables and map it to a single DTO in Spring Boot, you can consider using Spring Data JPA with native queries or JPQL (Java Persistence Query Language). 1. Create a DTO class: Define a class that represents the result set of your query. Ensure that the fields in the DTO match the columns you are retrieving from the query. public class YourResultDTO { private String field1; private String field2; // Add other fields as needed // Constructors, getters, setters } 2. Write a Repository Interface: Create a repository interface where you define your custom query using @Query annotation. This can be a native query or JPQL, depending on your preference. import org.springframework.data.jpa.repository.Query; import org.springframework.data.repository.query.Param; public interface YourRepository extends JpaRepository<YourEntity, Long> { @Query("SELECT new com.example.YourResultDTO(e.field1, e.field2) FROM YourEntity e WHERE ...") // Your custom query List<YourResultDTO> yourCustomQueryMethod(@Param("param1") Type param1, ...); } 3. Invoke the Query in Your Service: In your service class, use the repository method to execute the query and retrieve the results. @Service public class YourService { @Autowired private YourRepository yourRepository; public List<YourResultDTO> getResults() { // Invoke your custom query method return yourRepository.yourCustomQueryMethod(param1, ...); } } This approach helps you map the query results directly to a DTO, providing a clean and object-oriented way to handle the data. It also leverages the power of Spring Data JPA for database operations. Remember to replace placeholders like YourEntity, YourResultDTO, and method parameters with your actual entity and DTO names, as well as the appropriate fields and conditions in your query.

Похожие чаты

I have a 4 table. I created a join query

4 ответов

Похожие вопросы