Store the Java object received in table format in the related model

About this article

Receives tabular objects from the database in Java I was sick when storing that object in a structured object ...

A memo of the solution that doubles as a memorandum.

Introduction

I got this kind of table data from BD

|
|--Company A---------programming---------Basic summary
|   　       |                    |
|   　       |                    |----Even monkeys can understand
|    　      |                    |
|   　       |                    |----Out of order
|   　       |    
|   　       |        
|   　       |----Shogi------------Basic summary
|                                |
|   　        　                    |----Even monkeys can understand
|   　
|   　
|--Company B---------programming---------Basic summary
|    　      |                    
|   　       |----Shogi---------Basic summary

I want to map to a Java object like this.

When you select a publisher, the corresponding genre will appear, When you select a genre, the corresponding book information will come out ...

Finally I want a list of publishers.

Java object

Java object to get table information

BookResultMap

package dto;

import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class BookResultMap {
	private String publisherName;
	private String genreName;
	private String bookTitle;

	public BookResultMap() {}

	public BookResultMap(String publisherName, String genreName, String bookTitle) {
		this.publisherName = publisherName;
		this.genreName = genreName;
		this.bookTitle = bookTitle;
	}
}

Java object that finally stores the data

Book: A class that represents book information. Genre: A class that represents a genre. It has List as an element. Publisher: A class that represents publisher information. It has List as an element.

Book.java

package model;

import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class Book {
	private String bookTitle;
}

Genre.java

package model;

import java.util.List;

import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class Genre {
	private String genreName;
	private List<Book> bookList;
}

Publisher.java

package model;

import java.util.List;

import lombok.Getter;
import lombok.Setter;

@Setter
@Getter
public class Publisher {
	private String publisherName;
	private List<Genre> genreList;
}

Implementation

DataConvert.java

package logic;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import dto.BookResultMap;
import model.Book;
import model.Genre;
import model.Publisher;

public class DataConvert {
    public static List<Publisher> convertObject(List<BookResultMap> bookResultMaps) {

		/*A map that stores each relationship.
		 *The value of the map with publishName as the key,
		 *Set to the map with genreName as the key.
		*/
		Map<String, Map<String, List<Book>>> convertMap = new HashMap<>();
		for(int i = 0; i < bookResultMaps.size(); i++) {
			String publisherName = bookResultMaps.get(i).getPublisherName();
			String genreName = bookResultMaps.get(i).getGenreName();
			Book book = new Book();
			book.setBookTitle(bookResultMaps.get(i).getBookTitle());

			/*1.If publisherName doesn't exist as a key in convertMap
			 *Create a HashMap with publishName as the key in convertMap.
			*/
			if(!convertMap.containsKey(publisherName)) {
				convertMap.put(publisherName, new HashMap<>());
			}
			
			/*2.If geneName is convertMap.get(publisherName)If it didn't exist as a key to
			 * convertMap.get(publisherName)Create a HashMap with publishName as the key.
			*/
			if(!convertMap.get(publisherName).containsKey(genreName)) {
				convertMap.get(publisherName).put(genreName, new ArrayList<>());
			}
			/*1,By doing the work of 2
			 *Because you can get the ArrayList in the Genre related to the publisherName
			 *Store the Book there.
			 * */
			convertMap.get(publisherName).get(genreName).add(book);
		}

		//Replace the information stored in convertMap with a Java object.
		List<Publisher> publisherList = new ArrayList<>();
		for(String publisherName: convertMap.keySet()) {
			Publisher publisher = new Publisher();
			List<Genre> genreList = new ArrayList<>();
			publisher.setPublisherName(publisherName);
			publisher.setGenreList(genreList);
			publisherList.add(publisher);

			for(String genreName: convertMap.get(publisherName).keySet()) {
				Genre genre = new Genre();
				genre.setGenreName(genreName);
				genre.setBookList(convertMap.get(publisherName).get(genreName));
				genreList.add(genre);
			}
		}

		return publisherList;
	}
}

Verification

input

DataConvert.java

public class DataConvert {

	public static void main(String[] args) {

		//Object received as is from the database in the form of a table
		List<BookResultMap> bookResultMaps = new ArrayList<>();
		BookResultMap brm1_1_1 = new BookResultMap("Company A", "programming", "Basic summary");
		BookResultMap brm1_1_2 = new BookResultMap("Company A", "programming", "Even monkeys can understand");
		BookResultMap brm1_2_1 = new BookResultMap("Company A", "Shogi", "Basic summary");
		BookResultMap brm1_2_2 = new BookResultMap("Company A", "Shogi", "Even monkeys can understand");
		BookResultMap brm2_1_1 = new BookResultMap("Company B", "programming", "Basic summary");
		BookResultMap brm2_2_1 = new BookResultMap("Company B", "Shogi", "Basic summary");
		BookResultMap brm1_1_3 = new BookResultMap("Company A", "programming", "Out of order");
		bookResultMaps.add(brm1_1_1);
		bookResultMaps.add(brm1_1_2);
		bookResultMaps.add(brm1_2_1);
		bookResultMaps.add(brm1_2_2);
		bookResultMaps.add(brm2_1_1);
		bookResultMaps.add(brm2_2_1);
		bookResultMaps.add(brm1_1_3);

		//Data conversion
		List<Publisher> publisherList = convertObject(bookResultMaps);

		//Verification
		System.out.println("publisherList size:" + publisherList.size());
		for(Publisher publisher: publisherList) {
			System.out.println("-------------------"+ publisher.getPublisherName() +"-----------------------");
			System.out.println("size of genreList:" + publisher.getGenreList().size());
			for(Genre genre: publisher.getGenreList()) {
				System.out.println("-------"+ genre.getGenreName() +"--------");
				System.out.println("bookList size:"+  + genre.getBookList().size());
				for(Book book: genre.getBookList()) {
					System.out.println("----");
					System.out.println(publisher.getPublisherName());
					System.out.println(genre.getGenreName());
					System.out.println(book.getBookTitle());
				}
			}
		}
	}
}

Output result

publisherList size:2
-------------------Company B-----------------------
size of genreList:2
-------programming--------
bookList size:1
----
Company B
programming
Basic summary
-------Shogi--------
bookList size:1
----
Company B
Shogi
Basic summary
-------------------Company A-----------------------
size of genreList:2
-------programming--------
bookList size:3
----
Company A
programming
Basic summary
----
Company A
programming
Even monkeys can understand
----
Company A
programming
Out of order
-------Shogi--------
bookList size:2
----
Company A
Shogi
Basic summary
----
Company A
Shogi
Even monkeys can understand

I was able to associate this information with the publisher and genre.

At the end

I think there are other ways, but for the time being, I wrote my own solution. If you want to keep the order of the table, you can change HashMap to LinkedHashMap. I would be grateful if you could let me know if there are any better methods or improvements.

By sorting by SQL or changing the structure, I want you to get the table data in a form that is easier to process ...