Spring Data: Bridging Multiple Databases/

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Solution: Fine Calculation System

Solution: Fine Calculation System

Here's the solution to the fine calculation system challenge.

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Solution

Let’s discuss the solution for implementing a fine calculation system.

Update the Book document

First, we add the Boolean available property to the Book class.

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package com.smartdiscover.document;
import lombok.Data;
import org.springframework.data.annotation.*;
import org.springframework.data.mongodb.core.mapping.DBRef;
import org.springframework.data.mongodb.core.mapping.Document;
import java.util.Date;
import java.util.List;
import java.util.stream.Collectors;
@Data
@Document
public class Book {
    @Id
    private String id;
    private String name;
    private String summary;
    private Boolean available;
    @CreatedBy
    private String createdBy;
    @CreatedDate
    private Date createdDate;
    @LastModifiedBy
    private String lastModifiedBy;
    @LastModifiedDate
    private Date lastModifiedDate;
    @DBRef
    private List<Author> authors;
    @Override
    public String toString() {
        return "Book{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", summary='" + summary + '\'' +
                ((null != authors) ? ", authors=" + authors.stream().map(i -> i.getFirstName()).collect(Collectors.toList()) + '\'' : "") +
                ", createdBy='" + createdBy + '\'' +
                ", createdDate='" + createdDate + '\'' +
                ", lastModifiedBy='" + lastModifiedBy + '\'' +
                ", lastModifiedDate='" + lastModifiedDate + '\'' +
                '}';
    }
}

Update the BookRepository

Then, we add the findByNameAndAvailableIsNullOrAvailableIsTrue method in the BookRepository interface to search for a book by matching the name and its availability as Null or True.

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package com.smartdiscover.repository;
import com.smartdiscover.document.Book;
import org.springframework.data.mongodb.repository.MongoRepository;
import java.util.List;
public interface BookRepository extends MongoRepository<Book, String> {
    Book findFirstByName(String name);
    List<Book> findAllByName(String name);
    Book findByNameAndAvailableIsNullOrAvailableIsTrue(String name);
    
}

Create the BookLoanEntry document

Then, we create the BookLoanEntry class in the com.smartdiscover.document package.

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package com.smartdiscover.document;
import lombok.Data;
import org.springframework.data.annotation.*;
import org.springframework.data.mongodb.core.mapping.DBRef;
import org.springframework.data.mongodb.core.mapping.Document;
import java.util.Date;
@Data
@Document
public class BookLoanEntry {
    @Id
    private String id;
    private String userFirstName;
    private String userLastName;
    @DBRef
    private Book book;
    private Date loanDate;
    private Date dueDate;
    private Date returnDate;
    private String status;
    @CreatedBy
    private String createdBy;
    @CreatedDate
    private Date createdDate;
    @LastModifiedBy
    private String lastModifiedBy;
    @LastModifiedDate
    private Date lastModifiedDate;
}

Explanation:

  • Lines 10–12: We add annotations like @Data and @Document to transform a class into a document. ...