Spring Data: Bridging Multiple Databases/

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Solution: Book Loan System

Solution: Book Loan System

Here's the solution to the book loan system challenge.

We'll cover the following...

Solution

Let’s discuss the solution for implementing a book loan system.

Update the Book class

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

package com.smartdiscover.entity;
import jakarta.persistence.*;
import lombok.Data;
import org.springframework.data.annotation.CreatedBy;
import org.springframework.data.annotation.CreatedDate;
import org.springframework.data.annotation.LastModifiedBy;
import org.springframework.data.annotation.LastModifiedDate;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;
import java.util.Date;
import java.util.List;
import java.util.stream.Collectors;
@Data
@Entity
@EntityListeners(AuditingEntityListener.class)
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long 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;
    @ManyToMany
    @JoinTable(
            name = "book_authors",
            joinColumns = @JoinColumn(name = "book_id"),
            inverseJoinColumns = @JoinColumn(name = "author_id"))
    private List<Author> authors;
    @Override
    public String toString() {
        return "Book{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", summary='" + summary + '\'' +
                ", authors='" + (null != authors && authors.size() > 0 ? (authors.stream().map(i -> i.getFullName()).collect(Collectors.toList())) : "[]") + '\'' +
                ", createdBy='" + createdBy + '\'' +
                ", createdDate='" + createdDate + '\'' +
                ", lastModifiedBy='" + lastModifiedBy + '\'' +
                ", lastModifiedDate='" + lastModifiedDate + '\'' +
                '}';
    }
}

Update the BookRepository interface

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

package com.smartdiscover.repository;
import com.smartdiscover.entity.Book;
import org.springframework.data.jpa.repository.JpaRepository;
public interface BookRepository extends JpaRepository<Book, Long> {
    Book findByNameAndAvailableIsNullOrAvailableIsTrue(String name);
    Book findFirstBySummaryIsLikeOrderByNameAsc(String summary);
    
}

Create the BookLoanEntry class

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

package com.smartdiscover.entity;
import jakarta.persistence.*;
import lombok.Data;
import org.springframework.data.annotation.CreatedBy;
import org.springframework.data.annotation.CreatedDate;
import org.springframework.data.annotation.LastModifiedBy;
import org.springframework.data.annotation.LastModifiedDate;
import org.springframework.data.jpa.domain.support.AuditingEntityListener;
import java.util.Date;
@Data
@Entity
@EntityListeners(AuditingEntityListener.class)
public class BookLoanEntry {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String userFirstName;
    private String userLastName;
    @ManyToOne
    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;
}
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