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Spring Data: Bridging Multiple Databases

Solution: Book Review System

Explore how to build a book review system by modeling User and BookReview entities as Couchbase documents. Understand repository interfaces for querying data with consistency guarantees and implement core methods for saving reviews, fetching reviews by book, and calculating average ratings using Spring Data Couchbase.

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Solution

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

Create the User class

First, we create the User class in the com.smartdiscover.model package.

Java
package com.smartdiscover.model;
import lombok.Data;
import org.springframework.data.annotation.Id;
import org.springframework.data.couchbase.core.mapping.Document;
import org.springframework.data.couchbase.core.mapping.id.GeneratedValue;
import org.springframework.data.couchbase.core.mapping.id.GenerationStrategy;
@Data
@Document
public class User {
    @Id
    @GeneratedValue(strategy = GenerationStrategy.UNIQUE)
    private String id;
    private String firstName;
    private String lastName;
}

Code explanation:

  • Lines 9–11: We add annotations like @Data and @Document to transform a class into a Couchbase document.

  • Lines 13 and 14: We add the id identifier with a unique generation strategy.

  • Lines 17 and 19: We added the firstName and lastName properties.

Create the BookReview class

Then, we create the BookReview class in the com.smartdiscover.model package.

Java
package com.smartdiscover.model;
import lombok.Data;
import org.springframework.data.annotation.Id;
import org.springframework.data.couchbase.core.mapping.Document;
import org.springframework.data.couchbase.core.mapping.id.GeneratedValue;
import org.springframework.data.couchbase.core.mapping.id.GenerationStrategy;
@Data
@Document
public class BookReview {
    @Id
    @GeneratedValue(strategy = GenerationStrategy.UNIQUE)
    private String id;
    private User user;
    private Book book;
    private int rating;
    private String review;
}

Code explanation:

  • Lines 9–11: We add annotations like @Data and @Document to transform a class into ...