Interview ‐ Spring Data (JpaRepository, MongoRepository)

📘 Spring Data Repository Interface

Repository Hierarchy

Repository<T, ID>                               ← Marker interface (no methods)
  └── CrudRepository<T, ID>                     ← Basic CRUD operations
        └── PagingAndSortingRepository<T, ID>   ← + Sorting & Pagination
              ├── JpaRepository<T, ID>          ← + JPA-specific (flush, batch delete, getOne)
              └── MongoRepository<T, ID>        ← + Mongo-specific (insert)

Both JpaRepository and MongoRepository also extend QueryByExampleExecutor<T>.

JpaRepository	MongoRepository
package org.springframework.data.jpa.repository; import org.springframework.data.repository.PagingAndSortingRepository; import org.springframework.data.repository.query.QueryByExampleExecutor; @org.springframework.data.repository.NoRepositoryBean public interface JpaRepository<T, ID> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> { @Override List<T> findAll(); @Override List<T> findAll(Sort sort); @Override List<T> findAllById(Iterable<ID> ids); @Override <S extends T> List<S> saveAll(Iterable<S> entities); // Flushes all pending changes to the database. void flush(); // Saves an entity and flushes changes instantly. <S extends T> S saveAndFlush(S entity); void deleteInBatch(Iterable<T> entities); void deleteAllInBatch(); T getOne(ID id); @Override <S extends T> List<S> findAll(Example<S> example); @Override <S extends T> List<S> findAll(Example<S> example, Sort sort); }	package org.springframework.data.mongodb.repository; import org.springframework.data.repository.PagingAndSortingRepository; import org.springframework.data.repository.query.QueryByExampleExecutor; @org.springframework.data.repository.NoRepositoryBean public interface MongoRepository<T, ID> extends PagingAndSortingRepository<T, ID>, QueryByExampleExecutor<T> { @Override <S extends T> List<S> saveAll(Iterable<S> entities); @Override List<T> findAll(); @Override List<T> findAll(Sort sort); <S extends T> S insert(S entity); <S extends T> List<S> insert(Iterable<S> entities); @Override <S extends T> List<S> findAll(Example<S> example); @Override <S extends T> List<S> findAll(Example<S> example, Sort sort); }
package org.springframework.data.repository; // ── Paging & Sorting ────────────────────────────────────────────────────────── @NoRepositoryBean public interface PagingAndSortingRepository<T, ID> extends CrudRepository<T, ID> { Iterable<T> findAll(org.springframework.data.domain.Sort sort); // All records, sorted Page<T> findAll(org.springframework.data.domain.Pageable pageable); // Paginated + sorted result } // ── Basic CRUD ──────────────────────────────────────────────────────────────── @NoRepositoryBean public interface CrudRepository<T, ID> extends Repository<T, ID> { <S extends T> S save(S entity); // Insert or Update (upsert) <S extends T> Iterable<S> saveAll(Iterable<S> entities); // Bulk upsert Optional<T> findById(ID id); // Find by PK → Optional (never null) boolean existsById(ID id); // Check existence by PK Iterable<T> findAll(); // Fetch all records Iterable<T> findAllById(Iterable<ID> ids); // Fetch by list of PKs long count(); // Total row/document count void deleteById(ID id); // Delete by PK void delete(T entity); // Delete given entity void deleteAll(Iterable<? extends T> entities); // Delete given list void deleteAll(); // Delete everything — USE WITH CAUTION } // ── Marker interface ────────────────────────────────────────────────────────── @Indexed public interface Repository<T, ID> { }

Maven Dependency, application.properties

spring-boot-starter-data-jpa

spring-boot-starter-data-mongodb

Maven Dependency <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> <exclusions> <!-- Exclude HikariCP if using Tomcat JDBC pool instead --> <exclusion> <groupId>com.zaxxer</groupId> <artifactId>HikariCP</artifactId> </exclusion> </exclusions> </dependency> <!-- SQL Server JDBC driver --> <dependency> <groupId>com.microsoft.sqlserver</groupId> <artifactId>mssql-jdbc</artifactId> <scope>runtime</scope> </dependency> <!-- Tomcat JDBC Connection Pool (if replacing HikariCP) --> <dependency> <groupId>org.apache.tomcat</groupId> <artifactId>tomcat-jdbc</artifactId> </dependency> application.properties #----------------------------------------- # SQL Server DataBase Properties #----------------------------------------- spring.datasource.url=jdbc:sqlserver://localhost:1433;databaseName=finance spring.datasource.username=sa spring.datasource.password=Strong@123 spring.datasource.driver-class-name=com.microsoft.sqlserver.jdbc.SQLServerDriver spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.SQLServerDialect #----------------------------------------- # DataBase Connection Pool (Tomcat JDBC) #----------------------------------------- spring.datasource.type=org.apache.tomcat.jdbc.pool.DataSource spring.datasource.tomcat.test-on-borrow=true spring.datasource.tomcat.test-while-idle=true spring.datasource.tomcat.test-on-return=false spring.datasource.tomcat.validation-query=select 1 spring.datasource.tomcat.initial-size=15 spring.datasource.tomcat.max-wait=20000 spring.datasource.tomcat.max-active=50 spring.datasource.tomcat.max-idle=15 spring.datasource.tomcat.min-idle=8 spring.datasource.tomcat.default-auto-commit=true spring.datasource.tomcat.log-validation-errors=true spring.datasource.log-abandoned=true #----------------------------------------- # JPA / Hibernate Properties #----------------------------------------- # none | validate | update | create | create-drop spring.jpa.hibernate.ddl-auto=update spring.jpa.show-sql=false # Preserve column names as declared in @Column(name="...") spring.jpa.hibernate.naming.implicit-strategy=org.hibernate.boot.model.naming.ImplicitNamingStrategyLegacyJpaImpl spring.jpa.hibernate.naming.physical-strategy=org.hibernate.boot.model.naming.PhysicalNamingStrategyStandardImpl # Required for @CreatedDate / @LastModifiedDate to work spring.jpa.properties.javax.persistence.validation.mode=none

Maven Dependency <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-mongodb</artifactId> </dependency> #----------------------------------------- # MongoDB Properties #----------------------------------------- spring.data.mongodb.uri=mongodb://localhost:27017/local?authSource=admin&ssl=false&maxPoolSize=1000 # Alternative: individual properties # spring.data.mongodb.host=localhost # spring.data.mongodb.port=27017 # spring.data.mongodb.database=local # spring.data.mongodb.username=admin # spring.data.mongodb.password=secret