bean required in Spring application with JPARepository

Question

I have a problem with bean instantiation.

Parameter 0 of constructor in table.football.play.service.impl.PlayerServiceImpl required a bean of type 'table.football.play.repository.PlayerRepository' that could not be found.

error

this is my class

package table.football.play.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
import table.football.play.entity.Player;

@Repository
public interface PlayerRepository extends JpaRepository<Player,Long> {
  
}

and this is service implementation :

package table.football.play.service.impl;

import static table.football.play.util.ConvertEntityToDto.convertListPlayerEntityToListPlayerDto;

import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import table.football.play.dto.PlayerDTO;
import table.football.play.entity.Player;
import table.football.play.repository.PlayerRepository;
import table.football.play.service.interf.PlayerService;

@Service
public class PlayerServiceImpl implements PlayerService{
  
  private PlayerRepository playerRepository;
  
  @Autowired
  public PlayerServiceImpl(PlayerRepository playerRepository){
    this.playerRepository = playerRepository;
  }
  
  @Override
  public List<PlayerDTO> findAll(){
    List<Player> listPlayer = playerRepository.findAll();
    List<PlayerDTO> playerDTOList = convertListPlayerEntityToListPlayerDto(listPlayer);
    return playerDTOList;
  }


}

there a entity class

package table.football.play.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import lombok.Data;

@Data
@Entity
@Table(name="players")
public class Player {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;
  
  @Column(name="name")
  private String name;
  @Column(name="surname")
  private String surname;
  
}

lastly this is my pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.1.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>table.football</groupId>
    <artifactId>play</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>game</name>
    <description>calcio balilla project</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>javax.persistence</groupId>
            <artifactId>javax.persistence-api</artifactId>
            <version>2.2</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
            <version>3.1.5</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>${project.parent.version}</version>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

I try @Autowired also on field (it's a better practice? or it's good to post @Autowired on constructor? or it the same?)

I have read about some people talk about create a default constructor ... But Repository is an interface , how can i resolve it?

Can someone also explain me the theory behind this error ? It is not enough for me just that it works, I would like to understand.

Thank you very much!

Answer 1

The problem is in dependency injection that you are using in Service class(it not work so, please read the documentation).

Instead of:

private PlayerRepository playerRepository;
  
  @Autowired
  public PlayerServiceImpl(PlayerRepository playerRepository){
    this.playerRepository = playerRepository;
  }

Write field injection

@Autowired
private PlayerRepository playerRepository;

Or Constructor Injection:

private final PlayerRepository playerRepository;
  
  
  public PlayerServiceImpl(PlayerRepository playerRepository){
    this.playerRepository = playerRepository;
  }

And also the second problem is here

<dependency>
            <groupId>javax.persistence</groupId>
            <artifactId>javax.persistence-api</artifactId>
            <version>2.2</version>
        </dependency>

Because you are using spring boot > 3.x that are using Jakarta.persistence not javax just remove that dependency and follow next one steps.

To fix it replace

<dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
            <version>3.1.5</version>
        </dependency>

To

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
    <version>3.1.5</version>
</dependency>

And in Entity class replace all javax. imports to jakarta.

It is going to fix the problem.