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Vaadin object is not an instance of declaring class

I’m trying to call a method in class named (DataActions) to the dashboard view so the grid can be able to receive the objects given after the method execution, but still no luck solving this error (java.lang.IllegalArgumentException: object is not an instance of declaring class).

-Class (DataSession) is the class responsible for opening the database session. -Class (DataActions) is the class responsible for the methods used to extract information from the database using a session created by an (DataSession object) -Method updateGrid calls a method in (DataActions) using an object created.

This project was created with vaadin hello world example project, so it uses springboot (version 2.4.5) and vaadin flow (version 14.7.0).

–Dashboard View–

package com.example.application.views.dashboard;

import com.example.application.Controller.DataActions;
import com.vaadin.flow.component.grid.Grid;
import com.vaadin.flow.component.orderedlayout.VerticalLayout;
import com.example.application.Model.PatientsTblEntity;
import com.vaadin.flow.router.Route;
import com.vaadin.flow.router.PageTitle;
import com.example.application.views.MainLayout;
import com.vaadin.flow.router.RouteAlias;

@PageTitle("Dashboard")
@Route(value = "dashboard", layout = MainLayout.class)
@RouteAlias(value = "", layout = MainLayout.class)
public class DashboardView extends VerticalLayout {

    Grid<PatientsTblEntity> patients_grid = new Grid<>(PatientsTblEntity.class);
    DataActions actions = new DataActions();
    public DashboardView(){
        addClassName("list-view");
        configureGrid();
        add(patients_grid);
        updateGrid();

    }




    /*
        -Configuring grid properties, so it can handle data coming from another function
     */
    public void configureGrid(){
        patients_grid.addClassName("contact-grid");
        patients_grid.setSizeFull();
//        patients_grid.setColumns("txtCode", "txtName", "dblAge", "datDateOfBirth", "datOfLasttVisit");
        patients_grid.getColumns().forEach(patientsTblEntityColumn -> {
            patientsTblEntityColumn.setAutoWidth(true);
        });
    }

    /*
        -Update grid with information coming from the database using actions from class DataActions
     */
    public void updateGrid(){
            patients_grid.setItems(actions.getAllPatientsList());


    }

}

–DataActions class–

package com.example.application.Controller;

import com.example.application.Model.PatientsTblEntity;
import org.hibernate.Session;

import java.util.List;

public class DataActions {
    public DataActions(){}
    DataSessions dataSessions = new DataSessions();
    /*
        -Variable where session is created
        -Created as a variable, so it can be opened and closed at ease in every function
     */
    private Session session = dataSessions.getSession();


    public List<PatientsTblEntity> getAllPatientsList(){
        session.beginTransaction();
        List<PatientsTblEntity> list = session.getSession().createQuery("FROM PatientsTblEntity P").getResultList();
        session.close();
        return list;
    }

–Pom.xml file–

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <!-- Vaadin project from https://start.vaadin.com/project/a13f6a96-e47e-432d-bf78-e4e60571348e -->
    <groupId>com.example.application</groupId>
    <artifactId>asd-8</artifactId>
    <name>Project base for Spring Boot and Vaadin Flow</name>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <properties>
        <java.version>8</java.version>
        <vaadin.version>14.7.0</vaadin.version>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.5</version>
    </parent>

    <repositories>
        <!-- The order of definitions matters. Explicitly defining central here to make sure it has the highest priority. -->

        <!-- Main Maven repository -->
        <repository>
            <id>central</id>
            <url>https://repo.maven.apache.org/maven2</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
        <!-- Repository used by many Vaadin add-ons -->
        <repository>
            <id>Vaadin Directory</id>
            <url>https://maven.vaadin.com/vaadin-addons</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

    <pluginRepositories>
        <!-- Main Maven repository -->
        <pluginRepository>
            <id>central</id>
            <url>https://repo.maven.apache.org/maven2</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
    </pluginRepositories>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>com.vaadin</groupId>
                <artifactId>vaadin-bom</artifactId>
                <version>${vaadin.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>com.vaadin</groupId>
            <!-- Replace artifactId with vaadin-core to use only free components -->
            <artifactId>vaadin</artifactId>
            <exclusions>
                <!-- Webjars are only needed when running in Vaadin 13 compatibility mode -->
                <exclusion>
                    <groupId>com.vaadin.webjar</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.webjars.bowergithub.insites</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.webjars.bowergithub.polymer</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.webjars.bowergithub.polymerelements</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.webjars.bowergithub.vaadin</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.webjars.bowergithub.webcomponents</groupId>
                    <artifactId>*</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-spring-boot-starter</artifactId>
            <exclusions>
                <!-- Excluding so that webjars are not included. -->
                <exclusion>
                    <groupId>com.vaadin</groupId>
                    <artifactId>vaadin-core</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.vaadin.artur</groupId>
            <artifactId>a-vaadin-helper</artifactId>
            <version>1.7.1</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-testbench</artifactId>
            <scope>test</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.microsoft.sqlserver/mssql-jdbc -->
        <dependency>
            <groupId>com.microsoft.sqlserver</groupId>
            <artifactId>mssql-jdbc</artifactId>
            <version>9.2.1.jre8</version>
        </dependency>


        <!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.5.7.Final</version>
        </dependency>


        <!-- Include JUnit 4 support for TestBench and others -->
        <dependency>
            <groupId>org.junit.vintage</groupId>
            <artifactId>junit-vintage-engine</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.hamcrest</groupId>
                    <artifactId>hamcrest-core</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>io.github.bonigarcia</groupId>
            <artifactId>webdrivermanager</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <defaultGoal>spring-boot:run</defaultGoal>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <!-- Clean build and startup time for Vaadin apps sometimes may exceed
                     the default Spring Boot's 30sec timeout.  -->
                <configuration>
                    <wait>500</wait>
                    <maxAttempts>240</maxAttempts>
                </configuration>
            </plugin>

            <!--
                Take care of synchronizing java dependencies and imports in
                package.json and main.js files.
                It also creates webpack.config.js if not exists yet.
            -->
            <plugin>
                <groupId>com.vaadin</groupId>
                <artifactId>vaadin-maven-plugin</artifactId>
                <version>${vaadin.version}</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>prepare-frontend</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

    <profiles>
        <profile>
            <!-- Production mode is activated using -Pproduction -->
            <id>production</id>
            <build>
                <plugins>
                    <plugin>
                        <groupId>com.vaadin</groupId>
                        <artifactId>vaadin-maven-plugin</artifactId>
                        <version>${vaadin.version}</version>
                        <executions>
                            <execution>
                                <goals>
                                    <goal>build-frontend</goal>
                                </goals>
                                <phase>compile</phase>
                            </execution>
                        </executions>
                        <configuration>
                            <productionMode>true</productionMode>
                        </configuration>
                    </plugin>
                </plugins>
            </build>
        </profile>

        <profile>
            <id>it</id>
            <build>
                <plugins>
                    <plugin>
                        <groupId>org.springframework.boot</groupId>
                        <artifactId>spring-boot-maven-plugin</artifactId>
                        <executions>
                            <execution>
                                <id>start-spring-boot</id>
                                <phase>pre-integration-test</phase>
                                <goals>
                                    <goal>start</goal>
                                </goals>
                            </execution>
                            <execution>
                                <id>stop-spring-boot</id>
                                <phase>post-integration-test</phase>
                                <goals>
                                    <goal>stop</goal>
                                </goals>
                            </execution>
                        </executions>
                    </plugin>

                    <!-- Runs the integration tests (*IT) after the server is started -->
                    <plugin>
                        <groupId>org.apache.maven.plugins</groupId>
                        <artifactId>maven-failsafe-plugin</artifactId>
                        <executions>
                            <execution>
                                <goals>
                                    <goal>integration-test</goal>
                                    <goal>verify</goal>
                                </goals>
                            </execution>
                        </executions>
                        <configuration>
                            <trimStackTrace>false</trimStackTrace>
                            <enableAssertions>true</enableAssertions>
                        </configuration>
                    </plugin>
                </plugins>
            </build>
        </profile>

    </profiles>
</project>

Answer

I have found the solution, I was missing the annotation @Component in the class where the method is, and the annotation @Autowired where I want the instance of the class to be created.

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