Bug in Spring with Hibernate query code

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I have a problem, I am studying spring mvc with Hibernate and I ended up entering a bug where it returns the following exception "java.lang.Nullpointerexception", follows the codes:

Contactcontroller

package br.com.agenda.controllers;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

import br.com.agenda.services.ContactService;

@Controller
@RequestMapping("/contact")
public class ContactController {

    @RequestMapping(method=RequestMethod.GET)
    public ModelAndView listContact() {
        ContactService contactService = new ContactService();
        ModelAndView modelAndView = new ModelAndView("contacts");
        modelAndView.addObject("contacts", contactService.listAll());
        return modelAndView;
    }
}

Icontactservice

package br.com.agenda.interfaces;

import java.util.List;
import br.com.agenda.models.Contact;

public interface IContactService {

    public void save(Contact contact);

    public Contact searchId(Integer id);

    public List<Contact> listAll();

    public List<Contact> listSpecific(String field, String value);
}

Contactservice

package br.com.agenda.services;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;

import br.com.agenda.daos.ContactDAO;
import br.com.agenda.interfaces.IContactService;
import br.com.agenda.models.Contact;

public class ContactService implements IContactService {

    @Autowired
    private ContactDAO contactDAO = new ContactDAO();

    public void save(Contact contact) {
        contactDAO.save(contact);
    }

    public Contact searchId(Integer id) {
        return contactDAO.search(id);
    }

    public List<Contact> listAll() {
        return contactDAO.listAll();
    }

    public List<Contact> listSpecific(String field, String value) {
        return null;
    }
}

Contactdao

package br.com.agenda.daos;

import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceException;

import org.springframework.stereotype.Repository;

import br.com.agenda.models.Contact;

@Repository
public class ContactDAO {

    @PersistenceContext
    private EntityManager manager;

    public void save(Contact contact) {
        try {
            if (contact.getId() != null) {
                manager.persist(contact);
            } else {
                manager.merge(contact);
            }
        } catch(RuntimeException e) {
            System.out.println(e.getMessage());
        } catch(Exception e) {
            System.out.println(e.getMessage());
        }
    }

    public Contact search(Integer id) {
        try {
            return manager.find(Contact.class, id);
        } catch(RuntimeException e) {
            System.out.print(e.getMessage());
            return null;
        } catch(Exception e) {
            System.out.println(e.getMessage());
            return null;
        }
    }

    public List<Contact> listAll() {
        try {
            return manager
                .createQuery("select distinct(c) from tblContacts c join fetch c.phones", Contact.class)
                .getResultList();
        } catch(PersistenceException e) {
            System.out.println(e.getMessage());
            return null;
        }
    }
}

Contact

package br.com.agenda.models;

import java.util.List;

import javax.persistence.Column;
import javax.persistence.ElementCollection;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

import org.hibernate.validator.constraints.NotBlank;

import br.com.agenda.models.Phone;

@Entity
@Table(name="tblContacts")
public class Contact {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="idContacts")
    private Integer id;

    @NotBlank
    @Column(name="nameContacts")
    private String name;

    @NotBlank
    @Column(name="emailContacts")
    private String email;

    @ElementCollection
    private List<Phone> phones;

    public void addPhone(Phone phone) {
        phones.add(phone);
    }

    public List<Phone> getPhones() {
        return phones;
    }

    public void setPhones(List<Phone> phones) {
        this.phones = phones;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

Phone

package br.com.agenda.models;

import javax.persistence.Column;
import javax.persistence.Embeddable;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

import org.hibernate.validator.constraints.NotBlank;

@Entity
@Table(name = "tblPhones")
@Embeddable
public class Phone {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="idPhones")
    private Integer id;

    @NotBlank
    @Column(name="dddPhones")
    private Integer ddd;

    @NotBlank
    @Column(name="numberPhones")
    private Integer number;

    public Integer getDdd() {
        return ddd;
    }

    public void setDdd(Integer ddd) {
        this.ddd = ddd;
    }

    public Integer getNumber() {
        return number;
    }

    public void setNumber(Integer number) {
        this.number = number;
    }       
}

Stack of Errors

type Exception report

message Request processing failed; nested exception is java.lang.NullPointerException

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is java.lang.NullPointerException
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:982)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.NullPointerException
    br.com.agenda.daos.ContactDAO.listAll(ContactDAO.java:52)
    br.com.agenda.services.ContactService.listAll(ContactService.java:23)
    br.com.agenda.controllers.ContactController.listContact(ContactController.java:19)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:498)
    org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:220)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:134)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:116)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/8.5.11 logs.

-- Configuration Files --

Appwebconfiguration

package br.com.agenda.conf;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import br.com.agenda.controllers.IndexController;
import br.com.agenda.daos.ContactDAO;

@EnableWebMvc
@Configuration
@ComponentScan(basePackageClasses={IndexController.class, ContactDAO.class})
public class AppWebConfiguration extends WebMvcConfigurerAdapter {
    //Configurado pasta raiz das viewers e o suffix .jsp para as mesmas que serão carregadas
    @Bean
    public InternalResourceViewResolver internalResourceViewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/views/");
        resolver.setSuffix(".jsp");
        return resolver;
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {  
        registry.addResourceHandler("/resources/**").addResourceLocations("/resources/");
    }

    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }
}

Jpaconfiguration

package br.com.agenda.conf;

import java.util.Properties;

import javax.persistence.EntityManagerFactory;
import javax.sql.DataSource;
import org.springframework.context.annotation.Bean;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.JpaVendorAdapter;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@EnableTransactionManagement
public class JPAConfiguration {

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory()
    {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource());

        em.setPackagesToScan(new String[] {"br.com.agenda.models"});
        JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);
        em.setJpaProperties(additionalProperties());

        return em;

    }

    @Bean
    public DataSource dataSource()
    {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/agenda");
        dataSource.setUsername("root");
        dataSource.setPassword("");

        return dataSource;
    }

    private Properties additionalProperties()
    {
        Properties properties = new Properties();
        properties.setProperty("hibernate.hbm2ddl.auto", "update");
        properties.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL5Dialect");
        properties.setProperty("hibernate.show_sql", "true");

        return properties;
    }

    @Bean
    public PlatformTransactionManager transactionManager (EntityManagerFactory emf)
    {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(emf);
        return transactionManager;
    }
}

Servletspringmvc

package br.com.agenda.conf;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class ServletSpringMVC extends AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() 
    {
        return null;
    }

    //definido de onde vira as cofiguracoes para rodar as classes
    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{AppWebConfiguration.class, JPAConfiguration.class};
    }

    //indica a pasta raiz mappeando o servlet
    @Override
    protected String[] getServletMappings() 
    {
        return new String[] {"/"};
    }
}

Help me and/or make the corrections please, since thank you.

java hibernate spring spring-mvc

  • Edit the question and add the stack of errors too.

  • Was edited @diegofm.

1 answer

1


To NullPointerException is occurring because you are manually instantiating the classes ContactService and ContactDAO, so Spring doesn’t inject the EntityManager.

Change these snippets of code to:

Contactservice:

@Service
public class ContactService implements IContactService {

    @Autowired
    private ContactDAO contactDAO;

    //os seus métodos
}

Contactcontroller:

@Controller
@RequestMapping("/contact")
public class ContactController {

    @Autowired
    private IContactService contactService;

    @RequestMapping(method=RequestMethod.GET)
    public ModelAndView listContact() {
        ModelAndView modelAndView = new ModelAndView("contacts");
        modelAndView.addObject("contacts", contactService.listAll());
        return modelAndView;
    }
}

Editing:

Below is the complete code that worked with me without releasing any exceptions. If you are still facing an exception, it is likely that this exception is different from the one in your question and is caused by some other class that has not been listed to us.

That way, if an exception is released, I suggest you create another project with the files I’ll put below and gradually add the remaining classes/features to find out where the problem is. If any doubt arises, you may ask.

pom.xml

I use Maven to manage my dependencies, if you use another manager or need to add/replace dependencies, adjust according to your needs.

<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/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>
    <groupId>br.com.agenda</groupId>
    <artifactId>agenda</artifactId>
    <packaging>war</packaging>
    <version>0.0.1-SNAPSHOT</version>
    <name>agenda</name>
    <url>http://maven.apache.org</url>

    <properties>
        <log4j2.version>2.7</log4j2.version>
        <org.springframework.version>4.3.4.RELEASE</org.springframework.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${org.springframework.version}</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.2.5.Final</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.39</version>
        </dependency>

        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>${log4j2.version}</version>
        </dependency>

        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>${log4j2.version}</version>
        </dependency>

        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-jcl</artifactId>
            <version>${log4j2.version}</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>5.4.0.Final</version>
        </dependency>

        <dependency>
            <groupId>jstl</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
    </dependencies>

    <build>
        <finalName>agenda</finalName>
        <pluginManagement>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                    </configuration>
                </plugin>

                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-war-plugin</artifactId>
                    <version>3.0.0</version>
                    <configuration>
                        <failOnMissingWebXml>false</failOnMissingWebXml>
                    </configuration>
                </plugin>
            </plugins>
        </pluginManagement>
    </build>
</project>

Appwebconfiguration.java

package br.com.agenda.conf;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

@EnableWebMvc
@Configuration
@ComponentScan(basePackages={"br.com.agenda"})
public class AppWebConfiguration extends WebMvcConfigurerAdapter {

    @Bean
    public InternalResourceViewResolver internalResourceViewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/views/");
        resolver.setSuffix(".jsp");
        return resolver;
    }

    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {  
        registry.addResourceHandler("/resources/**").addResourceLocations("/resources/");
    }

    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }
}

Jpaconfiguration.java

Don’t forget to add your database username and password.

package br.com.agenda.conf;

import java.util.Properties;

import javax.persistence.EntityManagerFactory;
import javax.sql.DataSource;

import org.springframework.context.annotation.Bean;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.JpaVendorAdapter;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

@EnableTransactionManagement
public class JPAConfiguration {

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource());

        em.setPackagesToScan(new String[] {"br.com.agenda.models"});
        JpaVendorAdapter vendorAdapter = new HibernateJpaVendorAdapter();
        em.setJpaVendorAdapter(vendorAdapter);
        em.setJpaProperties(additionalProperties());

        return em;

    }

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");
        dataSource.setUrl("jdbc:mysql://localhost:3306/agenda?useSSL=false");
        dataSource.setUsername("");
        dataSource.setPassword("");

        return dataSource;
    }

    private Properties additionalProperties() {
        Properties properties = new Properties();
        properties.setProperty("hibernate.hbm2ddl.auto", "update");
        properties.setProperty("hibernate.dialect", "org.hibernate.dialect.MySQL57InnoDBDialect");
        properties.setProperty("hibernate.show_sql", "true");

        return properties;
    }

    @Bean
    public PlatformTransactionManager transactionManager (EntityManagerFactory emf) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(emf);
        return transactionManager;
    }
}

Servletspringmvc.java

package br.com.agenda.conf;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

public class ServletSpringMVC extends AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return null;
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[]{AppWebConfiguration.class, JPAConfiguration.class};
    }

    @Override
    protected String[] getServletMappings() {
        return new String[] {"/"};
    }
}

Contactdao.java

I changed the ContactDAO to an interface and created an implementation called JPAContactDAO:

package br.com.agenda.daos;

import java.util.List;
import java.util.Optional;

import br.com.agenda.models.Contact;

public interface ContactDAO {

    public void save(Contact contact);

    public Contact update(Contact contact);

    public void remove(Contact contact);

    public Optional<Contact> find(int identifier);

    public List<Contact> listAll();
}

Jpacontactdao.java

package br.com.agenda.daos;

import static java.util.Objects.requireNonNull;

import java.util.List;
import java.util.Optional;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.stereotype.Repository;

import br.com.agenda.models.Contact;

@Repository
public final class JPAContactDAO implements ContactDAO {

    @PersistenceContext
    private EntityManager manager;

    @Override
    public void save(Contact contact) {
        requireNonNull(contact, "contact cannot be null");
        manager.persist(contact);
    }

    @Override
    public Contact update(Contact contact) {
        requireNonNull(contact, "contact cannot be null");
        return manager.merge(contact);
    }

    @Override
    public void remove(Contact contact) {
        requireNonNull(contact, "contact cannot be null");
        manager.remove(contact);
    }

    @Override
    public Optional<Contact> find(int identifier) {
        return Optional.ofNullable(manager.find(Contact.class, identifier));
    }

    @Override
    public List<Contact> listAll() {
        return manager.createQuery("SELECT DISTINCT(c) FROM Contact c JOIN FETCH c.phones", Contact.class)
                    .getResultList();
    }
}

Contactservice.java

I changed the name of IContactService for ContactService and the implementation came to be called DefaultContactService.

package br.com.agenda.services;

import java.util.List;
import java.util.Optional;

import br.com.agenda.models.Contact;

public interface ContactService {

    public void save(Contact contact);

    public Contact update(Contact contact);

    public void remove(Contact contact);

    public Optional<Contact> find(int identifier);

    public List<Contact> listAll();
}

Defaultcontactservice.java

package br.com.agenda.services;

import static java.util.Objects.requireNonNull;

import java.util.List;
import java.util.Optional;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import br.com.agenda.daos.ContactDAO;
import br.com.agenda.models.Contact;

@Service
public final class DefaultContactService implements ContactService {

    @Autowired
    private ContactDAO contactDAO;

    @Override
    @Transactional
    public void save(Contact contact) {
        requireNonNull(contact, "contact cannot be null");
        contactDAO.save(contact);
    }

    @Override
    @Transactional
    public Contact update(Contact contact) {
        requireNonNull(contact, "contact cannot be null");
        return contactDAO.update(contact);
    }

    @Override
    @Transactional
    public void remove(Contact contact) {
        requireNonNull(contact, "contact cannot be null");
        contactDAO.remove(contact);
    }

    @Override
    public Optional<Contact> find(int identifier) {
        return contactDAO.find(identifier);
    }

    @Override
    public List<Contact> listAll() {
        return contactDAO.listAll();
    }
}

Contact java.

I’ve changed the relationship between Contact and Phone of @ElementCollection for @OneToMany:

package br.com.agenda.models;

import java.util.ArrayList;
import java.util.List;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.validation.Valid;

import org.hibernate.validator.constraints.NotBlank;

@Entity
@Table(name="tblContacts")
public class Contact {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="idContacts")
    private int id;

    @NotBlank
    @Column(name="nameContacts")
    private String name;

    @NotBlank
    @Column(name="emailContacts")
    private String email;

    @OneToMany(cascade=CascadeType.ALL)
    @Valid
    private List<Phone> phones = new ArrayList<>();

    public void addPhone(Phone phone) {
        phones.add(phone);
    }

    public List<Phone> getPhones() {
        return phones;
    }

    public void setPhones(List<Phone> phones) {
        this.phones = phones;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

Java phone.

package br.com.agenda.models;

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

@Entity
@Table(name = "tblPhones")
public class Phone {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="idPhones")
    private Integer id;

    @Column(name="dddPhones")
    private int ddd;

    @Column(name="numberPhones")
    private int number;

    public int getDdd() {
        return ddd;
    }

    public void setDdd(int ddd) {
        this.ddd = ddd;
    }

    public int getNumber() {
        return number;
    }

    public void setNumber(int number) {
        this.number = number;
    }       
}

Contactcontroller.java

package br.com.agenda.controllers;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

import br.com.agenda.models.Contact;
import br.com.agenda.services.ContactService;

@Controller
@RequestMapping("/contact")
public class ContactController {

    @Autowired
    private ContactService contactService;

    @RequestMapping(value="/all", method=RequestMethod.GET)
    public ModelAndView listContact() {
        ModelAndView modelAndView = new ModelAndView("contact-list");
        modelAndView.addObject("contacts", contactService.listAll());
        return modelAndView;
    }
}

contact-list.jsp

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
        <title>Contact List</title>
    </head>
    <body>
        <c:forEach var="contact" items="${contacts}">
            <label>${contact.name}</label><br />
        </c:forEach>
    </body>
</html>

  • Sure I understood, but I believe I will still continue with the problem, because the same is coming from the listAll() Return in the DAO layer, I do not know maybe the Hibernate query is incorrect.

  • @Marcospaulo A NullPointerException occurs within of the method listAll(). The exception is made because one is trying to evoke the method createQuery of a EntityManager null .

  • I did what you said but the error keeps being returned, I tested the implementation and the error is generated only in the listAll() method, you don’t realize that the way I’m listing all objects are wrong not?

  • @Marcospaulo There is an error in your query, it should use the name of the classes and not the tables. Your query should be SELECT DISTINCT(c) FROM Contact c JOIN FETCH c.phones. However, if your query was running, it would appear in the stack trace the exception org.hibernate.hql.internal.ast.QuerySyntaxException. Since this exception does not occur, it leads to believe that your query is not even executed. The problem is rather. Put the Hibernate/Spring configuration files please.

  • I edited the post with the 3 configuration files.

  • @Marcospaulo Tested with the files you placed and, applying the changes I mentioned earlier, the program worked and did not release any exceptions. The only change I had to make was changing class notes AppWebConfiguration of @ComponentScan(basePackageClasses={IndexController.class, ContactDAO.class}) for @ComponentScan(basePackages={"br.com.agenda"}) because Spring wasn’t finding any classes. If it doesn’t work for you, let me know that I edit my reply and put all the classes that are running with me for you to test.

  • Felipe, please if you can put the classes, my keep returning to Exception, I’ve already broken my head and to this day I could not solve.

  • @Marcospaulo added the classes.

  • I saw that the implementation of DAO together with the Service are very identical, it is really necessary both or it could be only 1 layer?

  • It depends on the complexity of the domain. The code I put in is very simple and the Service layer ends up being redundant and can be considered unnecessary. However, it is common for it to have to consume Web Services and contain the logic needed to interact with multiple Daos in more complex relationships between entities. The DAO should only serve to abstract access to persistence unit.

  • I understood, in the case of service type it would have the logic to persist the users and the accesses related to them, ai manipularia 2 DAOS.

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