Question

So i have this problem with testing Spring JPA, Here it’s my code:

ArticleService:

@Service("articleService")
@Transactional(propagation = Propagation.SUPPORTS, readOnly = true)
public class ArticleServiceImpl implements ArticleService {


private ArticleDao articleDao;

  @Autowired
  public ArticleServiceImpl(ArticleDao articleDao) {
    this.articleDao = articleDao;
  }

  public ArticleServiceImpl() {
  }

  @Transactional(propagation = Propagation.REQUIRED, readOnly = false)
  public void addArticle(Article article) {
    articleDao.saveArticle(article);
  }
}

My ArticleDao:

@Repository("articleDao")
public class ArticleDaoImpl implements ArticleDao {

  private EntityManager em;

  @PersistenceContext
  public void setEntityManager(EntityManager em) {
    this.em = em;
  }

  // To Save the article detail
  public void saveArticle(Article article) {
    article.setAddedDate(new Date());
    em.persist(article);
  }
}

Problem lies in executing those methods in the InputDatabaseServiceImpl class.

public class InputDatabaseServiceImpl implements InputDatabaseService {

public ArticleService articleService;


public InputDatabaseServiceImpl(ArticleService articleService){
    this.articleService= articleService;
}

public int inputArticle(Article article) {
    articleService.saveArticle(article);
    return 0;
}

aplication appContext.xml

<context:property-placeholder location="/WEB-INF/database.properties" />

<tx:annotation-driven transaction-manager="transactionManager" /> 

<!-- Declare a datasource that has pooling capabilities--> 
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close"
p:driverClass="${database.driver}"
p:jdbcUrl="${database.url}"
p:user="${database.user}"
p:password="${database.password}"
p:acquireIncrement="5"
p:idleConnectionTestPeriod="60"
p:maxPoolSize="100"
p:maxStatements="50"
p:minPoolSize="10" />

<!-- Declare a JPA entityManagerFactory-->
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean" >
<property name="persistenceXmlLocation" value="classpath*:META-INF/persistence.xml"></property>
<property name="persistenceUnitName" value="hibernatePersistenceUnit" />
<property name="dataSource" ref="dataSource"/>
<property name="jpaVendorAdapter">
<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter" >
<property name="showSql" value="true"/>
</bean>
</property>
</bean>

<!-- Declare a transaction manager-->
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean> 
</beans>

Whenever i call inputArticle Class from my endpoint i got NullPointerExpcetion in line articleService.saveArticle(article);

I knew it is the easiest Exception to solve but i am struggeling with this since a while and i need help.. Anyone could give me a hint what am i missing?

Answer 1

What is happening is that the ArticleService attribute is not initialized.

It can be due to a mismatch on the InputDatabaseServiceImpl bean configuration, or at the anotations to inject the dependency (if your beans are autowired).

Try this:

public class InputDatabaseServiceImpl implements InputDatabaseService {


   @Autowired
   public ArticleService articleService;

   public InputDatabaseServiceImpl(){
      //no need of arguments constructor
   }

   public int inputArticle(Article article) {
      articleService.saveArticle(article);
      return 0;
   }

}

To autowire a bean, this bean must present a public default contructor, which your ArticleServiceImpl class does not have. A fix form this would be refactoring ArticleServiceImpl:

@Service("articleService")
@Transactional(propagation = Propagation.SUPPORTS, readOnly = true)
public class ArticleServiceImpl implements ArticleService {

  @Autowired
  private ArticleDao articleDao;


  public ArticleServiceImpl() {
     //default constructor required for @Autowired
  }

  public ArticleServiceImpl() {
  }

  @Transactional(propagation = Propagation.REQUIRED, readOnly = false)
  public void addArticle(Article article) {
    articleDao.saveArticle(article);
  }
}