Persisting data problem

[Aleksandar Mitrev]

I'm new at spring I've start reading a book from Wrox - Beginning Spring Framework.
I'm orientating from this book examples on creating my first data persisting application using maven, spring, hsqldb.
For several days I'm trying to create the application but no luck I'm getting frustrate I can't sleep . I know my post is going to be big but I'm hoping someone read it and help me make it work
I've created the model - class Album in directory /MyProject/src/main/java/model

package model;
import java.io.Serializable;
import java.util.Date;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
public class Album implements Serializable{

	@Id
	@GeneratedValue
	private Integer id;

	private String user;

	private String name;

	private String description;

	@Temporal(TemporalType.TIMESTAMP)
	private Date creationDate = new Date();
	
	private String[] labels;


	public Album() {
	}

	public Album(String name, String user, String description, String[] labels) {
		this.name = name;
		this.user = user;
		this.description = description;
		this.labels = labels;
	}
             //below the co-responding bean properties methods 
            public void set.....
            public String get.........  
    ................................................}

I've also created Repository class in MyProject/src/main/java/dao directory called AlbumJpaRepository

package dao;

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

import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;

import model.Album;

@Repository
public class AlbumJpaRepository  {

	private EntityManager entityManager;

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

             @Transactional
              public void persistAlbum(Album album) {
		entityManager.persist(album);

	}
}

I've created a execution file with main method AlbumDao.java in MyProject/src/main/java/dao directory

package dao;
import model.Album;
public class AlbumDao {
	private AlbumJpaRepository repo;
	
	public void persistAlbum(Album album) {
		repo.persistAlbum(album);
	}
	
	public void setRepo(AlbumJpaRepository repo) {
		this.repo = repo;
	}
	
	public AlbumJpaRepository getRepo(){
	return repo;
	}
	
	public static void main(String[] s){
		AlbumDao dao = new AlbumDao();
		Album a = new Album("Odmor", "Aleksandar", "NaPlaza", new String[]{"H", "L"});
		dao.persistAlbum(a);
		
	}
}

I've created two configuration XML files beans.xml and persistanceContext.xml in MyProject/src/main/resources directory

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
      http://www.springframework.org/schema/beans/spring-beans-2.0.xsd">
     
	 <bean id="album" class="model.Album"/>
	 
</beans>

and the persistanceContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xmlns:p="http://www.springframework.org/schema/p"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:dwr="http://www.directwebremoting.org/schema/spring-dwr"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd
	http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd 
	http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd
    http://www.directwebremoting.org/schema/spring-dwr  http://www.directwebremoting.org/schema/spring-dwr-2.0.xsd
    ">
	
	<bean	class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />

	<bean	class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor" />	
		
    <bean id="albumJpa" class="dao.AlbumJpaRepository"/>
	
	<bean id="albumDao" class="dao.AlbumDao">
		<property name="repo" ref="albumJpa"/>
	</bean>
	
	<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
		<property name="dataSource" ref="dataSource" />
		<property name="jpaVendorAdapter">
			<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
				<property name="database" value="HSQL" />
			</bean>
		</property>
	</bean>

	<bean id="dataSource"
		class="org.springframework.jdbc.datasource.DriverManagerDataSource">
		<property name="driverClassName" value="org.hsqldb.jdbcDriver" />
		<property name="url" value="jdbc:hsqldb:hsql://localhost/pix" />
		<property name="username" value="sa" />
		<property name="password" value="" />
	</bean>
</beans>

I'm starting the HSQLDB server successfully from the directory where my hsqldb-1.8.0.7.jar file is with the command
java -cp hsqldb-1.8.0.7.jar org.hsqldb.Server -database.0 temp -dbname.0 pix
and also successfully compiling the MyProject without any errors with maven. But when I try to execute the main class AlbumDao with the comand
mvn exec:java -Dexec.mainClass=dao.AlbumDao
I'm getting error ending like this

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:291)
	at java.lang.Thred.run(Thread.java:619)
Caused by: java.lang.NullPointerException
	at dao.AlbumDao.persistAlbum(AlbumDao.java:7)
	at dao.AlbumDao.main(AlbumDao.java:21)
	... 6 more

I've set it the dependencies in the pom.xml file I've also added sqltool.rc file in my home directory C:\Users\account that contains the following :

# A personal Memory-Only database.
urlid mem
url jdbc:hsqldb:mem:memdbid
username sa
password

# This is for a hsqldb Server running with default settings on your local
# computer (and for which you have not changed the password for "sa").
urlid pix-sa
url jdbc:hsqldb:hsql://localhost/pix
username sa
password

and still getting the same error
Some help
I may be on a wrong track and there is no way I can make it work with this approach or with this three softwares (Maven, Spring, HSQLDB ) for example I may also need a server Tomcat

[Mark Spritzler]

If you are using Spring where are you creating your ApplicationContext?

I see in your main you just create instances of your objects directly with new, which means it isn't using Spring, just plain Java and therefore not using any of your SpringConfiguration. And therefore no JPA EntityManagerFactory being created and definitely no EntityManager being injected into your Repository. Therefore your EntityManager property in your Repository is not being set and that is a NullPointerException. And also no one is creating an instance your Repository so your dao method that uses it and calls one of its method throws a NullPointerException.

Try this in your DAO

public static void main(String[] s){  
        AlbumDao dao = new AlbumDao();  
        Album a = new Album("Odmor", "Aleksandar", "NaPlaza", new String[]{"H", "L"});  
        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml", "persistenceContext.xml");
        repo = context.getBean("albumJpaRepository", AlbumJpaRepository.class);
        dao.persistAlbum(a);  
          
    } 

Now another thing you should do with a Spring Application is to create interfaces for your classes and have them implement that interface and code to an interface.

Mark

[Aleksandar Mitrev]

Thanks Mark that was a big help for me you saved me days of headache