Creating two related entities using one transaction - Null

Support
#1

Hi all,

I have two entities: Project and Page. With a One to Many / Many to One relationship respectively (only relevant parts of the code are shown)

Project

@Entity
public class Project extends BaseIdentityIdEntity {

@Column(name = "NAME", nullable = false)
protected String name;

@OneToMany(mappedBy = "project")
protected List<Page> pages;

public List<Page> getPages() {
    if(pages != null){
        return Collections.unmodifiableList(pages);
    }
    return null;
}

public void addNewPage(Page page){
    pages.add(page);
}

}

Page

@Entity
public class Page extends BaseIdentityIdEntity {
    private static final long serialVersionUID = 1472149496370934955L;

    @Column(name = "NAME", nullable = false)
    protected String name;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "PROJECT_ID")
    protected Project project;

 (...)
}

After creating the Project i need to use its id to create a Page. I am using a Transaction for that but I am getting null value for Project id when I set a page. Here is the code of the Transaction below:

@Override
public Project createProject(Project project) {

    Transaction tx = persistence.createTransaction();
    try{
        EntityManager em = persistence.getEntityManager();
        project.setPublicProject(true);
        project.setPublished(false);
        em.persist(project);

        Page page = metadata.create(Page.class);
        page.setName("index");
        page.setTheme("yeti");
        page.setProject(project);
        em.persist(page);
        project.addNewPage(page);
        em.persist(project);
        
        tx.commit();

    } finally {
        tx.end();
    }

    return project;

}

Is it the right way of doing this ?

Thanks in advance

James

#2

Hi James,

The way you create entities looks correct except one extra closing bracket and the second em.persist(project) which are probably remains of a deleted code.

The reason why you don’t see IDs of entities after their creation is that they are BaseIdentityIdEntity - based on Identity PK, so they get identifiers only after inserting into the database, i.e. after the transaction commit. Does it cause any problems?

#3

Hi Konstantin,

You are right. That bracket was not supposed to be there. I edited and removed.

When I run this code I get an NullPointerException in this line

project.addNewPage(page);

I think that happens maybe because of the lack of the id in project object. So, what would be the best thing to do in this case ?

This is the exception full trace

java.lang.NullPointerException: null
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:982)
	org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:317)
	org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:127)
	org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:91)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:170)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	com.haulmont.restapi.auth.CubaAnonymousAuthenticationFilter.doFilter(CubaAnonymousAuthenticationFilter.java:66)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	org.springframework.security.oauth2.provider.authentication.OAuth2AuthenticationProcessingFilter.doFilter(OAuth2AuthenticationProcessingFilter.java:176)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	org.springframework.web.filter.CorsFilter.doFilterInternal(CorsFilter.java:96)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:56)
	org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:105)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:331)
	org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:214)
	org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:177)
	org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
	org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:262)
	com.haulmont.cuba.web.sys.CubaHttpFilter.handleNotFiltered(CubaHttpFilter.java:108)
	com.haulmont.cuba.web.sys.CubaHttpFilter.doFilter(CubaHttpFilter.java:95)
</pre><p><b>Root Cause</b></p><pre>com.haulmont.cuba.core.global.RemoteException:

Thanks for the reply

#4

Could you provide the full stack trace? I don’t see the line of code caused the exception.

#5

I have fixed the NullPointer error in my Project class.

public void addNewPage(Page page){
    if(pages == null){
        pages = new ArrayList<>();
    }
    pages.add(page);
}

But after the transaction finishes the Project is created but the Page not. What am I missing here ?

Thank you

#6

Could you check in the database if Page is not created at all or it is created but has no correct reference to Project?

#7

You were right. After cleaning the database and running it again the new Page was there. But it seems has incorrect reference to the project. I will investigate more and get it back to you in this same topic.

Thank you

#8

Everything worked. Thank you