Question

Currently I have the following Mapping in my Controller:

  @RequestMapping( value = "/add.html", method = RequestMethod.GET )
  public String showAddForm( Map<String, Object> map )
  {
    map.put( "person", new Person() );
    return "form";
  }

  @RequestMapping( value = "/add.html", method = RequestMethod.POST )
  public String processAddForm( @ModelAttribute( "person" ) @Valid Person person, BindingResult result, Map<String, Object> map )
  {
    if ( service.findByName( person.getName() ) != null )
    {
      result.addError( new FieldError( "person", "name", "Person already exists" ) );
    }

    if ( result.hasErrors() )
    {
      return "form";
    }

    service.save( person );
    return "redirect:/index.html";
  }

  @RequestMapping( value = "/{id}/edit.html", method = RequestMethod.GET )
  public String showEditForm( @PathVariable( "id" ) int id, Map<String, Object> map )
  {
    map.put( "person", service.load( id ) );
    return "form";
  }

  @RequestMapping( value = "/{id}/edit.html", method = RequestMethod.POST )
  public String processEditForm( @PathVariable( "id" ) int id, @ModelAttribute( "person" ) @Valid Person person, BindingResult result )
  {
    Person p;
    if ( ( p = service.findByName( person.getName() ) ) != null && person.getId() != id )
    {
      result.addError( new FieldError( "person", "name", "Person already exists" ) );
    }

    if ( result.hasErrors() )
    {
      return "form";
    }

    person.setId( id );
    service.save( person );
    return "redirect:/index.html";
  }

How is it possible to reduce the redundant code?
Maybe by setting the forms action to /save.html and combine processAddForm and processEditForm to

@RequestMapping( value = "/save.html", method = RequestMethod.POST )

But how the code should look like, then?
I just tried it and got some exceptions, because there was already an instance of Person# in Session…

EDIT
Here I given it a try…

Controller method:

  @RequestMapping( value = "/save.html", method = RequestMethod.POST )
  public String onSubmit( @ModelAttribute( "person" ) @Valid Person person, BindingResult result, Map<String, Object> map )
  {
    Person p;
    if ( ( p = service.findByName( person.getName() ) ) != null )
    {
      if ( person.getId() != p.getId() )
      {
        result.addError( new FieldError( "person", "name", "Person already exists" ) );
      }
    }

    if ( result.hasErrors() )
    {
      return "form";
    }

    service.save( person );
    return "redirect:/index.html";
  }

Form:

<c:url value="/save.html" var="formAction" />
<form:form modelAttribute="person" action="${formAction}" method="post">
  <form:errors path="*" cssClass="error" element="div" />
  <form:hidden path="id" />
  <form:label path="name">Name:</form:label>
  <form:input path="name" />
  <input type="submit" value="Submit" />
</form:form>

Adding works, but Editing gives the following Exception:

org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [com.example.entities.Person#7]
    org.hibernate.engine.StatefulPersistenceContext.checkUniqueness(StatefulPersistenceContext.java:637)
    org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performUpdate(DefaultSaveOrUpdateEventListener.java:305)
    org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsDetached(DefaultSaveOrUpdateEventListener.java:246)
    org.hibernate.event.def.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:112)
    org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:93)
    org.hibernate.impl.SessionImpl.fireSaveOrUpdate(SessionImpl.java:677)
    org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:669)
    org.hibernate.impl.SessionImpl.saveOrUpdate(SessionImpl.java:665)
    com.example.dao.PersonDaoImpl.save(PersonDaoImpl.java:30)
    com.example.dao.PersonDaoImpl.save(PersonDaoImpl.java:1)
    com.example.services.PersonServiceImpl.save(PersonServiceImpl.java:29)
    com.example.services.PersonServiceImpl.save(PersonServiceImpl.java:1)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:616)
    org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)
    org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:110)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
    $Proxy44.save(Unknown Source)
    com.example.controller.PersonController.onSubmit(PersonController.java:65)
    com.example.controller.PersonController$$FastClassByCGLIB$$9c2dc698.invoke(<generated>)
    net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
    org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:689)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    org.springframework.security.access.intercept.aopalliance.MethodSecurityInterceptor.invoke(MethodSecurityInterceptor.java:61)
    org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:622)
    com.example.controller.PersonController$$EnhancerByCGLIB$$a0aff0d2.onSubmit(<generated>)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:616)
    org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:212)
    org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:900)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
    org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:311)
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:116)
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
    org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
    org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:101)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
    org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
    org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:54)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
    org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
    org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:201)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
    org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:323)
    org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:173)
    org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:346)
    org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:259)
    org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:198)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)

EDIT2:
PersonServiceImpl:

  @Override
  @Transactional
  public void save( Person person )
  {
    dao.save( person );
  }

PersonDaoImpl:

  @Override
  public void save( Person person )
  {
    try
    {
      sessionFactory.getCurrentSession().saveOrUpdate( person );
    }
    catch( NonUniqueObjectException e )
    {
      sessionFactory.getCurrentSession().merge( person );
    }
  }

Is this the correct way? Maybe a better solution?

EDIT3

  @Override
  public void save( Person person )
  {
    if ( load( person.getId() ) != null)
    {
      sessionFactory.getCurrentSession().merge( person );
    }
    else
    {
      sessionFactory.getCurrentSession().save( person );
    }
  }

  @Override
  public Person load( int id )
  {
    return ( Person ) sessionFactory.getCurrentSession().load( Person.class, id );
  }

Is this a better solution?

Answer 1

It looks like you’re trying to save an object with the same id, and that object is not attached to the hibernate session.

You probably edited Person‘s name and tried to save it. The person with that name is not found, but the person with the same id exists in database, hence error.

Either use merge() or, in your service, fetch the person first (to make it connected to hibernate’s session), update necessary fields and save it to DB.

To explain better:

@RequestMapping( value = "/save.html", method = RequestMethod.POST )
  public String onSubmit( @ModelAttribute( "person" ) @Valid Person person, BindingResult result, Map<String, Object> map )
  {
    Person p;
  // You changed the name so it doesn't find anything here and proceeds without errors
    if ( ( p = service.findByName( person.getName() ) ) != null ) 
    {
      if ( person.getId() != p.getId() )
      {
        result.addError( new FieldError( "person", "name", "Person already exists" ) );
      }
    }

    if ( result.hasErrors() )
    {
      return "form";
    }

//the code breaks here, person is not attached to hibernate session and you're trying to save it. Modify your service code to use merge() or to fetch the person from database before saving it.
    service.save( person );  
    return "redirect:/index.html";
  }

edit

If you use merge() then you don’t have to test anything. Hibernate is clever enough to know if you’re saving new instance or saving changes to an already persisted one. The other way would be to test, in your controller, if person.id is set, and call an apropriate method in your service (service.save or service.update). It really depends on how much do you want to depend on hibernate’s cleverness.