Could not write JSON: could not initialize proxy - no Session error

Question

I'm trying to create a REST service using spring and JackSon JSON.

My DAOImpl:

    @Override
    @SuppressWarnings("unchecked")
    public Users findByUserName(String username) {

        Users user = new Users();
        session = getSessionFactory().openSession();
        try {
            transaction = session.beginTransaction();
            if (!username.isEmpty() && username != null) {
                List<Users> users = new ArrayList<Users>();
                users = session.createQuery("from Users where username=?")
                        .setParameter(0, username)
                        .list();

                if (!users.isEmpty()) {
                    user = users.get(0);
                }

                transaction.commit();
            }
        } catch (HibernateException e) {

            if (transaction != null) {
                transaction.rollback();
            }

            e.printStackTrace();
        } finally {
            session.close();
        }

        return user;
    }

My Controller class:

    @RequestMapping(value = "/rest/userbyname/{username}",
            method = RequestMethod.GET,
            headers = "Accept=application/json")
    public Users findByUserName(@PathVariable("username") String username) {

        return userDao.findByUserName(username);
    }

And I'm getting this error:

HTTP Status 500 - Could not write JSON: could not initialize proxy - no Session (through reference chain: com.spring.example.entities.Users["roles"]->com.enclaveit.brea.entities.Roles_$$_jvstd4_2["role"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: could not initialize proxy - no Session (through reference chain: com.enclaveit.brea.entities.Users["roles"]->com.enclaveit.brea.entities.Roles_$$_jvstd4_2["role"])

As I understand because the session is closed in DAOImpl class so in the controller the session is no more, is it correct? When I try to comment the code line session.close(); then the web work fine, I can receive the Json. But it is dangerous when a session couldn't close, right?

Looking for best solution.

NOTE: If you need more information please tell me.

Thank you.

UPDATE:

Hibernate config file:

<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:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd 
    http://www.springframework.org/schema/aop 
    http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
    http://www.springframework.org/schema/tx
    http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">

    <!-- MySQL data source -->
    <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource"
        destroy-method="close">
        <property name="driverClassName" value="com.mysql.jdbc.Driver" />
        <property name="url" value="jdbc:mysql://192.168.10.116:3306/brea" />
        <property name="username" value="root" />
        <property name="password" value="brea@123" />
        <property name="maxActive" value="-1"/>
    </bean>
    <!-- If request parameter "targetUrl" is existed, then forward to this url --> 
    <!-- For update login form -->
    <bean id="savedRequestAwareAuthenticationSuccessHandler"
        class="org.springframework.security.web.authentication.SavedRequestAwareAuthenticationSuccessHandler">
        <property name="targetUrlParameter" value="targetUrl" />
     </bean>
    <!-- Hibernate session factory -->
    <bean id="sessionFactory"
        class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <property name="mappingResources">
            <list>
                <value>orm/Roles.hbm.xml</value>
                <value>orm/Users.hbm.xml</value>
                <value>orm/UsersInfo.hbm.xml</value>
            </list>
        </property>
        <property name="hibernateProperties">
            <props>
            <prop key="hibernate.dialect">
                           org.hibernate.dialect.MySQL5Dialect
                        </prop>
            <prop key="hibernate.format_sql">true</prop>
            <prop key="hibernate.show_sql">true</prop>
            </props>
        </property>
    </bean>

    <bean id="userDao" class="com.enclaveit.brea.dao.UserDaoImpl">
        <property name="sessionFactory" ref="sessionFactory" />
    </bean>

    <bean id="myUserDetailsService" 
                class="com.enclaveit.brea.services.MyUserDetailsService">
        <property name="userDao" ref="userDao" />
    </bean>

    <tx:annotation-driven />

    <!-- MUST have transaction manager, using aop and aspects  -->
    <bean id="transactionManager"
        class="org.springframework.orm.hibernate4.HibernateTransactionManager">
        <property name="dataSource" ref="dataSource" />
        <property name="sessionFactory" ref="sessionFactory"></property>
    </bean>

    <tx:advice id="txAdvice" transaction-manager="transactionManager">
        <tx:attributes>
        <tx:method name="get*" read-only="true" />
        <tx:method name="find*" read-only="true" />
        <tx:method name="*" />
        </tx:attributes>
    </tx:advice>

    <aop:config>
        <aop:pointcut id="userServicePointCut"
        expression="execution(* com.enclaveit.brea.services.*Service.*(..))" />
        <aop:advisor advice-ref="txAdvice" pointcut-ref="userServicePointCut" />
    </aop:config>
</beans>

Error log:

com.fasterxml.jackson.databind.JsonMappingException: could not initialize proxy - no Session (through reference chain: com.spring.example.entities.Users["roles"]->com.spring.example.entities.Roles_$$_jvstdf1_2["role"])
    com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:232)
    com.fasterxml.jackson.databind.JsonMappingException.wrapWithPath(JsonMappingException.java:197)
    com.fasterxml.jackson.databind.ser.std.StdSerializer.wrapAndThrow(StdSerializer.java:184)
    com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:605)
    com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:142)
    com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:569)
    com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:597)
    com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:142)
    com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:118)
    com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1819)
    org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.writeInternal(MappingJackson2HttpMessageConverter.java:241)
    org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:207)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90)
    org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:193)
    org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:690)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:139)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:85)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)
    org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)

org.hibernate.LazyInitializationException: could not initialize proxy - no Session
    org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:164)
    org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:285)
    org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185)
    com.spring.example.entities.Roles_$$_jvstdf1_2.getRole(Roles_$$_jvstdf1_2.java)
    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:606)
    com.fasterxml.jackson.databind.ser.BeanPropertyWriter.get(BeanPropertyWriter.java:679)
    com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:534)
    com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:597)
    com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:142)
    com.fasterxml.jackson.databind.ser.BeanPropertyWriter.serializeAsField(BeanPropertyWriter.java:569)
    com.fasterxml.jackson.databind.ser.std.BeanSerializerBase.serializeFields(BeanSerializerBase.java:597)
    com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:142)
    com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:118)
    com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:1819)
    org.springframework.http.converter.json.MappingJackson2HttpMessageConverter.writeInternal(MappingJackson2HttpMessageConverter.java:241)
    org.springframework.http.converter.AbstractHttpMessageConverter.write(AbstractHttpMessageConverter.java:207)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:148)
    org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:90)
    org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:193)
    org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:71)
    org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:122)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)
    org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:690)
    org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
    org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
    org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
    org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
    org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330)
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:118)
    org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:84)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:113)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:103)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:113)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:139)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:154)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:45)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.www.BasicAuthenticationFilter.doFilter(BasicAuthenticationFilter.java:150)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:199)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:110)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.csrf.CsrfFilter.doFilterInternal(CsrfFilter.java:85)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:50)
    org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87)
    org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:342)
    org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:192)
    org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:160)
    org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)
    org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)

Don't handle transactions and sessions yourself. Use Spring to do it for you. Next either return everything you need to create the JSON response or use a OpenSessionInViewFilter to keep the session open until the request finishes processing. — M. Deinum
– M. Deinum, Commented Sep 16, 2015 at 8:30

kapishreshth · Accepted Answer · 2017-02-11 19:33:32Z

4

Adding the proxy annotation to the Entity class does the job.

@Entity @Table(name="Country") @Proxy(lazy = false) public class Country {}

answered Feb 11, 2017 at 19:33

kapishreshth

4,1386 gold badges30 silver badges50 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

M. Deinum · Accepted Answer · 2015-09-16 08:39:06Z

0

The quickest solution is to first remove the session and transaction handling code from your service and simply replace it with @Transactional in your code (and <tx:annotation-driven /> in your configuration.

@Override
@SuppressWarnings("unchecked")
@Transactional(readOnly="true")
public Users findByUserName(String username) {
    Session session = getSessionFactory().getCurrentSession();      
    return (Users) session
                    .createQuery("from Users where username=?")
                    .setParameter(0, username)
                    .uniqueResult();
}

Also note that session should be scoped to the method NEVER store the Session as in instance variable. (Imagine what would happen if 10 current calls to findByUserName are made what would happen to the instance variable session).

In your configuration enable annotation driven transaction management. (Assuming you already have a HibernateTransactionManager definedn!).

<tx:annotation-driven />

Next add an OpenSessionInViewFilter to your request handling chain (i.e. register the filter in your web.xml or initializer when using java config).

<filter>
    <filter-name>OpenSessionInViewFilter</filter-name>
    <filter-class>org.springframework.orm.hibernate4.support.OpenSessionInViewFilter</filter-class>
    <!-- Replace with hibernate3, hibernate4 or hibernate5 depending on the hibernate version one uses -->
</filter>

<filter-mapping>
    <filter-name>OpenSessionInViewFilter</filter-name>
    <servlet-name>dispatcher</servlet-name> <!-- name of your DispatcherServlet -->
</filter-mapping>

answered Sep 16, 2015 at 8:39

M. Deinum

127k22 gold badges235 silver badges253 bronze badges

1 Comment

M. Deinum Over a year ago

Then you haven't configured the OpenSessionInViewFilter correctly OR haven't implemented the method correctly. Note the getCurrentSession and not openSession!. Or your hibernate configuration is wrong and not properly integrated with Springs Tx management. Add the hibernate configuration to your question.

Lovababu Padala · Accepted Answer · 2015-09-16 09:01:08Z

0

Since you are working with Spring framework, make use of declarative transaction management instead of programmatic transactions.

I believe your Users entity has role property with lazy loading. Either you can change this to eager loading (not preferable) or in DAO method load the role information using getter user.getRole() before session close.

answered Sep 16, 2015 at 9:01

Lovababu Padala

2,4972 gold badges25 silver badges33 bronze badges

2 Comments

gamo Over a year ago

Is there any other choice to keep lazy loading?

Lovababu Padala Over a year ago

Yes in DAO method load the role information using getter (something like user.getRole()) before session close.

Collectives™ on Stack Overflow

Could not write JSON: could not initialize proxy - no Session error

3 Answers 3

Comments

1 Comment

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related