java - @OneToMany Column Returns LazyInitializationException - Spring -

i have following mapping in user dto store map of user properties:

@entity(name = "user") public class user{      @id     @column(name = "id")     private long userid;      @onetomany     @joincolumn(name = "properties")     private map<long, property> properties= new linkedhashmap<long, lkpait>();  }  @entity(name = "property") public class property{      @id     @column(name = "id")     private long propertyid;      @column(name = "name")     private string propertyname;  }  

and following @controller method

@requestmapping(value = "/getuser", produces = "application/json", method = requestmethod.get) public @responsebody page<lkpfeed> getlookupfeeds(model model) {     page = 1;     page<user> users = userrepo.getusers(new pagerequest(page, 100)); //returns 100 users     return feeds; } 

the @controller method executes fine (all users found) when return statement executes, following error:

org.hibernate.lazyinitializationexception: failed lazily initialize collection of role: com.myapp.dto.properties.properties, not initialize proxy - no session     org.hibernate.collection.internal.abstractpersistentcollection.throwlazyinitializationexception(abstractpersistentcollection.java:575)     org.hibernate.collection.internal.abstractpersistentcollection.withtemporarysessionifneeded(abstractpersistentcollection.java:214)     org.hibernate.collection.internal.abstractpersistentcollection.readsize(abstractpersistentcollection.java:155)     org.hibernate.collection.internal.persistentmap.isempty(persistentmap.java:145)     com.fasterxml.jackson.databind.ser.std.mapserializer.serialize(mapserializer.java:399)     com.fasterxml.jackson.databind.ser.std.mapserializer.serialize(mapserializer.java:27)     com.fasterxml.jackson.databind.ser.beanpropertywriter.serializeasfield(beanpropertywriter.java:505)     com.fasterxml.jackson.databind.ser.std.beanserializerbase.serializefields(beanserializerbase.java:639)     com.fasterxml.jackson.databind.ser.beanserializer.serialize(beanserializer.java:152)     com.fasterxml.jackson.databind.ser.impl.indexedlistserializer.serializecontents(indexedlistserializer.java:100) 

based on exception properties field what's causing error. i've experimented fetchtypes , persistencecontexts @ loss. ideas?

you can several things

1. add fetch eager in @onetomany

   @entity(name = "user") public class user{      @id     @column(name = "id")     private long userid;      @onetomany(fetch=fetchtype.eager)     @joincolumn(name = "properties")     private map<long, property> properties= new linkedhashmap<long, lkpait>();  } 

2. or if don't want properties in returned json when want list users. can add @jsonignore properties

   @entity(name = "user") public class user{      @id     @column(name = "id")     private long userid;      @jsonignore     @onetomany     @joincolumn(name = "properties")     private map<long, property> properties= new linkedhashmap<long, lkpait>();  }