Many to Many Relation Error Driving Me Mad

[rodrigo bengoechea]

Hi everyone!, I'm developing my first application using hibernate and I'm having an error while I'm mapping a many to many relation. I've tried several times to fix it but I haven't been able to do it so I decided to ask you.

Basically the relation is this: A Group is made of many Users and a User can be part of many Groups.

Please if anyone could tell me something it would be very useful since I have no experience with this framework. I know this post could be pretty long but I'm desperate to fix this.

Thanks in advance to everyone!
Regards.

Rodrigo

Here I give you the User class:

public class User {

	private long id;
	private String name;
	private String sirName;
	private String user;
	private List<Password> passwords;
	private String authentication;
	private Date registrationDate;
	private String email;
	private Date lastPasswordUpdate;
	private Set<Group> ownGroups;
	private Set<Group> subscribedGroups;
	
	public static final int MIN_NUM_UNIQUE_PASSWORDS = 1;
	public static final int UNIQUE_PASSWORDS = 3;
	public static final String UNIQUE_PASSWORD = "PU";
	
	public User(String name, String sirName, String user, 
			String authentication, String email,
			Date registrationDate, Date lastPasswordUpdate){
		
		this.id = -1;
		this.name = name;
		this.sirName = sirName;
		this.user = user;
		this.authentication = authentication;
		this.email = email;
		this.registrationDate = registrationDate;
		this.lastPasswordUpdate = lastPasswordUpdate;
		this.passwords = new ArrayList<Password>();
		this.ownGroups = new HashSet<Group>();
		this.subscribedGroups = new HashSet<Group>();
		this.email = email;		
		
	}
	
	public User(String name, String sirName, String user, 
			String authentication, String password, String email,
			Date registrationDate, Date lastPasswordUpdate){
		
		this.id = -1;
		this.name = name;
		this.sirName = sirName;
		this.user = user;
		this.authentication = authentication;
		this.email = email;
		this.registrationDate = registrationDate;
		this.lastPasswordUpdate = lastPasswordUpdate;
		this.passwords = new ArrayList<Password>();
		this.ownGroups = new HashSet<Group>();
		this.subscribedGroups = new HashSet<Group>();
		this.email = email;
		
		this.passwords.add(new Password(password));
		
	}
	
	public User(String name, String sirName, String user,
			String email, Date registrationDate, Date lastPasswordUpdate){
		
		this.id = -1;
		this.name = name;
		this.sirName = sirName;
		this.user = user;
		this.lastPasswordUpdate = lastPasswordUpdate;
		this.registrationDate = registrationDate;
		this.authentication = UNIQUE_PASSWORD;
		this.passwords = new ArrayList<Password>();
		this.ownGroups = new HashSet<Group>();
		this.subscribedGroups = new HashSet<Group>();
		this.email = email;
		
		generatePasswords();
	}
	
	public Date getLastPasswordUpdate() {
		return lastPasswordUpdate;
	}

	public void setLastPasswordUpdate(Date lastPasswordUpdate) {
		this.lastPasswordUpdate = lastPasswordUpdate;
	}

	public User(){
		passwords = new ArrayList<Password>();
	}
	
	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public long getId() {
		return id;
	}
	
	public void setId(long id) {
		this.id = id;
	}
	
	public String getName() {
		return name;
	}
	
	public void setName(String name) {
		this.name = name;
	}
	
	public String getSirName() {
		return sirName;
	}
	
	public void setSirName(String sirname) {
		this.sirName = sirname;
	}
	
	public String getUser() {
		return user;
	}
	
	public void setUser(String user) {
		this.user = user;
	}

	public String getAuthentication() {
		return authentication;
	}
	
	public void setAuthentication(String authentication) {
		this.authentication = authentication;
	}

	public Date getRegistrationDate() {
		return registrationDate;
	}

	public void setRegistrationDate(Date registrationDate) {
		this.registrationDate = registrationDate;
	}

	public List<Password> getPasswords() {
		return passwords;
	}

	public void setPasswords(List<Password> passwords) {
		this.passwords = passwords;
	}
	
	public void setPassword(String password){
		Password pass = new Password(password);
		
		passwords.add(pass);
	}
	
	public boolean hasPassword(String password){
		
		Iterator<Password> it = passwords.iterator();
		while(it.hasNext()){
			Password pass = (Password)it.next();
			if (pass.equals(password))
				return true;
		}
		
		return false;
	}
	
	public void removePassword(String password){
		
		Iterator<Password> it = passwords.iterator();
		boolean removed = false;
		Password passwordToRemove = new Password();
		
		while(it.hasNext() && !removed){
			passwordToRemove = (Password)it.next();
			
			if(passwordToRemove.equals(password)){
				removed = true;
			}
		}
		
		passwords.remove(passwordToRemove);
	}
	
	public int passwordsLeft(){
		return passwords.size();
	}
	
	public void generatePasswords(){
	
		for(int i = 0; i < UNIQUE_PASSWORDS; i++){
			Password newPassword = new Password(generateRandomPassword());
			passwords.add(newPassword);			
		}
	
	}

	public Set<Group> getOwnGroups() {
		return ownGroups;
	}

	public void setOwnGroups(Set<Group> ownGroups) {
		this.ownGroups = ownGroups;
	}
	
	public void addOwnGroup(Group newGroup){
		
		if(ownGroups == null)
			ownGroups = new HashSet<Group>();
		
		this.ownGroups.add(newGroup);
	}
	
	public void addPassword(String password){
		Password pass = new Password(password);
		
		if(passwords == null)
			passwords = new ArrayList<Password>();
		
		this.passwords.add(pass);
	}

	public boolean isAdmin(String groupName){
		Iterator<Group> it = ownGroups.iterator();
		
		while(it.hasNext()){
			Group group = it.next();
			
			if(group.getName().equals(groupName)){				
					return true;
			}
		}
		
		return false;
	}
	
	public Group getGroup(String groupName){
		Iterator<Group> it = ownGroups.iterator();
		
		while(it.hasNext()){
			Group group = it.next();
			
			if (group.getName().equals(groupName))
				return group;
		}
		
		return null;
	}
	
	public boolean isMember(String groupName){
		
		Iterator<Group> it = subscribedGroups.iterator();
		
		while(it.hasNext()){
			Group group = it.next();
			
			if(group.getName().equals(groupName))
				return true;
		}
		
		return false;
	}
	
	private String generateRandomPassword(){
		
		String ret = "";
		
		for(int i = 0; i < Password.STANDARD_LENGTH; i++){
			double randomNumber = Math.random();
			double randomNumberSetup = (randomNumber * 26 + 'a');
			ret += (char) randomNumberSetup;
		}
		
		return ret;
	}

	public Set<Group> getSubscribedGroups() {
		return subscribedGroups;
	}

	public void setSubscribedGroups(Set<Group> subscribedGroups) {
		this.subscribedGroups = subscribedGroups;
	}
	
	public void subscribeToGroup(Group group){
		if(subscribedGroups == null)
			subscribedGroups = new HashSet<Group>();
		
		subscribedGroups.add(group);
	}
	
	public void unsubscribeToGroup(Group group){
		if(subscribedGroups.contains(group))
			subscribedGroups.remove(group);
	}
	
	public Set<Group> getGroups(){
		Set<Group> set = ownGroups;
		set.addAll(subscribedGroups);
		
		return set;
	}	
}

Here's the User hbm:

	<class name="beans.User" table="User"> 
	  <id name="id" type="long" column="id" unsaved-value="0">
	    <generator class="increment"/>
	  </id>    
	  
	  <list name="passwords" cascade="all-delete-orphan">
	  	<key column="user_id" not-null="true"/>
	  	<list-index column="idx"/>
	  	<one-to-many class="beans.Password"/>
	  </list>
	      
	  <set name="ownGroups" cascade="all" inverse="true">
	  	<key column="admin_id" />
	  	<one-to-many class="beans.Group"/>
	  </set>
	  
	  <set name="subscribedGroups" table="webgroup_users" cascade="all">
        <key column="webgroupuser_id"/>
      	<many-to-many class="beans.Group"/>
	  </set>
	         
	  <property name="name" type="string" column="name"/>    
	  <property name="sirName" type="string" column="sir_name"/>
	  <property name="user" type="string" column="user"/>
	  <property name="authentication" type="string" column="authentication"/>
	  <property name="email" type="string" column="email"/>
	  <property name="registrationDate" type="date" column="registration_date"/>
	  <property name="lastPasswordUpdate" type="date" column="last_pass_update"/>
	</class>
	
	<class name="beans.Password" table="Password">
	  <id name="id" unsaved-value="0">
	    <generator class="increment"/>
	  </id>
	  <property name="value" type="string" column="value"/>  
	</class>

Here's the group class:

public class Group {
	
	private String name;
	private String category;
	private long id;
	private Date creationDate;
	private User admin;
	private List<Confirmacion> pendingConfirmations;
	private Set<User> users;	
	
	public Group(){}
	
	public User getAdmin() {
		return admin;
	}

	public void setAdmin(User admin) {
		this.admin= admin;
	}

	public Group (String name, String category, Date creationDate, User administrator){
		this.name = name;
		this.category = category;
		this.creationDate = creationDate;
		this.admin = administrator;
        this.users = new HashSet<User>();
	}
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getCategory() {
		return category;
	}
	public void setCategory(String category) {
		this.category = category;
	}
	public long getId() {
		return id;
	}
	public void setId(long id) {
		this.id = id;
	}
	public Date getCreationDate() {
		return creationDate;
	}
	public void setCreationDate(Date creationDate) {
		this.creationDate = creationDate;
	}
	public List<Confirmacion> getPendingConfirmations() {
		return pendingConfirmations;
	}
	public void setPendingConfirmations(List<Confirmacion> pedingConfirmations) {
		this.pendingConfirmations = pedingConfirmations;
	}	
	public void addPendingConfirmation(long userId){
		Confirmacion pendingConfirmation = new Confirmacion(userId);
		
		this.pendingConfirmations.add(pendingConfirmation);
	}
	public boolean hasPendingConfirmation(long userId){
		
		if(pendingConfirmations.isEmpty())
			return false;
		
		Iterator<Confirmacion> it = pendingConfirmations.iterator();
		
		while(it.hasNext()){
			Confirmacion pendingConfirmation = it.next();
			
			if(pendingConfirmation.getUserId() == userId)
				return true;			
		}
		
		return false;
	}
	
	public boolean hasPendingConfirmations(){
		return (!pendingConfirmations.isEmpty());
	}
	
	public void setUsers(Set<User> users){
		this.users = users;
	}
	
	public Set<User> getUsers(){
		return this.users;
	}
	
	public void addUser(User user){
		if (this.users == null)
			users = new HashSet<User>();
		
		this.users.add(user);
	}
	
	public void remove(User user){
		if(this.users != null){
			
			if(this.users.contains(user))
				this.users.remove(user);
		}
	}

	public void removePendingConfirmation(long userId){
		
		Iterator<Confirmacion> it = pendingConfirmations.iterator();
		
		while(it.hasNext()){
			
			Confirmacion confirmation = it.next();
			
			if(confirmation.getUserId() == userId){
				System.out.println("userId = "+confirmation.getUserId());
				System.out.println("groupId = "+confirmation.getGroupId());
				System.out.println("Id = "+confirmation.getId());
				pendingConfirmations.remove(confirmation);
				
				return;
			}
		}		
	}
}

Here's the Group hbm:

	<class name="beans.Group" table="WebGroup">
		<id name="id" unsaved-value="0">
			<generator class="increment"/>
		</id>
	   	<property name="name" type="string" column="name"/>
	   	<property name="category" type="string" column="category"/>
	   	<property name="creationDate" type="date" column="creation_date"/>
	   	
	   	<list name="pendingConfirmations" cascade="all-delete-orphan">
	    	<key column="group_id" not-null="true"/>
	    	<list-index column="idx"/>
	    	<one-to-many class="beans.Confirmacion"/>
	   	</list>
	   	
	  	<set name="users" table="webgroup_users" cascade="all">
        	<key column="webgroup_id"/>
      		<many-to-many class="beans.User"/>
	  	</set>
	   	
	   	<many-to-one name="admin" column="admin_id" not-null="true"/>
	</class>

Here's the code where I'm relating the user with the group:

	private String confirmUser(HttpServletRequest request){
		User user;
		
		HttpSession session = request.getSession();
		
		Group group = (Group)session.getAttribute("Group");
		
		String userToConfirm = (String)request.getParameter("user");
		
		List<User> usersToConfirm = (List<User>)session.getAttribute("usersToConfirm");
		
		Iterator<User> it = usersToConfirm.iterator();
		
		while(it.hasNext()){
			user = it.next();
			
			if(user.getUser().equals(userToConfirm)){
				usersToConfirm.remove(user);
				
				user.subscribeToGroup(group);
				group.addUser(user);

				group.removePendingConfirmation(user.getId());
				
				Service service = new ServiceImpl();
				
				service.saveGroup(group);
				
				service.saveUser(user);								
				break;
			}
		}						
		
		return FORWARD_groupPage;
	}

Here's the save group method:

	public boolean saveGroup(Group group){
		Session session = HibernateUtil.getSessionFactory().getCurrentSession();
		
		try{
			session.beginTransaction();
						
			session.saveOrUpdate(group);
			      
			session.getTransaction().commit();
		}
		catch (Exception e){
			e.printStackTrace();
			System.out.println("Error al hacer el delete junto al commit");
			return false;
		}
				
		return true;		
	}

And Finally the stacktrace:

20:12:37,078 INFO  [STDOUT] Hibernate: 
    insert 
    into
        webgroup_users
        (webgroup_id, elt) 
    values
        (?, ?)
20:12:37,125 INFO  [STDOUT] 20:12:37,125 WARN  [JDBCExceptionReporter] SQL Error: 1216, SQLState: 23000
20:12:37,125 INFO  [STDOUT] 20:12:37,125 ERROR [JDBCExceptionReporter] Cannot add or update a child row: a foreign key constraint fails
20:12:37,140 INFO  [STDOUT] 20:12:37,125 ERROR [AbstractFlushingEventListener] Could not synchronize database state with session
org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
	at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:71)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
	at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:202)
	at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:235)
	at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:142)
	at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:297)
	at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
	at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:985)
	at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:333)
	at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106)
	at dao.GroupDAOImpl.saveGroup(GroupDAOImpl.java:23)
	at services.ServiceImpl.saveGroup(ServiceImpl.java:60)
	at action.groupPage.GroupPageAction.confirmUser(GroupPageAction.java:124)
	at action.groupPage.GroupPageAction.execute(GroupPageAction.java:43)
	at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
	at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
	at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
	at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
	at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:182)
	at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.sql.BatchUpdateException: Cannot add or update a child row: a foreign key constraint fails
	at com.mysql.jdbc.PreparedStatement.executeBatchSerially(PreparedStatement.java:1693)
	at com.mysql.jdbc.PreparedStatement.executeBatch(PreparedStatement.java:1108)
	at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:58)
	at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:195)
	... 35 more
20:12:37,140 ERROR [STDERR] org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
	at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:71)
	at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
	at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:202)
	at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:235)
	at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:142)
	at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:297)
	at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:27)
	at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:985)
	at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:333)
	at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106)
	at dao.GroupDAOImpl.saveGroup(GroupDAOImpl.java:23)
	at services.ServiceImpl.saveGroup(ServiceImpl.java:60)
	at action.groupPage.GroupPageAction.confirmUser(GroupPageAction.java:124)
	at action.groupPage.GroupPageAction.execute(GroupPageAction.java:43)
	at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:431)
	at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236)
	at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196)
	at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
	at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:182)
	at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.sql.BatchUpdateException: Cannot add or update a child row: a foreign key constraint fails
	at com.mysql.jdbc.PreparedStatement.executeBatchSerially(PreparedStatement.java:1693)
	at com.mysql.jdbc.PreparedStatement.executeBatch(PreparedStatement.java:1108)
	at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:58)
	at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:195)
	... 35 more

[Santosh Ramachandrula]

Can you please check the values of webgroup_id and elt that the insert statement below is using. Do the values that you are trying to insert in the JOIN TABLE exist in the WebGroup and Users tables?

  insert    
    into   
        webgroup_users   
        (webgroup_id, elt)    
    values   
        (?, ?)  

[rodrigo bengoechea]

I think so, how can I display the parameter's value? I'm pretty lost with this...

Thanks!

[Santosh Ramachandrula]

1. Use log4j

### log JDBC bind parameters ###
log4j.logger.org.hibernate.type=debug

or
2. If using IDE use debugger/watch/inspect
or
3. System.out.


and "show_sql" should be set to true in hibernate.cfg.xml

[rodrigo bengoechea]

Hi! I've used the System.out and the parameter's values are correct... could be something else?

[Santosh Ramachandrula]

If you know that the values inserted in the JOIN table are not violating the constraints in MANY-MANY entity tables all I can suggest is(are) Junit(s).
or try inserting that row(s) using SQL in DEV DB.

[rodrigo bengoechea]

Santosh I've solved the problem it was a mistake in the hbm's mappings. Many thanks for all your help! Now my laptop doesn't have internet connection since I'm at work but if you want I'll post the changes in the mappings when I get home.

Thanks again!!!

Rodrigo.