Question

In my java spring webapp I have relationship: One account can have many groups and one group can have only one account.

Group entity:

@Entity
@Table(name = "group")
@Inheritance(strategy = InheritanceType.JOINED)
public class Group {

@Id
@GeneratedValue(generator = "group_id", strategy = GenerationType.SEQUENCE)
@SequenceGenerator(name = "group_id", sequenceName = "group_group_id_seq", allocationSize = 1)
@Column(name = "group_id")
private Long id;

@Basic
@NotBlank
@Column(name = "name")
private String name;

@ManyToOne(targetEntity = Account.class, fetch = FetchType.LAZY)
@JoinColumn(name = "account_id")
private Account account;

@Basic
@NotBlank
@Column(name = "all")
private boolean all;

@ManyToMany(targetEntity = Word.class, fetch = FetchType.LAZY)
@JoinTable(name = "group_word", joinColumns = {@JoinColumn(name="group_id")}, inverseJoinColumns = {@JoinColumn(name="word_id")})
private List<Word> words;

getters/setters...

Account entity:

@Entity
@JsonIgnoreProperties(ignoreUnknown = true)
@Table(name = "account")
@Inheritance(strategy = InheritanceType.JOINED)
public class Account  extends User implements UserDetails {

@Id
@GeneratedValue(generator = "account_id", strategy = GenerationType.SEQUENCE)
@SequenceGenerator(name = "account_id", sequenceName = "account_account_id_seq", allocationSize = 1)
@Column(name = "account_id")
private Long accountId;

@Column(name = "username")
private String username;

@Column(name = "password")
private String password;

@Transient
private String repeatedPassword;

@DateTimeFormat(iso = ISO.DATE_TIME)
@Column(name = "registration_date")
Date registrationDate = Calendar.getInstance().getTime();

@Column(name = "email")
private String email;

@ManyToMany(targetEntity = Role.class, fetch = FetchType.LAZY)
@JoinTable(name = "account_role", joinColumns = {@JoinColumn(name="account_id")}, inverseJoinColumns = {@JoinColumn(name="role_id")})
private List<Role> roles;

public List<Role> getRoles() {
    return roles;
}

public void setRoles(List<Role> roles) {
    this.roles = roles;
}

@OneToMany(mappedBy="account", fetch = FetchType.LAZY)
private List<Group> groups;

public List<Group> getGroups() {
    return groups;
}

public void setGroups(List<Group> groups) {
    this.groups = groups;

getters/setters...

When i invoke this service method:

public List<Group> listUserGroups(String username) {
    try {
        Account foundAccount = accountDao.findUserByUsername(username);
        List<Group> userGroups = foundAccount.getGroups();
        userGroups.size();
        return userGroups;
    } catch (UserNotFoundException unf) {
        logger.error("User not found: " + username, unf.getMessage());
        return Collections.emptyList();
    }
}

I have an error on line:

userGroups.size();

Error:

00:27:27,528 DEBUG [org.hibernate.engine.StatefulPersistenceContext] - initializing non-lazy collections
00:27:27,528 DEBUG [org.hibernate.loader.Loader] - loading collection: [pl.net.grodek.snd.model.Account.groups#116]
00:27:27,528 DEBUG [org.hibernate.jdbc.AbstractBatcher] - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
00:27:27,528 DEBUG [org.hibernate.SQL] - select groups0_.account_account_id as account4_20_1_, groups0_.group_id as group1_1_, groups0_.group_id as group1_19_0_, groups0_.account_account_id as account4_19_0_, groups0_.all as all19_0_, groups0_.name as name19_0_ from group groups0_ where groups0_.account_account_id=?
00:27:27,544 DEBUG [org.hibernate.jdbc.AbstractBatcher] - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
00:27:27,544 DEBUG [org.hibernate.util.JDBCExceptionReporter] - could not initialize a collection: [pl.net.grodek.snd.model.Account.groups#116] [select groups0_.account_account_id as account4_20_1_, groups0_.group_id as group1_1_, groups0_.group_id as group1_19_0_, groups0_.account_account_id as account4_19_0_, groups0_.all as all19_0_, groups0_.name as name19_0_ from group groups0_ where groups0_.account_account_id=?]
org.postgresql.util.PSQLException: ERROR: syntax error near "group"
Position: 227
at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2103)
at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1836)
at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:257)
at org.postgresql.jdbc2.AbstractJdbc2Statement.execute(AbstractJdbc2Statement.java:512)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:388)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:273)
at com.mchange.v2.c3p0.impl.NewProxyPreparedStatement.executeQuery(NewProxyPreparedStatement.java:76)
at org.hibernate.jdbc.AbstractBatcher.getResultSet(AbstractBatcher.java:208)
at org.hibernate.loader.Loader.getResultSet(Loader.java:1953)
at org.hibernate.loader.Loader.doQuery(Loader.java:802)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274)
at org.hibernate.loader.Loader.loadCollection(Loader.java:2166)
at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:62)
at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:627)
at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:83)
at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1863)
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:369)
at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:111)
at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:134)
at org.hibernate.collection.PersistentBag.size(PersistentBag.java:248)
at pl.net.grodek.snd.service.GroupServiceImpl.listUserGroups(GroupServiceImpl.java:47)
at pl.net.grodek.snd.service.GroupServiceImpl.listUserGroups(GroupServiceImpl.java:1)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at 

I think that the problem is in query generated by jpa:

select groups0_.account_account_id as account4_20_1_, groups0_.group_id as group1_1_, groups0_.group_id as group1_19_0_, groups0_.account_account_id as account4_19_0_, groups0_.all as all19_0_, groups0_.name as name19_0_ from group groups0_ where groups0_.account_account_id=?

where there are doubled account_id and group_id. But my question why this is happening. Please clarify for me this issue because I ran out of ideas 🙁

EDIT:

Oh i forgot about DB tables:

CREATE TABLE "group"
(
    group_id bigserial NOT NULL,
    name character varying(150)[] NOT NULL,
    "all" boolean NOT NULL DEFAULT false,
    account_id bigint NOT NULL,
    CONSTRAINT group_id_pk PRIMARY KEY (group_id ),
    CONSTRAINT account_id_fk FOREIGN KEY (account_id)
    REFERENCES account (account_id) MATCH SIMPLE
    ON UPDATE NO ACTION ON DELETE NO ACTION
)

CREATE TABLE account
(
    account_id bigserial NOT NULL,
    username character varying(32),
    password character varying(64),
    email character varying(100),
    registration_date timestamp with time zone NOT NULL,
    word_for_today bigint,
    groups_on_page integer NOT NULL,
    CONSTRAINT account_pk PRIMARY KEY (account_id ),
    CONSTRAINT word_fk FOREIGN KEY (word_for_today)
  REFERENCES word (word_id) MATCH SIMPLE
  ON UPDATE NO ACTION ON DELETE NO ACTION,
    CONSTRAINT unique_mail UNIQUE (email ),
    CONSTRAINT unique_username UNIQUE (username )
)

Answer 1

I changed group table name to groups and it works. but please can anyone tell me why is that. With earlier relationships i did not have such mysterious problems. I am loosing ma sanity. 🙁

Maybe someone sees a problem in my code? Are my account->group relationships well set?

EDIT: As @AdrianShum said group is a SQL keyword so that my mapping worked when I changed to another name