I have the following model;
Here is the UserEntity class:
class UserEntity {
private String username;
private List<RuleEntity> rules;
@Column(name = "username", nullable = false, unique = true)
public String getUsername() {
return username;
}
@ManyToMany(mappedBy="users" , fetch = FetchType.LAZY)
public List<RuleEntity> getRules() {
return rules;
}
...
}
And the RuleEntity class:
class RuleEntity {
private String name;
private List<UserEntity> users;
@Column(name = "name", nullable = false)
public String getRuleName() {
return ruleName;
}
@ManyToMany (fetch = FetchType.LAZY)
@JoinTable(name= "RULE_USER" ,joinColumns=@JoinColumn
(name=RuleEntity.RULE_ID, referencedColumnName="ID", insertable = true, updatable = false, nullable = false),
inverseJoinColumns=@JoinColumn
(name=UserEntity.USER_ID, referencedColumnName="ID", insertable = true, updatable = false, nullable = false),
uniqueConstraints = @UniqueConstraint(columnNames = {RuleEntity.RULE_ID, UserEntity.USER_ID}))
public List<UserEntity> getUsers() {
return users;
}
...
}
I am trying to implement a search whereby a user can search using:
So I am performing 2 HQL queries, one to return the matching users and one to return the matching rules eg
public SearchResults search(String maybePartialUsername, String maybePartialRuleName) {
List<UserEntity> userEntities = hqlQuery("select distinct users from UserEntity as users inner join users.rules as rules where users.username like :maybePartialUsername and rules.ruleName like :maybePartialRuleName");
List<RuleEntity> ruleEntities = hqlQuery("select distinct rules from RuleEntity as rules inner join rules.users as users where users.username like :maybePartialUsername and rules.ruleName like :maybePartialRuleName");
return SearchResults(userEntities, ruleEntities);
}
The first HQL query for finding users matching a username (and/or rulename) works fine when a user is a member of at least one rule, but it returns no results when a user has not been added to any rules.
Changing the 'inner join' to a 'left join' does not help. The problem lies in the 'rules.ruleName like :maybePartialRuleName' condition, if I remove this the query works, but I need this in the query in the cases where the join with the rules tables succeeds (ie a user DOES have rules), and thus I then need to filter by rule name as well as username.
select distinct users from UserEntity as users inner join users.rules as rules where users.username like :maybePartialUsername and rules.ruleName like :maybePartialRuleName
Try left join
select distinct users from UserEntity as users left join users.rules as rules where users.username like :maybePartialUsername and rules.ruleName like :maybePartialRuleName.
It will give you all that's int left side (userEntity in this case).
This is what worked for me (thanks @sergiu):
The following method creates the select part of the query:
public List<UserEntity> search(final String maybePartialUsername, final String maybePartialRuleName)
throws EntityException {
final String selectUsersStatement = "select distinct users from UserEntity as users";
final String joinUsersWithRulesClause = shouldFilterSearchBy(maybePartialRuleName) ? "inner join users.rules as rules" : null;
return search(Joiner.on(" ").skipNulls().join(selectUsersStatement, joinUsersWithRulesClause),
maybePartialUsername, maybePartialRuleName);
}
Which then calls a method (not shown) which calls the following to build the where parts of the query:
private String buildSearchQueryFrom(final String selectStatement, final String maybePartialUsername,
final String maybePartialRuleName) {
final Collection<String> searchFilters = Lists.newArrayListWithCapacity(2);
if (shouldFilterSearchBy(maybePartialUsername)) {
searchFilters.add("users.username like :maybePartialUsername");
}
if (shouldFilterSearchBy(maybePartialRuleName)) {
searchFilters.add("rules.ruleName like :maybePartialRuleName");
}
final String whereClauseParts = Joiner.on(" and ").skipNulls().join(searchFilters);
return Joiner.on(" where ").skipNulls().join(selectStatement, whereClauseParts);
}
And a helper method called by the method above:
protected boolean shouldFilterSearchBy(final String searchValue) {
return !Strings.isNullOrEmpty(searchValue);
}
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