How to use projections with hibernate lucene search

问题

I am doing hibernate lucene search .It is working fine with getting entire domain object.But my requirement is projections.It only getting single value on OneToMany associated fields.So how can I get all values of @IndexedEmbedded fields with projections.Please assists your suggestions. The following snippet is my code

    @Indexed(index="Skills")
                @AnalyzerDef(name = "skillAnalyzer",
                tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class),
                filters = {
                  @TokenFilterDef(factory = LowerCaseFilterFactory.class),
                  @TokenFilterDef(factory = SnowballPorterFilterFactory.class, params = {
                    @Parameter(name = "language", value = "English")
                  })
                })
                @Entity
                @Table(name = "skills")
                public class Skills {
                    @Id
                    @GeneratedValue(strategy = GenerationType.AUTO)
                    @Column(name = "skill_id")
                    @Field(name="skillIdPk",index=Index.YES, analyze=Analyze.YES, store=Store.YES)
                    private int skillId;

                    @Field(index=Index.YES, analyze=Analyze.YES, store=Store.YES)
                    @Column(name = "skill")
                    private String skill;

                    @Column(name = "skill_type")
                    private String skillType = "default";

                    //setters & getters
                }


            @Indexed(index = "JobSeeker")
            @AnalyzerDef(name = "jobSeekerAnalyzer", tokenizer = @TokenizerDef(factory = StandardTokenizerFactory.class), filters = {
                    @TokenFilterDef(factory = LowerCaseFilterFactory.class),
                    @TokenFilterDef(factory = SnowballPorterFilterFactory.class, params = {
                            @Parameter(name = "language", value = "English") }) })
            @Entity
            @Table(name = "jobseeker")
            @Component
            public class JobSeeker {
                @Id
                @GeneratedValue(strategy = GenerationType.AUTO)
                @Column(name = "jobseeker_id")
                private long jobSeekerId;

                @Column(name = "email_id", unique = true)
                private String emailId;

                @Column(name = "first_name")
                private String firstName;

                @Column(name = "middle_name")
                private String middleName;

                @Column(name = "last_name")
                private String lastName;

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


                @IndexedEmbedded
                private Set<JobSeekerSkills> jobSeekerSkills = new HashSet<JobSeekerSkills>();
            //setters & getters


            }


        @Indexed(index="JobSeekerSkills")
        @AnalyzerDef(name = "jobseekerSkillAnalyzer",
        tokenizer = @TokenizerDef(factory=StandardTokenizerFactory.class),
        filters = {
          @TokenFilterDef(factory = LowerCaseFilterFactory.class),
          @TokenFilterDef(factory = SnowballPorterFilterFactory.class, params = {
            @Parameter(name = "language", value = "English")
          })
        })
        @Entity
        @Table(name="jobseeker_skills")

        public class JobSeekerSkills 
        {
            @Id
            @GeneratedValue(strategy=GenerationType.AUTO)
            @Column(name="jobseeker_skill_id")
            private long jobSeekerSkillId;

            @ManyToOne
            @JoinColumn(name="jobseeker_jobseeker_id")
            private JobSeeker jobSeeker;

            @ManyToOne
            @JoinColumn(name="skills_skill_id")
            @IndexedEmbedded
                private Skills skills;


        //setters & getters

        }

//=======================================================================
//This is my Dao code
FullTextSession fullTextSession = Search.getFullTextSession(session);
        fullTextSession.createIndexer().startAndWait();
        QueryBuilder qb = fullTextSession.getSearchFactory().buildQueryBuilder().forEntity(JobSeeker.class).get();
        Query query = null;
        for (String string : skills) {
            query = qb.keyword().onField("jobSeekerSkills.skills.skillIdPk").matching(Integer.parseInt(string)).createQuery();
        }
        org.hibernate.search.FullTextQuery query1 =
                fullTextSession.createFullTextQuery(query, JobSeeker.class);
            query1.setProjection("jobSeekerId", "jobSeekerSkills.skills.skill");
            List results = query1.list();
            for (int i = 0; i < results.size(); i++) {
                Object[] object = (Object[]) results.get(i);
                System.out.println(object[0]);
                System.out.println(object[1]);
            }
        //  List<Skills> authorName1 = (List<Skills>) firstResult[1];
        //  System.out.println(authorName1);
        return results;

回答1:

As mentioned in the Hibernate Search documentation:

projection does not work on collections or maps which are indexed via @IndexedEmbedded

So in your case, trying to project on jobSeekerSkills.skills.skill, with jobSeekerSkills being a collection indexed via @IndexedEmbedded, is not a good idea.

I'd like to point out that, since you're only performing a keyword query on a numeric field, you'd probably be better off just doing a classic JQPL/SQL query using Hibernate ORM.

Anyway, if for whatever reason you really want to use Hibernate Search for this, judging from your query, you don't need to project on a collection. Instead, just add an @IndexedEmbedded(includePaths = "includePaths") to the jobSeeker property of JobSeekerSkills, and then rework your query to target the index for entity JobSeekerSkills:

    FullTextSession fullTextSession = Search.getFullTextSession(session);
    fullTextSession.createIndexer().startAndWait();
    QueryBuilder qb = fullTextSession.getSearchFactory().buildQueryBuilder().forEntity(JobSeeker.class).get();
    Query query = null;
    for (String string : skills) {
        query = qb.keyword().onField("skills.skillIdPk").matching(Integer.parseInt(string)).createQuery();
    }
    org.hibernate.search.FullTextQuery query1 =
            fullTextSession.createFullTextQuery(query, JobSeeker.class);
        query1.setProjection("jobSeeker.jobSeekerId", "skills.skill");
        List results = query1.list();
        for (int i = 0; i < results.size(); i++) {
            Object[] object = (Object[]) results.get(i);
            System.out.println(object[0]);
            System.out.println(object[1]);
        }
    //  List<Skills> authorName1 = (List<Skills>) firstResult[1];
    //  System.out.println(authorName1);
    return results;

Note: the includePaths on the new @IndexedEmbedded is only necessary because you already have an @IndexedEmbedded on the reverse side of the association (JobSeeker.jobSeekerSkills); it avoids infinite recursion (JobSeeker.jobSeekerSkills.jobSeeker.jobSeekerSkills.jobSeeker.jobSeekerSkills...). If you remove the @IndexedEmbedded on JobSeeker.jobSeekerSkills, then you can also remove the includePaths on the new @IndexedEmbedded.

来源：https://stackoverflow.com/questions/43370523/how-to-use-projections-with-hibernate-lucene-search