I have modelled a simple finite state machine graph in neo4j, where the domain consists of State entities and a FOLLOWED_BY relationship (in cypher: (s1:State)-[r:FOLLOWS]->(s2:State)).
Each has some properties. I need now to analyse relations among the states and don't know how the return type in
the repository interface should look like.
The (shortened) code for the entity and relationship classes (with lombok annotations):
#NodeEntity
#NoArgsConstructor
public class State {
#Getter
private String name;
#Getter
private String inputVariable;
#Getter
private String outputVariable;
}
#RelationshipEntity(type = "FOLLOWED_BY")
#NoArgsConstructor
public class Transition implements FlowTransition {
#Getter
#Property
private String guard;
#Getter
#StartNode
private State sourceState;
#Getter
#EndNode
private State targetState;
}
For some analysis which paths exists from an state to following states where the output variable of first state is used as
the input variable of the following state, I need the path returned from the query. As I'm using SDN I would like to have it
returned in a (custom) query from the repository.
#Repository
public interface StateRepository extends Neo4jRepository<State, Long> {
#Query("MATCH p=allShortestpaths((s1:State)-[r:FOLLOWED_BY*1..200]->(s2:State))"
+ " WHERE s1.outputVariable = s2.inputVariable AND id(s1) = {eId}"
+ " RETURN p)"
??? findAllByBpelPathRegEx(#Param("eId") String startId);
}
My question is: what class should I use as the return type to get the path object? EntityPath or EndResult doesn't seem to exists anymore in SDN5(maybe 4 also), so what to take? Maybe projections, but should they look like?
From this question and answers How do I query for paths in spring data neo4j 4?
:
EntityPath isn't supported since SDN 4 and you should use Iterable<Map<String, Object>> as return type (btw: List<Map<String, Object>> works either). The keys of the Map<String, Object> are the names of variables which you return in your Cypher query (in the example it's p from RETURN p).
BTW: It's maybe better you return RETURN nodes(p) AS nodes, relationships(p) (map-keys: nodes, relationships(p)) as this would return your defined #NodeEntity and #RelationshipEntity objects and not just the simple path objects (which contains just ids (as strings) and not the node objects themselves)
You can take the result in an object class or you need to create a class having #QueryResult annotation collect the s1 and s2.
Related
As Spring jpa Provides some usefull features to find Items from a repository by defining it in the method name. e .x findByTitle(String title) then Spring is automatically searching the Title Colum for the given String. If i have an int column named numberOfCopies and i want only to find the datasets with >0 greater then null how would define such a method ?
to filter out those books with the numberOfCopies equals 0 = zero
#Entity
public class Book {
#Id
private int id;
private String title;
private int numberOfCopies;
}
can i use the Repomethod
public List findBooksByNumberOfCopies.greater then 0 ?To Use this Spring Feature without some if or for loops
First, you should use Integer, since it is better, in my opinion, to use wrapper classes than to primitives, and enforce not null requirement through annotations, e.g. #Column(nullable = false)
#Entity
public class Book {
#Id
private Integer id;
private String title;
private Integer numberOfCopies;
}
Then you can add the following two methods in your BookRepository;
List<Book> findByNumberOfCopiesGreaterThan(Integer numberOfCopies);
default List<Book> findAllAvailableBooks() {
return findByNumberOfCopiesGreaterThan(0);
}
and use the default findAllAvailableBooks method, with hardcoded 0 value which is your requirement.
you can easily use
List<Book> findByNumberOfCopiesGreaterThanEqual(int numberOfCopies);
Pretty sure this would work:
public interface BookRepo extends JpaRepository<Book, Integer> {
#Query("SELECT b FROM Book b WHERE b.numberOfCopies >= 0")
public Optional<List<Book>> getTheBooksWithMultCopies();
}
// back in your component class:
{
...
Optional<List<Book>> optionalBookList = myBookRepo.getTheBooksWithMultCopies();
if (optionalBookList.isPresent()){
List<Book> bookList = optionalBookList.get();
}
}
Note that the language within the query is called HQL, which is what is used by Hibernate internally (which is used by JPA internally). It's really not very intimidating - just, know that you the objects in your POJO, which map to your database table, rather than your database table directly.
Also, I'd recommend using Integer over int in entity classes, at least if your value is nullable. Otherwise, numberOfCopies will always default to 0, which may not be desirable and may cause exceptions that are difficult to decipher.
GreaterThanEqual takes an Integer not int
List<Book> findByNumberOfCopiesGreaterThanEqual(Integer numberOfCopies);
Consider the document with complex object field:
#Getter #Setter
#Document
class A{
#Id
private String id;
#Field(
type = FieldType.Object,
includeInParent = true
)
private B b;
}
#Getter #Setter
class B{
String field1;
C c;
}
#Getter #Setter
class C{
String field1;
}
public interface ARepo extends ElasticsearchRepository<A, String> {
Optional<A> findByB(B b);
}
When I execute the aRepo.findByB(someB), the built query doesn't extract B fields, but contains the result of someB.toString() as filter for field b.
I have JPA background and expect similar behavior . If this is not supported, what is the recommended approach for these kind of queries ?
Thanks
What you are looking is the equivalent of Query By Example (QBE), this is not yet supported in Spring-Data-ES.
Searching on an class object should be dependend on your mapping, if your mapping is determined by application (#Field on fields with #Mapping and dynamic mapping set to false), and by looking at public interface ElasticsearchRepository<...> - you will have to manually build your query using QueryBuilder (Elastic abstraction) or Criteria (Spring-Data-ES abstraction) and then customizing your repository.
If your mapping is not determined by application (already set on elastic before), you would have to know it field types (is it a 'text', 'keyword', etc), then there might be different behavior expect for each type (match query, term query, filter, etc) - and this will also have to be custom-implemented with QueryBuilder or Criteria.
is it possible to have a projection with nested collection with Spring JPA?
I have the following 2 simple entity (to explain the problem)
#Entity
#Table(name = "person")
public class Person implements Serializable {
private Integer id;
private String name;
#OneToMany
private List<Address> addressList = new ArrayList<>();
}
#Entity
#Table(name = "address")
public class Address implements Serializable {
private Integer id;
private String city;
private String street;
}
Is it possible to have a projection of Person with following attributes filled in ? {person.name, address.city}
I might be wrong in semantics of word Projection. but the problem is what i need to achieve. Maybe it is not possible with Projection, but is there another way to achieve the end goal? Named Entity graph perhaps ?
P.S. please suggest a solution for Spring JPA not Spring Jpa REST
thanks in advance
You're right, Entity Graphs serve this exact purpose - control field loading.
Create entity graphs dynamically from the code or annotate target entities with Named Entity Graphs and then just use their name.
Here is how to modify your Person class to use Named Entity Graphs:
#Entity
#Table(name = "person")
#NamedEntityGraph(name = "persion.name.with.city",
attributeNodes = #NamedAttributeNode(value = "addressList", subgraph = "addresses.city"),
subgraphs = #NamedSubgraph(name = "addresses.city", attributeNodes = #NamedAttributeNode("city")))
public class Person implements Serializable {
private Integer id;
private String name;
#OneToMany
private List<Address> addressList;
}
And then when loading your person:
EntityGraph graph = em.getEntityGraph("person.name.with.city");
Map hints = new HashMap();
hints.put("javax.persistence.fetchgraph", graph);
return em.find(Person.class, personId, hints);
The same applies for queries, not only em.find method.
Look this tutorial for more details.
I think that that's not usual scenario of Data JPA usage. But you can achieve your goal with pure JPQL:
SELECT a.street, a.person.name FROM Address a WHERE …
This solution has 2 drawbacks:
It forces you to have bidirectional relationship Address ←→ Person
It returns List
Another solution (and that's preferred JPA way) is to create DTO like this:
class MyPersonDTO {
private String personName;
private List<String> cities;
public MyPersonDTO(String personName, List<Address> adresses) {
this.personName = personName;
cities = adresses
.stream()
.map(Address::getCity)
.collect(Collectors.toList());
}
}
And the execute JPQL query like this:
SELECT NEW package.MyPersonDTO(p.name, p.addressList) FROM Person p WHERE …
Return type will be List<MyPersonDTO> in that case.
Of course you can use any of this solutions inside #Query annotation and it should work.
I am implementing queries in my web application with JPA repositories. The two main tables I am querying from are FmReportTb and SpecimenTb.
Here are the two entity classes (only important attributes are listed).
//FmReportTb.java
#Entity
#Table(name="FM_REPORT_TB")
public class FmReportTb implements Serializable {
#Column(name="ROW_ID")
private long rowId;
#Column(name="FR_BLOCK_ID")
private String frBlockId;
#Column(name="FR_FULL_NAME")
private String frFullName;
#OneToOne
#JoinColumn(name="SPECIMEN_ID")
private SpecimenTb specimenTb;
FmReportTb has OneToOne relationship with SpecimenTb.
#Entity
#Table(name="SPECIMEN_TB")
public class SpecimenTb implements Serializable {
private String mrn;
#OneToOne(mappedBy="specimenTb", cascade=CascadeType.ALL)
private FmReportTb fmReportTb;
The query I am working on is to find all records in FmReportTb and show a few attributes from FmReportTb plus mrn from SpecimenTb.
Here is my JPA repository for FmReportTb:
#Repository
public interface FmReportRepository extends JpaRepository<FmReportTb, Long> {
#Query("select f from FmReportTb f where f.deleteTs is not null")
public List<FmReportTb> findAllFmReports();
Since, I am only showing part of the attributes from FmReportTb and one attribute from SpecimenTb, I decided to create a Value Object for FmReportTb. The constructor of the VO class assigns attributes from FmReportTb and grabs mrn attribute from SpecimenTb based on the OneToOne relationship. Another reason for using VO is because table FmReportTb has a lot of OneToMany children entities. For this particular query, I don't need any of them.
public class FmReportVO {
private String frBlockId;
private Date frCollectionDate;
private String frCopiedPhysician;
private String frDiagnosis;
private String frFacilityName;
private String frFullName;
private String frReportId;
private String filepath;
private String mrn;
public FmReportVO(FmReportTb fmReport) {
this.frBlockId = fmReport.getFrBlockId();
this.frCollectionDate = fmReport.getFrCollectionDate();
this.frCopiedPhysician = fmReport.getFrCopiedPhysician();
this.frDiagnosis = fmReport.getFrDiagnosis();
this.frFacilityName = fmReport.getFrFacilityName();
this.frFullName = fmReport.getFrFullName();
this.frReportId = fmReport.getFrReportId();
this.mrn = fmReport.getSpecimenTb().getMrn();
}
I implemented findall method in servicebean class to return a list of FmReportTb VOs.
//FmReportServiceBean.java
#Override
public List<FmReportVO> findAllFmReports() {
List<FmReportTb> reports = fmReportRepository.findAllFmReports();
if (reports == null) {
return null;
}
List<FmReportVO> fmReports = new ArrayList<FmReportVO>();
for (FmReportTb report : reports) {
FmReportVO reportVo = new FmReportVO(report);
String filepath = fileLoadRepository.findUriByFileLoadId(report.getFileLoadId().longValue());
reportVo.setFilepath(filepath);
fmReports.add(reportVo);
}
return fmReports;
}
Lastly, my controller looks like this:
#RequestMapping(
value = "/ristore/foundation/",
method = RequestMethod.GET,
produces = "application/json")
public ResponseEntity<List<FmReportVO>> getAllFmReports() {
List<FmReportVO> reports = ristoreService.findAllFmReports();
if (reports == null) {
return new ResponseEntity<List<FmReportVO>>(HttpStatus.NOT_FOUND);
}
return new ResponseEntity<List<FmReportVO>>(reports, HttpStatus.OK);
}
There are about 200 records in the database. Surprisingly, it took almost 2 full seconds to retrieve all the records in JSON. Even though I did not index all the tables, this is way too slow. Similar query takes about probably a few ms on the database directly. Is it because I am using Value Objects or JPA query tends to be this slow?
EDIT 1
This may have to do with the fact that FmReportTb has almost 20 OneToMany entities. Although the fetchmode of these child entities are set to LAZY, JPA Data repository tends to ignore the fetchmode. So I ended up using NamedEntityGraph to specify the attributes EAGER. This next section is added to the head of my FmReportTb entity class.
#Entity
#NamedEntityGraph(
name = "FmReportGraph",
attributeNodes = {
#NamedAttributeNode("fileLoadId"),
#NamedAttributeNode("frBlockId"),
#NamedAttributeNode("frCollectionDate"),
#NamedAttributeNode("frDiagnosis"),
#NamedAttributeNode("frFullName"),
#NamedAttributeNode("frReportId"),
#NamedAttributeNode("specimenTb")})
#Table(name="FM_REPORT_TB")
And then #EntityGraph("FmReportGraph") was added before the JPA repository query to find all records. After doing that, the performance is improved a little bit. Now fetching 1500 records only takes about 10 seconds. However, it still seems too slow given each json object is fairly small.
Answering for the benefit of others with slow JPA queries...
As #Ken Bekov hints in the comments, foreign keys can help a lot with JPA.
I had a couple of tables with a many to one relationship - a query of 100,000 records was taking hours to perform. Without any code changes I reduced this to seconds just by adding a foreign key.
In phpMyAdmin you do this by creating a Relationship from the "many" table to the "one" table. For a detailed explanation see this question: Setting up foreign keys in phpMyAdmin?
and the answer by #Devsi Odedra
I am trying to utilize a NamedEntityGraph to limit the return data for specific queries. Mainly I do not want to return full object details when listing the object. A very simple class example is below.
#Entity
#Table(name="playerreport",schema="dbo")
#NamedEntityGraphs({
#NamedEntityGraph(name = "report.simple",
attributeNodes =
{#NamedAttributeNode(value="intId")
}
)
})
public class PlayerReportEntity {
#Id
#Column(name="intid",columnDefinition="uniqueidentifier")
private String intId;
#Column(name="plyid",columnDefinition="uniqueidentifier")
#Basic(fetch=FetchType.LAZY)
private String plyId;
#ManyToOne(fetch=FetchType.LAZY)
#JoinColumn(name = "plyid", insertable=false,updatable=false)
private PlayerEntity player;
No matter what I do to plyId and player are always returned. Is there any way to only return the requested columns (intId) ?
As for the collection Hibernate does not do the join for the player object but it still returns player as null. So that part is working to an extent.
I am using a JPARepository below to generate Crud Statements for me
public interface PlayerReportRepository extends JpaRepository<PlayerReportEntity, String> {
#EntityGraph(value="report.simple")
List<PlayerIntelEntity> findByPlyId(#Param(value = "playerId") String playerId);
#Override
#EntityGraph(value="report.simple")
public PlayerIntelEntity findOne(String id);
}
A chunk of text from here - "Hence it seems that the #NamedEntityGraph only affects fields that are Collections, but fields that are not a Collection are always loaded." from JIRA
Please use the Example 47 on this page and use repositories accordingly.
In essence, hibernate is right now loading all the feilds in the class and for collections it will work if you follow the example stated above.
Thanks.