I am in need of help to create a hashmap.
public class Driver {
private String id;
private String name;
private List<Student> students;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Student> getStudents() {
return students;
}
public void setStudents(List<Student> students) {
this.students = students;
}
}
public class Student {
private String id;
private String name;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
There will be a List of Driver objects. Every Driver has List of Student objects. Could someone help me how to create this Map using streams: <Student.id, Driver.id>
Thanks!
You can use flatMap to build a Stream of all the (Student ID, Driver ID) pairs and then collect them into a Map:
List<Driver> drivers = new ArrayList<> ();
Map<String,String>
studentDrivers =
drivers.stream ()
.flatMap (drv -> drv.getStudents ()
.stream ()
.map (st -> new SimpleEntry<String,String> (st.getId (), drv.getId ())))
.collect (Collectors.toMap (Map.Entry::getKey,
Map.Entry::getValue));
Related
I want to connect Spring Boot with neo4j database, however, it returns an error like that. It says that the connection has been terminated. The error is as follow:
org.neo4j.driver.v1.exceptions.ServiceUnavailableException: Connection to the database terminated.
This is my Controller
#RequestMapping("/neo4j/Movie")
public class MovieController {
private final MovieRepository movieRepository;
public MovieController(MovieRepository movieRepository) {
this.movieRepository = movieRepository;
}
#GetMapping("/graph")
public List<Movie> graph() {
return (List<Movie>) movieRepository.findAll();
}
}
This is my Repository
#Repository
public interface MovieRepository extends Neo4jRepository<Movie,Long> {
#Query("MATCH(m:Movie)<-[relation:ActedIn]-(b:Actor) RETURN m,relation,b")
Collection<Movie> graph();
}
And the application.properties
spring.data.neo4j.username=neo4j
spring.data.neo4j.password=neo4j
spring.data.neo4j.uri=bolt://localhost:7687
NodeEntity of moview
#NodeEntity
public class Movie {
#Id
private int id;
private String title;
private String genre;
// #JsonIgnoreProperties("movie")
#Relationship(type = "ActedIn")
private List<Actor> actors;
// #Relationship(type = "ACTED_IN" , direction = Relationship.INCOMING)
// private List<Actress> actresses = new ArrayList<>();
public Movie() {
}
public List<Actor> getActors() {
return actors;
}
public void setActors(List<Actor> actors) {
this.actors = actors;
}
public Movie(int id, String title, String genre, List<Actor> actors) {
this.id = id;
this.title = title;
this.genre=genre;
this.actors=actors;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getGenre() {
return genre;
}
public void setGenre(String genre) {
this.genre=genre;
}
}
And NodeEntity of Actor
public class Actor {
#GraphId
private Long id;
private String name;
private int age;
public Actor() {
}
public Actor(Long id, String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
I also tried springboot + neo4j projects downloaded from github, and also followed the instructions from neo4j website, but the projects still failed on my computer, so is there any super tutorials for neo4j and springboot?
I faced with problem of null value in PK.
Here's an entity:
#Entity
#Table(name="space")
public class Space implements Serializable {
#Id
#GeneratedValue
#Column(nullable = false, unique = true)
private Long id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name="user_id")
private UserAccount user;
private String name;
private String description;
private Date createdTime;
private Date modifiedTime;
#OneToMany(mappedBy="space")
private Set<SpaceAccess> spaceAccesses = new HashSet<>();
public Set<SpaceAccess> getSpaceAccesses() {
return spaceAccesses;
}
public void setSpaceAccesses(Set<SpaceAccess> spaceAccesses) {
this.spaceAccesses = spaceAccesses;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Space() {}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public UserAccount getUser() {
return user;
}
public void setUser(UserAccount user) {
this.user = user;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Date getCreatedTime() {
return createdTime;
}
public void setCreatedTime(Date createdTime) {
this.createdTime = createdTime;
}
public Date getModifiedTime() {
return modifiedTime;
}
public void setModifiedTime(Date modifiedTime) {
this.modifiedTime = modifiedTime;
}
}
I wrote strategy to generate PK properly but I always get Null in id field when I create new instance of the Space:
Space space = new Space();
Here's content of the object:
What i should do to generate id of instance properly using hibernate/spring mechanisms?
application.properties:
spring.datasource.url="some_url"
spring.datasource.username=name
spring.datasource.password=password
spring.jpa.generate-ddl=true
P.S. I use spring-boot-starter-data-jpa with version: 2.3.4.RELEASE.
Use:
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
I want to display table data based on different parameters like price range as well as category.
#Entity
public class Item {
#Id
#GeneratedValue
private Long id;
private String name;
private Double price;
private String category;
public Item() {
super();
}
Item(String name, String category){
super();
this.name = name;
this.category = category;
}
public Item(Long id, String name,Double price,String category) {
super();
this.id = id;
this.name = name;
this.price = price;
this.category=category;
}
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 Double getPrice() {
return price;
}
public void setPrice(Double price) {
this.price = price;
}
public String getCategory() {
return category;
}
public void setCategory(String category) {
this.category = category;
}
}
#Repository
public interface ItemRepository extends JpaRepository<Item, Long >{
}
I want to use postman to display table data based on category and price range.
Due to the usage of long as a parameter, I am only able to retrieve item based on id number.
From your question what i understood was that you need to have methods to return data based on Category and Price rather than using the id.
#Repository
public interface ItemRepository extends JpaRepository<Item, Long >{
List<Item> findByCategory(String category);
List<Item> findByPrice(Double price);
}
You can use the Spring JPA Query methods to have default implementations for that as well.
For more information read Official Doc.
Another Example:
List<Item> findByCategoryAndPrice(String category,Double price);
I have a simple Model in Java called Member with fields - ID (Primary Key), Name (String), Position (String)
I want to expose an POST endpoint to update fields of a member. This method can accept payload like this
{ "id":1,"name":"Prateek"}
or
{ "id":1,"position":"Head of HR"}
and based on the payload received, I update only that particular field. How can I achieve that with JPARepository?
My repository interface is basic -
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;
#Repository("memberRepository")
public interface MemberRepository extends JpaRepository<Member, Integer>{
}
My Member model -
#Entity
#Table(name="members")
public class Member {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name="member_id")
private Integer id;
#Column(name="member_name")
#NotNull
private String name;
#Column(name="member_joining_date")
#NotNull
private Date joiningDate = new Date();
#Enumerated(EnumType.STRING)
#Column(name="member_type",columnDefinition="varchar(255) default 'ORDINARY_MEMBER'")
private MemberType memberType = MemberType.ORDINARY_MEMBER;
public Member(Integer id, String name, Date joiningDate) {
super();
this.id = id;
this.name = name;
this.joiningDate = joiningDate;
this.memberType = MemberType.ORDINARY_MEMBER;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getJoiningDate() {
return joiningDate;
}
public void setJoiningDate(Date joiningDate) {
this.joiningDate = joiningDate;
}
public MemberType getMemberType() {
return memberType;
}
public void setMemberType(MemberType memberType) {
this.memberType = memberType;
}
public Member(String name) {
this.memberType = MemberType.ORDINARY_MEMBER;
this.joiningDate = new Date();
this.name = name;
}
public Member() {
}
}
Something like this should do the trick
public class MemberService {
#Autowired
MemberRepository memberRepository;
public Member updateMember(Member memberFromRest) {
Member memberFromDb = memberRepository.findById(memberFromRest.getid());
//check if memberFromRest has name or position and update that to memberFromDb
memberRepository.save(memberFromDb);
}
}
I was wondering if it is possible to retrieve a specific column from an object named parameter in HQL.
Example
public class Product
{
private int id;
private Supplier supplier;
private String name;
private String description;
private double price;
public Product()
{
super();
}
public Product(String name, String description, double price)
{
super();
this.name = name;
this.description = description;
this.price = price;
}
public String getDescription()
{
return description;
}
public void setDescription(String description)
{
this.description = description;
}
public int getId()
{
return id;
}
public void setId(int id)
{
this.id = id;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
public Supplier getSupplier()
{
return supplier;
}
public void setSupplier(Supplier supplier)
{
this.supplier = supplier;
}
public double getPrice()
{
return price;
}
public void setPrice(double price)
{
this.price = price;
}
}
as you can see I created the product and it has a supplier object within it.
So when I do HQL and call
String hql = "from Product as product where product.supplier=:supplier";
Query query = session.createQuery(hql);
query.setEntity("supplier",supplier);
List results = query.list();
displayProductsList(results);
but is it possible to just get product's supplier's name?
and not just the whole supplier?
Just don't pass a Supplier instance to your query, but pass the supplier's name directly:
String hql = "from Product as product where product.supplier.name = :supplierName";
Query query = session.createQuery(hql);
query.setString("supplierName", supplier.getName());
List results = query.list();
displayProductsList(results);