Class Linker

java.lang.Object
com.erudika.para.core.Linker
All Implemented Interfaces:
Linkable, ParaObject, Votable, Serializable
public final class Linker extends Object implements ParaObject, Serializable
This class represents a many-to-many relationship (link) between two objects.
Author:
Alex Bogdanovski [[email protected]]
See Also:

  • Constructor Details

    • Linker

      public Linker()
      No-args constructor.

    • Linker

      public Linker(String type1, String type2, String id1, String id2)
      A link. The names of the objects are compared and sorted alphabetically.
      Parameters:
      type1 - the type of the first object
      type2 - the type of the second object
      id1 - the id of the first object
      id2 - the id of the second object

  • Method Details

    • getId2

      public String getId2()
      Returns the id of the second object in the link.
      Returns:
      the id

    • setId2

      public void setId2(String id2)
      Sets the id of the second object in the link.
      Parameters:
      id2 - a new id

    • getId1

      public String getId1()
      Returns the id of the first object in the link.
      Returns:
      the id

    • setId1

      public void setId1(String id1)
      Sets the id of the first object in the link.
      Parameters:
      id1 - a new id

    • getType1

      public String getType1()
      Returns the type of the first object in the link.
      Returns:
      the type

    • setType1

      public void setType1(String type1)
      Sets the type of the first object in the link.
      Parameters:
      type1 - the type

    • getType2

      public String getType2()
      Returns the type of the second object in the link.
      Returns:
      the type

    • setType2

      public void setType2(String type2)
      Sets the type of the second object in the link.
      Parameters:
      type2 - second type

    • getMetadata

      public String getMetadata()
      Returns the additional information about the link.
      Returns:
      some info

    • setMetadata

      public void setMetadata(String metadata)
      Sets additional information about the link.
      Parameters:
      metadata - some info

    • isFirst

      public boolean isFirst(String type2)
      Checks if the position of a given object is first or second.
      Parameters:
      type2 - the given class of object
      Returns:
      true if the object's type is equal to getType1()

    • getIdFieldNameFor

      public String getIdFieldNameFor(String type)
      Returns "id1" or "id2" depending on the alphabetical order of type.
      Parameters:
      type - the type
      Returns:
      id1 or id2

    • getNstd

      public List<Map<String,Object>> getNstd()
      Get the nested objects that are linked by this link.
      Returns:
      a 2-element array of objects or null

    • setNstd

      public void setNstd(List<Map<String,Object>> nstd)
      Sets the nested array of objects that are linked by this link.
      Parameters:
      nstd - an array of 2 objects only

    • addNestedObject

      public void addNestedObject(ParaObject obj)
      Add an object to nest inside the linker object. Used for joining queries when searching objects in a many-to-many relationship.
      Parameters:
      obj - object

    • getId

      public String getId()
      /////////////////////////////////////////////////////
      Specified by:
      getId in interface ParaObject
      Returns:
      the id

    • setId

      public void setId(String id)
      Description copied from interface: ParaObject
      Sets a new id. Must not be null or empty.
      Specified by:
      setId in interface ParaObject
      Parameters:
      id - the new id

    • getType

      public String getType()
      Description copied from interface: ParaObject
      The name of the object's class. This is equivalent to Class.getSimpleName().toLowerCase()
      Specified by:
      getType in interface ParaObject
      Returns:
      the simple name of the class

    • setType

      public void setType(String type)
      Description copied from interface: ParaObject
      Sets a new object type. Must not be null or empty.
      Specified by:
      setType in interface ParaObject
      Parameters:
      type - a new type

    • getAppid

      public String getAppid()
      Description copied from interface: ParaObject
      The application name. Added to support multiple separate apps. Every object must belong to an app.
      Specified by:
      getAppid in interface ParaObject
      Returns:
      the app id (name). default: para

    • setAppid

      public void setAppid(String appid)
      Description copied from interface: ParaObject
      Sets a new app name. Must not be null or empty.
      Specified by:
      setAppid in interface ParaObject
      Parameters:
      appid - the new app id (name)

    • getObjectURI

      public String getObjectURI()
      Description copied from interface: ParaObject
      The URI of this object. For example: /users/123
      Specified by:
      getObjectURI in interface ParaObject
      Returns:
      the URI
      See Also:

    • getTags

      public List<String> getTags()
      Description copied from interface: ParaObject
      The tags associated with this object. Tags must not be null or empty.
      Specified by:
      getTags in interface ParaObject
      Returns:
      a set of tags, or an empty set
      See Also:

    • setTags

      public void setTags(List<String> tags)
      Description copied from interface: ParaObject
      Merges the given tags with existing tags.
      Specified by:
      setTags in interface ParaObject
      Parameters:
      tags - the additional tags, or clears all tags if set to null

    • getStored

      public Boolean getStored()
      Description copied from interface: ParaObject
      Boolean flag which controls whether this object is stored in the database or not. Default is true.
      Specified by:
      getStored in interface ParaObject
      Returns:
      true if this object is stored in DB.

    • setStored

      public void setStored(Boolean stored)
      Description copied from interface: ParaObject
      Sets the "isStored" flag.
      Specified by:
      setStored in interface ParaObject
      Parameters:
      stored - when set to true, object is stored in DB.

    • getIndexed

      public Boolean getIndexed()
      Description copied from interface: ParaObject
      Boolean flag which controls whether this object is indexed by the search engine. Default is true.
      Specified by:
      getIndexed in interface ParaObject
      Returns:
      true if this object is indexed

    • setIndexed

      public void setIndexed(Boolean indexed)
      Description copied from interface: ParaObject
      Sets the "isIndexed" flag.
      Specified by:
      setIndexed in interface ParaObject
      Parameters:
      indexed - when set to true, object is indexed.

    • getCached

      public Boolean getCached()
      Description copied from interface: ParaObject
      Boolean flag which controls whether this object is cached. Default is true.
      Specified by:
      getCached in interface ParaObject
      Returns:
      true if this object is cached on update() and create().

    • setCached

      public void setCached(Boolean cached)
      Description copied from interface: ParaObject
      Sets the "isCached" flag.
      Specified by:
      setCached in interface ParaObject
      Parameters:
      cached - when set to true, object is cached.

    • getTimestamp

      public Long getTimestamp()
      Description copied from interface: ParaObject
      The time when the object was created, in milliseconds.
      Specified by:
      getTimestamp in interface ParaObject
      Returns:
      the timestamp of creation

    • setTimestamp

      public void setTimestamp(Long timestamp)
      Description copied from interface: ParaObject
      Sets the timestamp.
      Specified by:
      setTimestamp in interface ParaObject
      Parameters:
      timestamp - a new timestamp in milliseconds.

    • getCreatorid

      public String getCreatorid()
      Description copied from interface: ParaObject
      The id of the user who created this. Should point to a User id.
      Specified by:
      getCreatorid in interface ParaObject
      Returns:
      the id or null

    • setCreatorid

      public void setCreatorid(String creatorid)
      Description copied from interface: ParaObject
      Sets a new creator id. Must not be null or empty.
      Specified by:
      setCreatorid in interface ParaObject
      Parameters:
      creatorid - a new id

    • getName

      public String getName()
      Description copied from interface: ParaObject
      The name of the object. Can be anything.
      Specified by:
      getName in interface ParaObject
      Returns:
      the name. default: [type id]

    • setName

      public void setName(String name)
      Description copied from interface: ParaObject
      Sets a new name. Must not be null or empty.
      Specified by:
      setName in interface ParaObject
      Parameters:
      name - the new name

    • getPlural

      public String getPlural()
      Description copied from interface: ParaObject
      The plural name of the object. For example: user - users
      Specified by:
      getPlural in interface ParaObject
      Returns:
      the plural name

    • getParentid

      public String getParentid()
      Description copied from interface: ParaObject
      The id of the parent object.
      Specified by:
      getParentid in interface ParaObject
      Returns:
      the id of the parent or null

    • setParentid

      public void setParentid(String parentid)
      Description copied from interface: ParaObject
      Sets a new parent id. Must not be null or empty.
      Specified by:
      setParentid in interface ParaObject
      Parameters:
      parentid - a new id

    • getUpdated

      public Long getUpdated()
      Description copied from interface: ParaObject
      The last time this object was updated. Timestamp in ms.
      Specified by:
      getUpdated in interface ParaObject
      Returns:
      timestamp in milliseconds

    • setUpdated

      public void setUpdated(Long updated)
      Description copied from interface: ParaObject
      Sets the last updated timestamp.
      Specified by:
      setUpdated in interface ParaObject
      Parameters:
      updated - a new timestamp

    • create

      public String create()
      Description copied from interface: ParaObject
      Stores this object in the data store.
      Specified by:
      create in interface ParaObject
      Returns:
      the id of the object (a new id if object is new)
      See Also:

    • update

      public void update()
      Description copied from interface: ParaObject
      Updates the object permanently. Changes to Locked fields are ignored.
      Specified by:
      update in interface ParaObject
      See Also:

    • delete

      public void delete()
      Description copied from interface: ParaObject
      Deletes the object permanently by removing it from the data store.
      Specified by:
      delete in interface ParaObject
      See Also:

    • exists

      public boolean exists()
      Description copied from interface: ParaObject
      Checks if an object is stored in the data store.
      Specified by:
      exists in interface ParaObject
      Returns:
      true if the object is persisted to the data store.
      See Also:

    • voteUp

      public boolean voteUp(String userid)
      Description copied from interface: Votable
      Upvotes the object.
      Specified by:
      voteUp in interface Votable
      Parameters:
      userid - id of voter
      Returns:
      true if successful

    • voteDown

      public boolean voteDown(String userid)
      Description copied from interface: Votable
      Downvotes the object.
      Specified by:
      voteDown in interface Votable
      Parameters:
      userid - id of voter
      Returns:
      true if successful

    • getVotes

      public Integer getVotes()
      Description copied from interface: Votable
      Returns the total sum of all votes for this object. For example: (+6) + (-4) = 2
      Specified by:
      getVotes in interface Votable
      Returns:
      the total sum of votes

    • setVotes

      public void setVotes(Integer votes)
      Description copied from interface: Votable
      Sets the total votes for this object.
      Specified by:
      setVotes in interface Votable
      Parameters:
      votes - the number of votes

    • getVersion

      public Long getVersion()
      Description copied from interface: ParaObject
      Returns the version number for this object. Used primarily for optimistic locking.
      Specified by:
      getVersion in interface ParaObject
      Returns:
      a positive number, 0 if unused or -1, indicating a failed update.

    • setVersion

      public void setVersion(Long version)
      Description copied from interface: ParaObject
      Sets the version of this object. This value should come from the database.
      Specified by:
      setVersion in interface ParaObject
      Parameters:
      version - a positive number, different than the current value of the version field

    • countLinks

      public Long countLinks(String type2)
      Description copied from interface: Linkable
      Count the total number of links between this object and another type of object.
      Specified by:
      countLinks in interface Linkable
      Parameters:
      type2 - the other type of object
      Returns:
      the number of links

    • getLinks

      public List<Linker> getLinks(String type2, Pager... pager)
      Description copied from interface: Linkable
      Returns all links between this type object and another type of object.
      Specified by:
      getLinks in interface Linkable
      Parameters:
      type2 - the other type of object
      pager - a Pager
      Returns:
      a list of Linker objects in a many-to-many relationship with this object.

    • getLinkedObjects

      public <P extends ParaObject> List<P> getLinkedObjects(String type, Pager... pager)
      Description copied from interface: Linkable
      Similar to Linkable.getChildren(java.lang.String, com.erudika.para.core.utils.Pager...) but for many-to-many relationships.
      Specified by:
      getLinkedObjects in interface Linkable
      Type Parameters:
      P - type of linked objects
      Parameters:
      type - type of linked objects to look for
      pager - a Pager
      Returns:
      a list of linked objects

    • findLinkedObjects

      public <P extends ParaObject> List<P> findLinkedObjects(String type, String field, String query, Pager... pager)
      Description copied from interface: Linkable
      Similar to Linkable.findChildren(java.lang.String, java.lang.String, com.erudika.para.core.utils.Pager...) but for many-to-many relationships. Searches through all linked objects connected to this via a Linker object.
      Specified by:
      findLinkedObjects in interface Linkable
      Type Parameters:
      P - type of linked objects
      Parameters:
      type - type of linked objects to look for
      field - the name of the field to target (within a nested field "nstd")
      query - a query string
      pager - a Pager
      Returns:
      a list of linked objects matching the search query

    • isLinked

      public boolean isLinked(String type2, String id2)
      Description copied from interface: Linkable
      Checks if this object is linked to another.
      Specified by:
      isLinked in interface Linkable
      Parameters:
      type2 - the other type
      id2 - the other id
      Returns:
      true if the two are linked

    • isLinked

      public boolean isLinked(ParaObject toObj)
      Description copied from interface: Linkable
      Checks if a given object is linked to this one.
      Specified by:
      isLinked in interface Linkable
      Parameters:
      toObj - the other object
      Returns:
      true if linked

    • link

      public String link(String id2)
      Description copied from interface: Linkable
      Links an object to this one in a many-to-many relationship. Only a link is created. Objects are left untouched. The type of the second object is automatically determined on read.
      Specified by:
      link in interface Linkable
      Parameters:
      id2 - the other id
      Returns:
      the id of the Linker object that is created

    • unlink

      public void unlink(String type, String id2)
      Description copied from interface: Linkable
      Unlinks an object from this one. Only a link is deleted. Objects are left untouched.
      Specified by:
      unlink in interface Linkable
      Parameters:
      type - the other type
      id2 - the other id

    • unlinkAll

      public void unlinkAll()
      Description copied from interface: Linkable
      Unlinks all objects that are linked to this one. Deletes all Linker objects. Only the links are deleted. Objects are left untouched.
      Specified by:
      unlinkAll in interface Linkable

    • countChildren

      public Long countChildren(String type)
      Description copied from interface: Linkable
      Count the total number of child objects for this object.
      Specified by:
      countChildren in interface Linkable
      Parameters:
      type - the other type of object
      Returns:
      the number of links

    • getChildren

      public <P extends ParaObject> List<P> getChildren(String type, Pager... pager)
      Description copied from interface: Linkable
      Returns all child objects linked to this object.
      Specified by:
      getChildren in interface Linkable
      Type Parameters:
      P - the type of children
      Parameters:
      type - the type of children to look for
      pager - a Pager
      Returns:
      a list of ParaObject in a one-to-many relationship with this object

    • getChildren

      public <P extends ParaObject> List<P> getChildren(String type, String field, String term, Pager... pager)
      Description copied from interface: Linkable
      Returns all child objects linked to this object.
      Specified by:
      getChildren in interface Linkable
      Type Parameters:
      P - the type of children
      Parameters:
      type - the type of children to look for
      field - the field name to use as filter
      term - the field value to use as filter
      pager - a Pager
      Returns:
      a list of ParaObject in a one-to-many relationship with this object

    • findChildren

      public <P extends ParaObject> List<P> findChildren(String type, String query, Pager... pager)
      Description copied from interface: Linkable
      Search through all child objects. Only searches child objects directly connected to this parent via the parentid field.
      Specified by:
      findChildren in interface Linkable
      Type Parameters:
      P - the type of children
      Parameters:
      type - the type of children to look for
      query - a query string
      pager - a Pager
      Returns:
      a list of ParaObject in a one-to-many relationship with this object

    • deleteChildren

      public void deleteChildren(String type)
      Description copied from interface: Linkable
      Deletes all child objects permanently.
      Specified by:
      deleteChildren in interface Linkable
      Parameters:
      type - the children's type.

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object obj)
      Overrides:
      equals in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object