Class StatementClassMapping

java.lang.Object
org.datanucleus.store.rdbms.query.StatementClassMapping

public class StatementClassMapping extends Object
Definition of statement mapping for a particular class. Provides a definition of how the results of a datastore query are mapped on to the fields of a class. If we take the example of this being the candidate class retrieved, then the memberName will be null and any children represent persistent objects also retrieved in this statement. So we process all fields in the result-set for this class, then instantiate any child object (with its id field(s)), and process all of its fields, etc.

We can have a result set with fields for multiple objects and instantiate more than 1 related object. To give an example of what an object of this type can look like

 StatementClassMapping:class=null,member=null,mappings=
 [
    {field=0,mapping=mapping: org.datanucleus.store.rdbms.mapping.IntegerMapping@5995c31c column(s): [2]},
    {field=1,mapping=mapping: org.datanucleus.store.rdbms.mapping.PersistableMapping@5947d51d column(s): [3]},
    {field=2,mapping=mapping: org.datanucleus.store.rdbms.mapping.PersistableMapping@585e7d87 column(s): [7]},
    {field=-2,mapping=mapping: org.datanucleus.store.rdbms.mapping.VersionLongMapping@ce796 column(s): [11]},
 ],
 children=
 [
    {field=1,mapping=StatementClassMapping:class=org.datanucleus.test.CircRef,member=next,mappings=
       [
            {field=0,mapping=mapping: org.datanucleus.store.rdbms.mapping.IntegerMapping@5995c31c column(s): [3]},
            {field=1,mapping=mapping: org.datanucleus.store.rdbms.mapping.PersistableMapping@5947d51d column(s): [4]},
            {field=2,mapping=mapping: org.datanucleus.store.rdbms.mapping.PersistableMapping@585e7d87 column(s): [5]},
            {field=-2,mapping=mapping: org.datanucleus.store.rdbms.mapping.VersionLongMapping@ce796 column(s): [6]}
        ]},
    {field=2,mapping=StatementClassMapping:class=org.datanucleus.test.CircRef,member=prev,mappings=
        [
            {field=0,mapping=mapping: org.datanucleus.store.rdbms.mapping.IntegerMapping@5995c31c column(s): [7]},
            {field=1,mapping=mapping: org.datanucleus.store.rdbms.mapping.PersistableMapping@5947d51d column(s): [8]},
            {field=2,mapping=mapping: org.datanucleus.store.rdbms.mapping.PersistableMapping@585e7d87 column(s): [9]},
            {field=-2,mapping=mapping: org.datanucleus.store.rdbms.mapping.VersionLongMapping@ce796 column(s): [10]}
        ]}
 ]
In this example we have a persistable object as candidate, and it has 2 1-1 relations (field=1, field=2). These are both being retrieved in the same query, hence the sub-mappings. Note that the column(s) of the FK in the owner object is the same as the PK field(s) of the related object.
  • Field Details

    • className

      String className
      Name of the class.
    • memberName

      String memberName
      Name of the field/property in the parent class (null implies parent class).
    • dnTypeColumn

      String dnTypeColumn
      Name of a DN_TYPE column if used in this query for determining this class. Null otherwise.
    • memberNumbers

      int[] memberNumbers
      Numbers of fields/properties defined in the statement.
    • mappings

      Mappings for the members of this object defined in the statement, keyed by the member number.
    • children

      Mapping definition for a member that is a relation in this statement, keyed by the member number.
  • Constructor Details

    • StatementClassMapping

      public StatementClassMapping()
    • StatementClassMapping

      public StatementClassMapping(String className, String memberName)
  • Method Details

    • getClassName

      public String getClassName()
    • getMemberName

      public String getMemberName()
    • setNucleusTypeColumnName

      public void setNucleusTypeColumnName(String colName)
    • getNucleusTypeColumnName

      public String getNucleusTypeColumnName()
    • getMappingForMemberPosition

      public StatementMappingIndex getMappingForMemberPosition(int position)
      Accessor for the mapping information for the member at the specified position. Member positions start at 0 (first member in the root persistent class). Member position of -1 means datastore-identity. Member position of -2 means version. Member position of -3 means discriminator.
      Parameters:
      position - The member position
      Returns:
      The mapping information
    • getMappingDefinitionForMemberPosition

      public StatementClassMapping getMappingDefinitionForMemberPosition(int position)
      Accessor for the mapping definition for the object at the specified member position. Returns null if the member is not a relation field. Member positions start at 0 (first member in the root persistent class). Member position of -1 means datastore-identity. Member position of -2 means version. Member position of -3 means discriminator. Member position of -4 means multitenancy.
      Parameters:
      position - The position of the member in this class
      Returns:
      The mapping definition for the object at this member position
    • hasChildMappingDefinitions

      public boolean hasChildMappingDefinitions()
      Accessor for whether this definition has child object definitions.
      Returns:
      Whether there are sub-objects of this object mapped.
    • getMemberNumbers

      public int[] getMemberNumbers()
      Accessor for the numbers of the members present. Doesn't include any surrogate numbers since not real members.
      Returns:
      The member positions
    • addMappingForMember

      public void addMappingForMember(int position, StatementMappingIndex mapping)
    • addMappingDefinitionForMember

      public void addMappingDefinitionForMember(int position, StatementClassMapping defn)
    • cloneStatementMappingWithoutChildren

      public StatementClassMapping cloneStatementMappingWithoutChildren()
    • toString

      public String toString()
      Overrides:
      toString in class Object