Module org.eclipse.persistence.core
Package org.eclipse.persistence.internal.expressions

Class FunctionExpression

java.lang.Object
org.eclipse.persistence.expressions.Expression
org.eclipse.persistence.internal.expressions.BaseExpression
org.eclipse.persistence.internal.expressions.FunctionExpression
All Implemented Interfaces:
Serializable, Cloneable
Direct Known Subclasses:
ArgumentListFunctionExpression
public class FunctionExpression extends BaseExpression
Used for expressions that have 0 to n children. These include not, between and all functions.
See Also:

  • Field Details

  • Constructor Details

    • FunctionExpression

      public FunctionExpression()

  • Method Details

    • equals

      public boolean equals(Object object)
      INTERNAL: Return if the expression is equal to the other. This is used to allow dynamic expression's SQL to be cached. This must be over written by each subclass.
      Overrides:
      equals in class Expression

    • computeHashCode

      public int computeHashCode()
      INTERNAL: Compute a consistent hash-code for the expression. This is used to allow dynamic expression's SQL to be cached.
      Overrides:
      computeHashCode in class Expression

    • addChild

      public void addChild(Expression child)

    • aliasForTable

      public DatabaseTable aliasForTable(DatabaseTable table)
      INTERNAL: Find the alias for a given table
      Overrides:
      aliasForTable in class Expression

    • asOf

      public Expression asOf(AsOfClause clause)
      Description copied from class: Expression
      Sets all tables represented by this expression to be queried as of a past time.

      Example: 

        EclipseLink: employee.asOf(new AsOfClause(pastTime))
  Java: None
  SQL (Flashback): SELECT ... FROM EMPLOYEE AS OF TIMESTAMP (pastTime) t0 ...
  SQL (Generic): .. WHERE (t1.START <= pastTime) AND ((t1.END IS NULL) OR t1.END > pastTime)

      Set an as of clause at the expression level to still query for current objects while expressing selection criteria like:

      • query objects as of one time that met some condition at another time.
      • query objects that changed a certain way over a certain interval (querying for change).

      Simultaneously querying on two versions of the same object (one past one present) lets you express these advanced selection criteria.

      Example: Querying on past attributes using parallel expressions. 

         // Finds all employees who lived in Ottawa as of a past time.
   ExpressionBuilder employee = new ExpressionBuilder();
   ExpressionBuilder pastEmployee = new ExpressionBuilder(Employee.class);
   pastEmployee.asOf(pastTime);
   Expression pastAddress = pastEmployee.get("address"); // by default address will also be as of past time.
   Expression selectionCriteria = pastAddress.get("city").equal("Ottawa").and(
       employee.equal(pastEmployee));

      The advantage of the parallel expression is that you can still read current objects, the as of clause will affect only the where clause / selection criteria.

      You may be tempted to rewrite the above as employee.get("address").asOf(pastTime). That is allowed but see below for the finer points involved in this.

      Example: Querying on object changes using parallel expressions. 

         // Finds all employees who recently received a raise.  Note that current
   // objects are returned, so can be cached normally.
   ExpressionBuilder employee = new ExpressionBuilder();
   Expression pastEmployee = new ExpressionBuilder(Employee.class);
   pastEmployee.asOf(yesterday);
   Expression parallelJoin = employee.equal(pastEmployee);
   Expression selectionCriteria = parallelJoin.and(
       employee.get("salary").greaterThan(pastEmployee.get("salary")));

      Example: Querying on object changes using custom query keys 

         // First define the custom query key and add it to your descriptor.
   ExpressionBuilder builder = new ExpressionBuilder(Employee.class);
   Expression joinCriteria = builder.getField("EMPLOYEE.EMP_ID").equal(builder.getParameter("EMPLOYEE.EMP_ID"));
   OneToOneQueryKey selfReferential = new OneToOneQueryKey();
   selfReferential.setName("this");
   selfReferential.setJoinCriteria(joinCriteria);
   selfReferential.setReferenceClass(Employee.class);
   getSession().getDescriptor(Employee.class).addQueryKey(selfReferential);

   // Now build query as before.
   Expression employee = new ExpessionBuilder();
   Expression pastEmployee = employee.get("this").asOf(yesterday);
   Expression selectionCriteria = employee.get("salary").greaterThan(pastEmployee.get("salary"));

      Note in general that any parallel expression can be rewritten using a custom query key. EclipseLink will even automatically interpret x.get("this") for you so you do not need to define the above query key first.

      Full Reference:

      If an object is mapped to multiple tables, then each table will be as of the same time. Two objects mapped to the same table can not have different as of times. Conversely only expressions which have associated tables can have an as of clause.

      If an as of clause is not explicitly set an expression will use the clause of its base expression, and so on recursively until one is found or an ExpressionBuilder is reached. Some usage scenarios follow:

      • employee.asOf(pastTime).anyOf("projects"): projects as of past time.
      • expressionBuilder.asOf(pastTime): entire expression as of past time.
      • employee.asOf(pastTime).anyOf("projects").asOf(null): projects as of current time.
      • employee.anyOf("projects").asOf(pastTime): projects only as of past time.

      Watch out for x.asOf(oneTime).get("y").asOf(anotherTime).

      • emp.anyOf("phoneNumbers").asOf(yesterday) = emp.asOf(yesterday).anyOf("phoneNumbers") but:
      • emp.get("address").asOf(yesterday) != emp.asOf(yesterday).get("address").
      Whether the join is also as of yesterday depends on which table the foreign key field resides on. In an anyOf the foreign key is always on the right, but in a get (1-1) it could be on either side. For this reason employee.get("address").asOf(yesterday) is undefined as it can mean either 'my address as of yesterday', or 'my address, as of yesterday.'
      Overrides:
      asOf in class Expression
      Parameters:
      clause - A read only data object used to represent a past time.
      Returns:
      this
      See Also:

    • create

      public Expression create(Expression base, Object singleArgument, ExpressionOperator anOperator)
      INTERNAL:
      Overrides:
      create in class Expression

    • createWithBaseLast

      public Expression createWithBaseLast(Expression base, Object singleArgument, ExpressionOperator anOperator)
      INTERNAL: added for Trim support. TRIM([trim_character FROM] string_primary)
      Overrides:
      createWithBaseLast in class Expression

    • create

      public Expression create(Expression base, List arguments, ExpressionOperator anOperator)
      INTERNAL:
      Overrides:
      create in class Expression

    • descriptionOfNodeType

      public String descriptionOfNodeType()
      INTERNAL: Used for debug printing.
      Overrides:
      descriptionOfNodeType in class Expression

    • doesConform

      public boolean doesConform(Object object, AbstractSession session, AbstractRecord translationRow, int valueHolderPolicy, boolean isObjectUnregistered)
      INTERNAL: Check if the object conforms to the expression in memory. This is used for in-memory querying. If the expression in not able to determine if the object conform throw a not supported exception.
      Overrides:
      doesConform in class Expression
      Parameters:
      isObjectUnregistered - true if object possibly not a clone, but is being conformed against the unit of work cache; if object is not in the UOW cache but some of its attributes are, use the registered versions of object's attributes for the purposes of this method.

    • getChildren

      public Vector<Expression> getChildren()

    • getFields

      public List<DatabaseField> getFields()
      INTERNAL: Not to be confused with the public getField(String) This returns a collection of all fields associated with this object. Really only applies to query keys representing an object or to expression builders.
      Overrides:
      getFields in class Expression

    • getSelectionFields

      public List<DatabaseField> getSelectionFields(ReadQuery query)
      INTERNAL:
      Overrides:
      getSelectionFields in class Expression

    • getOperator

      public ExpressionOperator getOperator()
      Description copied from class: Expression
      INTERNAL: Most expression have operators, so this is just a convenience method.
      Overrides:
      getOperator in class Expression

    • getPlatformOperator

      public ExpressionOperator getPlatformOperator(DatabasePlatform platform)

    • getResultType

      public Class<?> getResultType()

    • hasResultType

      public boolean hasResultType()

    • initializePlatformOperator

      public void initializePlatformOperator(DatabasePlatform platform)
      INTERNAL:

    • isFunctionExpression

      public boolean isFunctionExpression()
      Description copied from class: Expression
      INTERNAL:
      Overrides:
      isFunctionExpression in class Expression

    • isObjectComparison

      protected boolean isObjectComparison()
      INTERNAL: Return if the represents an object comparison.

    • iterateOn

      public void iterateOn(ExpressionIterator iterator)
      INTERNAL: For iterating using an inner class
      Overrides:
      iterateOn in class Expression

    • normalize

      public Expression normalize(ExpressionNormalizer normalizer)
      INTERNAL: Normalize into a structure that is printable. Also compute printing information such as outer joins. This checks for object isNull, notNull, in and notIn comparisons.
      Overrides:
      normalize in class Expression

    • postCopyIn

      protected void postCopyIn(Map alreadyDone)
      INTERNAL: Used for cloning.
      Overrides:
      postCopyIn in class BaseExpression

    • printSQL

      public void printSQL(ExpressionSQLPrinter printer)
      INTERNAL: Print SQL using the operator.
      Specified by:
      printSQL in class Expression

    • printJava

      public void printJava(ExpressionJavaPrinter printer)
      INTERNAL: Print java for project class generation
      Overrides:
      printJava in class Expression

    • rebuildOn

      public Expression rebuildOn(Expression newBase)
      INTERNAL: This expression is built on a different base than the one we want. Rebuild it and return the root of the new tree
      Specified by:
      rebuildOn in class Expression
      See Also:

    • resetPlaceHolderBuilder

      public void resetPlaceHolderBuilder(ExpressionBuilder queryBuilder)
      INTERNAL: Search the tree for any expressions (like SubSelectExpressions) that have been built using a builder that is not attached to the query. This happens in case of an Exists call using a new ExpressionBuilder(). This builder needs to be replaced with one from the query.
      Overrides:
      resetPlaceHolderBuilder in class BaseExpression

    • setLocalBase

      public void setLocalBase(Expression exp)
      Description copied from class: Expression
      INTERNAL: Set the local base expression, ie the one on the other side of the operator Most types will ignore this, since they don't need it.
      Overrides:
      setLocalBase in class Expression

    • setOperator

      public void setOperator(ExpressionOperator theOperator)

    • setResultType

      public void setResultType(Class<?> resultType)

    • twistedForBaseAndContext

      public Expression twistedForBaseAndContext(Expression newBase, Expression context, Expression oldBase)
      INTERNAL: Rebuild myself against the base, with the values of parameters supplied by the context expression. This is used for transforming a standalone expression (e.g. the join criteria of a mapping) into part of some larger expression. You normally would not call this directly, instead calling twist See the comment there for more details"
      Overrides:
      twistedForBaseAndContext in class Expression

    • valueFromObject

      public Object valueFromObject(Object object, AbstractSession session, AbstractRecord translationRow, int valueHolderPolicy, boolean isObjectUnregistered)
      INTERNAL: Return the value for in memory comparison. This is only valid for valueable expressions.
      Overrides:
      valueFromObject in class Expression
      Parameters:
      isObjectUnregistered - true if object possibly not a clone, but is being conformed against the unit of work cache.

    • writeDescriptionOn

      public void writeDescriptionOn(BufferedWriter writer) throws IOException
      INTERNAL: Used to print a debug form of the expression tree.
      Overrides:
      writeDescriptionOn in class Expression
      Throws:
      IOException

    • writeFields

      public void writeFields(ExpressionSQLPrinter printer, List<DatabaseField> newFields, SQLSelectStatement statement)
      INTERNAL: called from SQLSelectStatement.writeFieldsFromExpression(...)
      Overrides:
      writeFields in class Expression

    • writeSubexpressionsTo

      public void writeSubexpressionsTo(BufferedWriter writer, int indent) throws IOException
      INTERNAL: Used in SQL printing.
      Overrides:
      writeSubexpressionsTo in class Expression
      Throws:
      IOException

    • prepareObjectAttributeCount

      public void prepareObjectAttributeCount(ExpressionNormalizer normalizer, ReportItem item, ReportQuery query, Map clonedExpressions)
      INTERNAL: JPQL allows count([distinct] e), where e can be an object, not just a single field, however the database only allows a single field, so object needs to be translated to a single field. If the descriptor has a single pk, it is used, otherwise any pk is used if distinct, otherwise a subselect is used. If the object was obtained through an outer join, then the subselect also will not work, so an error is thrown.

    • getLeafQueryKeyFor

      protected QueryKey getLeafQueryKeyFor(DatabaseQuery query, Expression expression, ClassDescriptor rootDescriptor, AbstractSession session) throws QueryException
      INTERNAL: Lookup the query key for this item. If an aggregate of foreign mapping is found it is traversed.
      Throws:
      QueryException

    • getMappingOfFirstPrimaryKey

      protected DatabaseMapping getMappingOfFirstPrimaryKey(ClassDescriptor descriptor)

    • getLeafMapping

      public DatabaseMapping getLeafMapping(DatabaseQuery query, ClassDescriptor rootDescriptor, AbstractSession session)
      INTERNAL: Lookup the mapping for this item by traversing its expression recursively.
      Overrides:
      getLeafMapping in class Expression