org.apache.torque.util.functions

## Class AbstractFunction

- java.lang.Object
- - org.apache.torque.util.functions.AbstractFunction

- All Implemented Interfaces:
    Column, SQLFunction

      public abstract class AbstractFunction
      extends Object
      implements SQLFunction

  A default framework that implements the core SQLFunction interface requirements that can be used to build specific functions on.
  Version:
    $Id: AbstractFunction.java 1879896 2020-07-15 15:03:46Z gk $
  Author:
    Greg Monroe

- - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `AbstractFunction()` Functions should only be created via the FunctionFactory class.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `addArgument(Object arg)` Add an argument to the function argument list
    `Object` | `getArgument(int index)` Return the object representation of the function parameter at the specified index.
    `protected List<Object>` | `getArgumentList()` Get the full list of function arguments
    `Object[]` | `getArguments()` Return all the parameters as an object array.
    `Column` | `getColumn()` Returns the column to which this function is applied.
    `String` | `getColumnName()` Returns the column name.
    `String` | `getFullTableName()` Returns the table name prefixed with the schema name if it exists from the function argument(s).
    `String` | `getSchemaName()` Returns the name of any fixed schema prefix for the column's table (if any) from the function argument(s).
    `abstract String` | `getSqlExpression()` This should return the SQL string that can be used when constructing the query.
    `String` | `getTableName()` Returns the name of the associated table (not prefixed by the schema name) from the function argument(s).
    `protected void` | `setArgumentList(List<Object> args)` Set the full function argument list.
    `void` | `setArguments(Object... args)` Sets the function arguments.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### AbstractFunction

          protected AbstractFunction()

      Functions should only be created via the FunctionFactory class.

  - ### Method Detail

    - #### getSqlExpression

          public abstract String getSqlExpression()

      This should return the SQL string that can be used when constructing the query. E.g. "AVG( table.column )" or CONCAT(table.column, " foobar");
      Specified by:
        `getSqlExpression` in interface `Column`
      Returns:
        The SQL String.

    - #### getArguments

          public Object[] getArguments()

      Return all the parameters as an object array. This allow for processing of the parameters in their original format rather than just in String format. E.g. a parameter might be specified as a Date object, or a Column object.
      Specified by:
        `getArguments` in interface `SQLFunction`
      Returns:
        Should return a valid Object array and not null. E.g. implementors should return new Object[0] if there are no parameters.

    - #### setArguments

          public void setArguments(Object... args)

      Sets the function arguments.
      Specified by:
        `setArguments` in interface `SQLFunction`
      Parameters:
        `args` - the function arguments, not null.

    - #### getColumn

          public Column getColumn()

      Returns the column to which this function is applied.
      Specified by:
        `getColumn` in interface `SQLFunction`
      Returns:
        the column, not null.
      Throws:
        `IllegalStateException` - if the column cannot be determined.

    - #### getArgument

          public Object getArgument(int index)

      Return the object representation of the function parameter at the specified index. Will be null if parameter does not exist.
      Specified by:
        `getArgument` in interface `SQLFunction`
      Parameters:
        `index` - The 0 based index of the parameter to get.
      Returns:
        The parameter object. Null if one does not exist.

    - #### addArgument

          protected void addArgument(Object arg)

      Add an argument to the function argument list
      Parameters:
        `arg` - The argument object.

    - #### setArgumentList

          protected void setArgumentList(List<Object> args)

      Set the full function argument list.
      Parameters:
        `args` - The new argument list

    - #### getArgumentList

          protected List<Object> getArgumentList()

      Get the full list of function arguments
      Returns:
        The argument list

    - #### getColumnName

          public String getColumnName()

      Returns the column name. This implementation always return null because we do not reference a real column.
      Specified by:
        `getColumnName` in interface `Column`
      Returns:
        the column name, always null.

    - #### getTableName

          public String getTableName()

      Returns the name of the associated table (not prefixed by the schema name) from the function argument(s). In case that no unique table name can be determined, null is returned.
      Specified by:
        `getTableName` in interface `Column`
      Returns:
        the name of the table, may be null but not blank.

    - #### getSchemaName

          public String getSchemaName()

      Returns the name of any fixed schema prefix for the column's table (if any) from the function argument(s). In case that no unique schema can be determined, null is returned.
      Specified by:
        `getSchemaName` in interface `Column`
      Returns:
        the schema name, or null if the schema is not known.

    - #### getFullTableName

          public String getFullTableName()

      Returns the table name prefixed with the schema name if it exists from the function argument(s). I.e. if a schema name exists, the result will be schemaName.tableName, and otherwise it will just be tableName. In case that no unique full table can be determined, null is returned.
      Specified by:
        `getFullTableName` in interface `Column`
      Returns:
        the fully qualified table name may be null but not blank.

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