com.sleepycat.persist.impl

Interface Accessor

All Known Implementing Classes:

EnhancedAccessor, RawAccessor, ReflectionAccessor

interface Accessor

Field binding operations implemented via reflection (ReflectionAccessor) or bytecode enhancement (EnhancedAccessor).

Normally we read the set of all secondary key fields first and then the set of all non-key fields, reading each set in order of field name. But when reading an old format record we must account for the following class evolution conversions:

• Convert a field: pass value thru converter
• Widen a field type: pass value thru widener
• Add a field: don't read the new field
• Delete a field: skip the deleted field
• Rename a field: read field in a different order

To support these operations, the methods for reading fields allow reading specific ranges of fields as well as all fields. For example, all fields up to a deleted field could be read, and then all fields from the following field onward.

Author:

Mark Hayes

Field Summary

Fields

Modifier and Type	Field and Description
static int	MAX_FIELD_NUM A large field value to use instead of Integer.MAX_VALUE, to work around Java JIT compiler bug when doing an (X <= Integer.MAX_VALUE) as would be done in readXxxKeyFields methods.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.Object	getField(java.lang.Object o, int field, int superLevel, boolean isSecField) Returns the value of a given field, representing primitives as primitive wrapper objects.
boolean	isPriKeyFieldNullOrZero(java.lang.Object o) Returns whether the primary key field is null (for a reference type) or zero (for a primitive integer type).
java.lang.Object	newArray(int len) Creates a new one dimensional array of the given length, having the target class as its component type.
java.lang.Object	newInstance() Creates a new instance of the target class using its default constructor.
void	readNonKeyFields(java.lang.Object o, EntityInput input, int startField, int endField, int superLevel) Reads a range of non-key field values from the given EntityInput, reading fields in super classes first and in name order within class.
void	readPriKeyField(java.lang.Object o, EntityInput input) Reads the primary key field value from the given EntityInput.
void	readSecKeyFields(java.lang.Object o, EntityInput input, int startField, int endField, int superLevel) Reads a range of secondary key field values from the given EntityInput, reading fields in super classes first and in name order within class.
void	setField(java.lang.Object o, int field, int superLevel, boolean isSecField, java.lang.Object value) Changes the value of a given field, representing primitives as primitive wrapper objects.
void	writeNonKeyFields(java.lang.Object o, EntityOutput output) Writes all non-key field values to the given EntityOutput, writing fields in super classes first and in name order within class.
void	writePriKeyField(java.lang.Object o, EntityOutput output) Writes the primary key field value to the given EntityOutput.
void	writeSecKeyFields(java.lang.Object o, EntityOutput output) Writes all secondary key field values to the given EntityOutput, writing fields in super classes first and in name order within class.

Field Detail

MAX_FIELD_NUM

static final int MAX_FIELD_NUM

A large field value to use instead of Integer.MAX_VALUE, to work around Java JIT compiler bug when doing an (X <= Integer.MAX_VALUE) as would be done in readXxxKeyFields methods.

See Also:

Constant Field Values

Method Detail

newInstance

java.lang.Object newInstance()

Creates a new instance of the target class using its default constructor.

newArray

java.lang.Object newArray(int len)

Creates a new one dimensional array of the given length, having the target class as its component type.

Using a special method for a one dimensional array, which can be implemented by bytecode generation, is a compromise. We use reflection to create multidimensional arrays. We could in the future generate code to create arrays as they are encountered, if there is a need to avoid reflection for multidimensional arrays.

isPriKeyFieldNullOrZero

boolean isPriKeyFieldNullOrZero(java.lang.Object o)

Returns whether the primary key field is null (for a reference type) or zero (for a primitive integer type). Null and zero are used as an indication that the key should be assigned from a sequence.

writePriKeyField

void writePriKeyField(java.lang.Object o,
                    EntityOutput output)

Writes the primary key field value to the given EntityOutput.

To write a primary key with a reference type, this method must call EntityOutput.writeKeyObject.

Parameters:

o - is the object whose primary key field is to be written.

output - the output data to write to.

readPriKeyField

void readPriKeyField(java.lang.Object o,
                   EntityInput input)

Reads the primary key field value from the given EntityInput.

To read a primary key with a reference type, this method must call EntityInput.readKeyObject.

Parameters:

o - is the object whose primary key field is to be read.

input - the input data to read from.

writeSecKeyFields

void writeSecKeyFields(java.lang.Object o,
                     EntityOutput output)

Writes all secondary key field values to the given EntityOutput, writing fields in super classes first and in name order within class.

Parameters:

o - is the object whose secondary key fields are to be written.

If the primary key has a reference type, this method must call EntityOutput.registerPriKeyObject before writing any other fields.

output - the output data to write to.

readSecKeyFields

void readSecKeyFields(java.lang.Object o,
                    EntityInput input,
                    int startField,
                    int endField,
                    int superLevel)

Reads a range of secondary key field values from the given EntityInput, reading fields in super classes first and in name order within class.

If the primary key has a reference type, this method must call EntityInput.registerPriKeyObject before reading any other fields.

To read all fields, pass -1 for superLevel, zero for startField and MAX_FIELD_NUM for endField. Fields from super classes are read first.

To read a specific range of fields, pass a non-negative number for superLevel and the specific indices of the field range to be read in the class at that level.

Parameters:

o - is the object whose secondary key fields are to be read.

input - the input data to read from.

startField - the starting field index in the range of fields to read. To read all fields, the startField should be zero.

endField - the ending field index in the range of fields to read. To read all fields, the endField should be MAX_FIELD_NUM.

superLevel - is a non-negative number to read the fields of the class that is the Nth super instance; or a negative number to read fields in all classes.

writeNonKeyFields

void writeNonKeyFields(java.lang.Object o,
                     EntityOutput output)

Writes all non-key field values to the given EntityOutput, writing fields in super classes first and in name order within class.

Parameters:

o - is the object whose non-key fields are to be written.

output - the output data to write to.

readNonKeyFields

void readNonKeyFields(java.lang.Object o,
                    EntityInput input,
                    int startField,
                    int endField,
                    int superLevel)

Reads a range of non-key field values from the given EntityInput, reading fields in super classes first and in name order within class.

To read all fields, pass -1 for superLevel, zero for startField and MAX_FIELD_NUM for endField. Fields from super classes are read first.

To read a specific range of fields, pass a non-negative number for superLevel and the specific indices of the field range to be read in the class at that level.

Parameters:

o - is the object whose non-key fields are to be read.

input - the input data to read from.

startField - the starting field index in the range of fields to read. To read all fields, the startField should be zero.

endField - the ending field index in the range of fields to read. To read all fields, the endField should be MAX_FIELD_NUM.

superLevel - is a non-negative number to read the fields of the class that is the Nth super instance; or a negative number to read fields in all classes.

getField

java.lang.Object getField(java.lang.Object o,
                        int field,
                        int superLevel,
                        boolean isSecField)

Returns the value of a given field, representing primitives as primitive wrapper objects.

Parameters:

o - is the object containing the key field.

field - is the field index.

superLevel - is a positive number to identify the field of the class that is the Nth super instance; or zero to identify the field in this class.

isSecField - is true for a secondary key field or false for a non-key field.

Returns:

the current field value, or null for a reference type field that is null.

setField

void setField(java.lang.Object o,
            int field,
            int superLevel,
            boolean isSecField,
            java.lang.Object value)

Changes the value of a given field, representing primitives as primitive wrapper objects.

Parameters:

o - is the object containing the key field.

field - is the field index.

superLevel - is a positive number to identify the field of the class that is the Nth super instance; or zero to identify the field in this class.

isSecField - is true for a secondary key field or false for a non-key field.

value - is the new value of the field, or null to set a reference type field to null.