org.javarosa.core.model.instance.utils

Class CompactInstanceWrapper

java.lang.Object

org.javarosa.core.model.instance.utils.CompactInstanceWrapper

All Implemented Interfaces:

WrappingStorageUtility.SerializationWrapper, Externalizable

public class CompactInstanceWrapper
extends Object
implements WrappingStorageUtility.SerializationWrapper

An alternate serialization format for FormInstances (saved form instances) that drastically reduces the resultant record size by cutting out redundant information. Size savings are typically 90-95%. The trade-off is that in order to deserialize, a template FormInstance (typically from the original FormDef) must be provided. In general, the format is thus: 1) write the fields from the FormInstance object (e.g., date saved), excluding those that never change for a given form type (e.g., schema). 2) walk the tree depth-first. for each node: if repeatable, write the number of repetitions at the current level; if not, write a boolean indicating if the node is relevant. non-relevant nodes are not descended into. repeated nodes (i.e., several nodes with the same name at the current level) are handled in order 3) for each leaf (data) node, write a boolean whether the node is empty or has data 4) if the node has data, serialize the data. do not specify the data type -- it can be determined from the template. multiple choice questions use a more compact format than normal. 4a) in certain situations where the data differs from its prescribed data type (can happen as the result of 'calculate' expressions), flag the actual data type by hijacking the 'empty' flag above

Author:

Drew Roos

Field Summary

Fields

Modifier and Type	Field and Description
static int	CHOICE_INDEX
static int	CHOICE_MODE
static int	CHOICE_VALUE

Constructor Summary

Constructors

Constructor and Description
CompactInstanceWrapper()
CompactInstanceWrapper(InstanceTemplateManager templateMgr)

Method Summary

Modifier and Type	Method and Description
Class	baseType() return type of underlying object
static Class	classForDataType(int dataType) map xforms data types to the Class that represents that data in a FormInstance
void	clean()
Externalizable	getData() retrieve the underlying object (to be followed by a call to readExternal)
static FormInstance	loadTemplateInstance(int formID) load a template instance fresh from the original FormDef, retrieved from RMS
void	readExternal(DataInputStream in, PrototypeFactory pf) deserialize a compact instance.
void	setData(Externalizable e) set the underlying object (to be followed by a call to writeExternal)
void	writeExternal(DataOutputStream out) serialize a compact instance

Methods inherited from class java.lang.Object

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

Field Detail

CHOICE_VALUE

public static final int CHOICE_VALUE

See Also:

Constant Field Values

CHOICE_INDEX

public static final int CHOICE_INDEX

See Also:

Constant Field Values

CHOICE_MODE

public static final int CHOICE_MODE

See Also:

Constant Field Values

Constructor Detail

CompactInstanceWrapper

public CompactInstanceWrapper()

CompactInstanceWrapper

public CompactInstanceWrapper(InstanceTemplateManager templateMgr)

Parameters:

templateMgr - template provider; if null, template is always fetched on-demand from RMS (slow!)

Method Detail

baseType

public Class baseType()

Description copied from interface: WrappingStorageUtility.SerializationWrapper

return type of underlying object

Specified by:

baseType in interface WrappingStorageUtility.SerializationWrapper

Returns:

setData

public void setData(Externalizable e)

Description copied from interface: WrappingStorageUtility.SerializationWrapper

set the underlying object (to be followed by a call to writeExternal)

Specified by:

setData in interface WrappingStorageUtility.SerializationWrapper

getData

public Externalizable getData()

Description copied from interface: WrappingStorageUtility.SerializationWrapper

retrieve the underlying object (to be followed by a call to readExternal)

Specified by:

getData in interface WrappingStorageUtility.SerializationWrapper

Returns:

readExternal

public void readExternal(DataInputStream in,
                         PrototypeFactory pf)
                  throws IOException,
                         DeserializationException

deserialize a compact instance. note the retrieval of the template data instance

Specified by:

readExternal in interface Externalizable

Throws:

IOException

DeserializationException

writeExternal

public void writeExternal(DataOutputStream out)
                   throws IOException

serialize a compact instance

Specified by:

writeExternal in interface Externalizable

Throws:

IOException

loadTemplateInstance

public static FormInstance loadTemplateInstance(int formID)

load a template instance fresh from the original FormDef, retrieved from RMS

Parameters:

formID -

Returns:

clean

public void clean()

Specified by:

clean in interface WrappingStorageUtility.SerializationWrapper

classForDataType

public static Class classForDataType(int dataType)

map xforms data types to the Class that represents that data in a FormInstance

Parameters:

dataType -

Returns: