com.databasesandlife.util

Class OutOfHeapTemporaryStorage

java.lang.Object

com.databasesandlife.util.OutOfHeapTemporaryStorage

public class OutOfHeapTemporaryStorage
extends Object

A temporary file which can store arbitrary data for the duration of a process. If we are dealing with a 4GB XML file, we don't want lots of seldom accessed strings hanging around the heap. Currently strings and XML documents may be stored.

Usage: For each object to be stored, firstly a "container" is created and then data is appended/written to the container. In this way, it's possible for an XML SAX parser, finding an XML [myObject type="x"] tag, to create the container and place it in the appropriate place in the destination data structure (e.g. if its place dependent on the element's attribute), but for the container to be actually filled with data while processing further tags, e.g. child elements of the original tag.

     OutOfHeapTemporaryFileStorage file = new OutOfHeapTemporaryFileStorage();            // file created in /tmp
     
     // Persisting and loading a string
     OutOfHeapString str = file.newStringContainer();
     str.append("xyz");        
     System.out.println("str is: " + str.toString()); // fetches string from file
     
     // Persisting and loading chunks of XML
     org.w3c.dom.Element anElement = ....;
     OutOfHeapXml xml = file.newXmlContainer();
     xml.setXml(anElement); // call only once
     org.w3c.dom.Element afterLoading = x.toXmlDomElement();
 

Author:

This source is copyright Adrian Smith and licensed under the LGPL 3.

See Also:

Project on GitHub

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	OutOfHeapTemporaryStorage.OutOfHeapString
class	OutOfHeapTemporaryStorage.OutOfHeapXml

Constructor Summary

Constructors

Constructor and Description
OutOfHeapTemporaryStorage()

Method Summary

Modifier and Type	Method and Description
protected void	appendToString(OutOfHeapTemporaryStorage.OutOfHeapString s, String suffix)
OutOfHeapTemporaryStorage.OutOfHeapString	newStringContainer() Returns a new string container for the empty string
OutOfHeapTemporaryStorage.OutOfHeapString	newStringContainer(String initialValue)
OutOfHeapTemporaryStorage.OutOfHeapXml	newXmlContainer()
protected String	readString(OutOfHeapTemporaryStorage.OutOfHeapString s)
protected Element	readXml(OutOfHeapTemporaryStorage.OutOfHeapXml inFile)
protected void	writeXml(OutOfHeapTemporaryStorage.OutOfHeapXml xml, Element element)

Methods inherited from class java.lang.Object

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

Constructor Detail

OutOfHeapTemporaryStorage

public OutOfHeapTemporaryStorage()

Method Detail

newStringContainer

public OutOfHeapTemporaryStorage.OutOfHeapString newStringContainer()

Returns a new string container for the empty string

newStringContainer

public OutOfHeapTemporaryStorage.OutOfHeapString newStringContainer(String initialValue)

appendToString

protected void appendToString(OutOfHeapTemporaryStorage.OutOfHeapString s,
                              String suffix)

readString

protected String readString(OutOfHeapTemporaryStorage.OutOfHeapString s)

newXmlContainer

public OutOfHeapTemporaryStorage.OutOfHeapXml newXmlContainer()

writeXml

protected void writeXml(OutOfHeapTemporaryStorage.OutOfHeapXml xml,
                        Element element)

readXml

protected Element readXml(OutOfHeapTemporaryStorage.OutOfHeapXml inFile)