Mega Code Archive
JDOM based XML properties
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/*
* Copyright 2003-2005 the original author or authors.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.input.SAXBuilder;
import org.jdom.output.XMLOutputter;
import com.jdon.util.jdom.DataUnformatFilter;
/**
* Provides the the ability to use simple XML property files. Each property is
* in the form X.Y.Z, which would map to an XML snippet of:
* <pre>
* <X>
* <Y>
* <Z>someValue</Z>
* </Y>
* </X>
* </pre>
*
* The XML file is passed in to the constructor and must be readable and
* writtable. Setting property values will automatically persist those value
* to disk or outputStream.
*/
public class XMLProperties {
private Document doc;
/**
* Parsing the XML file every time we need a property is slow. Therefore,
* we use a Map to cache property values that are accessed more than once.
*/
private Map propertyCache = new HashMap();
/**
* Creates a new XMLProperties object.
*
* @parm file the full path the file that properties should be read from
* and written to.
*/
public XMLProperties(String fileName) {
try {
SAXBuilder builder = new SAXBuilder();
// Strip formatting
DataUnformatFilter format = new DataUnformatFilter();
builder.setXMLFilter(format);
doc = builder.build(new File(fileName));
}
catch (Exception e) {
System.err.println("Error creating XML parser in "
+ "PropertyManager.java");
e.printStackTrace();
}
}
/**
* Creates a new XMLProperties object.
*
* @parm file the full path the file that properties should be read from
* and written to.
*/
public XMLProperties(InputStream inputStream) {
try {
SAXBuilder builder = new SAXBuilder();
// Strip formatting
DataUnformatFilter format = new DataUnformatFilter();
builder.setXMLFilter(format);
doc = builder.build(inputStream);
}
catch (Exception e) {
System.err.println("Error creating XML parser in "
+ "PropertyManager.java");
e.printStackTrace();
}
}
public XMLProperties(Reader reader) {
try {
SAXBuilder builder = new SAXBuilder();
// Strip formatting
DataUnformatFilter format = new DataUnformatFilter();
builder.setXMLFilter(format);
doc = builder.build(reader);
}
catch (Exception e) {
System.err.println("Error creating XML parser in "
+ "PropertyManager.java");
e.printStackTrace();
}
}
/**
* Returns the value of the specified property.
*
* @param name the name of the property to get.
* @return the value of the specified property.
*/
public String getProperty(String name) {
if (propertyCache.containsKey(name)) {
return (String)propertyCache.get(name);
}
String[] propName = parsePropertyName(name);
// Search for this property by traversing down the XML heirarchy.
Element element = doc.getRootElement();
for (int i = 0; i < propName.length; i++) {
element = element.getChild(propName[i]);
if (element == null) {
// This node doesn't match this part of the property name which
// indicates this property doesn't exist so return null.
return null;
}
}
// At this point, we found a matching property, so return its value.
// Empty strings are returned as null.
String value = element.getText();
if ("".equals(value)) {
return null;
}
else {
// Add to cache so that getting property next time is fast.
value = value.trim();
propertyCache.put(name, value);
return value;
}
}
/**
* Return all children property names of a parent property as a String array,
* or an empty array if the if there are no children. For example, given
* the properties <tt>X.Y.A</tt>, <tt>X.Y.B</tt>, and <tt>X.Y.C</tt>, then
* the child properties of <tt>X.Y</tt> are <tt>A</tt>, <tt>B</tt>, and
* <tt>C</tt>.
*
* @param parent the name of the parent property.
* @return all child property values for the given parent.
*/
public String [] getChildrenProperties(String parent) {
String[] propName = parsePropertyName(parent);
// Search for this property by traversing down the XML heirarchy.
Element element = doc.getRootElement();
for (int i = 0; i < propName.length; i++) {
element = element.getChild(propName[i]);
if (element == null) {
// This node doesn't match this part of the property name which
// indicates this property doesn't exist so return empty array.
return new String [] { };
}
}
// We found matching property, return names of children.
List children = element.getChildren();
int childCount = children.size();
String [] childrenNames = new String[childCount];
for (int i=0; i<childCount; i++) {
childrenNames[i] = ((Element)children.get(i)).getName();
}
return childrenNames;
}
/**
* Sets the value of the specified property. If the property doesn't
* currently exist, it will be automatically created.
*
* @param name the name of the property to set.
* @param value the new value for the property.
*/
public void setProperty(String name, String value) {
// Set cache correctly with prop name and value.
propertyCache.put(name, value);
String[] propName = parsePropertyName(name);
// Search for this property by traversing down the XML heirarchy.
Element element = doc.getRootElement();
for (int i=0; i<propName.length; i++) {
// If we don't find this part of the property in the XML heirarchy
// we add it as a new node
if (element.getChild(propName[i]) == null) {
element.addContent(new Element(propName[i]));
}
element = element.getChild(propName[i]);
}
// Set the value of the property in this node.
element.setText(value);
}
/**
* Deletes the specified property.
*
* @param name the property to delete.
*/
public void deleteProperty(String name) {
String[] propName = parsePropertyName(name);
// Search for this property by traversing down the XML heirarchy.
Element element = doc.getRootElement();
for (int i=0; i<propName.length-1; i++) {
element = element.getChild(propName[i]);
// Can't find the property so return.
if (element == null) {
return;
}
}
// Found the correct element to remove, so remove it...
element.removeChild(propName[propName.length-1]);
}
/**
* Saves the properties to disk as an XML document. A temporary file is
* used during the writing process for maximum safety.
*/
public synchronized void saveProperties(String fileName) {
OutputStream out = null;
boolean error = false;
File file = new File(fileName);
// Write data out to a temporary file first.
File tempFile = null;
try {
tempFile = new File(file.getParentFile(), file.getName() + ".tmp");
// Use JDOM's XMLOutputter to do the writing and formatting. The
// file should always come out pretty-printed.
XMLOutputter outputter = new XMLOutputter();
out = new BufferedOutputStream(new FileOutputStream(tempFile));
outputter.output(doc, out);
}
catch (Exception e) {
e.printStackTrace();
// There were errors so abort replacing the old property file.
error = true;
}
finally {
try { out.close(); }
catch (Exception e) {
e.printStackTrace();
error = true;
}
}
// No errors occured, so we should be safe in replacing the old
if (!error) {
// Delete the old file so we can replace it.
file.delete();
// Rename the temp file. The delete and rename won't be an
// automic operation, but we should be pretty safe in general.
// At the very least, the temp file should remain in some form.
tempFile.renameTo(file);
}
}
public synchronized void savePropertiesToStream(OutputStream out) {
boolean error = false;
try {
// Use JDOM's XMLOutputter to do the writing and formatting. The
// file should always come out pretty-printed.
XMLOutputter outputter = new XMLOutputter();
outputter.output(doc, out);
}
catch (Exception e) {
e.printStackTrace();
}
finally {
try { out.close(); }
catch (Exception e) {
e.printStackTrace();
}
}
}
public synchronized void savePropertiesToStream(Writer writer) {
boolean error = false;
try {
// Use JDOM's XMLOutputter to do the writing and formatting. The
// file should always come out pretty-printed.
XMLOutputter outputter = new XMLOutputter();
outputter.output(doc, writer);
}
catch (Exception e) {
e.printStackTrace();
}
finally {
try { writer.close(); }
catch (Exception e) {
e.printStackTrace();
}
}
}
/**
* Returns an array representation of the given Jive property. Jive
* properties are always in the format "prop.name.is.this" which would be
* represented as an array of four Strings.
*
* @param name the name of the Jive property.
* @return an array representation of the given Jive property.
*/
private String[] parsePropertyName(String name) {
// Figure out the number of parts of the name (this becomes the size
// of the resulting array).
int size = 1;
for (int i=0; i<name.length(); i++) {
if (name.charAt(i) == '.') {
size++;
}
}
String[] propName = new String[size];
// Use a StringTokenizer to tokenize the property name.
StringTokenizer tokenizer = new StringTokenizer(name, ".");
int i = 0;
while (tokenizer.hasMoreTokens()) {
propName[i] = tokenizer.nextToken();
i++;
}
return propName;
}
}
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