org.apache.commons.configuration

Class PropertiesConfiguration

public class PropertiesConfiguration extends AbstractFileConfiguration

This is the "classic" Properties loader which loads the values from a single or multiple files (which can be chained with "include =". All given path references are either absolute or relative to the file name supplied in the constructor.

In this class, empty PropertyConfigurations can be built, properties added and later saved. include statements are (obviously) not supported if you don't construct a PropertyConfiguration from a file.

The properties file syntax is explained here, basically it follows the syntax of the stream parsed by java.util.Properties#load and adds several useful extensions:

Here is an example of a valid extended properties file:

      # lines starting with # are comments

      # This is the simplest property
      key = value

      # A long property may be separated on multiple lines
      longvalue = aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \
                  aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

      # This is a property with many tokens
      tokens_on_a_line = first token, second token

      # This sequence generates exactly the same result
      tokens_on_multiple_lines = first token
      tokens_on_multiple_lines = second token

      # commas may be escaped in tokens
      commas.escaped = Hi\, what'up?

      # properties can reference other properties
      base.prop = /base
      first.prop = ${base.prop}/first
      second.prop = ${first.prop}/second
 

A PropertiesConfiguration object is associated with an instance of the PropertiesConfigurationLayout class, which is responsible for storing the layout of the parsed properties file (i.e. empty lines, comments, and such things). The getLayout() method can be used to obtain this layout object. With setLayout() a new layout object can be set. This should be done before a properties file was loaded.

Version: $Id: PropertiesConfiguration.java 439648 2006-09-02 20:42:10Z oheger $

Author: Stefano Mazzocchi Jon S. Stevens Dave Bryson Geir Magnusson Jr. Leon Messerschmidt Kent Johnson Daniel Rall Ilkka Priha Jason van Zyl Martin Poeschl Henning P. Schmiedehausen Eric Pugh Oliver Heger Emmanuel Bourg

See Also: java.util.Properties#load

Nested Class Summary
static classPropertiesConfiguration.PropertiesReader
This class is used to read properties lines.
static classPropertiesConfiguration.PropertiesWriter
This class is used to write properties lines.
Field Summary
static StringCOMMENT_CHARS
Constant for the supported comment characters.
static StringDEFAULT_ENCODING
The default encoding (ISO-8859-1 as specified by http://java.sun.com/j2se/1.5.0/docs/api/java/util/Properties.html)
static intHEX_RADIX
Constant for the radix of hex numbers.
static Stringinclude
This is the name of the property that can point to other properties file for including other properties files.
booleanincludesAllowed
Allow file inclusion or not
PropertiesConfigurationLayoutlayout
Stores the layout object.
static StringLINE_SEPARATOR
Constant for the platform specific line separator.
static char[]SEPARATORS
The list of possible key/value separators
static intUNICODE_LEN
Constant for the length of a unicode literal.
static char[]WHITE_SPACE
The white space characters used as key/value separators.
Constructor Summary
PropertiesConfiguration()
Creates an empty PropertyConfiguration object which can be used to synthesize a new Properties file by adding values and then saving().
PropertiesConfiguration(String fileName)
Creates and loads the extended properties from the specified file.
PropertiesConfiguration(File file)
Creates and loads the extended properties from the specified file.
PropertiesConfiguration(URL url)
Creates and loads the extended properties from the specified URL.
Method Summary
Objectclone()
Creates a copy of this object.
protected PropertiesConfigurationLayoutcreateLayout()
Creates the associated layout object.
StringgetHeader()
Return the comment header.
static StringgetInclude()
Gets the property value for including other properties files.
booleangetIncludesAllowed()
Reports the status of file inclusion.
PropertiesConfigurationLayoutgetLayout()
Returns the associated layout object.
static booleanisCommentLine(String line)
Tests whether a line is a comment, i.e. whether it starts with a comment character.
voidload(Reader in)
Load the properties from the given reader.
voidloadIncludeFile(String fileName)
Helper method for loading an included properties file.
booleanpropertyLoaded(String key, String value)
This method is invoked by the associated PropertiesConfigurationLayout object for each property definition detected in the parsed properties file.
voidsave(Writer writer)
Save the configuration to the specified stream.
voidsetBasePath(String basePath)
Extend the setBasePath method to turn includes on and off based on the existence of a base path.
voidsetHeader(String header)
Set the comment header.
static voidsetInclude(String inc)
Sets the property value for including other properties files.
protected voidsetIncludesAllowed(boolean includesAllowed)
Controls whether additional files can be loaded by the include = statement or not.
voidsetLayout(PropertiesConfigurationLayout layout)
Sets the associated layout object.
protected static StringunescapeJava(String str, char delimiter)

Unescapes any Java literals found in the String to a Writer.

This is a slightly modified version of the StringEscapeUtils.unescapeJava() function in commons-lang that doesn't drop escaped separators (i.e '\,').

Field Detail

COMMENT_CHARS

static final String COMMENT_CHARS
Constant for the supported comment characters.

DEFAULT_ENCODING

private static final String DEFAULT_ENCODING
The default encoding (ISO-8859-1 as specified by http://java.sun.com/j2se/1.5.0/docs/api/java/util/Properties.html)

HEX_RADIX

private static final int HEX_RADIX
Constant for the radix of hex numbers.

include

private static String include
This is the name of the property that can point to other properties file for including other properties files.

includesAllowed

private boolean includesAllowed
Allow file inclusion or not

layout

private PropertiesConfigurationLayout layout
Stores the layout object.

LINE_SEPARATOR

private static final String LINE_SEPARATOR
Constant for the platform specific line separator.

SEPARATORS

private static final char[] SEPARATORS
The list of possible key/value separators

UNICODE_LEN

private static final int UNICODE_LEN
Constant for the length of a unicode literal.

WHITE_SPACE

private static final char[] WHITE_SPACE
The white space characters used as key/value separators.

Constructor Detail

PropertiesConfiguration

public PropertiesConfiguration()
Creates an empty PropertyConfiguration object which can be used to synthesize a new Properties file by adding values and then saving().

PropertiesConfiguration

public PropertiesConfiguration(String fileName)
Creates and loads the extended properties from the specified file. The specified file can contain "include = " properties which then are loaded and merged into the properties.

Parameters: fileName The name of the properties file to load.

Throws: ConfigurationException Error while loading the properties file

PropertiesConfiguration

public PropertiesConfiguration(File file)
Creates and loads the extended properties from the specified file. The specified file can contain "include = " properties which then are loaded and merged into the properties.

Parameters: file The properties file to load.

Throws: ConfigurationException Error while loading the properties file

PropertiesConfiguration

public PropertiesConfiguration(URL url)
Creates and loads the extended properties from the specified URL. The specified file can contain "include = " properties which then are loaded and merged into the properties.

Parameters: url The location of the properties file to load.

Throws: ConfigurationException Error while loading the properties file

Method Detail

clone

public Object clone()
Creates a copy of this object.

Returns: the copy

createLayout

protected PropertiesConfigurationLayout createLayout()
Creates the associated layout object. This method is invoked when the layout object is accessed and has not been created yet. Derived classes can override this method to hook in a different layout implementation.

Returns: the layout object to use

Since: 1.3

getHeader

public String getHeader()
Return the comment header.

Returns: the comment header

Since: 1.1

getInclude

public static String getInclude()
Gets the property value for including other properties files. By default it is "include".

Returns: A String.

getIncludesAllowed

public boolean getIncludesAllowed()
Reports the status of file inclusion.

Returns: True if include files are loaded.

getLayout

public PropertiesConfigurationLayout getLayout()
Returns the associated layout object.

Returns: the associated layout object

Since: 1.3

isCommentLine

static boolean isCommentLine(String line)
Tests whether a line is a comment, i.e. whether it starts with a comment character.

Parameters: line the line

Returns: a flag if this is a comment line

Since: 1.3

load

public void load(Reader in)
Load the properties from the given reader. Note that the clear() method is not called, so the properties contained in the loaded file will be added to the actual set of properties.

Parameters: in An InputStream.

Throws: ConfigurationException if an error occurs

loadIncludeFile

private void loadIncludeFile(String fileName)
Helper method for loading an included properties file. This method is called by load() when an include property is encountered. It tries to resolve relative file names based on the current base path. If this fails, a resolution based on the location of this properties file is tried.

Parameters: fileName the name of the file to load

Throws: ConfigurationException if loading fails

propertyLoaded

boolean propertyLoaded(String key, String value)
This method is invoked by the associated PropertiesConfigurationLayout object for each property definition detected in the parsed properties file. Its task is to check whether this is a special property definition (e.g. the include property). If not, the property must be added to this configuration. The return value indicates whether the property should be treated as a normal property. If it is false, the layout object will ignore this property.

Parameters: key the property key value the property value

Returns: a flag whether this is a normal property

Throws: ConfigurationException if an error occurs

Since: 1.3

save

public void save(Writer writer)
Save the configuration to the specified stream.

Parameters: writer the output stream used to save the configuration

Throws: ConfigurationException if an error occurs

setBasePath

public void setBasePath(String basePath)
Extend the setBasePath method to turn includes on and off based on the existence of a base path.

Parameters: basePath The new basePath to set.

setHeader

public void setHeader(String header)
Set the comment header.

Parameters: header the header to use

Since: 1.1

setInclude

public static void setInclude(String inc)
Sets the property value for including other properties files. By default it is "include".

Parameters: inc A String.

setIncludesAllowed

protected void setIncludesAllowed(boolean includesAllowed)
Controls whether additional files can be loaded by the include = statement or not. Base rule is, that objects created by the empty C'tor can not have included files.

Parameters: includesAllowed includesAllowed True if Includes are allowed.

setLayout

public void setLayout(PropertiesConfigurationLayout layout)
Sets the associated layout object.

Parameters: layout the new layout object; can be null, then a new layout object will be created

Since: 1.3

unescapeJava

protected static String unescapeJava(String str, char delimiter)

Unescapes any Java literals found in the String to a Writer.

This is a slightly modified version of the StringEscapeUtils.unescapeJava() function in commons-lang that doesn't drop escaped separators (i.e '\,').

Parameters: str the String to unescape, may be null delimiter the delimiter for multi-valued properties

Returns: the processed string

Throws: IllegalArgumentException if the Writer is null