Package org.apache.commons.configuration2

Class PropertiesConfiguration

java.lang.Object
org.apache.commons.configuration2.event.BaseEventSource
org.apache.commons.configuration2.AbstractConfiguration
org.apache.commons.configuration2.BaseConfiguration
org.apache.commons.configuration2.PropertiesConfiguration
All Implemented Interfaces:
Cloneable, Configuration, EventSource, FileBasedConfiguration, ImmutableConfiguration, FileBased, FileLocatorAware, SynchronizerSupport
public class PropertiesConfiguration extends BaseConfiguration implements FileBasedConfiguration, FileLocatorAware
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 Properties.load(java.io.Reader) and adds several useful extensions:

  • Each property has the syntax key <separator> value. The separators accepted are '=', ':' and any white space character. Examples: 
      key1 = value1
  key2 : value2
  key3   value3
  • The key may use any character, separators must be escaped: 
      key\:foo = bar
  • value may be separated on different lines if a backslash is placed at the end of the line that continues below.
  • The list delimiter facilities provided by AbstractConfiguration are supported, too. If an appropriate ListDelimiterHandler is set (for instance a D efaultListDelimiterHandler object configured with a comma as delimiter character), value can contain value delimiters and will then be interpreted as a list of tokens. So the following property definition 
      key = This property, has multiple, values
    will result in a property with three values. You can change the handling of delimiters using the AbstractConfiguration.setListDelimiterHandler(ListDelimiterHandler) method. Per default, list splitting is disabled.
  • Commas in each token are escaped placing a backslash right before the comma.
  • If a key is used more than once, the values are appended like if they were on the same line separated with commas. Note: When the configuration file is written back to disk the associated PropertiesConfigurationLayout object (see below) will try to preserve as much of the original format as possible, i.e. properties with multiple values defined on a single line will also be written back on a single line, and multiple occurrences of a single key will be written on multiple lines. If the addProperty() method was called multiple times for adding multiple values to a property, these properties will per default be written on multiple lines in the output file, too. Some options of the PropertiesConfigurationLayout class have influence on that behavior.
  • Blank lines and lines starting with character '#' or '!' are skipped.
  • If a property is named "include" (or whatever is defined by setInclude() and getInclude() and the value of that property is the full path to a file on disk, that file will be included into the configuration. You can also pull in files relative to the parent configuration file. So if you have something like the following: include = additional.properties Then "additional.properties" is expected to be in the same directory as the parent configuration file. The properties in the included file are added to the parent configuration, they do not replace existing properties with the same key.
  • You can define custom error handling for the special key "include" by using setIncludeListener(ConfigurationConsumer).

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.

Like other Configuration implementations, this class uses a Synchronizer object to control concurrent access. By choosing a suitable implementation of the Synchronizer interface, an instance can be made thread-safe or not. Note that access to most of the properties typically set through a builder is not protected by the Synchronizer. The intended usage is that these properties are set once at construction time through the builder and after that remain constant. If you wish to change such properties during life time of an instance, you have to use the lock() and unlock() methods manually to ensure that other threads see your changes.

As this class extends AbstractConfiguration, all basic features like variable interpolation, list handling, or data type conversions are available as well. This is described in the chapter Basic features and AbstractConfiguration of the user's guide. There is also a separate chapter dealing with Properties files in special.

See Also:

  • Field Details

    • DEFAULT_INCLUDE_LISTENER

      public static final ConfigurationConsumer<ConfigurationException> DEFAULT_INCLUDE_LISTENER
      Defines default error handling for the special "include" key by throwing the given exception.
      Since:
      2.6

    • NOOP_INCLUDE_LISTENER

      public static final ConfigurationConsumer<ConfigurationException> NOOP_INCLUDE_LISTENER
      Defines error handling as a noop for the special "include" key.
      Since:
      2.6

    • DEFAULT_ENCODING

      public static final String DEFAULT_ENCODING
      The default encoding (ISO-8859-1 as specified by https://docs.oracle.com/javase/8/docs/api/java/util/Properties.html)

    • COMMENT_CHARS

      static final String COMMENT_CHARS
      Constant for the supported comment characters.
      See Also:

    • DEFAULT_SEPARATOR

      static final String DEFAULT_SEPARATOR
      Constant for the default properties separator.
      See Also:

    • UNESCAPE_CHARACTERS

      private static final String UNESCAPE_CHARACTERS
      A string with special characters that need to be unescaped when reading a properties file. Properties escapes these characters when writing out a properties file.
      See Also:

    • include

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

    • includeOptional

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

      If the file is absent, processing continues normally.

    • SEPARATORS

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

    • WHITE_SPACE

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

    • LINE_SEPARATOR

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

    • HEX_RADIX

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

    • UNICODE_LEN

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

    • layout

      private PropertiesConfigurationLayout layout
      Stores the layout object.

    • includeListener

      private ConfigurationConsumer<ConfigurationException> includeListener
      The include listener for the special "include" key.

    • ioFactory

      private PropertiesConfiguration.IOFactory ioFactory
      The IOFactory for creating readers and writers.

    • locator

      private FileLocator locator
      The current FileLocator.

    • includesAllowed

      private boolean includesAllowed
      Allow file inclusion or not

  • Constructor Details

    • PropertiesConfiguration

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

  • Method Details

    • countTrailingBS

      private static int countTrailingBS(String line)
      Returns the number of trailing backslashes. This is sometimes needed for the correct handling of escape characters.
      Parameters:
      line - the string to investigate
      Returns:
      the number of trailing backslashes

    • getInclude

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

    • getIncludeOptional

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

      If the file is absent, processing continues normally.

      Returns:
      A String.
      Since:
      2.5

    • 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

    • needsUnescape

      private static boolean needsUnescape(char ch)
      Checks whether the specified character needs to be unescaped. This method is called when during reading a property file an escape character ('\') is detected. If the character following the escape character is recognized as a special character which is escaped per default in a Java properties file, it has to be unescaped.
      Parameters:
      ch - the character in question
      Returns:
      a flag whether this character has to be unescaped

    • 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.

    • setIncludeOptional

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

      If the file is absent, processing continues normally.

      Parameters:
      inc - A String.
      Since:
      2.5

    • unescapeJava

      protected static String unescapeJava(String str)

      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
      Returns:
      the processed string
      Throws:
      IllegalArgumentException - if the Writer is null

    • unescapeJava

      protected static String unescapeJava(String str, boolean jupCompatible)
      Unescapes Java literals found in the String to a Writer.

      When the parameter jupCompatible is false, the classic behavior is used (see unescapeJava(String)). When it's true a slightly different behavior that's compatible with Properties is used (see PropertiesConfiguration.JupIOFactory).

      Parameters:
      str - the String to unescape, may be null
      jupCompatible - whether unescaping is compatible with Properties; otherwise the classic behavior is used
      Returns:
      the processed string
      Throws:
      IllegalArgumentException - if the Writer is null

    • clone

      public Object clone()
      Creates a copy of this object.
      Overrides:
      clone in class BaseConfiguration
      Returns:
      the copy

    • createLayout

      private PropertiesConfigurationLayout createLayout()
      Creates a standard layout object. This configuration is initialized with such a standard layout.
      Returns:
      the newly created layout object

    • getFooter

      public String getFooter()
      Gets the footer comment. This is a comment at the very end of the file.
      Returns:
      the footer comment
      Since:
      2.0

    • getHeader

      public String getHeader()
      Gets the comment header.
      Returns:
      the comment header
      Since:
      1.1

    • getIncludeListener

      public ConfigurationConsumer<ConfigurationException> getIncludeListener()
      Gets the current include listener, never null.
      Returns:
      the current include listener, never null.
      Since:
      2.6

    • getIOFactory

      public PropertiesConfiguration.IOFactory getIOFactory()
      Gets the IOFactory to be used for creating readers and writers when loading or saving this configuration.
      Returns:
      the IOFactory
      Since:
      1.7

    • getLayout

      public PropertiesConfigurationLayout getLayout()
      Gets the associated layout object.
      Returns:
      the associated layout object
      Since:
      1.3

    • initFileLocator

      public void initFileLocator(FileLocator locator)
      Stores the current FileLocator for a following IO operation. The FileLocator is needed to resolve include files with relative file names.
      Specified by:
      initFileLocator in interface FileLocatorAware
      Parameters:
      locator - the current FileLocator
      Since:
      2.0

    • installLayout

      private void installLayout(PropertiesConfigurationLayout layout)
      Installs a layout object. It has to be ensured that the layout is registered as change listener at this configuration. If there is already a layout object installed, it has to be removed properly.
      Parameters:
      layout - the layout object to be installed

    • isIncludesAllowed

      public boolean isIncludesAllowed()
      Reports the status of file inclusion.
      Returns:
      True if include files are loaded.

    • loadIncludeFile

      private void loadIncludeFile(String fileName, boolean optional, Deque<URL> seenStack) throws ConfigurationException
      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
      optional - whether or not the fileName is optional
      seenStack - Stack of seen include URLs
      Throws:
      ConfigurationException - if loading fails

    • locateIncludeFile

      private URL locateIncludeFile(String basePath, String fileName)
      Tries to obtain the URL of an include file using the specified (optional) base path and file name.
      Parameters:
      basePath - the base path
      fileName - the file name
      Returns:
      the URL of the include file or null if it cannot be resolved

    • propertyLoaded

      boolean propertyLoaded(String key, String value, Deque<URL> seenStack) throws ConfigurationException
      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
      seenStack - the stack of seen include URLs
      Returns:
      a flag whether this is a normal property
      Throws:
      ConfigurationException - if an error occurs
      Since:
      1.3

    • read

      public void read(Reader in) throws ConfigurationException, IOException
      Reads the content of this object from the given reader. Client code should not call this method directly, but use a FileHandler for reading data. This implementation delegates to the associated layout object which does the actual loading. Note that this method does not do any synchronization. This lies in the responsibility of the caller. (Typically, the caller is a FileHandler object which takes care for proper synchronization.)
      Specified by:
      read in interface FileBased
      Parameters:
      in - the reader
      Throws:
      ConfigurationException - if a non-I/O related problem occurs, e.g. the data read does not have the expected format
      IOException - if an I/O error occurs.
      Since:
      2.0

    • setFooter

      public void setFooter(String footer)
      Sets the footer comment. If set, this comment is written after all properties at the end of the file.
      Parameters:
      footer - the footer comment
      Since:
      2.0

    • setHeader

      public void setHeader(String header)
      Sets the comment header.
      Parameters:
      header - the header to use
      Since:
      1.1

    • setIncludeListener

      public void setIncludeListener(ConfigurationConsumer<ConfigurationException> includeListener)
      Sets the current include listener, may not be null.
      Parameters:
      includeListener - the current include listener, may not be null.
      Throws:
      IllegalArgumentException - if the includeListener is null.
      Since:
      2.6

    • setIncludesAllowed

      public void setIncludesAllowed(boolean includesAllowed)
      Controls whether additional files can be loaded by the include = <xxx> statement or not. This is true per default.
      Parameters:
      includesAllowed - True if Includes are allowed.

    • setIOFactory

      public void setIOFactory(PropertiesConfiguration.IOFactory ioFactory)
      Sets the IOFactory to be used for creating readers and writers when loading or saving this configuration. Using this method a client can customize the reader and writer classes used by the load and save operations. Note that this method must be called before invoking one of the load() and save() methods. Especially, if you want to use a custom IOFactory for changing the PropertiesReader, you cannot load the configuration data in the constructor.
      Parameters:
      ioFactory - the new IOFactory (must not be null)
      Throws:
      IllegalArgumentException - if the IOFactory is null
      Since:
      1.7

    • 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

    • write

      public void write(Writer out) throws ConfigurationException, IOException
      Writes the content of this object to the given writer. Client code should not call this method directly, but use a FileHandler for writing data. This implementation delegates to the associated layout object which does the actual saving. Note that, analogous to read(Reader), this method does not do any synchronization.
      Specified by:
      write in interface FileBased
      Parameters:
      out - the writer
      Throws:
      ConfigurationException - if a non-I/O related problem occurs, e.g. the data read does not have the expected format
      IOException - if an I/O error occurs.
      Since:
      2.0