net.yura.mobile.util

Class Properties

java.lang.Object

java.util.Dictionary<K,V>

java.util.Hashtable

net.yura.mobile.util.Properties

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, java.util.Map

public class Properties
extends java.util.Hashtable

The Properties class represents a persistent set of properties. The Properties can be saved to a stream or loaded from a stream. Each key and its corresponding value in the property list is a string.

A property list can contain another property list as its "defaults"; this second property list is searched if the property key is not found in the original property list.

Because Properties inherits from Hashtable, the put and putAll methods can be applied to a Properties object. Their use is strongly discouraged as they allow the caller to insert entries whose keys or values are not Strings. The setProperty method should be used instead. If the store or save method is called on a "compromised" Properties object that contains a non-String key or value, the call will fail. Similarly, the call to the propertyNames or list method will fail if it is called on a "compromised" Properties object that contains a non-String key.

The load(Reader) / store(Writer, String) methods load and store properties from and to a character based stream in a simple line-oriented format specified below. The load(InputStream) / store(OutputStream, String) methods work the same way as the load(Reader)/store(Writer, String) pair, except the input/output stream is encoded in ISO 8859-1 character encoding. Characters that cannot be directly represented in this encoding can be written using Unicode escapes ; only a single 'u' character is allowed in an escape sequence. The native2ascii tool can be used to convert property files to and from other character encodings.

See Also:

native2ascii tool for Solaris, native2ascii tool for Windows, Properties, Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected Properties	defaults A property list that contains default values for any keys not found in this property list.

Constructor Summary

Constructors

Constructor and Description
Properties() Creates an empty property list with no default values.
Properties(Properties defaults) Creates an empty property list with the specified defaults.

Method Summary

Modifier and Type	Method and Description
java.lang.String	getProperty(java.lang.String key) Searches for the property with the specified key in this property list.
java.lang.String	getProperty(java.lang.String key, java.lang.String defaultValue) Searches for the property with the specified key in this property list.
java.lang.String	getString(java.lang.String key)
void	list(java.io.PrintStream out) Prints this property list out to the specified output stream.
void	load(java.io.InputStream inStream) Reads a property list (key and element pairs) from the input byte stream.
void	load(java.io.Reader reader) Reads a property list (key and element pairs) from the input character stream in a simple line-oriented format.
java.util.Enumeration	propertyNames() Returns an enumeration of all the keys in this property list, including distinct keys in the default property list if a key of the same name has not already been found from the main properties list.
java.lang.Object	setProperty(java.lang.String key, java.lang.String value) Calls the Hashtable method put.

Methods inherited from class java.util.Hashtable

clear, clone, compute, computeIfAbsent, computeIfPresent, contains, containsKey, containsValue, elements, entrySet, equals, forEach, get, getOrDefault, hashCode, isEmpty, keys, keySet, merge, put, putAll, putIfAbsent, rehash, remove, remove, replace, replace, replaceAll, size, toString, values

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

defaults

protected Properties defaults

A property list that contains default values for any keys not found in this property list.

Constructor Detail

Properties

public Properties()

Creates an empty property list with no default values.

Properties

public Properties(Properties defaults)

Creates an empty property list with the specified defaults.

Parameters:

defaults - the defaults.

Method Detail

setProperty

public java.lang.Object setProperty(java.lang.String key,
                                    java.lang.String value)

Calls the Hashtable method put. Provided for parallelism with the getProperty method. Enforces use of strings for property keys and values. The value returned is the result of the Hashtable call to put.

Parameters:

key - the key to be placed into this property list.

value - the value corresponding to key.

Returns:

the previous value of the specified key in this property list, or null if it did not have one.

Since:

1.2

See Also:

getProperty(java.lang.String)

load

public void load(java.io.Reader reader)
          throws java.io.IOException

Reads a property list (key and element pairs) from the input character stream in a simple line-oriented format.

Properties are processed in terms of lines. There are two kinds of line, natural lines and logical lines. A natural line is defined as a line of characters that is terminated either by a set of line terminator characters (\n or \r or \r\n) or by the end of the stream. A natural line may be either a blank line, a comment line, or hold all or some of a key-element pair. A logical line holds all the data of a key-element pair, which may be spread out across several adjacent natural lines by escaping the line terminator sequence with a backslash character \. Note that a comment line cannot be extended in this manner; every natural line that is a comment must have its own comment indicator, as described below. Lines are read from input until the end of the stream is reached.

A natural line that contains only white space characters is considered blank and is ignored. A comment line has an ASCII '#' or '!' as its first non-white space character; comment lines are also ignored and do not encode key-element information. In addition to line terminators, this format considers the characters space (' ', '\u0020'), tab ('\t', '\u0009'), and form feed ('\f', '\u000C') to be white space.

If a logical line is spread across several natural lines, the backslash escaping the line terminator sequence, the line terminator sequence, and any white space at the start of the following line have no affect on the key or element values. The remainder of the discussion of key and element parsing (when loading) will assume all the characters constituting the key and element appear on a single natural line after line continuation characters have been removed. Note that it is not sufficient to only examine the character preceding a line terminator sequence to decide if the line terminator is escaped; there must be an odd number of contiguous backslashes for the line terminator to be escaped. Since the input is processed from left to right, a non-zero even number of 2n contiguous backslashes before a line terminator (or elsewhere) encodes n backslashes after escape processing.

The key contains all of the characters in the line starting with the first non-white space character and up to, but not including, the first unescaped '=', ':', or white space character other than a line terminator. All of these key termination characters may be included in the key by escaping them with a preceding backslash character; for example,

\:\=

would be the two-character key ":=". Line terminator characters can be included using \r and \n escape sequences. Any white space after the key is skipped; if the first non-white space character after the key is '=' or ':', then it is ignored and any white space characters after it are also skipped. All remaining characters on the line become part of the associated element string; if there are no remaining characters, the element is the empty string "". Once the raw character sequences constituting the key and element are identified, escape processing is performed as described above.

As an example, each of the following three lines specifies the key "Truth" and the associated element value "Beauty":

 Truth = Beauty
        Truth:Beauty
 Truth                  :Beauty
 

As another example, the following three lines specify a single property:

 fruits                           apple, banana, pear, \
                                  cantaloupe, watermelon, \
                                  kiwi, mango
 

The key is "fruits" and the associated element is:

"apple, banana, pear, cantaloupe, watermelon, kiwi, mango"

Note that a space appears before each \ so that a space will appear after each comma in the final result; the \, line terminator, and leading white space on the continuation line are merely discarded and are not replaced by one or more other characters.

As a third example, the line:

cheeses
 

specifies that the key is "cheeses" and the associated element is the empty string "".

Characters in keys and elements can be represented in escape sequences similar to those used for character and string literals (see §3.3 and §3.10.6 of the Java Language Specification). The differences from the character escape sequences and Unicode escapes used for characters and strings are:

• Octal escapes are not recognized.
• The character sequence \b does not represent a backspace character.
• The method does not treat a backslash character, \, before a non-valid escape character as an error; the backslash is silently dropped. For example, in a Java string the sequence "\z" would cause a compile time error. In contrast, this method silently drops the backslash. Therefore, this method treats the two character sequence "\b" as equivalent to the single character 'b'.
• Escapes are not necessary for single and double quotes; however, by the rule above, single and double quote characters preceded by a backslash still yield single and double quote characters, respectively.
• Only a single 'u' character is allowed in a Uniocde escape sequence.

The specified stream remains open after this method returns.

Parameters:

reader - the input character stream.

Throws:

java.io.IOException - if an error occurred when reading from the input stream.

java.lang.IllegalArgumentException - if a malformed Unicode escape appears in the input.

Since:

1.6

load

public void load(java.io.InputStream inStream)
          throws java.io.IOException

Reads a property list (key and element pairs) from the input byte stream. The input stream is in a simple line-oriented format as specified in load(Reader) and is assumed to use the ISO 8859-1 character encoding; that is each byte is one Latin1 character. Characters not in Latin1, and certain special characters, are represented in keys and elements using Unicode escapes.

The specified stream remains open after this method returns.

Parameters:

inStream - the input stream.

Throws:

java.io.IOException - if an error occurred when reading from the input stream.

java.lang.IllegalArgumentException - if the input stream contains a malformed Unicode escape sequence.

Since:

1.2

getProperty

public java.lang.String getProperty(java.lang.String key)

Searches for the property with the specified key in this property list. If the key is not found in this property list, the default property list, and its defaults, recursively, are then checked. The method returns null if the property is not found.

Parameters:

key - the property key.

Returns:

the value in this property list with the specified key value.

See Also:

setProperty(java.lang.String, java.lang.String), defaults

getString

public java.lang.String getString(java.lang.String key)

See Also:

ResourceBundle.getString

getProperty

public java.lang.String getProperty(java.lang.String key,
                                    java.lang.String defaultValue)

Searches for the property with the specified key in this property list. If the key is not found in this property list, the default property list, and its defaults, recursively, are then checked. The method returns the default value argument if the property is not found.

Parameters:

key - the hashtable key.

defaultValue - a default value.

Returns:

the value in this property list with the specified key value.

See Also:

setProperty(java.lang.String, java.lang.String), defaults

propertyNames

public java.util.Enumeration propertyNames()

Returns an enumeration of all the keys in this property list, including distinct keys in the default property list if a key of the same name has not already been found from the main properties list.

Returns:

an enumeration of all the keys in this property list, including the keys in the default property list.

Throws:

java.lang.ClassCastException - if any key in this property list is not a string.

See Also:

Enumeration, Properties.defaults, Properties.stringPropertyNames()

list

public void list(java.io.PrintStream out)

Prints this property list out to the specified output stream. This method is useful for debugging.

Parameters:

out - an output stream.

Throws:

java.lang.ClassCastException - if any key in this property list is not a string.