| java.lang.Object
 java.util.Hashtable
java.util.Properties
| Properties | | public class Properties extends Hashtable (Code) | | 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.
When saving properties to a stream or loading them from a stream, the
ISO 8859-1 character encoding is used. For characters that cannot be directly
represented in this encoding,
Unicode escapes
are used; however, 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
See Also: native2ascii tool for Windows
author:
Arthur van Hoff
author:
Michael McCloskey
version:
1.61, 05/03/00
since:
JDK1.0 |
| Field Summary | |
| protected Properties | defaults
A property list that contains default values for any keys not
found in this property list. |
| Constructor Summary | |
| public | Properties()
Creates an empty property list with no default values. | | public | Properties(Properties defaults)
Creates an empty property list with the specified defaults. |
| Method Summary | |
| public String | getProperty(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. | | public String | getProperty(String key, 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. | | public void | list(PrintStream out)
Prints this property list out to the specified output stream. | | public void | list(PrintWriter out)
Prints this property list out to the specified output stream. | | public synchronized void | load(InputStream inStream)
Reads a property list (key and element pairs) from the input
stream. | | public 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. | | public synchronized void | save(OutputStream out, String header)
Calls the store(OutputStream out, String header) method
and suppresses IOExceptions that were thrown. | | public synchronized Object | setProperty(String key, String value)
Calls the Hashtable method put. | | public synchronized void | store(OutputStream out, String header)
Writes this property list (key and element pairs) in this
Properties table to the output stream in a format suitable
for loading into a Properties table using the
Properties.load(InputStream) load method.
The stream is written using the ISO 8859-1 character encoding.
Properties from the defaults table of this Properties
table (if any) are not written out by this method.
If the header argument is not null, then an ASCII #
character, the header string, and a line separator are first written
to the output stream. |
| defaults | | protected Properties defaults(Code) | | A property list that contains default values for any keys not
found in this property list.
|
| Properties | | public Properties()(Code) | | Creates an empty property list with no default values.
|
| Properties | | public Properties(Properties defaults)(Code) | | Creates an empty property list with the specified defaults.
Parameters:
defaults - the defaults. |
| getProperty | | public String getProperty(String key)(Code) | | 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. the value in this property list with the specified key value.
See Also: Properties.setProperty
See Also: Properties.defaults |
| getProperty | | public String getProperty(String key, String defaultValue)(Code) | | 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.
Parameters:
defaultValue - a default value. the value in this property list with the specified key value.
See Also: Properties.setProperty
See Also: Properties.defaults |
| list | | public void list(PrintStream out)(Code) | | Prints this property list out to the specified output stream.
This method is useful for debugging.
Parameters:
out - an output stream. |
| list | | public void list(PrintWriter out)(Code) | | Prints this property list out to the specified output stream.
This method is useful for debugging.
Parameters:
out - an output stream.
since:
JDK1.1 |
| load | | public synchronized void load(InputStream inStream) throws IOException(Code) | | Reads a property list (key and element pairs) from the input
stream. The stream is assumed to be using the ISO 8859-1
character encoding; that is each byte is one Latin1 character.
Characters not in Latin1, and certain special characters, can
be represented in keys and elements using 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 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.
An IllegalArgumentException is thrown if a
malformed Unicode escape appears in the input.
This method processes input in terms of lines. A natural line
of input is terminated either by a set of line terminator
characters (\n or \r or
\r\n) or by the end of the file. A natural line
may be either a blank line, a comment line, or hold some part
of a key-element pair. The logical line holding all the data
for a key-element pair 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. If a logical line is continued over several natural
lines, the continuation lines receive further processing, also
described below. Lines are read from the input stream until
end of file 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 method 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 the
following line have no affect on the key or element values.
The remainder of the discussion of key and element parsing 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 to see 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 "".
Parameters:
inStream - the input stream.
exception:
IOException - if an error occurred when reading from theinput stream.
throws:
IllegalArgumentException - if the input stream contains amalformed Unicode escape sequence. |
| propertyNames | | public Enumeration propertyNames()(Code) | | 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.
an enumeration of all the keys in this property list, includingthe keys in the default property list.
See Also: java.util.Enumeration
See Also: java.util.Properties.defaults |
| save | | public synchronized void save(OutputStream out, String header)(Code) | | Calls the store(OutputStream out, String header) method
and suppresses IOExceptions that were thrown.
Parameters:
out - an output stream.
Parameters:
header - a description of the property list.
exception:
ClassCastException - if this Properties objectcontains any keys or values that are not Strings. |
| setProperty | | public synchronized Object setProperty(String key, String value)(Code) | | 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.
Parameters:
value - the value corresponding to key. the previous value of the specified key in this propertylist, or null if it did not have one.
See Also: Properties.getProperty
since:
1.2 |
| store | | public synchronized void store(OutputStream out, String header) throws IOException(Code) | | Writes this property list (key and element pairs) in this
Properties table to the output stream in a format suitable
for loading into a Properties table using the
Properties.load(InputStream) load method.
The stream is written using the ISO 8859-1 character encoding.
Properties from the defaults table of this Properties
table (if any) are not written out by this method.
If the header argument is not null, then an ASCII #
character, the header string, and a line separator are first written
to the output stream. Thus, the header can serve as an
identifying comment.
Next, a comment line is always written, consisting of an ASCII
# character, the current date and time (as if produced
by the toString method of Date for the
current time), and a line separator as generated by the Writer.
Then every entry in this Properties table is
written out, one per line. For each entry the key string is
written, then an ASCII =, then the associated
element string. Each character of the key and element strings
is examined to see whether it should be rendered as an escape
sequence. The ASCII characters \, tab, form feed,
newline, and carriage return are written as \\,
\t, \f \n, and
\r, respectively. Characters less than
\u0020 and characters greater than
\u007E are written as
\uxxxx for the appropriate hexadecimal
value xxxx. For the key, all space characters are
written with a preceding \ character. For the
element, leading space characters, but not embedded or trailing
space characters, are written with a preceding \
character. The key and element characters #,
!, =, and : are written
with a preceding backslash to ensure that they are properly loaded.
After the entries have been written, the output stream is flushed. The
output stream remains open after this method returns.
Parameters:
out - an output stream.
Parameters:
header - a description of the property list.
exception:
IOException - if writing this property list to the specifiedoutput stream throws an IOException.
exception:
ClassCastException - if this Properties objectcontains any keys or values that are not Strings.
exception:
NullPointerException - if out is null.
since:
1.2 |
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