java.util.Dictionary<K,V>
java.util.Hashtable<Object,Object>
java.util.Properties
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JavaTM 2 Platform Standard Ed. 5.0 |
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java.lang.Object
public class Properties
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.
The load and store methods load and store
properties in a simple line-oriented format specified below. This format
uses the 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.
The loadFromXML(InputStream) and storeToXML(OutputStream, String, String) methods load and store properties
in a simple XML format. By default the UTF-8 character encoding is used,
however a specific encoding may be specified if required. An XML properties
document has the following DOCTYPE declaration:
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">Note that the system URI (http://java.sun.com/dtd/properties.dtd) is not accessed when exporting or importing properties; it merely serves as a string to uniquely identify the DTD, which is:
<?xml version="1.0" encoding="UTF-8"?>
<!-- DTD for properties -->
<!ELEMENT properties ( comment?, entry* ) >
<!ATTLIST properties version CDATA #FIXED "1.0">
<!ELEMENT comment (#PCDATA) >
<!ELEMENT entry (#PCDATA) >
<!ATTLIST entry key CDATA #REQUIRED>
| Field Summary | |
|---|---|
protected Properties |
defaults
A property list that contains default values for any keys not found in this property list. |
| Constructor Summary | |
|---|---|
Properties()
Creates an empty property list with no default values. |
|
Properties(Properties defaults)
Creates an empty property list with the specified defaults. |
|
| Method Summary | |
|---|---|
String |
getProperty(String key)
Searches for the property with the specified key in this property list. |
String |
getProperty(String key,
String defaultValue)
Searches for the property with the specified key in this property list. |
void |
list(PrintStream out)
Prints this property list out to the specified output stream. |
void |
list(PrintWriter out)
Prints this property list out to the specified output stream. |
void |
load(InputStream inStream)
Reads a property list (key and element pairs) from the input stream. |
void |
loadFromXML(InputStream in)
Loads all of the properties represented by the XML document on the specified input stream into this properties table. |
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. |
void |
save(OutputStream out,
String comments)
Deprecated. This method does not throw an IOException if an I/O error occurs while saving the property list. The preferred way to save a properties list is via the store(OutputStream out,
String comments) method or the
storeToXML(OutputStream os, String comment) method. |
Object |
setProperty(String key,
String value)
Calls the Hashtable method put. |
void |
store(OutputStream out,
String comments)
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
load method. |
void |
storeToXML(OutputStream os,
String comment)
Emits an XML document representing all of the properties contained in this table. |
void |
storeToXML(OutputStream os,
String comment,
String encoding)
Emits an XML document representing all of the properties contained in this table, using the specified encoding. |
| Methods inherited from class java.util.Hashtable |
|---|
clear, clone, contains, containsKey, containsValue, elements, entrySet, equals, get, hashCode, isEmpty, keys, keySet, put, putAll, rehash, remove, size, toString, values |
| Methods inherited from class java.lang.Object |
|---|
finalize, getClass, notify, notifyAll, wait, wait, wait |
| Field Detail |
|---|
protected Properties defaults
| Constructor Detail |
|---|
public Properties()
public Properties(Properties defaults)
defaults - the defaults.| Method Detail |
|---|
public Object setProperty(String key,
String value)
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.
key - the key to be placed into this property list.value - the value corresponding to key.
null if it did not have one.getProperty(java.lang.String)
public void load(InputStream inStream)
throws IOException
\b does not
represent a backspace 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'.
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 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:
cheesesspecifies that the key is
"cheeses" and the associated
element is the empty string "".
inStream - the input stream.
IOException - if an error occurred when reading from the
input stream.
IllegalArgumentException - if the input stream contains a
malformed Unicode escape sequence.
@Deprecated
public void save(OutputStream out,
String comments)
store(OutputStream out,
String comments) method or the
storeToXML(OutputStream os, String comment) method.
store(OutputStream out, String comments) method
and suppresses IOExceptions that were thrown.
out - an output stream.comments - a description of the property list.
ClassCastException - if this Properties object
contains any keys or values that are not
Strings.
public void store(OutputStream out,
String comments)
throws IOException
Properties table to the output stream in a format suitable
for loading into a Properties table using the
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 comments argument is not null, then an ASCII #
character, the comments string, and a line separator are first written
to the output stream. Thus, the comments 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.
out - an output stream.comments - a description of the property list.
IOException - if writing this property list to the specified
output stream throws an IOException.
ClassCastException - if this Properties object
contains any keys or values that are not Strings.
NullPointerException - if out is null.
public void loadFromXML(InputStream in)
throws IOException,
InvalidPropertiesFormatException
The XML document must have the following DOCTYPE declaration:
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">Furthermore, the document must satisfy the properties DTD described above.
The specified stream remains open after this method returns.
in - the input stream from which to read the XML document.
IOException - if reading from the specified input stream
results in an IOException.
InvalidPropertiesFormatException - Data on input stream does not
constitute a valid XML document with the mandated document type.
NullPointerException - if in is null.storeToXML(OutputStream, String, String)
public void storeToXML(OutputStream os,
String comment)
throws IOException
An invocation of this method of the form props.storeToXML(os, comment) behaves in exactly the same way as the invocation props.storeToXML(os, comment, "UTF-8");.
os - the output stream on which to emit the XML document.comment - a description of the property list, or null
if no comment is desired.
IOException - if writing to the specified output stream
results in an IOException.
NullPointerException - if os is null.loadFromXML(InputStream)
public void storeToXML(OutputStream os,
String comment,
String encoding)
throws IOException
The XML document will have the following DOCTYPE declaration:
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
If the specified comment is null then no comment
will be stored in the document.
The specified stream remains open after this method returns.
os - the output stream on which to emit the XML document.comment - a description of the property list, or null
if no comment is desired.
IOException - if writing to the specified output stream
results in an IOException.
NullPointerException - if os is null,
or if encoding is null.loadFromXML(InputStream)public String getProperty(String key)
null if the property is not found.
key - the property key.
setProperty(java.lang.String, java.lang.String),
defaults
public String getProperty(String key,
String defaultValue)
key - the hashtable key.defaultValue - a default value.
setProperty(java.lang.String, java.lang.String),
defaultspublic Enumeration<?> propertyNames()
Enumeration,
defaultspublic void list(PrintStream out)
out - an output stream.public void list(PrintWriter out)
out - an output stream.
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JavaTM 2 Platform Standard Ed. 5.0 |
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Copyright 2004 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy.