プロパティを使用して Java の構成ファイルを変更しようとしています。
Properties.store、load、および setProperty を使用して行を正常に読み取り、書き込み、および変更しましたが、そのような操作を行った後、ファイルが上書きされ、キーと値のペアではない構成ファイルのすべての行が失われていることに気付きました。つまり、コメントを失います。
java.util を使用してそのような行を保持する方法はありますか?
各行にプレフィックスを配置しても問題ありません。行ごとに「手動で」読み取る方法を知っています。私は代わりに代わりを求めています
私はそれが可能だとは思わない。また、プロパティは、load() から store() へ、またはある store() から別の store() への順序が同じであることを保証しないことに注意してください。可能であれば、Properties の javadoc でその方法が説明されています。
import java.io.*;
import java.util.*;
/**
* The CommentedProperties class is an extension of java.util.Properties
* to allow retention of comment lines and blank (whitespace only) lines
* in the properties file.
*
* Written for Java version 1.4
*/
public class CommentedProperties extends java.util.Properties {
/**
* Use a Vector to keep a copy of lines that are a comment or 'blank'
*/
public Vector lineData = new Vector(0, 1);
/**
* Use a Vector to keep a copy of lines containing a key, i.e. they are a property.
*/
public Vector keyData = new Vector(0, 1);
/**
* Load properties from the specified InputStream.
* Overload the load method in Properties so we can keep comment and blank lines.
* @param inStream The InputStream to read.
*/
public void load(InputStream inStream) throws IOException
{
// The spec says that the file must be encoded using ISO-8859-1.
BufferedReader reader =
new BufferedReader(new InputStreamReader(inStream, "ISO-8859-1"));
String line;
while ((line = reader.readLine()) != null) {
char c = 0;
int pos = 0;
// Leading whitespaces must be deleted first.
while ( pos < line.length()
&& Character.isWhitespace(c = line.charAt(pos))) {
pos++;
}
// If empty line or begins with a comment character, save this line
// in lineData and save a "" in keyData.
if ( (line.length() - pos) == 0
|| line.charAt(pos) == '#' || line.charAt(pos) == '!') {
lineData.add(line);
keyData.add("");
continue;
}
// The characters up to the next Whitespace, ':', or '='
// describe the key. But look for escape sequences.
// Try to short-circuit when there is no escape char.
int start = pos;
boolean needsEscape = line.indexOf('\\', pos) != -1;
StringBuffer key = needsEscape ? new StringBuffer() : null;
while ( pos < line.length()
&& ! Character.isWhitespace(c = line.charAt(pos++))
&& c != '=' && c != ':') {
if (needsEscape && c == '\\') {
if (pos == line.length()) {
// The line continues on the next line. If there
// is no next line, just treat it as a key with an
// empty value.
line = reader.readLine();
if (line == null)
line = "";
pos = 0;
while ( pos < line.length()
&& Character.isWhitespace(c = line.charAt(pos)))
pos++;
} else {
c = line.charAt(pos++);
switch (c) {
case 'n':
key.append('\n');
break;
case 't':
key.append('\t');
break;
case 'r':
key.append('\r');
break;
case 'u':
if (pos + 4 <= line.length()) {
char uni = (char) Integer.parseInt
(line.substring(pos, pos + 4), 16);
key.append(uni);
pos += 4;
} // else throw exception?
break;
default:
key.append(c);
break;
}
}
} else if (needsEscape)
key.append(c);
}
boolean isDelim = (c == ':' || c == '=');
String keyString;
if (needsEscape)
keyString = key.toString();
else if (isDelim || Character.isWhitespace(c))
keyString = line.substring(start, pos - 1);
else
keyString = line.substring(start, pos);
while ( pos < line.length()
&& Character.isWhitespace(c = line.charAt(pos)))
pos++;
if (! isDelim && (c == ':' || c == '=')) {
pos++;
while ( pos < line.length()
&& Character.isWhitespace(c = line.charAt(pos)))
pos++;
}
// Short-circuit if no escape chars found.
if (!needsEscape) {
put(keyString, line.substring(pos));
// Save a "" in lineData and save this
// keyString in keyData.
lineData.add("");
keyData.add(keyString);
continue;
}
// Escape char found so iterate through the rest of the line.
StringBuffer element = new StringBuffer(line.length() - pos);
while (pos < line.length()) {
c = line.charAt(pos++);
if (c == '\\') {
if (pos == line.length()) {
// The line continues on the next line.
line = reader.readLine();
// We might have seen a backslash at the end of
// the file. The JDK ignores the backslash in
// this case, so we follow for compatibility.
if (line == null)
break;
pos = 0;
while ( pos < line.length()
&& Character.isWhitespace(c = line.charAt(pos)))
pos++;
element.ensureCapacity(line.length() - pos +
element.length());
} else {
c = line.charAt(pos++);
switch (c) {
case 'n':
element.append('\n');
break;
case 't':
element.append('\t');
break;
case 'r':
element.append('\r');
break;
case 'u':
if (pos + 4 <= line.length()) {
char uni = (char) Integer.parseInt
(line.substring(pos, pos + 4), 16);
element.append(uni);
pos += 4;
} // else throw exception?
break;
default:
element.append(c);
break;
}
}
} else
element.append(c);
}
put(keyString, element.toString());
// Save a "" in lineData and save this
// keyString in keyData.
lineData.add("");
keyData.add(keyString);
}
}
/**
* Write the properties to the specified OutputStream.
*
* Overloads the store method in Properties so we can put back comment
* and blank lines.
*
* @param out The OutputStream to write to.
* @param header Ignored, here for compatability w/ Properties.
*
* @exception IOException
*/
public void store(OutputStream out, String header) throws IOException
{
// The spec says that the file must be encoded using ISO-8859-1.
PrintWriter writer
= new PrintWriter(new OutputStreamWriter(out, "ISO-8859-1"));
// We ignore the header, because if we prepend a commented header
// then read it back in it is now a comment, which will be saved
// and then when we write again we would prepend Another header...
String line;
String key;
StringBuffer s = new StringBuffer ();
for (int i=0; i<lineData.size(); i++) {
line = (String) lineData.get(i);
key = (String) keyData.get(i);
if (key.length() > 0) { // This is a 'property' line, so rebuild it
formatForOutput (key, s, true);
s.append ('=');
formatForOutput ((String) get(key), s, false);
writer.println (s);
} else { // was a blank or comment line, so just restore it
writer.println (line);
}
}
writer.flush ();
}
/**
* Need this method from Properties because original code has StringBuilder,
* which is an element of Java 1.5, used StringBuffer instead (because
* this code was written for Java 1.4)
*
* @param str - the string to format
* @param buffer - buffer to hold the string
* @param key - true if str the key is formatted, false if the value is formatted
*/
private void formatForOutput(String str, StringBuffer buffer, boolean key)
{
if (key) {
buffer.setLength(0);
buffer.ensureCapacity(str.length());
} else
buffer.ensureCapacity(buffer.length() + str.length());
boolean head = true;
int size = str.length();
for (int i = 0; i < size; i++) {
char c = str.charAt(i);
switch (c) {
case '\n':
buffer.append("\\n");
break;
case '\r':
buffer.append("\\r");
break;
case '\t':
buffer.append("\\t");
break;
case ' ':
buffer.append(head ? "\\ " : " ");
break;
case '\\':
case '!':
case '#':
case '=':
case ':':
buffer.append('\\').append(c);
break;
default:
if (c < ' ' || c > '~') {
String hex = Integer.toHexString(c);
buffer.append("\\u0000".substring(0, 6 - hex.length()));
buffer.append(hex);
} else
buffer.append(c);
}
if (c != ' ')
head = key;
}
}
/**
* Add a Property to the end of the CommentedProperties.
*
* @param keyString The Property key.
* @param value The value of this Property.
*/
public void add(String keyString, String value)
{
put(keyString, value);
lineData.add("");
keyData.add(keyString);
}
/**
* Add a comment or blank line or comment to the end of the CommentedProperties.
*
* @param line The string to add to the end, make sure this is a comment
* or a 'whitespace' line.
*/
public void addLine(String line)
{
lineData.add(line);
keyData.add("");
}
}