更新或添加properties文件（保留存在的properties文件的原有格式）

轉載： http://www.javashuo.com/article/p-yssudkeh-a.html

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.Writer;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

/**
 * 擴展properties工具類
 * 
 * @author tangming
 * @date 2017-11-10
 */
public class SafeProperties {

    /**
     * 內部屬性表
     */
    private final Properties props;

    /**
     * 保存key與comment的映射， 同時利用這個映射來保證key的順序。
     */
    private final LinkedHashMap<String, String> keyCommentMap = new LinkedHashMap<String, String>();

    private static final String BLANK = "";

    public SafeProperties() {
        super();
        props = new Properties();
    }

    public SafeProperties(Properties defaults) {
        super();
        props = new Properties(defaults);
    }

    /**
     * 設置一個屬性，若是key已經存在，那麼將其對應value值覆蓋。
     * 
     * @param key
     * @param value
     * @return
     */
    public String setProperty(String key, String value) {
        return setProperty(key, value, BLANK);
    }

    /**
     * 設置一個屬性，若是key已經存在，那麼將其對應value值覆蓋。
     * 
     * @param key 鍵
     * @param value 與鍵對應的值
     * @param comment 對鍵值對的說明
     * @return
     */
    public synchronized String setProperty(String key, String value, String comment) {
        Object oldValue = props.setProperty(key, value);
        if (BLANK.equals(comment)) {
            if (!keyCommentMap.containsKey(key)) {
                keyCommentMap.put(key, comment);
            }
        } else {
            keyCommentMap.put(key, comment);
        }
        return (String) oldValue;
    }

    /**
     * 根據key獲取屬性表中相應的value。
     * 
     * @param key
     * @return
     */
    public String getProperty(String key) {
        return props.getProperty(key);
    }

    /**
     * 根據key獲取屬性表中相應的value。 若是沒找到相應的value，返回defaultValue。
     * 
     * @param key
     * @param defaultValue
     * @return
     */
    public String getProperty(String key, String defaultValue) {
        return props.getProperty(key, defaultValue);
    }

    /**
     * 從一個字符流中讀取屬性到屬性表中
     * 
     * @param reader
     * @throws IOException
     */
    public synchronized void load(Reader reader) throws IOException {
        load0(new LineReader(reader));
    }

    /**
     * 從一個字節流中讀取屬性到屬性表中
     * 
     * @param inStream
     * @throws IOException
     */
    public synchronized void load(InputStream inStream) throws IOException {
        load0(new LineReader(inStream));
    }

    /**
     * 從一個字節流中讀取屬性到屬性表中
     * 
     * @param inStream
     * @param charset
     * @throws IOException
     */
    public synchronized void load(InputStream inStream, String charset) throws IOException {
        InputStreamReader reader = new InputStreamReader(inStream, charset);
        load0(new LineReader(reader));
    }

    /**
     * 從一個文件中讀取屬性到屬性表中
     * 
     * @param file 屬性文件
     * @param charset 字符集
     * @throws IOException
     */
    public synchronized void load(File file, String charset) throws IOException {
        FileInputStream inputStream = new FileInputStream(file);
        InputStreamReader reader = new InputStreamReader(inputStream, charset);
        load0(new LineReader(reader));
    }

    /**
     * 從一個文件中讀取屬性到屬性表中 默認字符集爲utf-8
     * 
     * @param file 屬性文件
     * @throws IOException
     */
    public synchronized void load(File file) throws IOException {
        FileInputStream inputStream = new FileInputStream(file);
        InputStreamReader reader = new InputStreamReader(inputStream, "utf-8");
        load0(new LineReader(reader));
    }

    /**
     * 將屬性表中的屬性寫到字符流裏面。
     * 
     * @param writer
     * @throws IOException
     */
    public void store(Writer writer) throws IOException {
        store0((writer instanceof BufferedWriter) ? (BufferedWriter) writer : new BufferedWriter(writer), false);
    }

    /**
     * 將屬性表中的屬性寫到字節流裏面。
     * 
     * @param out
     * @throws IOException
     */
    public void store(OutputStream out) throws IOException {
        store0(new BufferedWriter(new OutputStreamWriter(out, "utf-8")), true);
    }

    /**
     * 若是屬性表中某個key對應的value值和參數value相同 那麼返回true，不然返回false。
     * 
     * @param value
     * @return
     */
    public boolean containsValue(String value) {
        return props.containsValue(value);
    }

    /**
     * 若是屬性表中存在參數key，返回true，不然返回false。
     * 
     * @param key
     * @return
     */
    public boolean containsKey(String key) {
        return props.containsKey(key);
    }

    /**
     * 獲取屬性表中鍵值對數量
     * 
     * @return
     */
    public int size() {
        return props.size();
    }

    /**
     * 檢查屬性表是否爲空
     * 
     * @return
     */
    public boolean isEmpty() {
        return props.isEmpty();
    }

    /**
     * 清空屬性表
     */
    public synchronized void clear() {
        props.clear();
        keyCommentMap.clear();
    }

    /**
     * 獲取屬性表中全部key的集合。
     * 
     * @return
     */
    public Set<String> propertyNames() {
        return props.stringPropertyNames();
    }

    public synchronized String toString() {
        StringBuffer buffer = new StringBuffer();
        Iterator<Map.Entry<String, String>> kvIter = keyCommentMap.entrySet().iterator();
        buffer.append("[");
        while (kvIter.hasNext()) {
            buffer.append("{");
            Map.Entry<String, String> entry = kvIter.next();
            String key = entry.getKey();
            String val = getProperty(key);
            String comment = entry.getValue();
            buffer.append("key=" + key + ",value=" + val + ",comment=" + comment);
            buffer.append("}");
        }
        buffer.append("]");
        return buffer.toString();
    }

    public boolean equals(Object o) {
        // 不考慮註釋說明是否相同
        return props.equals(o);
    }

    public int hashCode() {
        return props.hashCode();
    }

    private void load0(LineReader lr) throws IOException {
        char[] convtBuf = new char[1024];
        int limit;
        int keyLen;
        int valueStart;
        char c;
        boolean hasSep;
        boolean precedingBackslash;
        StringBuffer buffer = new StringBuffer();

        while ((limit = lr.readLine()) >= 0) {
            c = 0;
            keyLen = 0;
            valueStart = limit;
            hasSep = false;
            // 獲取註釋
            c = lr.lineBuf[keyLen];
            if (c == '#' || c == '!') {
                String comment = loadConvert(lr.lineBuf, 1, limit - 1, convtBuf);
                if (buffer.length() > 0) {
                    buffer.append("\n");
                }
                buffer.append(comment);
                continue;
            }
            precedingBackslash = false;
            while (keyLen < limit) {
                c = lr.lineBuf[keyLen];
                // need check if escaped.
                if ((c == '=' || c == ':') && !precedingBackslash) {
                    valueStart = keyLen + 1;
                    hasSep = true;
                    break;
                } else if ((c == ' ' || c == '\t' || c == '\f') && !precedingBackslash) {
                    valueStart = keyLen + 1;
                    break;
                }
                if (c == '\\') {
                    precedingBackslash = !precedingBackslash;
                } else {
                    precedingBackslash = false;
                }
                keyLen++;
            }
            while (valueStart < limit) {
                c = lr.lineBuf[valueStart];
                if (c != ' ' && c != '\t' && c != '\f') {
                    if (!hasSep && (c == '=' || c == ':')) {
                        hasSep = true;
                    } else {
                        break;
                    }
                }
                valueStart++;
            }
            String key = loadConvert(lr.lineBuf, 0, keyLen, convtBuf);
            String value = loadConvert(lr.lineBuf, valueStart, limit - valueStart, convtBuf);
            setProperty(key, value, buffer.toString());
            // reset buffer
            buffer = new StringBuffer();
        }
    }

    /*
     * 基於java.util.Properties.LineReader進行改造
     * 
     * Read in a "logical line" from an InputStream/Reader, skip all comment and blank lines and filter out those leading whitespace characters ( , and ) from the beginning of a "natural line". Method
     * returns the char length of the "logical line" and stores the line in "lineBuf".
     */
    class LineReader {
        public LineReader(InputStream inStream) {
            this.inStream = inStream;
            inByteBuf = new byte[8192];
        }

        public LineReader(Reader reader) {
            this.reader = reader;
            inCharBuf = new char[8192];
        }

        byte[] inByteBuf;
        char[] inCharBuf;
        char[] lineBuf = new char[1024];
        int inLimit = 0;
        int inOff = 0;
        InputStream inStream;
        Reader reader;

        int readLine() throws IOException {
            int len = 0;
            char c = 0;

            boolean skipWhiteSpace = true;
            boolean isNewLine = true;
            boolean appendedLineBegin = false;
            boolean precedingBackslash = false;
            boolean skipLF = false;

            while (true) {
                if (inOff >= inLimit) {
                    inLimit = (inStream == null) ? reader.read(inCharBuf) : inStream.read(inByteBuf);
                    inOff = 0;
                    if (inLimit <= 0) {
                        if (len == 0) {
                            return -1;
                        }
                        return len;
                    }
                }
                if (inStream != null) {
                    // The line below is equivalent to calling a
                    // ISO8859-1 decoder.
                    c = (char) (0xff & inByteBuf[inOff++]);
                } else {
                    c = inCharBuf[inOff++];
                }
                if (skipLF) {
                    skipLF = false;
                    if (c == '\n') {
                        continue;
                    }
                }
                if (skipWhiteSpace) {
                    if (c == ' ' || c == '\t' || c == '\f') {
                        continue;
                    }
                    if (!appendedLineBegin && (c == '\r' || c == '\n')) {
                        continue;
                    }
                    skipWhiteSpace = false;
                    appendedLineBegin = false;
                }
                if (isNewLine) {
                    isNewLine = false;
                }

                if (c != '\n' && c != '\r') {
                    lineBuf[len++] = c;
                    if (len == lineBuf.length) {
                        int newLength = lineBuf.length * 2;
                        if (newLength < 0) {
                            newLength = Integer.MAX_VALUE;
                        }
                        char[] buf = new char[newLength];
                        System.arraycopy(lineBuf, 0, buf, 0, lineBuf.length);
                        lineBuf = buf;
                    }
                    // flip the preceding backslash flag
                    if (c == '\\') {
                        precedingBackslash = !precedingBackslash;
                    } else {
                        precedingBackslash = false;
                    }
                } else {
                    // reached EOL
                    if (len == 0) {
                        isNewLine = true;
                        skipWhiteSpace = true;
                        len = 0;
                        continue;
                    }
                    if (inOff >= inLimit) {
                        inLimit = (inStream == null) ? reader.read(inCharBuf) : inStream.read(inByteBuf);
                        inOff = 0;
                        if (inLimit <= 0) {
                            return len;
                        }
                    }
                    if (precedingBackslash) {
                        len -= 1;
                        // skip the leading whitespace characters in following line
                        skipWhiteSpace = true;
                        appendedLineBegin = true;
                        precedingBackslash = false;
                        if (c == '\r') {
                            skipLF = true;
                        }
                    } else {
                        return len;
                    }
                }
            }
        }
    }

    /*
     * Converts encoded &#92;uxxxx to unicode chars and changes special saved chars to their original forms
     */
    private String loadConvert(char[] in, int off, int len, char[] convtBuf) {
        if (convtBuf.length < len) {
            int newLen = len * 2;
            if (newLen < 0) {
                newLen = Integer.MAX_VALUE;
            }
            convtBuf = new char[newLen];
        }
        char aChar;
        char[] out = convtBuf;
        int outLen = 0;
        int end = off + len;

        while (off < end) {
            aChar = in[off++];
            if (aChar == '\\') {
                aChar = in[off++];
                if (aChar == 'u') {
                    // Read the xxxx
                    int value = 0;
                    for (int i = 0; i < 4; i++) {
                        aChar = in[off++];
                        switch (aChar) {
                        case '0':
                        case '1':
                        case '2':
                        case '3':
                        case '4':
                        case '5':
                        case '6':
                        case '7':
                        case '8':
                        case '9':
                            value = (value << 4) + aChar - '0';
                            break;
                        case 'a':
                        case 'b':
                        case 'c':
                        case 'd':
                        case 'e':
                        case 'f':
                            value = (value << 4) + 10 + aChar - 'a';
                            break;
                        case 'A':
                        case 'B':
                        case 'C':
                        case 'D':
                        case 'E':
                        case 'F':
                            value = (value << 4) + 10 + aChar - 'A';
                            break;
                        default:
                            throw new IllegalArgumentException("Malformed \\uxxxx encoding.");
                        }
                    }
                    out[outLen++] = (char) value;
                } else {
                    if (aChar == 't')
                        aChar = '\t';
                    else if (aChar == 'r')
                        aChar = '\r';
                    else if (aChar == 'n')
                        aChar = '\n';
                    else if (aChar == 'f')
                        aChar = '\f';
                    out[outLen++] = aChar;
                }
            } else {
                out[outLen++] = (char) aChar;
            }
        }
        return new String(out, 0, outLen);
    }

    private void store0(BufferedWriter bw, boolean escUnicode) throws IOException {
        synchronized (this) {
            Iterator<Map.Entry<String, String>> kvIter = keyCommentMap.entrySet().iterator();
            while (kvIter.hasNext()) {
                Map.Entry<String, String> entry = kvIter.next();
                String key = entry.getKey();
                String val = getProperty(key);
                String comment = entry.getValue();
                key = saveConvert(key, true, escUnicode);
                /*
                 * No need to escape embedded and trailing spaces for value, hence pass false to flag.
                 */
                val = saveConvert(val, false, escUnicode);
                if (!comment.equals(BLANK))
                    writeComments(bw, comment);
                bw.write(key + "=" + val);
                bw.newLine();
            }
        }
        bw.flush();
    }

    private static void writeComments(BufferedWriter bw, String comments) throws IOException {
        bw.write("#");
        int len = comments.length();
        int current = 0;
        int last = 0;
        while (current < len) {
            char c = comments.charAt(current);
            if (c > '\u00ff' || c == '\n' || c == '\r') {
                if (last != current)
                    bw.write(comments.substring(last, current));
                if (c > '\u00ff') {
                    bw.write(c);
                } else {
                    bw.newLine();
                    if (c == '\r' && current != len - 1 && comments.charAt(current + 1) == '\n') {
                        current++;
                    }
                    if (current == len - 1
                            || (comments.charAt(current + 1) != '#' && comments.charAt(current + 1) != '!'))
                        bw.write("#");
                }
                last = current + 1;
            }
            current++;
        }
        if (last != current)
            bw.write(comments.substring(last, current));
        bw.newLine();
    }

    /*
     * Converts unicodes to encoded &#92;uxxxx and escapes special characters with a preceding slash
     */
    private String saveConvert(String theString, boolean escapeSpace, boolean escapeUnicode) {
        int len = theString.length();
        int bufLen = len * 2;
        if (bufLen < 0) {
            bufLen = Integer.MAX_VALUE;
        }
        StringBuffer outBuffer = new StringBuffer(bufLen);

        for (int x = 0; x < len; x++) {
            char aChar = theString.charAt(x);
            // Handle common case first, selecting largest block that
            // avoids the specials below
            if ((aChar > 61) && (aChar < 127)) {
                if (aChar == '\\') {
                    outBuffer.append('\\');
                    outBuffer.append('\\');
                    continue;
                }
                outBuffer.append(aChar);
                continue;
            }
            switch (aChar) {
            case ' ':
                if (x == 0 || escapeSpace)
                    outBuffer.append('\\');
                outBuffer.append(' ');
                break;
            case '\t':
                outBuffer.append('\\');
                outBuffer.append('t');
                break;
            case '\n':
                outBuffer.append('\\');
                outBuffer.append('n');
                break;
            case '\r':
                outBuffer.append('\\');
                outBuffer.append('r');
                break;
            case '\f':
                outBuffer.append('\\');
                outBuffer.append('f');
                break;
            case '=': // Fall through
            case ':': // Fall through
            case '#': // Fall through
            case '!':
                outBuffer.append('\\');
                outBuffer.append(aChar);
                break;
            default:
                if (((aChar < 0x0020) || (aChar > 0x007e)) & escapeUnicode) {
                    outBuffer.append('\\');
                    outBuffer.append('u');
                    outBuffer.append(toHex((aChar >> 12) & 0xF));
                    outBuffer.append(toHex((aChar >> 8) & 0xF));
                    outBuffer.append(toHex((aChar >> 4) & 0xF));
                    outBuffer.append(toHex(aChar & 0xF));
                } else {
                    outBuffer.append(aChar);
                }
            }
        }
        return outBuffer.toString();
    }

    /**
     * Convert a nibble to a hex character
     * 
     * @param nibble the nibble to convert.
     */
    private static char toHex(int nibble) {
        return hexDigit[(nibble & 0xF)];
    }

    /** A table of hex digits */
    private static final char[] hexDigit = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E',
            'F' };

}

測試：

package main.java;


import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class PropertiesGen {

    
    public static void main(String[] args) {
        updateProperties("askd.iu.er", "12336");
    }
    
    public static void updateProperties(String keyname,String keyvalue) {   
        try {
            //Properties props = new Properties();
            SafeProperties props = new SafeProperties();
            props.load(new FileInputStream("D:/test/cd.properties"));   
          
            OutputStream fos = new FileOutputStream("D:/test/cd.properties");              
            props.setProperty(keyname, keyvalue);   
            props.store(fos);  
        } catch (IOException e) {
            System.err.println("屬性文件更新錯誤");   
        }   
    }   
    
}