Java ME平台中的URLEncoder实现类
2007-12-23 12:25:20 来源：WEB开发网这个类是从java.net.URLEncoder修改来的 经测试能够正常完成URL编码的工作，在几部手机上测试过。使用的时候直接调用URLEncoder.encode("中国")即可 如果向服务器端发送。可以使用如下的办法对中文进行编码，然后发送向服务器。
String data = "para="+URLEncoder.encode("参数");
outputStream.write(data.getBytes());
.......
在服务器端 以servlet为例 request.getParameter("para")即可获得“参数”
package com.j2medev.httpme.tools;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
/**
* Utility class for form encoding.this class is modified form java.net.URLEncoder so that it can work well in cldc env.
* This class contains static methods
* for converting a String to the <CODE>application/x-www-form-urlencoded</CODE> MIME
* format. For more information about Html form encoding, consult the HTML
* <A HREF="http://www.w3.org/TR/html4/">specification</A>.
*
* <p>
* When encoding a String, the following rules apply:
*
* <p>
* <ul>
* <li>The alphanumeric characters "<code>a</code>" through
* "<code>z</code>", "<code>A</code>" through
* "<code>Z</code>" and "<code>0</code>"
* through "<code>9</code>" remain the same.
* <li>The special characters "<code>.</code>",
* "<code>-</code>", "<code>*</code>", and
* "<code>_</code>" remain the same.
* <li>The space character "<code> </code>" is
* converted into a plus sign "<code>+</code>".
* <li>All other characters are unsafe and are first converted into
* one or more bytes using some encoding scheme. Then each byte is
* rePResented by the 3-character string
* "<code>%<i>xy</i></code>", where <i>xy</i> is the
* two-digit hexadecimal representation of the byte.
* The recommended encoding scheme to use is UTF-8. However,
* for compatibility reasons, if an encoding is not specified,
* then the default encoding of the platform is used.
* </ul>
*
* <p>
* For example using UTF-8 as the encoding scheme the string "The
* string ü@foo-bar" would get converted to
* "The+string+%C3%BC%40foo-bar" because in UTF-8 the character
* ü is encoded as two bytes C3 (hex) and BC (hex), and the
* character @ is encoded as one byte 40 (hex).
*
* @author mingjava
* @version 0.1 05/06/2006
* @since httpme 0.1
*/
public class URLEncoder {
/** The characters which do not need to be encoded. */
private static boolean[] dontNeedEncoding;
private static String defaultEncName = "";
static final int caseDiff = ('a' - 'A');
static {
dontNeedEncoding = new boolean[256];
int i;
for (i = 'a'; i <= 'z'; i++) {
dontNeedEncoding[i] = true;
}
for (i = 'A'; i <= 'Z'; i++) {
dontNeedEncoding[i] = true;
}
for (i = '0'; i <= '9'; i++) {
dontNeedEncoding[i] = true;
}
dontNeedEncoding[' '] = true; // encoding a space to a + is done in the encode() method
dontNeedEncoding['-'] = true;
dontNeedEncoding['_'] = true;
dontNeedEncoding['.'] = true;
dontNeedEncoding['*'] = true;
defaultEncName = System.getProperty("microedition.encoding");
if(defaultEncName == null defaultEncName.trim().length() == 0){
defaultEncName = "UTF-8";
}
}
public static final int MIN_RADIX = 2;
/**
* The maximum radix available for conversion to and from strings.
*/
public static final int MAX_RADIX = 36;
/**
* The class is not meant to be instantiated.
*/
private URLEncoder() { }
/**
* Translates a string into "<CODE>x-www-form-urlencoded</CODE>"
* format.This method uses the platform's default encoding
* as the encoding scheme to oBTain the bytes for unsafe characters.
*
* @param s the string to be translated.
*
* @return The resulting string.
*/
public static String encode(String s) {
String str = null;
str = encode(s, defaultEncName);
return str;
}
/**
* Translates a string into <code>application/x-www-form-urlencoded</code>
* format using a specific encoding scheme. This method uses the
* supplied encoding scheme to obtain the bytes for unsafe
* characters.
* <p>
* <em><strong>Note:</strong> The <a href=
* "http://www.w3.org/TR/html40/appendix/notes.html#non-ascii-chars">
* World Wide Web Consortium Recommendation</a> states that
* UTF-8 should be used. Not doing so may introdUCe
* incompatibilites.</em>
*
* @param s <code>String</code> to be translated.
* @param enc The name of a supported character encoding such as UTF-8
* @return the translated <code>String</code>.
*/
public static String encode(String s, String enc) {
boolean needToChange = false;
boolean wroteUnencodedChar = false;
int maxBytesPerChar = 10; // rather arbitrary limit, but safe for now
StringBuffer out = new StringBuffer(s.length());
ByteArrayOutputStream buf = new ByteArrayOutputStream(maxBytesPerChar);
OutputStreamWriter writer = null;
try {
writer = new OutputStreamWriter(buf, enc);
} catch (UnsupportedEncodingException ex) {
try {
writer = new OutputStreamWriter(buf,defaultEncName);
} catch (UnsupportedEncodingException e) {
//never reach
}
}
for (int i = 0; i < s.length(); i++) {
int c = (int) s.charAt(i);
//System.out.println("Examining character: " + c);
if (c <256 && dontNeedEncoding[c]) {
if (c == ' ') {
c = '+';
needToChange = true;
}
//System.out.println("Storing: " + c);
out.append((char)c);
wroteUnencodedChar = true;
} else {
// convert to external encoding before hex conversion
try {
if (wroteUnencodedChar) { // Fix for 4407610
writer = new OutputStreamWriter(buf, enc);
wroteUnencodedChar = false;
}
if(writer !
= null)
writer.write(c);
/*
* If this character represents the start of a Unicode
* surrogate pair, then pass in two characters. It's not
* clear what should be done if a bytes reserved in the
* surrogate pairs range occurs outside of a legal
* surrogate pair. For now, just treat it as if it were
* any other character.
*/
if (c >= 0xD800 && c <= 0xDBFF) {
/*
System.out.println(Integer.toHexString(c)
+ " is high surrogate");
*/
if ( (i+1) < s.length()) {
int d = (int) s.charAt(i+1);
/*
System.out.println("\tExamining "
+ Integer.toHexString(d));
*/
if (d >= 0xDC00 && d <= 0xDFFF) {
/*
System.out.println("\t"
+ Integer.toHexString(d)
+ " is low surrogate");
*/
writer.write(d);
i++;
}
}
}
writer.flush();
} catch(IOException e) {
buf.reset();
continue;
}
byte[] ba = buf.toByteArray();
for (int j = 0; j < ba.length; j++) {
out.append('%');
char ch = forDigit((ba[j] >> 4) & 0xF, 16);
if (isLetter(ch)) {
ch -= caseDiff;
}
out.append(ch);
ch = forDigit((ba[j] & 0xF), 16);
//ch = forDigit(ba[j] & 0xF, 16);
if (isLetter(ch)) {
ch -= caseDiff;
}
out.append(ch);
}
buf.reset();
needToChange = true;
}
}
return (needToChange?
out.toString() : s);
}
private static boolean isLetter(char c){
if( (c >= 'a' && c <= 'z') (c >='A' && c <= 'Z'))
return true;
return false;
}
private static char forDigit(int digit,int radix){
if ((digit >= radix) (digit < 0)) {
return '\0'; }
if ((radix < MIN_RADIX) (radix > MAX_RADIX)) {
return '\0';
}
if (digit < 10) {
return (char)('0' + digit);
}
return (char)('a' - 10 + digit);
}
}
（出处：http://www.cncms.com）
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