由于MIDP没有J2SE对应的java.net.URLEncoder类，因此，要向服务器发送HTTP请求，必须自己进行URL编码，参考JDK1.4.2的src代码，将其改为一个能用在MIDP环境中的URLEncoder类，源码如下：

package com.liaoxuefeng.javame.util;

import java.io.*;

/**
 * Encode url, just like java.net.URLEncoder.encode() in J2SE.
 * NOTE: This class is modified from java.net.URLEncoder class in J2SE 1.4.
 */
public class URLEncoder {

    private static final int MAX_BYTES_PER_CHAR = 10; // rather arbitrary limit, but safe for now

    private static boolean[] dontNeedEncoding;
    private static final int caseDiff = ('a' - 'A');

    static {
        dontNeedEncoding = new boolean[256];
        for (int i='a'; i<='z'; i++) {
            dontNeedEncoding[i] = true;
        }
        for (int i='A'; i<='Z'; i++) {
            dontNeedEncoding[i] = true;
        }
        for (int i='0'; i<='9'; i++) {
            dontNeedEncoding[i] = true;
        }
        dontNeedEncoding[' '] = true;
        dontNeedEncoding['-'] = true;
        dontNeedEncoding['_'] = true;
        dontNeedEncoding['.'] = true;
        dontNeedEncoding['*'] = true;
    }

    private URLEncoder() {}

    public static String encode(String s) {
        boolean wroteUnencodedChar = false;
        StringBuffer out = new StringBuffer(s.length());
        ByteArrayOutputStream buf = new ByteArrayOutputStream(MAX_BYTES_PER_CHAR);
        OutputStreamWriter writer = new OutputStreamWriter(buf);

        for (int i = 0; i < s.length(); i++) {
            int c = (int) s.charAt(i);
            if (c<256 && dontNeedEncoding[c]) {
                out.append((char) (c==' ' ? '+' : c));
                wroteUnencodedChar = true;
            } else {
                // convert to external encoding before hex conversion
                try {
                    if (wroteUnencodedChar) {
                        writer = new OutputStreamWriter(buf);
                        wroteUnencodedChar = false;
                    }
                    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) {
                        if ((i + 1) < s.length()) {
                            int d = (int) s.charAt(i + 1);
                            if (d >= 0xDC00 && d <= 0xDFFF) {
                                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 = toHex((ba[j] >> 4) & 0xF);
                    // converting to use uppercase letter as part of
                    // the hex value if ch is a letter.
                    if (isLetter(ch)) {
                        ch -= caseDiff;
                    }
                    out.append(ch);
                    ch = toHex(ba[j] & 0xF);
                    if (isLetter(ch)) {
                        ch -= caseDiff;
                    }
                    out.append(ch);
                }
                buf.reset();
            }
        }
        return out.toString();
    }

    private static char toHex(int digit) {
        if ((digit >= 16) || (digit < 0)) {
            return '\0';
        }
        if (digit < 10) {
            return (char)('0' + digit);
        }
        return (char)('a' - 10 + digit);
    }

    private static boolean isLetter(char c) {
        return (c>='a' && c<='z');
    }
}

J2SE的URLEncoder依赖于java.lang.Character的许多特性，将其全部剔除并改造为基本运算，即可在J2ME MIDP环境中使用，中文测试也一切正常。