Trouble Percent-Encoding Spaces in Java

Question

I am using the URLUTF8Encoder.java class from W3C ( www.w3.org/International/URLUTF8Encoder.java ).

Currently, it will encode any blank spaces ' ' into plus signs '+'.

I am having difficulty modifying the code to percent-encode the blank space into '%20'. Unfortunately, I am not too familiar with hex. Can anyone help me out? I need to modify this snippet...

else if (ch == ' ') { // space
                sbuf.append('+');

in the following code:

final static String[] hex = { "%00", "%01", "%02", "%03", "%04", "%05",
            "%06", "%07", "%08", "%09", "%0A", "%0B", "%0C", "%0D", "%0E",
            "%0F", "%10", "%11", "%12", "%13", "%14", "%15", "%16", "%17",
            "%18", "%19", "%1A", "%1B", "%1C", "%1D", "%1E", "%1F", "%20",
            "%21", "%22", "%23", "%24", "%25", "%26", "%27", "%28", "%29",
            "%2A", "%2B", "%2C", "%2D", "%2E", "%2F", "%30", "%31", "%32",
            "%33", "%34", "%35", "%36", "%37", "%38", "%39", "%3A", "%3B",
            "%3C", "%3D", "%3E", "%3F", "%40", "%41", "%42", "%43", "%44",
            "%45", "%46", "%47", "%48", "%49", "%4A", "%4B", "%4C", "%4D",
            "%4E", "%4F", "%50", "%51", "%52", "%53", "%54", "%55", "%56",
            "%57", "%58", "%59", "%5A", "%5B", "%5C", "%5D", "%5E", "%5F",
            "%60", "%61", "%62", "%63", "%64", "%65", "%66", "%67", "%68",
            "%69", "%6A", "%6B", "%6C", "%6D", "%6E", "%6F", "%70", "%71",
            "%72", "%73", "%74", "%75", "%76", "%77", "%78", "%79", "%7A",
            "%7B", "%7C", "%7D", "%7E", "%7F", "%80", "%81", "%82", "%83",
            "%84", "%85", "%86", "%87", "%88", "%89", "%8A", "%8B", "%8C",
            "%8D", "%8E", "%8F", "%90", "%91", "%92", "%93", "%94", "%95",
            "%96", "%97", "%98", "%99", "%9A", "%9B", "%9C", "%9D", "%9E",
            "%9F", "%A0", "%A1", "%A2", "%A3", "%A4", "%A5", "%A6", "%A7",
            "%A8", "%A9", "%AA", "%AB", "%AC", "%AD", "%AE", "%AF", "%B0",
            "%B1", "%B2", "%B3", "%B4", "%B5", "%B6", "%B7", "%B8", "%B9",
            "%BA", "%BB", "%BC", "%BD", "%BE", "%BF", "%C0", "%C1", "%C2",
            "%C3", "%C4", "%C5", "%C6", "%C7", "%C8", "%C9", "%CA", "%CB",
            "%CC", "%CD", "%CE", "%CF", "%D0", "%D1", "%D2", "%D3", "%D4",
            "%D5", "%D6", "%D7", "%D8", "%D9", "%DA", "%DB", "%DC", "%DD",
            "%DE", "%DF", "%E0", "%E1", "%E2", "%E3", "%E4", "%E5", "%E6",
            "%E7", "%E8", "%E9", "%EA", "%EB", "%EC", "%ED", "%EE", "%EF",
            "%F0", "%F1", "%F2", "%F3", "%F4", "%F5", "%F6", "%F7", "%F8",
            "%F9", "%FA", "%FB", "%FC", "%FD", "%FE", "%FF" };

public static String encode(String s) {
        StringBuffer sbuf = new StringBuffer();
        int len = s.length();
        for (int i = 0; i < len; i++) {
            int ch = s.charAt(i);
            if ('A' <= ch && ch <= 'Z') { // 'A'..'Z'
                sbuf.append((char) ch);
            } else if ('a' <= ch && ch <= 'z') { // 'a'..'z'
                sbuf.append((char) ch);
            } else if ('0' <= ch && ch <= '9') { // '0'..'9'
                sbuf.append((char) ch);
            } else if (ch == ' ') { // space
                sbuf.append('+');
            } else if (ch == '-'
                    || ch == '_' // unreserved
                    || ch == '.' || ch == '!' || ch == '~' || ch == '*'
                    || ch == '\'' || ch == '(' || ch == ')') {
                sbuf.append((char) ch);
            } else if (ch <= 0x007f) { // other ASCII
                sbuf.append(hex[ch]);
            } else if (ch <= 0x07FF) { // non-ASCII <= 0x7FF
                sbuf.append(hex[0xc0 | (ch >> 6)]);
                sbuf.append(hex[0x80 | (ch & 0x3F)]);
            } else { // 0x7FF < ch <= 0xFFFF
                sbuf.append(hex[0xe0 | (ch >> 12)]);
                sbuf.append(hex[0x80 | ((ch >> 6) & 0x3F)]);
                sbuf.append(hex[0x80 | (ch & 0x3F)]);
            }
        }
        return sbuf.toString();
    }

Thanks!

Answer 1

You might want to check out Apache Common's codec package, it's probably a lot more robust : http://commons.apache.org/codec/ - The package you're using is about 14 years old and only encodes into one type of encoding (www-url-form-encoded) - which REQUIRES spaces to be encoded as '+'. If you're trying do do standard URL encoding (which wants spaces as %20), you'll need to use a different package entirely.

Answer 2

Why are you using this class instead of the API method?

java.net.URLEncoder.encode("your string", "utf-8");

And why is it a problem that spaces are encoded as + characters? That is exactly how URL safe character encoding is supposed to work.

Answer 3

I won't ask why you're doing this, and just answer your question directly. Please read other answers to determine if you really want to be modifying this code. If you just remove the code:

else if (ch == ' ') { // space
   sbuf.append('+');
} 

It will do what you want, because the space character will be taken care of by the code:

else if (ch <= 0x007f) { // other ASCII
   sbuf.append(hex[ch]);
} 

Answer 4

Just do this:

String str = "Hello World+You";
String encodedStr = URLEncoder.encode(str, "UTF-8");
encodedStr = encodedStr.replace("+", "%20");
System.out.println("Encoded String: " + encodedStr);

Answer 5

You can use the built-in java.net.URI class, which is normally used via it's static builder as URI.create("http://example.com/search?param=42") but in case when a parameter contains literal space you can use it as:

URI uri = new URI("http", // scheme
    null,                 // user authentication info
    "example.com",        // domain
    -1,                   // port (use -1 for default port 80)
    "/search",            // path
    "param=four and two", // one or more parameters
    null);                // fragment (appended with the # char)
System.out.println(uri)
// OUTPUT:
// http://example.com/search?param=four%20and%20two

If you look inside this particular URI constructor you'll see that -1 can be used to specify the default port ( 80 ); explicitly passing 80 as constructor value will create a URL like http://example.com:80/search?param=four%20and%20two which you probably do not want.

The same constructor can be used to build only the query part of the URL which you can append to an existing string:

URI uri2 = new URI(null, null, null, -1, null, "param=four and two", null);
System.out.println(uri2)
// OUTPUT:
// ?param=four%20and%20two

^{Might be worth mentioning that a URI is not the same as a URL : file:/// is a valid URI but not a valid URL.}

Answer 6

It's working correctly; it should work with + as well as it would with %20.

Maybe try java.net.URLEncoder("url", "UTF-8") ?