关于urlDecode和tomcat一些源码

1. 看下面源码，找到%号，每次加2，然后将16进制转换为int，也就是%号后两位加2得到16进制，转换为int

                   while ( ((i+) < numChars) && (c=='%')) {
                        int v = Integer.parseInt(s.substring(i+,i+),);
                        if (v < )
                            throw new IllegalArgumentException("URLDecoder: Illegal hex characters in escape (%) pattern - negative value");
                        bytes[pos++] = (byte) v;
                        i+= ;
                        if (i < numChars)
                            c = s.charAt(i);
                    }

这就是为什么url中不能有%号的原因，

2. 下面错就有可能url中有特殊字符，比如 %

Note that the name and value quoted here may be corrupted due to the failed decoding. Use debug level logging to see the original, non-corrupted values.
Note: further occurrences of Parameter errors will be logged at DEBUG level.

3. request.getParameter("Json");这个获得的是 null，urldecode之后的，因为urldecode出错了，所以会是null

4. request.getQueryString();这个得到的是，没有urldecode的，也就是原始的

二、 关于看tomcat源码的一些知识点，这是一个链接到达tomcat之后，要执行的过程，为什么要总结呢，request.getParameter("Json");中，如果Json中有特殊符号，如%，服务器会的到null，就是因为urldecode导致，看了源码什么都懂了

String an = request.getQueryString();   //获取没有被urldecode的参数值

String an = request.getParameter("Json"); //获取被urldecode解码后的参数值

1.  org.apache.catalina.connector.Connector  ，其中还有很多关于配置的在这个类中，自己看

 public Connector(String protocol) {
        setProtocol(protocol);
        // Instantiate protocol handler
        try {
            Class<?> clazz = Class.forName(protocolHandlerClassName);
            this.protocolHandler = (ProtocolHandler) clazz.newInstance();
        } catch (Exception e) {
            log.error(sm.getString(
                    "coyoteConnector.protocolHandlerInstantiationFailed"), e);
        }
    }

构造函数中  protocol  对应  server.xml  protocol="HTTP/1.1"   所以构造函数中的 protocol 值为 HTTP/1.1

<Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" maxHttpHeaderSize="1048576"/>

2. org.apache.catalina.connector.RequestFacade implements HttpServletRequest

 public String getParameter(String name) { //不是这个方法，下面那个方法

        if (request == null) {
            throw new IllegalStateException(
                            sm.getString("requestFacade.nullRequest"));
        }

        if (Globals.IS_SECURITY_ENABLED){
            return AccessController.doPrivileged(
                new GetParameterPrivilegedAction(name));
        } else {
            return request.getParameter(name);
        }
    }

 @Override
    public Map<String,String[]> getParameterMap() {//这个方法

        if (request == null) {
            throw new IllegalStateException(
                            sm.getString("requestFacade.nullRequest"));
        }

        if (Globals.IS_SECURITY_ENABLED){
            return AccessController.doPrivileged(
                new GetParameterMapPrivilegedAction());
        } else {
            return request.getParameterMap();
        }
    }

 public Map<String, String[]> getParameterMap() {

        if (parameterMap.isLocked()) {
            return parameterMap;
        }

        Enumeration<String> enumeration = getParameterNames();
        while (enumeration.hasMoreElements()) {
            String name = enumeration.nextElement();
            String[] values = getParameterValues(name);
            parameterMap.put(name, values);
        }

        parameterMap.setLocked(true);

        return parameterMap;

    }

 public Enumeration<String> getParameterNames() {

        if (!parametersParsed) {
            parseParameters();
        }

        return coyoteRequest.getParameters().getParameterNames();

    }

3. org.apache.catalina.connector.Request implements HttpServletRequest

 public String getParameter(String name) {

        if (!parametersParsed) {
            parseParameters();
        }

        return coyoteRequest.getParameters().getParameter(name);

    }

4. org.apache.catalina.connector.Request implements HttpServletRequest

protected void parseParameters() {

        parametersParsed = true;

        Parameters parameters = coyoteRequest.getParameters();
        boolean success = false;
        try {
            // Set this every time in case limit has been changed via JMX
            parameters.setLimit(getConnector().getMaxParameterCount());  //参数的数量最多为10000

            // getCharacterEncoding() may have been overridden to search for
            // hidden form field containing request encoding
            String enc = getCharacterEncoding();

            boolean useBodyEncodingForURI = connector.getUseBodyEncodingForURI();
            if (enc != null) {
                parameters.setEncoding(enc);
                if (useBodyEncodingForURI) {
                    parameters.setQueryStringEncoding(enc);
                }
            } else {
                parameters.setEncoding
                    (org.apache.coyote.Constants.DEFAULT_CHARACTER_ENCODING);
                if (useBodyEncodingForURI) {
                    parameters.setQueryStringEncoding
                        (org.apache.coyote.Constants.DEFAULT_CHARACTER_ENCODING);
                }
            }

            parameters.handleQueryParameters();

            if (usingInputStream || usingReader) {
                success = true;
                return;
            }

            if( !getConnector().isParseBodyMethod(getMethod()) ) {
                success = true;
                return;
            }

            String contentType = getContentType();
            if (contentType == null) {
                contentType = "";
            }
            int semicolon = contentType.indexOf(';');
            if (semicolon >= ) {
                contentType = contentType.substring(, semicolon).trim();
            } else {
                contentType = contentType.trim();
            }

            if ("multipart/form-data".equals(contentType)) {
                parseParts();
                success = true;
                return;
            }

            if (!("application/x-www-form-urlencoded".equals(contentType))) {
                success = true;
                return;
            }

            int len = getContentLength();

            if (len > ) {
                int maxPostSize = connector.getMaxPostSize();
                if ((maxPostSize > ) && (len > maxPostSize)) {
                    if (context.getLogger().isDebugEnabled()) {
                        context.getLogger().debug(
                                sm.getString("coyoteRequest.postTooLarge"));
                    }
                    checkSwallowInput();
                    return;
                }
                byte[] formData = null;
                if (len < CACHED_POST_LEN) {
                    if (postData == null) {
                        postData = new byte[CACHED_POST_LEN];
                    }
                    formData = postData;
                } else {
                    formData = new byte[len];
                }
                try {
                    if (readPostBody(formData, len) != len) {
                        return;
                    }
                } catch (IOException e) {
                    // Client disconnect
                    if (context.getLogger().isDebugEnabled()) {
                        context.getLogger().debug(
                                sm.getString("coyoteRequest.parseParameters"), e);
                    }
                    return;
                }
                parameters.processParameters(formData, , len);
            } else if ("chunked".equalsIgnoreCase(
                    coyoteRequest.getHeader("transfer-encoding"))) {
                byte[] formData = null;
                try {
                    formData = readChunkedPostBody();
                } catch (IOException e) {
                    // Client disconnect or chunkedPostTooLarge error
                    if (context.getLogger().isDebugEnabled()) {
                        context.getLogger().debug(
                                sm.getString("coyoteRequest.parseParameters"), e);
                    }
                    return;
                }
                if (formData != null) {
                    parameters.processParameters(formData, , formData.length);
                }
            }
            success = true;
        } finally {
            if (!success) {
                parameters.setParseFailed(true);
            }
        }

    }

5. org.apache.tomcat.util.http.Parameters  中  processParameters

  private void processParameters(byte bytes[], int start, int len,
                                  Charset charset) {

        if(log.isDebugEnabled()) {
            log.debug(sm.getString("parameters.bytes",
                    new String(bytes, start, len, DEFAULT_CHARSET)));
        }

        int decodeFailCount = ;

        int pos = start;
        int end = start + len;

        while(pos < end) {
            int nameStart = pos;
            int nameEnd = -;
            int valueStart = -;
            int valueEnd = -;

            boolean parsingName = true;
            boolean decodeName = false;
            boolean decodeValue = false;
            boolean parameterComplete = false;

            do {
                switch(bytes[pos]) {
                    case '=':
                        if (parsingName) {
                            // Name finished. Value starts from next character
                            nameEnd = pos;
                            parsingName = false;
                            valueStart = ++pos;
                        } else {
                            // Equals character in value
                            pos++;
                        }
                        break;
                    case '&':
                        if (parsingName) {
                            // Name finished. No value.
                            nameEnd = pos;
                        } else {
                            // Value finished
                            valueEnd  = pos;
                        }
                        parameterComplete = true;
                        pos++;
                        break;
                    case '%':
                    case '+':
                        // Decoding required
                        if (parsingName) {
                            decodeName = true;
                        } else {
                            decodeValue = true;
                        }
                        pos ++;
                        break;
                    default:
                        pos ++;
                        break;
                }
            } while (!parameterComplete && pos < end);

            if (pos == end) {
                if (nameEnd == -) {
                    nameEnd = pos;
                } else if (valueStart > - && valueEnd == -){
                    valueEnd = pos;
                }
            }

            if (log.isDebugEnabled() && valueStart == -) {
                log.debug(sm.getString("parameters.noequal",
                        Integer.valueOf(nameStart), Integer.valueOf(nameEnd),
                        new String(bytes, nameStart, nameEnd-nameStart,
                                DEFAULT_CHARSET)));
            }

            if (nameEnd <= nameStart ) {
                if (valueStart == -) {
                    // &&
                    if (log.isDebugEnabled()) {
                        log.debug(sm.getString("parameters.emptyChunk"));
                    }
                    // Do not flag as error
                    continue;
                }
                // &=foo&
                UserDataHelper.Mode logMode = userDataLog.getNextMode();
                if (logMode != null) {
                    String extract;
                    if (valueEnd > nameStart) {
                        extract = new String(bytes, nameStart, valueEnd
                                - nameStart, DEFAULT_CHARSET);
                    } else {
                        extract = "";
                    }
                    String message = sm.getString("parameters.invalidChunk",
                            Integer.valueOf(nameStart),
                            Integer.valueOf(valueEnd), extract);
                    switch (logMode) {
                        case INFO_THEN_DEBUG:
                            message += sm.getString("parameters.fallToDebug");
                            //$FALL-THROUGH$
                        case INFO:
                            log.info(message);
                            break;
                        case DEBUG:
                            log.debug(message);
                    }
                }
                parseFailed = true;
                continue;
                // invalid chunk - it's better to ignore
            }

            tmpName.setBytes(bytes, nameStart, nameEnd - nameStart);
            if (valueStart >= ) {
                tmpValue.setBytes(bytes, valueStart, valueEnd - valueStart);
            } else {
                tmpValue.setBytes(bytes, , );
            }

            // Take copies as if anything goes wrong originals will be
            // corrupted. This means original values can be logged.
            // For performance - only done for debug
            if (log.isDebugEnabled()) {
                try {
                    origName.append(bytes, nameStart, nameEnd - nameStart);
                    if (valueStart >= ) {
                        origValue.append(bytes, valueStart, valueEnd - valueStart);
                    } else {
                        origValue.append(bytes, , );
                    }
                } catch (IOException ioe) {
                    // Should never happen...
                    log.error(sm.getString("parameters.copyFail"), ioe);
                }
            }

            try {
                String name;
                String value;

                if (decodeName) {
                    urlDecode(tmpName);
                }
                tmpName.setCharset(charset);
                name = tmpName.toString();

                if (valueStart >= ) {
                    if (decodeValue) {
                        urlDecode(tmpValue);
                    }
                    tmpValue.setCharset(charset); //ISO-8859-1
                    value = tmpValue.toString();
                } else {
                    value = "";
                }

                try {
                    addParameter(name, value);  // 添加到参数集合中
                } catch (IllegalStateException ise) {
                    // Hitting limit stops processing further params but does
                    // not cause request to fail.
                    parseFailed = true;
                    UserDataHelper.Mode logMode = maxParamCountLog.getNextMode();
                    if (logMode != null) {
                        String message = ise.getMessage();
                        switch (logMode) {
                            case INFO_THEN_DEBUG:
                                message += sm.getString(
                                        "parameters.maxCountFail.fallToDebug");
                                //$FALL-THROUGH$
                            case INFO:
                                log.info(message);
                                break;
                            case DEBUG:
                                log.debug(message);
                        }
                    }
                    break;
                }
            } catch (IOException e) {
                parseFailed = true;
                decodeFailCount++;
                if (decodeFailCount ==  || log.isDebugEnabled()) {
                    if (log.isDebugEnabled()) {
                        log.debug(sm.getString("parameters.decodeFail.debug",
                                origName.toString(), origValue.toString()), e);
                    } else if (log.isInfoEnabled()) {
                        UserDataHelper.Mode logMode = userDataLog.getNextMode();
                        if (logMode != null) {
                            String message = sm.getString(
                                    "parameters.decodeFail.info",
                                    tmpName.toString(), tmpValue.toString());
                            switch (logMode) {
                                case INFO_THEN_DEBUG:
                                    message += sm.getString("parameters.fallToDebug");
                                    //$FALL-THROUGH$
                                case INFO:
                                    log.info(message);
                                    break;
                                case DEBUG:
                                    log.debug(message);
                            }
                        }
                    }
                }
            }

            tmpName.recycle();
            tmpValue.recycle();
            // Only recycle copies if we used them
            if (log.isDebugEnabled()) {
                origName.recycle();
                origValue.recycle();
            }
        }

        if (decodeFailCount >  && !log.isDebugEnabled()) {
            UserDataHelper.Mode logMode = userDataLog.getNextMode();
            if (logMode != null) {
                String message = sm.getString(
                        "parameters.multipleDecodingFail",
                        Integer.valueOf(decodeFailCount));
                switch (logMode) {
                    case INFO_THEN_DEBUG:
                        message += sm.getString("parameters.fallToDebug");
                        //$FALL-THROUGH$
                    case INFO:
                        log.info(message);
                        break;
                    case DEBUG:
                        log.debug(message);
                }
            }
        }
    }

6. org.apache.tomcat.util.buf.UDecoder

public final String convert(String str, boolean query)
    {
        if (str == null) {
            return  null;
        }

        if( (!query || str.indexOf( '+' ) < ) && str.indexOf( '%' ) <  ) {
            return str;
        }

        final boolean noSlash = !(ALLOW_ENCODED_SLASH || query);

        StringBuilder dec = new StringBuilder();    // decoded string output
        int strPos = ;
        int strLen = str.length();

        dec.ensureCapacity(str.length());
        while (strPos < strLen) {
            int laPos;        // lookahead position

            // look ahead to next URLencoded metacharacter, if any
            for (laPos = strPos; laPos < strLen; laPos++) {
                char laChar = str.charAt(laPos);
                if ((laChar == '+' && query) || (laChar == '%')) {
                    break;
                }
            }

            // if there were non-metacharacters, copy them all as a block
            if (laPos > strPos) {
                dec.append(str.substring(strPos,laPos));
                strPos = laPos;
            }

            // shortcut out of here if we're at the end of the string
            if (strPos >= strLen) {
                break;
            }

            // process next metacharacter
            char metaChar = str.charAt(strPos);
            if (metaChar == '+') {
                dec.append(' ');
                strPos++;
                continue;
            } else if (metaChar == '%') {
                // We throw the original exception - the super will deal with
                // it
                //                try {
                char res = (char) Integer.parseInt(   //得到%号后面两个字符，之后以16进制转换成int类型再转换成char类型，之后追加到dec上
                        str.substring(strPos + 1, strPos + 3), 16);
                if (noSlash && (res == '/')) {
                    throw new IllegalArgumentException("noSlash");
                }
                dec.append(res);
                strPos += 3;
            }
        }

        return dec.toString();
    }