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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.jboss.netty.handler.codec.http;

import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URLEncoder;
import java.nio.charset.Charset;
import java.nio.charset.UnsupportedCharsetException;
import java.util.ArrayList;
import java.util.List;

/**
 * Creates an URL-encoded URI from a path string and key-value parameter pairs.
 * This encoder is for one time use only.  Create a new instance for each URI.
 *
 *  * {@link QueryStringEncoder} encoder = new {@link QueryStringEncoder}("/hello");
 * encoder.addParam("recipient", "world");
 * assert encoder.toString().equals("/hello?recipient=world");
 * 
 * @see QueryStringDecoder
 *
 * @apiviz.stereotype utility
 * @apiviz.has        org.jboss.netty.handler.codec.http.HttpRequest oneway - - encodes
 */
public class QueryStringEncoder {

    private final Charset charset;
    private final String uri;
    private final List params = new ArrayList();

    /**
     * Creates a new encoder that encodes a URI that starts with the specified
     * path string.  The encoder will encode the URI in UTF-8.
     */
    public QueryStringEncoder(String uri) {
        this(uri, HttpConstants.DEFAULT_CHARSET);
    }

    /**
     * Creates a new encoder that encodes a URI that starts with the specified
     * path string in the specified charset.
     */
    public QueryStringEncoder(String uri, Charset charset) {
        if (uri == null) {
            throw new NullPointerException("uri");
        }
        if (charset == null) {
            throw new NullPointerException("charset");
        }

        this.uri = uri;
        this.charset = charset;
    }

    /**
     * Adds a parameter with the specified name and value to this encoder.
     */
    public void addParam(String name, String value) {
        if (name == null) {
            throw new NullPointerException("name");
        }
        if (value == null) {
            throw new NullPointerException("value");
        }
        params.add(new Param(name, value));
    }

    /**
     * Returns the URL-encoded URI object which was created from the path string
     * specified in the constructor and the parameters added by
     * {@link #addParam(String, String)} method.
     */
    public URI toUri() throws URISyntaxException {
        return new URI(toString());
    }

    /**
     * Returns the URL-encoded URI which was created from the path string
     * specified in the constructor and the parameters added by
     * {@link #addParam(String, String)} method.
     */
    @Override
    public String toString() {
        if (params.isEmpty()) {
            return uri;
        } else {
            StringBuilder sb = new StringBuilder(uri).append('?');
            for (int i = 0; i < params.size(); i++) {
                Param param = params.get(i);
                sb.append(encodeComponent(param.name, charset));
                sb.append('=');
                sb.append(encodeComponent(param.value, charset));
                if (i != params.size() - 1) {
                    sb.append('&');
                }
            }
            return sb.toString();
        }
    }

    private static String encodeComponent(String s, Charset charset) {
        try {
            return URLEncoder.encode(s, charset.name()).replaceAll("\\+", "%20");
        } catch (UnsupportedEncodingException e) {
            throw new UnsupportedCharsetException(charset.name());
        }
    }

    private static final class Param {

        final String name;
        final String value;

        Param(String name, String value) {
            this.value = value;
            this.name = name;
        }
    }
}