com.swdouglass.joid.server.ReCaptcha.java Source code

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Here is the source code for com.swdouglass.joid.server.ReCaptcha.java

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/*
 * Copyright 2009 Scott Douglass <scott@swdouglass.com>
 * Licensed 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 com.swdouglass.joid.server;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.methods.PostMethod;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * Implements support for the
 * <a href="http://recaptcha.net/apidocs/captcha/">reCAPTCHA</a> system
 * for identifying human computer operators.
 * 
 * @author scott
 */
public class ReCaptcha {

    private static final Log log = LogFactory.getLog(ReCaptcha.class);
    private static final String VERIFY_URL = "http://api-verify.recaptcha.net/verify";
    public static final String PARAM_RECAPTCHA_CHALLENGE = "recaptcha_challenge_field";
    public static final String PARAM_RECAPTCHA_RESPONSE = "recaptcha_response_field";
    public static final String PARAM_RECAPTCHA_ERROR = "error";

    /**
     * This method posts the four parameters necessary to solve a
     * <a href="http://recaptcha.net/apidocs/captcha/">captcha</a>.
     * 
     * @param privateKey Your recaptcha private key
     * @param remoteAddr The IP address of the end user
     * @param challenge The mangled text displayed
     * @param response Then end-user's interpretation of that text
     * @return null if successful, error message if not
     */
    public static String check(String privateKey, String remoteAddr, String challenge, String response) {
        String message = null;
        String str = null;
        if (challenge == null || response == null) {
            message = "Challenge and response strings can't be null!";
        } else {
            try {

                HttpClient client = new HttpClient();
                PostMethod post = new PostMethod(VERIFY_URL);
                post.addParameter("privatekey", privateKey);
                post.addParameter("remoteip", remoteAddr);
                post.addParameter("challenge", challenge);
                post.addParameter("response", response);
                client.executeMethod(post);
                BufferedReader in = new BufferedReader(new InputStreamReader(post.getResponseBodyAsStream()));
                str = in.readLine(); // read the first line of the response
                if (str == null) {
                    message = "Null read from server."; // treat this as not verfied
                } else {
                    boolean valid = "true".equals(str);
                    if (!valid) {
                        str = in.readLine(); // get next line which has message
                        if (str.length() > 1) {
                            message = str;
                        } else {
                            message = "missing error message?";
                        }
                    }
                }

            } catch (IOException ex) {
                log.error(ex);
                ex.printStackTrace();
            }
        }
        if (log.isDebugEnabled()) {
            log.debug("Response: " + str);
        }
        return message;
    }
}