閒來無事，封裝了一個簡單的工具類，用於向某個URL傳送請求並獲取響應的文字內容。傳送HTTP請求的方式比較簡單，但用來發送HTTPS請求卻不行的。
於是查了一些資料，根據前人經驗寫了這個工具類，能夠區分URL是HTTP型別還是HTTPS型別的，但對HTTPS方式的原理的研究尚淺，也只是拿來便用。
因為是工具類，所有方法均為static修飾，但只對外部提供了getSourceFromUrl(String url,String charsetName) 和 getSourceFromUrl(String url) 
兩個過載的方法，第一個可以按指定編碼讀取流。
碼源如下，JDK1.7下測試通過，僅使用JDK提供的Jar包：
 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.security.SecureRandom;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

import
 
 javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

/**
 * 通用工具類
 * 更新：2016-12-3 16:13:27
 * 版本：1.0.0
 */
public final class CommonNetUtil {
    //預設編碼
    private final static String CHARSETNAME = "UTF-8"
 
;

    //協議型別
    private final static String HTTP = "http:";
    private final static String HTTPS = "https:";


    /**
     * 判斷協議型別，轉發到不同的方法進行處理
     * @throws IOException 
     */
    private static String chooseProtocol(String url,String charsetName) throws IOException{
        if (url == null) {
            throw new RuntimeException("url shouldn't be null.");
        }
        //字元編碼格式
        if (charsetName == null){
            throw new NullPointerException("charsetName shouldn't be null.");
        }

        if (!url.startsWith(HTTP) && !url.startsWith(HTTPS)) {
            throw new RuntimeException("url format is not supported.");
        }
        //如果是http協議
        if (url.startsWith(HTTP)) {
            return getFromHttp(url,charsetName);

        }else if (url.startsWith(HTTPS)) {
            //如果是https協議
            return getFromHttps(url, charsetName);
        }
        return null;
    }

    /**
     * http協議的url
     * @param url
     * @param charsetName
     * @return
     * @throws IOException
     */
    private static String getFromHttp(String url,String charsetName) throws IOException{
        HttpURLConnection con = null;
        try {
            // 開啟網頁
            con = (HttpURLConnection) new URL(url).openConnection();
            con.connect();
            //判斷狀態碼
            if (con.getResponseCode() == 200) {
                //讀取流
                return getTextFromCon(con,charsetName);
            }
        } catch (IOException e) {
            throw new IOException("Connet exception.", e);
        } finally { 
            if (con != null) {
                con.disconnect();
            }
        }

        return null;
    }

    /**
     * https協議的url
     * @param url
     * @param charsetName
     * @return
     * @throws IOException
     */
    private static String getFromHttps(String url,String charsetName) throws IOException{
        HttpsURLConnection httpsConn = null;
        try {
            //構造TrustManager 物件陣列
            TrustManager[] tm = {new X509TrustManager() {

                @Override
                public X509Certificate[] getAcceptedIssuers() {
                    return null;
                }

                @Override
                public void checkServerTrusted(X509Certificate[] chain, String authType)
                        throws CertificateException {

                }

                @Override
                public void checkClientTrusted(X509Certificate[] chain, String authType)
                        throws CertificateException {

                }
            }}; 

            //建立SSLContext物件，並使用我們指定的信任管理器初始化
            SSLContext sslContext = SSLContext.getInstance("SSL","SunJSSE"); 
            sslContext.init(null, tm, new SecureRandom());

            //從上述SSLContext物件中得到SSLSocketFactory物件
            SSLSocketFactory ssf = sslContext.getSocketFactory();

            //建立HttpsURLConnection物件，並設定其SSLSocketFactory物件
            httpsConn = (HttpsURLConnection)new URL(url).openConnection();
            httpsConn.setSSLSocketFactory(ssf);
            //連線
            httpsConn.connect();

            //判斷狀態碼
            if (httpsConn.getResponseCode() == 200) {
                //讀取流
                return getTextFromCon(httpsConn,charsetName);
            }

        } catch (Exception e) {
            throw new IOException("Connet exception.", e);
        }finally{
            if (httpsConn != null) {
                httpsConn.disconnect();
            }

        }
        return null;
    }

    /**
     * 從流中讀取資料
     * @param con
     * @param charsetName
     * @return
     * @throws IOException
     */
    private static String getTextFromCon(URLConnection con,String charsetName) throws IOException{
        StringBuffer sb = new StringBuffer();
        try(
                BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream(),charsetName));
                ) {
            String s = null;
            while ((s = br.readLine()) != null)  {
                //sb.append(s);  //不換行
                sb.append(s + "\n"); //換行
            }
            return sb.toString();

        } catch (IOException e) {
            throw new IOException("Read stream exception.", e);
        }
    }


    /**
     * 根據URL獲取碼源
     * @param url
     * @return 返回字串型碼源
     * @throws IOException
     */
    public static String getSourceFromUrl(String url) throws IOException {
        return chooseProtocol(url, CHARSETNAME);
    }

    /**
     * 根據URL獲取碼源，可指定用何種編碼進行解碼
     * @param url 
     * @param charsetName 編碼型別
     * @return 返回字串型碼源
     * @throws IOException
     */
    public static String getSourceFromUrl(String url,String charsetName) throws IOException {

        return chooseProtocol(url, charsetName);

    }

}

測試類：

import java.io.IOException;
/* 測試類*/
public class Test {

    public static void main(String[] args) {

        String url = "https://www.baidu.com";
        try {
            String content= CommonNetUtil.getSourceFromUrl(url);
            System.out.println(content);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

結果：

記錄到此。

傳送HTTPS請求參考了此文，http://blog.csdn.net/lifj07/article/details/8638098，表示感謝。