Java 发送HTTP或HTTPS请求获取网页码源（1）

闲来无事，封装了一个简单的工具类，用于向某个URL发送请求并获取响应的文本内容。发送HTTP请求的方式比较简单，但用来发送HTTPS请求却不行的。
于是查了一些资料，根据前人经验写了这个工具类，能够区分URL是HTTP类型还是HTTPS类型的，但对HTTPS方式的原理的研究尚浅，也只是拿来便用。
因为是工具类，所有方法均为static修饰，但只对外部提供了getSourceFromUrl(String url,String charsetName) 和 getSourceFromUrl(String url)
两个重载的方法，第一个可以按指定编码读取流。
码源如下，JDK1.7下测试通过，仅使用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;

/**
* 通用工具类
* 更新：2016-12-3 16:13:27
* 版本：1.0.0
*/
public final class CommonNetUtil {
//默认编码
private final static String CHARSETNAME = "UTF-8";

//协议类型
private final static String HTTP = "http:";
private final static String HTTPS = "https:";

/**
* 判断协议类型，转发到不同的方法进行处理
* @throws IOException
*/
private static String chooseProtocol(String url,String charsetName) throws IOException{
if (url == null) {
throw new RuntimeException("url shouldn't be null.");
}
//字符编码格式
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协议
if (url.startsWith(HTTP)) {
return getFromHttp(url,charsetName);

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

/**
* http协议的url
* @param url
* @param charsetName
* @return
* @throws IOException
*/
private static String getFromHttp(String url,String charsetName) throws IOException{
HttpURLConnection con = null;
try {
// 打开网页
con = (HttpURLConnection) new URL(url).openConnection();
con.connect();
//判断状态码
if (con.getResponseCode() == 200) {
//读取流
return getTextFromCon(con,charsetName);
}
} catch (IOException e) {
throw new IOException("Connet exception.", e);
} finally {
if (con != null) {
con.disconnect();
}
}

return null;
}

/**
* https协议的url
* @param url
* @param charsetName
* @return
* @throws IOException
*/
private static String getFromHttps(String url,String charsetName) throws IOException{
HttpsURLConnection httpsConn = null;
try {
//构造TrustManager 对象数组
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 {

}
}};

//创建SSLContext对象，并使用我们指定的信任管理器初始化
SSLContext sslContext = SSLContext.getInstance("SSL","SunJSSE");
sslContext.init(null, tm, new SecureRandom());

//从上述SSLContext对象中得到SSLSocketFactory对象
SSLSocketFactory ssf = sslContext.getSocketFactory();

//创建HttpsURLConnection对象，并设置其SSLSocketFactory对象
httpsConn = (HttpsURLConnection)new URL(url).openConnection();
httpsConn.setSSLSocketFactory(ssf);
//连接
httpsConn.connect();

//判断状态码
if (httpsConn.getResponseCode() == 200) {
//读取流
return getTextFromCon(httpsConn,charsetName);
}

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

}
return null;
}

/**
* 从流中读取数据
* @param con
* @param charsetName
* @return
* @throw
a2fe
s 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);  //不换行
sb.append(s + "\n"); //换行
}
return sb.toString();

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

/**
* 根据URL获取码源
* @param url
* @return 返回字符串型码源
* @throws IOException
*/
public static String getSourceFromUrl(String url) throws IOException {
return chooseProtocol(url, CHARSETNAME);
}

/**
* 根据URL获取码源，可指定用何种编码进行解码
* @param url
* @param charsetName 编码类型
* @return 返回字符串型码源
* @throws IOException
*/
public static String getSourceFromUrl(String url,String charsetName) throws IOException {

return chooseProtocol(url, charsetName);

}

}

import java.io.IOException;
/* 测试类*/
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();
}
}
}