关于JAVA发送Https请求（HttpsURLConnection和HttpURLConnection）

https协议对于开发者而言其实只是多了一步证书验证的过程。这个证书正常情况下被jdk/jre/security/cacerts所管理。里面证书包含两种情况：

1、机构所颁发的被认证的证书，这种证书的网站在浏览器访问时https头显示为绿色如百度

2、个人所设定的证书，这种证书的网站在浏览器里https头显示为红色×，且需要点击信任该网站才能继续访问。而点击信任这一步的操作就是我们在java代码访问https网站时区别于http请求需要做的事情。

所以JAVA发送Https请求有两种情况，三种解决办法：

第一种情况：Https网站的证书为机构所颁发的被认证的证书，这种情况下和http请求一模一样，无需做任何改变，用HttpsURLConnection或者HttpURLConnection都可以

[code]public static void main(String[] args) throws Exception{
URL serverUrl = new URL("https://xxxx");
HttpURLConnection conn = (HttpURLConnection) serverUrl.openConnection();
conn.setRequestMethod("GET");
conn.setRequestProperty("Content-type", "application/json");
//必须设置false，否则会自动redirect到重定向后的地址
conn.setInstanceFollowRedirects(false);
conn.connect();
String result = getReturn(conn);
}

/*请求url获取返回的内容*/
public static String getReturn(HttpURLConnection connection) throws IOException{
StringBuffer buffer = new StringBuffer();
//将返回的输入流转换成字符串
try(InputStream inputStream = connection.getInputStream();
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, ConstantInfo.CHARSET);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);){
String str = null;
while ((str = bufferedReader.readLine()) != null) {
buffer.append(str);
}
String result = buffer.toString();
return result;
}
}

第二种情况：个人所设定的证书，这种证书默认不被信任，需要我们自己选择信任，信任的办法有两种：

A、将证书导入java的运行环境中

• 从该网站下载或者从网站开发者出获取证书cacert.crt
• 运行命令将证书导入java运行环境：keytool -import -keystore %JAVA_HOME%\jre\lib\security\cacerts -file cacert.crt -alias xxx
• 完成。java代码中发送https的请求和http一样，同第一种情况。

B、忽略证书验证过程，忽略之后任何Https协议网站皆能正常访问，同第一种情况

[code]import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import javax.net.ssl.X509TrustManager;
public class MyX509TrustManager implements X509TrustManager {

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

@Override
public void checkServerTrusted(X509Certificate[] ax509certificate,String s) throws CertificateException {
}

@Override
public X509Certificate[] getAcceptedIssuers() {
// TODO Auto-generated method stub
return null;
}
}

[code]public static void main(String[] args) throws Exception{
SSLContext sslcontext = SSLContext.getInstance("SSL","SunJSSE");
sslcontext.init(null, new TrustManager[]{new MyX509TrustManager()}, new java.security.SecureRandom());
URL url = new URL("https://xxxx");
HostnameVerifier ignoreHostnameVerifier = new HostnameVerifier() {
public boolean verify(String s, SSLSession sslsession) {
System.out.println("WARNING: Hostname is not matched for cert.");
return true;
}
};
HttpsURLConnection.setDefaultHostnameVerifier(ignoreHostnameVerifier);
HttpsURLConnection.setDefaultSSLSocketFactory(sslcontext.getSocketFactory());
//之后任何Https协议网站皆能正常访问，同第一种情况
}

C、java代码中加载证书，必须使用HttpsURLConnection方式

[code]public static void main(String[] args) throws Exception{
SSLContext sslcontext = SSLContext.getInstance("SSL","SunJSSE");
sslcontext.init(null, new TrustManager[]{new MyX509TrustManager()}, new java.security.SecureRandom());
URL serverUrl = new URL("https://xxxx");
HttpsURLConnection conn = (HttpsURLConnection) serverUrl.openConnection();
conn.setSSLSocketFactory(sslcontext.getSocketFactory());
conn.setRequestMethod("GET");
conn.setRequestProperty("Content-type", "application/json");
//必须设置false，否则会自动redirect到重定向后的地址
conn.setInstanceFollowRedirects(false);
conn.connect();
String result = getReturn(conn);
}

/*请求url获取返回的内容*/
public static String getReturn(HttpsURLConnection connection) throws IOException{
StringBuffer buffer = new StringBuffer();
//将返回的输入流转换成字符串
try(InputStream inputStream = connection.getInputStream();
InputStreamReader inputStreamReader = new InputStreamReader(inputStream, ConstantInfo.CHARSET);
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);){
String str = null;
while ((str = bufferedReader.readLine()) != null) {
buffer.append(str);
}
String result = buffer.toString();
return result;
}
}