Https系列會在下面幾篇文章中分別作介紹：
一：https的簡單介紹及SSL證書的生成
二：https的SSL證書在服務器端的部署，基於tomcat,spring boot
三：讓服務器同時支持http、https，基於spring boot
四：https的SSL證書在Android端基於okhttp，Retrofit的使用
所有文章會優先在：
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先來回顧一下
前面已分別介紹了https,SSL證書的生成，並完成了服務器端的https的部署
並提到一個重要的用於客戶端的證書：公鑰證書
在前面文章中，自簽名SSL證書對應的公鑰證書為：mycer.cer（當然這名字是自己隨便定的）;在阿里雲申請的CA證書中對應的公鑰證書為：*.pem
如果有不清楚的，請看我之前介紹過的文章
Android自帶的可信任的CA公鑰證書
還要說明一下，Android系統有自帶的安卓認可的證書頒發機構（如:Wosign)頒發的可信任的CA公鑰證書，大概有100多個，
可自己查看，各個手機的查看方法可能不一樣，在我的手機中，能在下面的位置中找到：
“設置”->”更多設置“->”系統安全“->”信任的憑據”
也就是說，如果你服務器的證書是安卓認可的證書頒發機構頒發的，那么你並不需要在Android端額外安裝公鑰證書，否則，你就需要安裝。
注：在不同版本的Android系統上，可信任的CA證書可能是不一樣的，如果你擔心在別人的Android系統上可能此CA證書不被信任，那你統一都安裝也是沒問題的
我在阿里雲上申請的免費型DV SSL證書，是屬於安卓認可的證書頒發機構頒發的，不需要額外安裝，當然我們的自簽名證書，是必需要安裝的
其實我在測試的過程中，把自簽名證書和阿里雲上申請的免費型DV SSL證書都用同樣的方法安裝了，都是OK的
我們下面就開始基於okhttp來安裝公鑰證書了
先看看我的okhttp和retrofit的gradle版本
compile 'com.squareup.okhttp3:okhttp:3.8.1'
compile 'com.squareup.retrofit2:retrofit:2.3.0'
增加一個OkhttpManager類
統一處理OkHttpClient的證書，完整的代碼如下：
import android.content.Context;
import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.security.KeyStore;
import java.security.cert.Certificate;
import java.security.cert.CertificateFactory;
import java.util.Arrays;
import java.util.Collection;
import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSocketFactory;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;
import okhttp3.OkHttpClient;
public class OkhttpManager {
static private OkhttpManager mOkhttpManager=null;
private InputStream mTrustrCertificate;
static public OkhttpManager getInstance()
{
if(mOkhttpManager==null)
{
mOkhttpManager=new OkhttpManager();
}
return mOkhttpManager;
}
private KeyStore newEmptyKeyStore(char[] password) throws GeneralSecurityException {
try {
KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
InputStream in = null; // By convention, 'null' creates an empty key store.
keyStore.load(in, password);
return keyStore;
} catch (IOException e) {
throw new AssertionError(e);
}
}
private X509TrustManager trustManagerForCertificates(InputStream in)
throws GeneralSecurityException {
CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
Collection<? extends Certificate> certificates = certificateFactory.generateCertificates(in);
if (certificates.isEmpty()) {
throw new IllegalArgumentException("expected non-empty set of trusted certificates");
}
// Put the certificates a key store.
char[] password = "password".toCharArray(); // Any password will work.
KeyStore keyStore = newEmptyKeyStore(password);
int index = 0;
for (Certificate certificate : certificates) {
String certificateAlias = Integer.toString(index++);
keyStore.setCertificateEntry(certificateAlias, certificate);
}
// Use it to build an X509 trust manager.
KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
keyManagerFactory.init(keyStore, password);
TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
trustManagerFactory.init(keyStore);
TrustManager[] trustManagers = trustManagerFactory.getTrustManagers();
if (trustManagers.length != 1 || !(trustManagers[0] instanceof X509TrustManager)) {
throw new IllegalStateException("Unexpected default trust managers:" + Arrays.toString(trustManagers));
}
return (X509TrustManager) trustManagers[0];
}
public void setTrustrCertificates(InputStream in)
{
mTrustrCertificate=in;
}
public InputStream getTrustrCertificates()
{
return mTrustrCertificate;
}
public OkHttpClient build()
{
OkHttpClient okHttpClient=null;
if(getTrustrCertificates()!=null)
{
X509TrustManager trustManager;
SSLSocketFactory sslSocketFactory;
try {
trustManager = trustManagerForCertificates(getTrustrCertificates());
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(null, new TrustManager[] { trustManager }, null);
sslSocketFactory = sslContext.getSocketFactory();
} catch (GeneralSecurityException e) {
throw new RuntimeException(e);
}
okHttpClient=new OkHttpClient.Builder()
.sslSocketFactory(sslSocketFactory, trustManager)
.build();
}
else
{
okHttpClient=new OkHttpClient.Builder()
.build();
}
return okHttpClient;
}
}
代碼解釋
代碼不少，其實最核心的代碼為：
public OkHttpClient build()
{
.......
trustManager = trustManagerForCertificates(getTrustrCertificates());
.......
okHttpClient=new OkHttpClient.Builder()
.sslSocketFactory(sslSocketFactory, trustManager)
.build();
..........
return okHttpClient;
}
也就是通過
void setTrustrCertificates(InputStream in)
把自己的證書對應的文件set進去
然后通過
trustManager =trustManagerForCertificates(getTrustrCertificates());
再
okHttpClient=new OkHttpClient.Builder()
.sslSocketFactory(sslSocketFactory, trustManager)
.build();
就能生成安裝好了可信任證書的okHttpClient
OkhttpManager說完了，接下來，就是：
Activity中使用OkhttpManager
1：先把公鑰證書文件（如：自簽名的mycer.cer或CA證書的：*.pem)放到assets下，
如果使用AndroidStudio的同學，可能沒有assets文件夾，自己建此文件夾，如我的為：app\src\main\assets
2：直接貼Activity主要的代碼：
public class MyActivity extends AppCompatActivity {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
try {
OkhttpManager.getInstance().setTrustrCertificates(getAssets().open("mycer.cer");
OkHttpClient mOkhttpClient= OkhttpManager.getInstance().build();
} catch (IOException e) {
e.printStackTrace();
}
}
簡單吧，主要代碼就那兩句，就生成了已安裝公鑰證書”mycer.cer”的mOkhttpClient
接下來的mOkhttpClient怎樣使用，大家都應該清楚了吧，如果不清楚只能看OkHttpClient的基礎內容了
好了，OkHttpClient搞掂了
接下來就到Retrofit了
大家應該知到Retrofit默認是以OkHttpClient來作為傳輸的，既然OkHttpClient搞掂了，那Retrofit就簡單了
還是直接貼代碼：
Retrofit retrofit = new Retrofit.Builder()
.client(mOkhttpClient)
.baseUrl("your_serverl_url")
.build();
看，只需在Retrofit中多加一句
.client(mOkhttpClient)
就把已安裝了證書的mOkhttpClient作為Retrofit的傳輸了
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