访问 https 接口时，，是需要进行证书检查的，如果证书检查不通过，会报如下错误：
javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1949)
at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:302)
at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:296)
at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1514)
at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:216)
at sun.security.ssl.Handshaker.processLoop(Handshaker.java:1026)
at sun.security.ssl.Handshaker.process_record(Handshaker.java:961)
at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1062)
at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1375)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1403)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1387)
at org.apache.http.conn.ssl.SSLConnectionSocketFactory.createLayeredSocket(SSLConnectionSocketFactory.java:396)
at org.apache.http.conn.ssl.SSLConnectionSocketFactory.connectSocket(SSLConnectionSocketFactory.java:355)
at org.apache.http.impl.conn.DefaultHttpClientConnectionOperator.connect(DefaultHttpClientConnectionOperator.java:142)
at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.connect(PoolingHttpClientConnectionManager.java:373)
at org.apache.http.impl.execchain.MainClientExec.establishRoute(MainClientExec.java:381)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:237)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:111)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:108)
at com.inspur.iot.hub.common.Test.httpGet(Test.java:42)
at com.inspur.iot.hub.common.Test.main(Test.java:27)
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:387)
at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:292)
at sun.security.validator.Validator.validate(Validator.java:260)
at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:324)
at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:229)
at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:124)
at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1496)
... 21 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.provider.certpath.SunCertPathBuilder.build(SunCertPathBuilder.java:141)
at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:126)
at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:280)
at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:382)
... 27 more
遇到这种错误，一般需要将服务器的证书信息保存到 服务调用方的TrustStore中。
当然，还有一种做法，就是不进行证书的检查，示例如下：
import java.io.IOException;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import javax.net.ssl.SSLContext;
import javax.net.ssl.X509TrustManager;
import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.util.EntityUtils;
public class Test {
public static void main(String[] args) {
String url = "https://*******";
System.out.println(httpGet(url));
}
public static String httpGet(String url) {
String content = null;
// since 4.3 不再使用 DefaultHttpClient
CloseableHttpClient closeableHttpClient =
HttpClients
.custom()
.setConnectionManager(createConnManager())
.build();
HttpGet httpGet = new HttpGet(url);
CloseableHttpResponse httpResponse = null;
try {
httpResponse = closeableHttpClient.execute(httpGet);
HttpEntity entity = httpResponse.getEntity();
content = EntityUtils.toString(entity, "utf-8");
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
httpResponse.close();
} catch (IOException e) {
e.printStackTrace();
}
}
try {
closeableHttpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
return content;
}
private static PoolingHttpClientConnectionManager createConnManager(){
SSLContext sslcontext = null;
try {
sslcontext = createIgnoreVerifySSL();
} catch (Exception e) {
throw new RuntimeException(e);
}
// 设置协议http和https对应的处理socket链接工厂的对象
Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder
.<ConnectionSocketFactory> create()
.register("http", PlainConnectionSocketFactory.INSTANCE)
.register("https", new SSLConnectionSocketFactory(sslcontext))
.build();
PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager(socketFactoryRegistry);
return connManager;
}
private static SSLContext createIgnoreVerifySSL()
throws NoSuchAlgorithmException, KeyManagementException {
SSLContext sc = SSLContext.getInstance("SSLv3"); // 等同 TLS
X509TrustManager trustManager = new X509TrustManager() {
@Override
public void checkClientTrusted(
java.security.cert.X509Certificate[] paramArrayOfX509Certificate,
String paramString) throws CertificateException {
}
@Override
public void checkServerTrusted(
java.security.cert.X509Certificate[] paramArrayOfX509Certificate,
String paramString) throws CertificateException {
}
@Override
public java.security.cert.X509Certificate[] getAcceptedIssuers() {
return null;
}
};
sc.init(null, new X509TrustManager[] { trustManager }, null);
return sc;
}
}
当然，并不是访问所有的https接口都需要配置TrustStore，或者设置不检查证书，那就是经过CA签名的，那么只要保存着CA的根证书即可（因为jdk或者OS或者浏览器，默认已经包含了这些CA的根证书了）。
自签名证书，一般都需要单独设置。
Spring RestTemplate 底层仍然是使用的Httpclient，所有也可以通过上述方式设置不检查证书。
RestTemplate构造函数
public RestTemplate(ClientHttpRequestFactory requestFactory) {
this();
setRequestFactory(requestFactory);
}
ClientHttpRequestFactory 是一个接口，
HttpComponentsClientHttpRequestFactory 实现了接口 ClientHttpRequestFactory
HttpComponentsClientHttpRequestFactory 有一个 setHttpClient方法，允许注入 httpclient 对象。
public void setHttpClient(HttpClient httpClient) {
Assert.notNull(httpClient, "HttpClient must not be null");
this.httpClient = httpClient;
}