如果“他们”使用自签名证书，则由他们采取必要的步骤使他们的服务器可用。具体来说，这意味着以一种值得信赖的方式离线向您提供他们的证书。所以让他们这么做。然后，按照JSSE参考指南中的描述，使用keytool将其导入到您的信任库中。不要想这里发布的不安全的TrustManager。

EDIT For the benefit of the seventeen (!) downvoters, and numerous commenters below, who clearly have not actually read what I have written here, this is not a jeremiad against self-signed certificates. There is nothing wrong with self-signed certificates when implemented correctly. But, the correct way to implement them is to have the certificate delivered securely via an offline process, rather than via the unauthenticated channel they are going to be used to authenticate. Surely this is obvious? It is certainly obvious to every security-aware organization I have ever worked for, from banks with thousands of branches to my own companies. The client-side code-base 'solution' of trusting all certificates, including self-signed certificates signed by absolutely anybody, or any arbitary body setting itself up as a CA, is ipso facto not secure. It is just playing at security. It is pointless. You are having a private, tamperproof, reply-proof, injection-proof conversation with ... somebody. Anybody. A man in the middle. An impersonator. Anybody. You may as well just use plaintext.

您可以通过在RestTemplate级别禁用它来实现这一点。 注意，此TrustStrategy将信任所有证书，并且使用NoopHostnameVerifier()禁用了主机名验证。

public RestTemplate getRestTemplate() throws KeyStoreException, NoSuchAlgorithmException, KeyManagementException {
    TrustStrategy acceptingTrustStrategy = (x509Certificates, s) -> true;
    SSLContext sslContext = org.apache.http.ssl.SSLContexts.custom().loadTrustMaterial(null, acceptingTrustStrategy).build();
    SSLConnectionSocketFactory csf = new SSLConnectionSocketFactory(sslContext, new NoopHostnameVerifier());
    CloseableHttpClient httpClient = HttpClients.custom().setSSLSocketFactory(csf).build();
    HttpComponentsClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory();
    requestFactory.setHttpClient(httpClient);
    return new RestTemplate(requestFactory);
}       

而不是设置默认的套接字工厂(这在我看来是一件坏事)- yhis只会影响当前连接，而不是你试图打开的每一个SSL连接:

URLConnection connection = url.openConnection();
    // JMD - this is a better way to do it that doesn't override the default SSL factory.
    if (connection instanceof HttpsURLConnection)
    {
        HttpsURLConnection conHttps = (HttpsURLConnection) connection;
        // Set up a Trust all manager
        TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager()
        {

            public java.security.cert.X509Certificate[] getAcceptedIssuers()
            {
                return null;
            }

            public void checkClientTrusted(
                java.security.cert.X509Certificate[] certs, String authType)
            {
            }

            public void checkServerTrusted(
                java.security.cert.X509Certificate[] certs, String authType)
            {
            }
        } };

        // Get a new SSL context
        SSLContext sc = SSLContext.getInstance("TLSv1.2");
        sc.init(null, trustAllCerts, new java.security.SecureRandom());
        // Set our connection to use this SSL context, with the "Trust all" manager in place.
        conHttps.setSSLSocketFactory(sc.getSocketFactory());
        // Also force it to trust all hosts
        HostnameVerifier allHostsValid = new HostnameVerifier() {
            public boolean verify(String hostname, SSLSession session) {
                return true;
            }
        };
        // and set the hostname verifier.
        conHttps.setHostnameVerifier(allHostsValid);
    }
InputStream stream = connection.getInputStream();

我找到了一个证书提供者，该提供者不属于JDK 8u74的默认JVM受信任主机。提供者是www.identrust.com，但这不是我试图连接的域。该域已从该提供者获得其证书。请参见交叉根覆盖信任JDK/JRE中的默认列表?——读几个条目。另请参阅哪些浏览器和操作系统支持Let 's Encrypt。

因此，为了连接到我感兴趣的域名，它有一个由identrust.com颁发的证书，我执行了以下步骤。基本上，我必须获得identrust.com (DST根CA X3)证书才能被JVM信任。我可以使用Apache HttpComponents 4.5这样做:

1:从证书链下载说明中的indettrust获取证书。单击DST根CA X3链接。

2:保存到“DST Root CA X3.pem”文件中。确保在文件的开头和结尾添加行“-----BEGIN CERTIFICATE-----”和“-----END CERTIFICATE-----”。

3:创建java的keystore文件cacerts。JKS，命令如下:

keytool -import -v -trustcacerts -alias IdenTrust -keypass yourpassword -file dst_root_ca_x3.pem -keystore cacerts.jks -storepass yourpassword

4:复制生成的cacerts。将JKS密钥存储库保存到java/(maven)应用程序的资源目录中。

5:使用以下代码加载该文件，并将其附加到Apache 4.5 HttpClient。这将解决所有拥有indetrust.com颁发的证书的域的问题，util oracle将证书包含到JRE默认的密钥存储库中。

SSLContext sslcontext = SSLContexts.custom()
        .loadTrustMaterial(new File(CalRestClient.class.getResource("/cacerts.jks").getFile()), "yourpasword".toCharArray(),
                new TrustSelfSignedStrategy())
        .build();
// Allow TLSv1 protocol only
SSLConnectionSocketFactory sslsf = new SSLConnectionSocketFactory(
        sslcontext,
        new String[] { "TLSv1" },
        null,
        SSLConnectionSocketFactory.getDefaultHostnameVerifier());
CloseableHttpClient httpclient = HttpClients.custom()
        .setSSLSocketFactory(sslsf)
        .build();

当项目构建时，cacerts。JKS将被复制到类路径中并从那里加载。我没有，在这个时间点上，测试其他ssl站点，但如果上面的代码“链”在这个证书，那么他们也会工作，但是，我不知道。

参考:自定义SSL上下文和如何使用Java HttpsURLConnection接受自签名证书?

这不是解决全部问题的解决方案，但是oracle有关于如何使用这个keytool的详细文档。这解释了如何

使用keytool。 使用keytool生成证书/自签名证书。 将生成的证书导入Java客户端。

https://docs.oracle.com/cd/E54932_01/doc.705/e54936/cssg_create_ssl_cert.htm#CSVSG178

有一个更好的替代信任所有证书的方法:创建一个TrustStore，它专门信任给定的证书，并使用它来创建一个SSLContext，从中获取SSLSocketFactory在HttpsURLConnection上进行设置。以下是完整的代码:

File crtFile = new File("server.crt");
Certificate certificate = CertificateFactory.getInstance("X.509").generateCertificate(new FileInputStream(crtFile));
// Or if the crt-file is packaged into a jar file:
// CertificateFactory.getInstance("X.509").generateCertificate(this.class.getClassLoader().getResourceAsStream("server.crt"));


KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
keyStore.load(null, null);
keyStore.setCertificateEntry("server", certificate);

TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
trustManagerFactory.init(keyStore);

SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(null, trustManagerFactory.getTrustManagers(), null);

HttpsURLConnection connection = (HttpsURLConnection) new URL(url).openConnection();
connection.setSSLSocketFactory(sslContext.getSocketFactory());

您也可以直接从文件加载KeyStore，或者从任何受信任的来源检索X.509证书。

注意，对于这段代码，将不使用cacerts中的证书。这个特定的HttpsURLConnection将只信任这个特定的证书。