Apache HttpClient 4.5支持接受自签名证书:

SSLContext sslContext = SSLContexts.custom()
    .loadTrustMaterial(new TrustSelfSignedStrategy())
    .build();
SSLConnectionSocketFactory socketFactory =
    new SSLConnectionSocketFactory(sslContext);
Registry<ConnectionSocketFactory> reg =
    RegistryBuilder.<ConnectionSocketFactory>create()
    .register("https", socketFactory)
    .build();
HttpClientConnectionManager cm = new PoolingHttpClientConnectionManager(reg);        
CloseableHttpClient httpClient = HttpClients.custom()
    .setConnectionManager(cm)
    .build();
HttpGet httpGet = new HttpGet(url);
CloseableHttpResponse sslResponse = httpClient.execute(httpGet);

这将构建一个SSL套接字工厂，它将使用TrustSelfSignedStrategy，将其注册到自定义连接管理器，然后使用该连接管理器执行HTTP GET。

我同意那些高呼“不要在生产环境中这样做”的人，但是在生产环境之外接受自签名证书是有用例的;我们在自动化集成测试中使用它们，因此即使不在生产硬件上运行，我们也在使用SSL(就像在生产中一样)。

Kotlin中的变体

    @SuppressLint("CustomX509TrustManager", "TrustAllX509TrustManager")
    fun ignoreSsl() {
        val trustAllCerts: Array<TrustManager> = arrayOf(
            object : X509TrustManager {
                override fun getAcceptedIssuers(): Array<X509Certificate>? = null
                override fun checkClientTrusted(certs: Array<X509Certificate?>?, authType: String?) {}
                override fun checkServerTrusted(certs: Array<X509Certificate?>?, authType: String?) {}
            })
        val sc = SSLContext.getInstance("SSL")
        sc.init(null, trustAllCerts, SecureRandom())
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.socketFactory)
    }

受下面annser的启发，我找到了一种信任自签名CA并保持信任默认CA的方法。

    File file = new File(System.getProperty("java.home"), "lib/security/cacerts");
    KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
    keyStore.load(new FileInputStream(file), "changeit".toCharArray());


    InputStream resourceAsStream = getClass().getClassLoader().getResourceAsStream("testCer.cer");
    Certificate certificate = CertificateFactory.getInstance("X.509").generateCertificate(resourceAsStream);
    keyStore.setCertificateEntry("my-server-alias", certificate);

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

    SSLContext sslContext = SSLContexts.createDefault();
    sslContext.init(null, trustManagerFactory.getTrustManagers(), null);


    // check domain
    // SSLConnectionSocketFactory socketFactory = new SSLConnectionSocketFactory(sslContext);

    // not check domain
    SSLConnectionSocketFactory socketFactory = new SSLConnectionSocketFactory(sslContext,
            new String[]{"TLSv1","TLSv1.1","TLSv1.2","SSLv3"},null, NoopHostnameVerifier.INSTANCE);

    CloseableHttpClient httpClient = HttpClients.custom().setSSLSocketFactory(socketFactory).build();
    factory.setHttpClient(httpClient);
    RestTemplate restTemplate = new RestTemplate(factory);

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();

我遇到了这个问题，因为依赖项来自maven repo，它是我的本地服务器，具有自签名证书和自签名CA证书。为了解决这个错误，我必须运行以下两个命令:

<my_java_install_dir>\bin\keytool.exe -importcert -file <my-self-signed-CA-cert>.crt -keystore <my_java_install_dir>\lib\security\cacerts -alias my-CA-cert

然后

<my_java_install_dir>\jdk11.0.14_10\bin\keytool.exe -importcert -file <my-self-signed-maven-repo-cert>.crt -keystore <my_java_install_dir>\lib\security\cacerts -alias my-maven-repo-cert

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);
}