如何使用JDK1.8支持TLS1.3协议？

请把你的JDK版本升至1.8_291版本以上，原因请见8u291发行说明:

https://www.oracle.com/java/technologies/javase/8u291-relnotes.html

禁用了TLS 1.0 和 1.1 的协议版本，并已被更安全和现代的版本（TLS 1.2 和 1.3）取代。 

 测试是否支持版本：

public static void main(String[] args) throws Exception {  
        SSLContext context = SSLContext.getInstance("TLS");  
        context.init(null, null, null);  

        SSLSocketFactory factory = (SSLSocketFactory) context.getSocketFactory();  
        SSLSocket socket = (SSLSocket) factory.createSocket();  

        String[] protocols = socket.getSupportedProtocols();  

        System.out.println("Supported Protocols: " + protocols.length);  
        for (int i = 0; i < protocols.length; i++) {  
            System.out.println(" " + protocols[i]);  
        }  

        protocols = socket.getEnabledProtocols();  

        System.out.println("Enabled Protocols: " + protocols.length);  
        for (int i = 0; i < protocols.length; i++) {  
            System.out.println(" " + protocols[i]);  
        }  

    }