In Java, you can use a custom java.net.InetAddress implementation to solve the problem of virtual hosts

In Java, you can use custom java.net.InetAddressimplementations to solve the problem of virtual hosts. This allows you to intercept calls to DNS resolution and return custom IP addresses.

Here is a simple example showing how to use a custom InetAddressimplementation to solve the virtual hosts problem:

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.HashMap;
import java.util.Map;

public class CustomInetAddress extends InetAddress {
    
    
    private static Map<String, String> virtualHosts = new HashMap<>();

    static {
    
    
        // 添加虚拟hosts
        virtualHosts.put("myhost", "1.2.3.4");
    }

    @Override
    public String getHostAddress() {
    
    
        return null;
    }

    @Override
    public String getHostName() {
    
    
        return null;
    }

    @Override
    public byte[] getAddress() {
    
    
        return new byte[0];
    }

    public static InetAddress[] getAllByName(String host) throws UnknownHostException {
    
    
        if (virtualHosts.containsKey(host)) {
    
    
            // 返回虚拟IP地址
            return new InetAddress[]{
    
    InetAddress.getByName(virtualHosts.get(host))};
        } else {
    
    
            // 使用默认解析
            return InetAddress.getAllByName(host);
        }
    }
}

The above example creates a custom InetAddressimplementation that uses an in-memory map to resolve virtual hosts. You can modify the content in the map as needed.

To use a custom implementation, you need to specify and system properties InetAddresswhen starting your Java program . For example:-Djava.net.preferIPv4Stack=true-Dsun.net.spi.nameservice.provider.1=dns,CustomInetAddress

java -Djava.net.preferIPv4Stack=true -Dsun.net.spi.nameservice.provider.1=dns,CustomInetAddress -jar myapp.jar

After completing these steps, your Java program will use your custom InetAddressimplementation to resolve hostnames.