java.net.InetAddress java class doesn't resolv

问题:

When I run this code below inside container Docker running Java JDK 8 on Alpine Linux

import java.io.*;
import java.util.*;
import java.net.*;

public class SomaDBTest {
  public static void main(String... args) throws Throwable {

    InetAddress ip = InetAddress.getByName("mysql");    
    System.out.println("Begin -  mysql IP Addr = " + ip.getHostAddress());
    . . . 
  }
}

I get the error:

  Picked up JAVA_TOOL_OPTIONS: -Dfile.encoding=UTF8
  Exception in thread "main" java.net.UnknownHostException: mysql: unknown error
    at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method)
    at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:928)
    at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1323)
    at java.net.InetAddress.getAllByName0(InetAddress.java:1276)
    at java.net.InetAddress.getAllByName(InetAddress.java:1192)
    at java.net.InetAddress.getAllByName(InetAddress.java:1126)
    at java.net.InetAddress.getByName(InetAddress.java:1076)
    at SomaDBTest.main(SomaDBTest.java:52)

Any Ideas ?

By the way, I can run the ping mysql and nslookup command successfully.

# ping mysql 
PING mysql (172.17.0.2): 56 data bytes
64 bytes from 172.17.0.2: seq=0 ttl=64 time=0.185 ms
64 bytes from 172.17.0.2: seq=1 ttl=64 time=0.283 ms
64 bytes from 172.17.0.2: seq=2 ttl=64 time=0.424 ms

# nslookup mysql
Server:    (null)
Address 1: ::1 localhost
Address 2: 127.0.0.1 localhost

Name:      mysql
Address 1: 172.17.0.2 mysql

My Dockerfile is very simple:

FROM frolvlad/alpine-oraclejdk8
ADD bin /
WORKDIR /

The files SomaDBTest.java and SomaDBTest.class is in bin directory.

To run the container you do :

docker build -t testInetAddress .
docker run -i -t testInetAddress java SomaDBTest

回答1:

You can put the command bellow on your Dockerfile to solve this problem

RUN echo 'hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4' >> /etc/nsswitch.conf