.meta 支持多个host配置（逗号分割）

apollo-core/src/main/java/com/ctrip/framework/apollo/core/MetaDomainConsts.java

 package com.ctrip.framework.apollo.core;
 
 import com.ctrip.framework.apollo.core.enums.Env;
+import com.ctrip.framework.apollo.core.utils.NetUtil;
 import com.ctrip.framework.apollo.core.utils.ResourceUtils;
 
 import java.util.HashMap;
@@ -38,6 +39,8 @@ public class MetaDomainConsts {
   }
 
   public static String getDomain(Env env) {
-    return String.valueOf(domains.get(env));
+    String metaAddress = String.valueOf(domains.get(env));
+    String validAddress = NetUtil.getValidAddress( metaAddress );
+    return validAddress;
   }
 }

apollo-core/src/main/java/com/ctrip/framework/apollo/core/utils/NetUtil.java

+package com.ctrip.framework.apollo.core.utils;
+
+import java.net.HttpURLConnection;
+import java.net.URL;
+
+/**
+ * Created by gl49 on 2018/6/8.
+ */
+public class NetUtil {
+    public static int getUrlStatus(String address){
+        int statusCode = 0;
+        try {
+            URL urlObj = new URL(address);
+            HttpURLConnection oc = (HttpURLConnection) urlObj.openConnection();
+            oc.setUseCaches(false);
+            oc.setConnectTimeout(5000);
+            statusCode = oc.getResponseCode();
+            if (200 == statusCode) {
+                return statusCode;
+            }
+        } catch (Exception ignore) {
+        }
+        return statusCode;
+    }
+
+    public static boolean checkUrl(String address){
+        int status = getUrlStatus(address);
+        if( 0 == status ){ //异常状态重试一次
+            status = getUrlStatus(address);
+        }
+        if( 200 == status ){
+            return true;
+        }
+        return false;
+    }
+
+    public static String getValidAddress(String metaAddress) {
+        String validAddress = null;
+        String[] addressArr = changeAddressArr(metaAddress);
+        for(String address : addressArr){
+            if(NetUtil.checkUrl(address)){
+                validAddress = address;
+                break;
+            }
+        }
+        if(null == validAddress){
+            throw new RuntimeException("invalid meta address, please check $env_meta config!");
+        }
+        return validAddress;
+    }
+
+    private static String[] changeAddressArr(String address) {
+        String[] addressArr =  address.split(",");
+        return addressArr;
+    }
+}

apollo-core/src/test/java/com/ctrip/framework/apollo/core/utils/NetUtilTest.java

+package com.ctrip.framework.apollo.core.utils;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Created by gl49 on 2018/6/8.
+ */
+public class NetUtilTest {
+    @Test
+    public void testCheckUrl(){
+        String apolloUrl = "http://www.ctrip.com";
+        Assert.assertEquals( NetUtil.checkUrl(apolloUrl), true);
+    }
+
+    @Test
+    public void testGetValidAddress(){
+        String addressStr = "http://www.ctrip.com,http://www.ctrip.com2";
+        String address = NetUtil.getValidAddress(addressStr);
+        Assert.assertEquals( address, "http://www.ctrip.com");
+    }
+}