Make ip field parsing easier to read (backport of #76363) (#76369)

This makes the IP parsing code in `IpFieldMapper` a little easier to
read by removing the string/object juggling. It also pulls the value
parsing bit out into a very sensible and readable method. As a bonus,
this method is reusable and we *do* plan to reuse it.

server/src/main/java/org/elasticsearch/index/mapper/IpFieldMapper.java

@@ -18,11 +18,12 @@
 import org.apache.lucene.util.ArrayUtil;
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.Version;
-import org.elasticsearch.core.Nullable;
-import org.elasticsearch.core.Tuple;
 import org.elasticsearch.common.logging.DeprecationCategory;
 import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.network.InetAddresses;
+import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.core.Nullable;
+import org.elasticsearch.core.Tuple;
 import org.elasticsearch.index.fielddata.IndexFieldData;
 import org.elasticsearch.index.fielddata.ScriptDocValues;
 import org.elasticsearch.index.fielddata.plain.SortedSetOrdinalsIndexFieldData;
@@ -413,34 +414,28 @@ protected String contentType() {
 
     @Override
     protected void parseCreateField(DocumentParserContext context) throws IOException {
-        Object addressAsObject = context.parser().textOrNull();
-
-        if (addressAsObject == null) {
-            addressAsObject = nullValue;
-        }
-
-        if (addressAsObject == null) {
-            return;
-        }
-
-        String addressAsString = addressAsObject.toString();
         InetAddress address;
-        if (addressAsObject instanceof InetAddress) {
-            address = (InetAddress) addressAsObject;
-        } else {
-            try {
-                address = InetAddresses.forString(addressAsString);
-            } catch (IllegalArgumentException e) {
-                if (ignoreMalformed) {
-                    context.addIgnoredField(fieldType().name());
-                    return;
-                } else {
-                    throw e;
-                }
+        try {
+            address = value(context.parser(), nullValue);
+        } catch (IllegalArgumentException e) {
+            if (ignoreMalformed) {
+                context.addIgnoredField(fieldType().name());
+                return;
+            } else {
+                throw e;
             }
         }
+        if (address != null) {
+            indexValue(context, address);
+        }
+    }
 
-        indexValue(context, address);
+    private static InetAddress value(XContentParser parser, InetAddress nullValue) throws IOException {
+        String value = parser.textOrNull();
+        if (value == null) {
+            return nullValue;
+        }
+        return InetAddresses.forString(value);
     }
 
     private void indexValue(DocumentParserContext context, InetAddress address) {
@@ -467,5 +462,4 @@ protected void indexScriptValues(SearchLookup searchLookup, LeafReaderContext re
     public FieldMapper.Builder getMergeBuilder() {
         return new Builder(simpleName(), scriptCompiler, ignoreMalformedByDefault, indexCreatedVersion).init(this);
     }
-
 }