Optionally require a valid content type for all rest requests with content (#22691)

This change adds a strict mode for xcontent parsing on the rest layer. The strict mode will be off by default for 5.x and in a separate commit will be enabled by default for 6.0. The strict mode, which can be enabled by setting `http.content_type.required: true` in 5.x, will require that all incoming rest requests have a valid and supported content type header before the request is dispatched. In the non-strict mode, the Content-Type header will be inspected and if it is not present or not valid, we will continue with auto detection of content like we have done previously.

The content type header is parsed to the matching XContentType value with the only exception being for plain text requests. This value is then passed on with the content bytes so that we can reduce the number of places where we need to auto-detect the content type.

As part of this, many transport requests and builders were updated to provide methods that
accepted the XContentType along with the bytes and the methods that would rely on auto-detection have been deprecated.

In the non-strict mode, deprecation warnings are issued whenever a request with body doesn't provide the Content-Type header.

See #19388 

1 files changed, 16 insertions, 6 deletions

diff --git a/core/src/main/java/org/elasticsearch/index/mapper/SourceToParse.java b/core/src/main/java/org/elasticsearch/index/mapper/SourceToParse.java
index 0cafc50bbe..a8a983ecde 100644
--- a/core/src/main/java/org/elasticsearch/index/mapper/SourceToParse.java
+++ b/core/src/main/java/org/elasticsearch/index/mapper/SourceToParse.java
@@ -23,15 +23,18 @@ import java.util.Objects;
 
 import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.bytes.BytesReference;
+import org.elasticsearch.common.xcontent.XContentFactory;
+import org.elasticsearch.common.xcontent.XContentType;
 
 public class SourceToParse {
 
-    public static SourceToParse source(String index, String type, String id, BytesReference source) {
-        return source(Origin.PRIMARY, index, type, id, source);
+    public static SourceToParse source(String index, String type, String id, BytesReference source, XContentType contentType) {
+        return source(Origin.PRIMARY, index, type, id, source, contentType);
     }
 
-    public static SourceToParse source(Origin origin, String index, String type, String id, BytesReference source) {
-        return new SourceToParse(origin, index, type, id, source);
+    public static SourceToParse source(Origin origin, String index, String type, String id, BytesReference source,
+                                       XContentType contentType) {
+        return new SourceToParse(origin, index, type, id, source, contentType);
     }
 
     private final Origin origin;
@@ -48,14 +51,17 @@ public class SourceToParse {
 
     private String parentId;
 
-    private SourceToParse(Origin origin, String index, String type, String id, BytesReference source) {
+    private XContentType xContentType;
+
+    private SourceToParse(Origin origin, String index, String type, String id, BytesReference source, XContentType xContentType) {
         this.origin = Objects.requireNonNull(origin);
         this.index = Objects.requireNonNull(index);
         this.type = Objects.requireNonNull(type);
         this.id = Objects.requireNonNull(id);
         // we always convert back to byte array, since we store it and Field only supports bytes..
         // so, we might as well do it here, and improve the performance of working with direct byte arrays
-        this.source = new BytesArray(source.toBytesRef());
+        this.source = new BytesArray(Objects.requireNonNull(source).toBytesRef());
+        this.xContentType = Objects.requireNonNull(xContentType);
     }
 
     public Origin origin() {
@@ -91,6 +97,10 @@ public class SourceToParse {
         return this.routing;
     }
 
+    public XContentType getXContentType() {
+        return this.xContentType;
+    }
+
     public SourceToParse routing(String routing) {
         this.routing = routing;
         return this;