ARROW-8305: [Java] ExtensionTypeVector should make sure underlyingVec…

…tor not null

Related to [ARROW-8305](https://issues.apache.org/jira/browse/ARROW-8305).

In ExtensionTypeVector seems not check nullability for underlyingVector, and it will throw exception when it is null in some api like accept/reset/getField etc.

it's better to do null check when create ExtensionTypeVector rather than when really use it.

Closes #6798 from tianchen92/ARROW-8305

Authored-by: tianchen <niki.lj@alibaba-inc.com>
Signed-off-by: David Li <li.davidm96@gmail.com>

java/vector/src/main/java/org/apache/arrow/vector/ExtensionTypeVector.java

@@ -22,6 +22,7 @@
 
 import org.apache.arrow.memory.BufferAllocator;
 import org.apache.arrow.memory.OutOfMemoryException;
+import org.apache.arrow.util.Preconditions;
 import org.apache.arrow.vector.compare.VectorVisitor;
 import org.apache.arrow.vector.complex.reader.FieldReader;
 import org.apache.arrow.vector.ipc.message.ArrowFieldNode;
@@ -50,6 +51,7 @@ public abstract class ExtensionTypeVector<T extends BaseValueVector & FieldVecto
    */
   public ExtensionTypeVector(String name, BufferAllocator allocator, T underlyingVector) {
     super(allocator);
+    Preconditions.checkNotNull(underlyingVector, "underlyingVector can not be null.");
     this.name = name;
     this.underlyingVector = underlyingVector;
   }

java/vector/src/test/java/org/apache/arrow/vector/types/pojo/TestExtensionType.java

@@ -17,6 +17,9 @@
 
 package org.apache.arrow.vector.types.pojo;
 
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
 import java.io.File;
 import java.io.IOException;
 import java.nio.ByteBuffer;
@@ -155,6 +158,19 @@ public void readUnderlyingType() throws IOException {
     }
   }
 
+  @Test
+  public void testNullCheck() {
+    NullPointerException e = assertThrows(NullPointerException.class,
+        () -> {
+          try (final BufferAllocator allocator = new RootAllocator(Integer.MAX_VALUE);
+               final ExtensionTypeVector vector = new UuidVector("uuid", allocator, null)) {
+            vector.getField();
+            vector.allocateNewSafe();
+          }
+        });
+    assertTrue(e.getMessage().contains("underlyingVector can not be null."));
+  }
+
   static class UuidType extends ExtensionType {
 
     @Override