}
}

// only sqlite, postgres, sqlserver support returning
func TestSoftDeleteReturning(t *testing.T) {
	if DB.Dialector.Name() != "sqlite" && DB.Dialector.Name() != "postgres" && DB.Dialector.Name() != "sqlserver" {
		return
	}

	users := []*User{
		GetUser("delete-returning-1", Config{}),
		GetUser("delete-returning-2", Config{}),
		GetUser("delete-returning-3", Config{}),
	}
	DB.Create(&users)

	callbacks.RegisterDefaultCallbacks(db, &callbacks.Config{
		CreateClauses:        []string{"INSERT", "VALUES", "ON CONFLICT", "RETURNING"},
		UpdateClauses:        []string{"UPDATE", "SET", "WHERE", "RETURNING"},
		DeleteClauses:        []string{"DELETE", "FROM", "WHERE", "RETURNING"},
		LastInsertIDReversed: true,
	})

	return nil
}

func (DummyDialector) DefaultValueOf(field *schema.Field) clause.Expression {

{!../../docs_src/custom_response/tutorial004.py!}
```

In this example, the function `generate_html_response()` already generates and returns a `Response` instead of returning the HTML in a `str`.

By returning the result of calling `generate_html_response()`, you are already returning a `Response` that will override the default **FastAPI** behavior.

# Middleware

You can add middleware to **FastAPI** applications.

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.

              }
            },
            directExecutor()));
    thingToCancel[0] = serializer.submit(Callables.returning(null), directExecutor());
    results.add(thingToCancel[0]);
    // Enqueue more than enough tasks to force reentrancy.
    for (int i = 0; i < 5; i++) {
      results.add(serializer.submit(Callables.returning(null), directExecutor()));
    }

    manualExecutorTask[0].run();

////

FastAPI will use this return type to:

* **Validate** the returned data.
    * If the data is invalid (e.g. you are missing a field), it means that *your* app code is broken, not returning what it should, and it will return a server error instead of returning incorrect data. This way you and your clients can be certain that they will receive the data and the data shape expected.
* Add a **JSON Schema** for the response, in the OpenAPI *path operation*.

              }
            },
            directExecutor()));
    thingToCancel[0] = serializer.submit(Callables.returning(null), directExecutor());
    results.add(thingToCancel[0]);
    // Enqueue more than enough tasks to force reentrancy.
    for (int i = 0; i < 5; i++) {
      results.add(serializer.submit(Callables.returning(null), directExecutor()));
    }

    manualExecutorTask[0].run();

	}

	// mariadb with returning, values will be appended with id map
	if len(values) == beforeLen*2 {
		t.Skipf("This test case skipped, because the db supports returning")
	}

	for i := range values {
		v, ok := values[i]["id"]
		if !ok {
			t.Fatal("failed to create data from map with table, returning map has no primary key")
		}

		var result User

    assertEquals(1, prepender.times);
  }

  public void testConstructor_returning() throws Exception {
    Invokable<?, Prepender> delegate =
        Prepender.constructor(String.class, int.class).returning(Prepender.class);
    Prepender prepender = delegate.invoke(null, "a", 1);
    assertEquals("a", prepender.prefix);
    assertEquals(1, prepender.times);
  }

    assertEquals(1, prepender.times);
  }

  public void testConstructor_returning() throws Exception {
    Invokable<?, Prepender> delegate =
        Prepender.constructor(String.class, int.class).returning(Prepender.class);
    Prepender prepender = delegate.invoke(null, "a", 1);
    assertEquals("a", prepender.prefix);
    assertEquals(1, prepender.times);
  }