# Body - Fields { #body-fields }

The same way you can declare additional validation and metadata in *path operation function* parameters with `Query`, `Path` and `Body`, you can declare validation and metadata inside of Pydantic models using Pydantic's `Field`.

## Import `Field` { #import-field }

First, you have to import it:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[4] *}


/// warning

        List<String> readings = Arrays.asList("reading1", "reading2");
        List<String> fields = Arrays.asList("field1", "field2", "field3");
        List<String> tags = Arrays.asList("tag1", "tag2");
        List<String> roles = Arrays.asList("role1", "role2", "role3");

        elevateWord = new ElevateWord(word, boost, readings, fields, tags, roles);
        SuggestItem suggestItem = elevateWord.toSuggestItem();

    @Test
    public void testGetKeywordsWithEmptyField() {
        // Test with empty field array
        String query = "test query";
        String[] fields = {};
        List<String> keywords = SuggestUtil.getKeywords(query, fields);
        assertNotNull(keywords);
        assertEquals(0, keywords.size()); // No keywords because no fields match
    }

    @Test
    public void testGetKeywordsWithComplexQuery() {

<div class="screenshot">
<img src="/img/tutorial/request-form-models/image01.png">
</div>

## Forbid Extra Form Fields { #forbid-extra-form-fields }

In some special use cases (probably not very common), you might want to **restrict** the form fields to only those declared in the Pydantic model. And **forbid** any **extra** fields.

/// note

This is supported since FastAPI version `0.114.0`. 🤓

///

        item.setReadings(newReadings);
        assertArrayEquals(newReadings, item.getReadings());

        // Test fields
        String[] fields = { "field1", "field2" };
        item.setFields(fields);
        assertArrayEquals(fields, item.getFields());

        // Test tags
        String[] tags = { "tag1", "tag2" };
        item.setTags(tags);

The `HeroUpdate` *data model* is somewhat special, it has **all the same fields** that would be needed to create a new hero, but all the fields are **optional** (they all have a default value). This way, when you update a hero, you can send just the fields that you want to update.

Because all the **fields actually change** (the type now includes `None` and they now have a default value of `None`), we need to **re-declare** them.

            parser.setDefaultOperator(StandardQueryConfigHandler.Operator.AND);

            // Parse with the first field if available, otherwise use "default"
            String defaultField = fields != null && fields.length > 0 ? fields[0] : "default";
            termQueryList = getTermQueryList(parser.parse(q, defaultField), fields);
        } catch (final Exception e) {
            return keywords;
        }

For example, in one of the ways the OAuth2 specification can be used (called "password flow") it is required to send a `username` and `password` as form fields.

The <abbr title="specification">spec</abbr> requires the fields to be exactly named `username` and `password`, and to be sent as form fields, not JSON.

The files and form fields will be uploaded as form data and you will receive the files and form fields.

And you can declare some of the files as `bytes` and some as `UploadFile`.

/// warning

| `terms_of_service` | `str` | A URL to the Terms of Service for the API. If provided, this has to be a URL. |