* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package org.codelibs.core.convert;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertEquals;

import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;

 */
package org.codelibs.core.beans.converter;

import static org.codelibs.core.lang.StringUtil.isEmpty;
import static org.codelibs.core.misc.AssertionUtil.assertArgumentNotEmpty;
import static org.codelibs.core.misc.AssertionUtil.assertArgumentNotNull;

import java.util.Date;

import org.codelibs.core.beans.Converter;
import org.codelibs.core.convert.DateConversionUtil;

 */
package org.codelibs.core.beans.converter;

import static org.codelibs.core.misc.AssertionUtil.assertArgumentNotEmpty;
import static org.codelibs.core.misc.AssertionUtil.assertArgumentNotNull;

import java.util.Date;

import org.codelibs.core.beans.Converter;
import org.codelibs.core.convert.DateConversionUtil;
import org.codelibs.core.convert.StringConversionUtil;
import org.codelibs.core.lang.StringUtil;

 */
package org.codelibs.core.beans.converter;

import static org.codelibs.core.lang.StringUtil.isEmpty;
import static org.codelibs.core.misc.AssertionUtil.assertArgumentNotEmpty;
import static org.codelibs.core.misc.AssertionUtil.assertArgumentNotNull;

import java.util.Date;

import org.codelibs.core.beans.Converter;
import org.codelibs.core.convert.StringConversionUtil;

	policyCondStartsWith    = "starts-with"
	policyCondContentLength = "content-length-range"
)

// toString - Safely convert interface to string without causing panic.
func toString(val interface{}) string {
	switch v := val.(type) {
	case string:
		return v
	default:
		return ""
	}
}

// toLowerString - safely convert interface to lower string
func toLowerString(val interface{}) string {

So, even with the code above that doesn't use Pydantic explicitly, FastAPI is using Pydantic to convert those standard dataclasses to Pydantic's own flavor of dataclasses.

And of course, it supports the same:

* data validation
* data serialization
* data documentation, etc.

from typing import Annotated

from fastapi import FastAPI, Header

app = FastAPI()


@app.get("/items/")
async def read_items(
    strange_header: Annotated[str | None, Header(convert_underscores=False)] = None,
):

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package org.codelibs.core.convert;

import java.math.BigDecimal;
import java.text.SimpleDateFormat;

import org.codelibs.core.lang.StringUtil;

/**
 * {@link BigDecimal}用の変換ユーティリティです。
 *
 * @author higa
 */

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package org.codelibs.core.convert;

import junit.framework.TestCase;

/**
 * @author higa
 *
 */
public class ShortConversionUtilTest extends TestCase {

    /**
     * @throws Exception
     */

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */
package org.codelibs.core.convert;

import static org.codelibs.core.misc.AssertionUtil.assertArgument;

/**
 * byte配列用の変換ユーティリティです。
 *
 * @author higa
 */
public abstract class BinaryConversionUtil {

    /**