# JSON Compatible Encoder { #json-compatible-encoder }

There are some cases where you might need to convert a data type (like a Pydantic model) to something compatible with JSON (like a `dict`, `list`, etc).

For example, if you need to store it in a database.

For that, **FastAPI** provides a `jsonable_encoder()` function.

## Using the `jsonable_encoder` { #using-the-jsonable-encoder }

     */
    @Override
    public int size() {
        return this.len;
    }

    /**
     * {@inheritDoc}
     *
     * @see jcifs.Encodable#encode(byte[], int)
     */
    @Override
    public int encode(final byte[] dst, final int dstIndex) {
        System.arraycopy(this.bytes, this.off, dst, dstIndex, this.len);
        return this.len;
    }

/// warning

You can declare multiple `File` and `Form` parameters in a *path operation*, but you can't also declare `Body` fields that you expect to receive as JSON, as the request will have the body encoded using `multipart/form-data` instead of `application/json`.

This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Recap { #recap }

import java.net.ProtocolException
import okio.Buffer
import okio.BufferedSource
import okio.ByteString
import okio.ForwardingSource
import okio.Source
import okio.buffer

/**
 * Streaming decoder of data encoded following Abstract Syntax Notation One (ASN.1). There are
 * multiple variants of ASN.1, including:
 *
 *  * DER: Distinguished Encoding Rules. This further constrains ASN.1 for deterministic encoding.

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#include "../../../../../runtime/textflag.h"

TEXT asmtest(SB),DUPOK|NOSPLIT,$0
	// Instructions that were encoded with BYTE sequences.
	// Included to simplify validation of CL that fixed that.
	MOVQ (AX), M0  // 0f6f00
	MOVQ M0, 8(SP) // 0f7f442408
	MOVQ 8(SP), M0 // 0f6f442408
	MOVQ M0, (AX)  // 0f7f00
	MOVQ M0, (BX)  // 0f7f03

    val expected =
      Buffer()
        .writeByte(0x40) // Literal header, new name.
        .writeByte(0x82) // String literal is Huffman encoded (len = 2).
        .writeByte(0x94) // 'foo' Huffman encoded.
        .writeByte(0xE7)
        .writeByte(3) // String literal not Huffman encoded (len = 3).
        .writeByte('b'.code)
        .writeByte('a'.code)
        .writeByte('r'.code)
        .readByteString()

        // CharUtil.isUrlChar does NOT include { }, so they get percent-encoded
        String result = DocumentUtil.encodeUrl("http://example.com/{id}");
        assertEquals("http://example.com/%7Bid%7D", result);
    }

    @Test
    public void test_encodeUrl_unicodeChars() {
        // Non-ASCII characters are percent-encoded; encoding depends on request context

//
// returns ErrNone if matches. S3 errors otherwise.
func doesPresignV2SignatureMatch(r *http.Request) APIErrorCode {
	// r.RequestURI will have raw encoded URI as sent by the client.
	tokens := strings.SplitN(r.RequestURI, "?", 2)
	encodedResource := tokens[0]
	encodedQuery := ""
	if len(tokens) == 2 {
		encodedQuery = tokens[1]
	}

	var (

     * @return The string encoded in <code>application/x-www-form-urlencoded</code> format.
     */
    public static String encode(final String s, final String enc) {
        assertArgumentNotEmpty("s", s);
        assertArgumentNotEmpty("enc", enc);

        try {
            return URLEncoder.encode(s, enc);
        } catch (final UnsupportedEncodingException e) {

        return null;
    }

    /**
     * Encodes a URL by encoding non-URL-safe characters.
     * Uses the request's character encoding if available, otherwise defaults to UTF-8.
     * Only encodes characters that are not considered URL-safe according to CharUtil.
     *
     * @param url the URL to encode
     * @return the encoded URL with non-URL-safe characters properly encoded
     */