# Encoders - `jsonable_encoder`

     * @param bufferIndex the starting offset in the buffer
     * @param len the length of data to decode
     * @throws IOException if an I/O error occurs during decoding
     */
    public SecurityDescriptor(final byte[] buffer, final int bufferIndex, final int len) throws IOException {
        this.decode(buffer, bufferIndex, len);
    }

    /**
     * Decodes a security descriptor from a byte buffer.
     *

Si vous ne déclarez pas de modèle de réponse, FastAPI utilise le `jsonable_encoder` expliqué dans [Encodeur compatible JSON](../tutorial/encoder.md) et le place dans une `JSONResponse`.

Vous pouvez également créer directement une `JSONResponse` et la renvoyer.

/// tip | Astuce

Import `EventSourceResponse` from `fastapi.sse`:

{* ../../docs_src/server_sent_events/tutorial001_py310.py ln[1:25] hl[4,22] *}

Each yielded item is encoded as JSON and sent in the `data:` field of an SSE event.

If you declare the return type as `AsyncIterable[Item]`, FastAPI will use it to **validate**, **document**, and **serialize** the data using Pydantic.

        assertArrayEquals(rawBytes, avTargetName.getRaw(), "Raw bytes should match the input");
    }

    /**
     * Test constructor with a target name string.
     * Verifies that the string is correctly encoded to UTF-16LE bytes and stored.
     */
    @Test
    void testConstructorWithString() {
        String targetName = "AnotherTargetName";
        AvTargetName avTargetName = new AvTargetName(targetName);

  private val bytesIn = Buffer()
  private val hpackReader = Hpack.Reader(bytesIn, 4096)

  protected fun testDecoder(story: Story) {
    for (testCase in story.cases) {
      val encoded = testCase.wire ?: continue
      bytesIn.write(encoded)
      hpackReader.readHeaders()
      assertSetEquals(
        "seqno=$testCase.seqno",
        testCase.headersList,
        hpackReader.getAndResetHeaderList(),
      )
    }
  }

    the proxy selectors are different. Ugh!


## Version 4.2.0

_2019-09-10_

 *  New: API to decode a certificate and private key to create a `HeldCertificate`. This accepts a
    string containing both a certificate and PKCS #8-encoded private key.

    ```kotlin
    val heldCertificate = HeldCertificate.decode("""
        |-----BEGIN CERTIFICATE-----
        |MIIBYTCCAQegAwIBAgIBKjAKBggqhkjOPQQDAjApMRQwEgYDVQQLEwtlbmdpbmVl

Si vous ne déclarez pas de modèle de réponse, FastAPI utilisera le `jsonable_encoder` expliqué dans [Encodeur compatible JSON](../tutorial/encoder.md) et le placera dans une `JSONResponse`.

        this.mechanismListMIC = mechanismListMIC;
    }

    /**
     * Encodes this SPNEGO token to a byte array
     * @return the encoded token bytes
     */
    public abstract byte[] toByteArray();

    /**
     * Parses the provided token bytes to populate this SPNEGO token
     * @param token the token bytes to parse
     * @throws IOException if parsing fails
     */

    /**
     * Downloads a log file by its encoded ID.
     *
     * @param id the Base64 encoded filename of the log file to download
     * @return ActionResponse containing the log file stream
     */
    @Execute
    @Secured({ ROLE, ROLE + VIEW })
    public ActionResponse download(final String id) {
        final String filename = sanitizeFilename(new String(Base64.getDecoder().decode(id), StandardCharsets.UTF_8));