# 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 }

  val tag: Long,
  /** Encode and decode the value once tags are handled. */
  private val codec: Codec<T>,
  /** True if the default value should be used if this value is absent during decoding. */
  val isOptional: Boolean = false,
  /** The value to return if this value is absent. Undefined unless this is optional. */
  val defaultValue: T? = null,
  /** True to set the encoded or decoded value as the type hint for the current SEQUENCE. */

     *
     * @return the last modified timestamp
     */
    public ZonedDateTime getLastModified() {
        return lastModified;
    }

    /**
     * Returns the base64-encoded ID of the item.
     *
     * @return the encoded ID
     */
    public String getEncodedId() {
        return encodedId;
    }

    /**
     * When lastWriteTime is zero the encoded unsigned time must be all 1s.
     */
    @Test
    @DisplayName("edge: writeParameterWordsWireFormat with lastWriteTime=0")
    void testWriteParameterWordsZeroUTime() {
        SmbComClose close = new SmbComClose(42, 0L);
        byte[] buffer = new byte[6];
        close.writeParameterWordsWireFormat(buffer, 0);
        // first two bytes encode fid 42

            byte[] buffer = new byte[EXPECTED_SIZE * 3];

            // When
            int offset1 = chunk1.encode(buffer, 0);
            int offset2 = chunk2.encode(buffer, offset1);
            int offset3 = chunk3.encode(buffer, offset1 + offset2);

            // Then
            assertEquals(EXPECTED_SIZE, offset1);
            assertEquals(EXPECTED_SIZE, offset2);

            return null;
        }

        return newDictionaryFile(encodePath(path), path, timestamp);
    }

    /**
     * Encodes a file path using Base64 URL-safe encoding.
     *
     * @param path the file path to encode
     * @return the Base64 encoded path
     */
    protected String encodePath(final String path) {
        return Base64.getUrlEncoder().encodeToString(path.getBytes(Constants.CHARSET_UTF_8));

        // Should encode all 15 characters
        assertTrue(length >= 34);
        assertEquals(0x20, dst[0]);
    }

    @Test
    void readWireFormat_withTrailingSpaces_shouldTrimCorrectly() {
        // Prepare encoded data for "TEST    " (with trailing spaces)
        byte[] src = new byte[100];
        src[0] = 0x20;

        // Encode "TEST" correctly

        }
    }

    /**
     * Decodes a similar document hash from its compressed and encoded form.
     * Reverses the encoding process applied by encodeSimilarDocHash.
     *
     * @param hash the encoded hash string to decode
     * @return the decoded hash string, or the original hash if decoding fails
     */
    public String decodeSimilarDocHash(final String hash) {

/**
 * The first two bytes of each value is a header that includes its tag (field ID) and length.
 */
internal data class DerHeader(
  /**
   * Namespace of the tag.
   *
   * This value is encoded in bits 7 and 8 of the first byte of each value.
   *
   * ```
   * 0b00xxxxxx Universal
   * 0b01xxxxxx Application
   * 0b10xxxxxx Context-Specific
   * 0b11xxxxxx Private
   * ```
   */
  var tagClass: Int,

            SrvCopychunkCopy copy = new SrvCopychunkCopy(sourceKey, mockChunk1, mockChunk2);
            byte[] buffer = new byte[200];

            // When
            copy.encode(buffer, 0);

            // Then
            verify(mockChunk1, times(1)).encode(eq(buffer), eq(HEADER_SIZE));