# Header Parameters { #header-parameters }

You can define Header parameters the same way you define `Query`, `Path` and `Cookie` parameters.

## Import `Header` { #import-header }

First import `Header`:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## Declare `Header` parameters { #declare-header-parameters }

Then declare the header parameters using the same structure as with `Path`, `Query` and `Cookie`.

# Header Parameter Models { #header-parameter-models }

If you have a group of related **header parameters**, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

      Header("content-disposition", ""),
      Header("content-encoding", ""),
      Header("content-language", ""),
      Header("content-length", ""),
      Header("content-location", ""),
      Header("content-range", ""),
      Header("content-type", ""),
      Header("cookie", ""),
      Header("date", ""),
      Header("etag", ""),
      Header("expect", ""),
      Header("expires", ""),

import org.codelibs.core.lang.StringUtil;

/**
 * Represents an HTTP request header with a name and value.
 * This class is used to encapsulate the header information for HTTP requests.
 * It provides methods to get and set the name and value of the header,
 * as well as a method to validate the header.
 *
 * <p>Example usage:</p>
 * <pre>
 *     RequestHeader header = new RequestHeader("Content-Type", "application/json");

	}
}

var isHTTPHeaderSizeTooLargeTests = []struct {
	header     http.Header
	shouldFail bool
}{
	{header: generateHeader(0, 0), shouldFail: false},
	{header: generateHeader(1024, 0), shouldFail: false},
	{header: generateHeader(2048, 0), shouldFail: false},
	{header: generateHeader(8*1024+1, 0), shouldFail: true},
	{header: generateHeader(0, 1024), shouldFail: false},
	{header: generateHeader(0, 2048), shouldFail: true},

          }
          line[0] == ':' -> {
            // Work around empty header names and header names that start with a colon (created by old
            // broken SPDY versions of the response cache).
            addLenient("", line.substring(1)) // Empty header name.
          }
          else -> {
            // No header name.
            addLenient("", line)
          }
        }
      }

	// set object-related metadata headers
	w.Header().Set(xhttp.LastModified, objInfo.ModTime.UTC().Format(http.TimeFormat))

	if objInfo.ETag != "" {
		w.Header()[xhttp.ETag] = []string{"\"" + objInfo.ETag + "\""}
	}

	if objInfo.VersionID != "" {
		w.Header()[xhttp.AmzVersionID] = []string{objInfo.VersionID}
	}

	if !objInfo.Expires.IsZero() {

    static final long serialVersionUID = 1L;

    private transient Entry header = new Entry(null, null, null);

    private transient int size = 0;

    /**
     * Creates an {@link SLinkedList}.
     */
    public SLinkedList() {
        header.next = header;
        header.previous = header;
    }

    /**
     * Returns the first element.
     *
     * @return the first element

	defer func(flag bool) { globalIsTLS = flag }(globalIsTLS)
	globalIsTLS = true
	for i, test := range encryptRequestTests {
		content := bytes.NewReader(make([]byte, 64))
		req := &http.Request{Header: http.Header{}}
		for k, v := range test.header {
			req.Header.Set(k, v)
		}
		_, _, err := EncryptRequest(content, req, "bucket", "object", test.metadata)
		if err != nil {
			t.Fatalf("Test %d: Failed to encrypt request: %v", i, err)
		}

        byte[] header = buildHeader(NtStatus.NT_STATUS_INVALID_PARAMETER);
        byte[] body = buildErrorBody(2, 3, new byte[] { (byte) 0xAA, (byte) 0xBB, (byte) 0xCC });
        byte[] packet = new byte[header.length + body.length];
        System.arraycopy(header, 0, packet, 0, header.length);
        System.arraycopy(body, 0, packet, header.length, body.length);