Module java.net.http
Package java.net.http

Class HttpHeaders

  • public final class HttpHeaders
extends Object
    A read-only view of a set of HTTP headers.

    An HttpHeaders is not typically created directly, but rather returned from an HttpRequest or an HttpResponse. Specific HTTP headers can be set for a request through one of the request builder's headers methods.

    The methods of this class ( that accept a String header name ), and the Map returned by the map method, operate without regard to case when retrieving the header value(s).

    An HTTP header name may appear more than once in the HTTP protocol. As such, headers are represented as a name and a list of values. Each occurrence of a header value is added verbatim, to the appropriate header name list, without interpreting its value. In particular, HttpHeaders does not perform any splitting or joining of comma separated header value strings. The order of elements in a header value list is preserved when building a request. For responses, the order of elements in a header value list is the order in which they were received. The Map returned by the map method, however, does not provide any guarantee with regard to the ordering of its entries.

    HttpHeaders instances are immutable.

    Since:
    11

    • Method Detail

      • firstValue

        public Optional<String> firstValue​(String name)
        Returns an Optional containing the first header string value of the given named (and possibly multi-valued) header. If the header is not present, then the returned Optional is empty.
        Parameters:
        name - the header name
        Returns:
        an Optional<String> containing the first named header string value, if present

      • firstValueAsLong

        public OptionalLong firstValueAsLong​(String name)
        Returns an OptionalLong containing the first header string value of the named header field. If the header is not present, then the Optional is empty. If the header is present but contains a value that does not parse as a Long value, then an exception is thrown.
        Parameters:
        name - the header name
        Returns:
        an OptionalLong
        Throws:
        NumberFormatException - if a value is found, but does not parse as a Long

      • allValues

        public List<String> allValues​(String name)
        Returns an unmodifiable List of all of the header string values of the given named header. Always returns a List, which may be empty if the header is not present.
        Parameters:
        name - the header name
        Returns:
        a List of headers string values

      • map

        public Map<String,​List<String>> map()
        Returns an unmodifiable multi Map view of this HttpHeaders.
        Returns:
        the Map

      • equals

        public final boolean equals​(Object obj)
        Tests this HTTP headers instance for equality with the given object.

        If the given object is not an HttpHeaders then this method returns false. Two HTTP headers are equal if each of their corresponding maps are equal.

        This method satisfies the general contract of the Object.equals method.

        Overrides:
        equals in class Object
        Parameters:
        obj - the object to which this object is to be compared
        Returns:
        true if, and only if, the given object is an HttpHeaders that is equal to this HTTP headers
        See Also:
        Object.hashCode(), HashMap

      • toString

        public String toString()
        Returns this HTTP headers as a string.
        Overrides:
        toString in class Object
        Returns:
        a string describing the HTTP headers

      • of

        public static HttpHeaders of​(Map<String,​List<String>> headerMap,
                             BiPredicate<String,​String> filter)
        Returns an HTTP headers from the given map. The given map's key represents the header name, and its value the list of string header values for that header name.

        An HTTP header name may appear more than once in the HTTP protocol. Such, multi-valued, headers must be represented by a single entry in the given map, whose entry value is a list that represents the multiple header string values. Leading and trailing whitespaces are removed from all string values retrieved from the given map and its lists before processing. Only headers that, after filtering, contain at least one, possibly empty string, value will be added to the HTTP headers.

        API Note:
        The primary purpose of this method is for testing frameworks. Per-request headers can be set through one of the HttpRequest headers methods.
        Parameters:
        headerMap - the map containing the header names and values
        filter - a filter that can be used to inspect each header-name-and-value pair in the given map to determine if it should, or should not, be added to the to the HTTP headers
        Returns:
        an HTTP headers instance containing the given headers
        Throws:
        NullPointerException - if any of: headerMap, a key or value in the given map, or an entry in the map's value list, or filter, is null
        IllegalArgumentException - if the given headerMap contains any two keys that are equal ( without regard to case ); or if the given map contains any key whose length, after trimming whitespaces, is 0