Module jdk.httpserver
Package com.sun.net.httpserver

Class Headers

  • All Implemented Interfaces:
    Map<String,List<String>>

    public class Headers
extends Object
implements Map<String,List<String>>
    HTTP request and response headers are represented by this class which implements the interface Map<String, List <String>>. The keys are case-insensitive Strings representing the header names and the value associated with each key is a List<String> with one element for each occurrence of the header name in the request or response.

    For example, if a response header instance contains one key "HeaderName" with two values "value1 and value2" then this object is output as two header lines: 

     HeaderName: value1
 HeaderName: value2

    All the normal Map methods are provided, but the following additional convenience methods are most likely to be used:

    • getFirst(String) returns a single valued header or the first value of a multi-valued header.
    • add(String,String) adds the given header value to the list for the given key
    • set(String,String) sets the given header field to the single value given overwriting any existing values in the value list.

    All methods in this class accept null values for keys and values. However, null keys will never will be present in HTTP request headers, and will not be output/sent in response headers. Null values can be represented as either a null entry for the key (i.e. the list is null) or where the key has a list, but one (or more) of the list's values is null. Null values are output as a header line containing the key but no associated value.

    Since:
    1.6

    • Constructor Detail

      • Headers

        public Headers​()

    • Method Detail

      • size

        public int size​()
        Description copied from interface: Map
        Returns the number of key-value mappings in this map. If the map contains more than Integer.MAX_VALUE elements, returns Integer.MAX_VALUE.
        Specified by:
        size in interface Map<String,List<String>>
        Returns:
        the number of key-value mappings in this map

      • isEmpty

        public boolean isEmpty​()
        Description copied from interface: Map
        Returns true if this map contains no key-value mappings.
        Specified by:
        isEmpty in interface Map<String,List<String>>
        Returns:
        true if this map contains no key-value mappings

      • containsKey

        public boolean containsKey​(Object key)
        Description copied from interface: Map
        Returns true if this map contains a mapping for the specified key. More formally, returns true if and only if this map contains a mapping for a key k such that Objects.equals(key, k). (There can be at most one such mapping.)
        Specified by:
        containsKey in interface Map<String,List<String>>
        Parameters:
        key - key whose presence in this map is to be tested
        Returns:
        true if this map contains a mapping for the specified key

      • containsValue

        public boolean containsValue​(Object value)
        Description copied from interface: Map
        Returns true if this map maps one or more keys to the specified value. More formally, returns true if and only if this map contains at least one mapping to a value v such that Objects.equals(value, v). This operation will probably require time linear in the map size for most implementations of the Map interface.
        Specified by:
        containsValue in interface Map<String,List<String>>
        Parameters:
        value - value whose presence in this map is to be tested
        Returns:
        true if this map maps one or more keys to the specified value

      • get

        public List<String> get​(Object key)
        Description copied from interface: Map
        Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

        More formally, if this map contains a mapping from a key k to a value v such that Objects.equals(key, k), then this method returns v; otherwise it returns null. (There can be at most one such mapping.)

        If this map permits null values, then a return value of null does not necessarily indicate that the map contains no mapping for the key; it's also possible that the map explicitly maps the key to null. The containsKey operation may be used to distinguish these two cases.

        Specified by:
        get in interface Map<String,List<String>>
        Parameters:
        key - the key whose associated value is to be returned
        Returns:
        the value to which the specified key is mapped, or null if this map contains no mapping for the key

      • getFirst

        public String getFirst​(String key)
        returns the first value from the List of String values for the given key (if at least one exists).
        Parameters:
        key - the key to search for
        Returns:
        the first string value associated with the key

      • put

        public List<String> put​(String key,
                        List<String> value)
        Description copied from interface: Map
        Associates the specified value with the specified key in this map (optional operation). If the map previously contained a mapping for the key, the old value is replaced by the specified value. (A map m is said to contain a mapping for a key k if and only if m.containsKey(k) would return true.)
        Specified by:
        put in interface Map<String,List<String>>
        Parameters:
        key - key with which the specified value is to be associated
        value - value to be associated with the specified key
        Returns:
        the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key, if the implementation supports null values.)

      • add

        public void add​(String key,
                String value)
        adds the given value to the list of headers for the given key. If the mapping does not already exist, then it is created
        Parameters:
        key - the header name
        value - the header value to add to the header

      • set

        public void set​(String key,
                String value)
        sets the given value as the sole header value for the given key. If the mapping does not already exist, then it is created
        Parameters:
        key - the header name
        value - the header value to set.

      • remove

        public List<String> remove​(Object key)
        Description copied from interface: Map
        Removes the mapping for a key from this map if it is present (optional operation). More formally, if this map contains a mapping from key k to value v such that Objects.equals(key, k), that mapping is removed. (The map can contain at most one such mapping.)

        Returns the value to which this map previously associated the key, or null if the map contained no mapping for the key.

        If this map permits null values, then a return value of null does not necessarily indicate that the map contained no mapping for the key; it's also possible that the map explicitly mapped the key to null.

        The map will not contain a mapping for the specified key once the call returns.

        Specified by:
        remove in interface Map<String,List<String>>
        Parameters:
        key - key whose mapping is to be removed from the map
        Returns:
        the previous value associated with key, or null if there was no mapping for key.

      • putAll

        public void putAll​(Map<? extends String,? extends List<String>> t)
        Description copied from interface: Map
        Copies all of the mappings from the specified map to this map (optional operation). The effect of this call is equivalent to that of calling put(k, v) on this map once for each mapping from key k to value v in the specified map. The behavior of this operation is undefined if the specified map is modified while the operation is in progress.
        Specified by:
        putAll in interface Map<String,List<String>>
        Parameters:
        t - mappings to be stored in this map

      • clear

        public void clear​()
        Description copied from interface: Map
        Removes all of the mappings from this map (optional operation). The map will be empty after this call returns.
        Specified by:
        clear in interface Map<String,List<String>>

      • keySet

        public Set<String> keySet​()
        Description copied from interface: Map
        Returns a Set view of the keys contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll, and clear operations. It does not support the add or addAll operations.
        Specified by:
        keySet in interface Map<String,List<String>>
        Returns:
        a set view of the keys contained in this map

      • values

        public Collection<List<String>> values​()
        Description copied from interface: Map
        Returns a Collection view of the values contained in this map. The collection is backed by the map, so changes to the map are reflected in the collection, and vice-versa. If the map is modified while an iteration over the collection is in progress (except through the iterator's own remove operation), the results of the iteration are undefined. The collection supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Collection.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.
        Specified by:
        values in interface Map<String,List<String>>
        Returns:
        a collection view of the values contained in this map

      • entrySet

        public Set<Map.Entry<String,List<String>>> entrySet​()
        Description copied from interface: Map
        Returns a Set view of the mappings contained in this map. The set is backed by the map, so changes to the map are reflected in the set, and vice-versa. If the map is modified while an iteration over the set is in progress (except through the iterator's own remove operation, or through the setValue operation on a map entry returned by the iterator) the results of the iteration are undefined. The set supports element removal, which removes the corresponding mapping from the map, via the Iterator.remove, Set.remove, removeAll, retainAll and clear operations. It does not support the add or addAll operations.
        Specified by:
        entrySet in interface Map<String,List<String>>
        Returns:
        a set view of the mappings contained in this map

      • equals

        public boolean equals​(Object o)
        Description copied from class: Object
        Indicates whether some other object is "equal to" this one.

        The equals method implements an equivalence relation on non-null object references:

        • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
        • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
        • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
        • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
        • For any non-null reference value x, x.equals(null) should return false.

        The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

        Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

        Specified by:
        equals in interface Map<String,List<String>>
        Overrides:
        equals in class Object
        Parameters:
        o - the reference object with which to compare.
        Returns:
        true if this object is the same as the obj argument; false otherwise.
        See Also:
        Object.hashCode(), HashMap

      • hashCode

        public int hashCode​()
        Description copied from class: Object
        Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

        The general contract of hashCode is:

        • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
        • If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
        • It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

        As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (The hashCode may or may not be implemented as some function of an object's memory address at some point in time.)

        Specified by:
        hashCode in interface Map<String,List<String>>
        Overrides:
        hashCode in class Object
        Returns:
        a hash code value for this object.
        See Also:
        Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)