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

Class Headers

java.lang.Object
com.sun.net.httpserver.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.

An instance of Headers is either mutable or immutable. A mutable headers allows to add, remove, or modify header names and values, e.g. the instance returned by HttpExchange.getResponseHeaders(). An immutable headers disallows any modification to header names or values, e.g. the instance returned by HttpExchange.getRequestHeaders(). The mutator methods for an immutable headers instance unconditionally throw UnsupportedOperationException.

All methods in this class reject null values for keys and values. null keys will never be present in HTTP request or response headers.

Since:
1.6

  • Constructor Details

    • Headers

      public Headers()
      Creates an empty instance of Headers.

    • Headers

      public Headers(Map<String,List<String>> headers)
      Creates a mutable Headers from the given headers with the same header names and values.
      Parameters:
      headers - a map of header names and values
      Throws:
      NullPointerException - if headers or any of its names or values are null, or if any value contains null.
      Since:
      18

  • Method Details

    • 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, or null if no mapping for the key exists.
      Parameters:
      key - the key to search for
      Returns:
      the first String value associated with the key, or null if no mapping for the key exists

    • 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 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. If the specified map has a defined encounter order, processing of its mappings generally occurs in that order.
      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.

      An equivalence relation partitions the elements it operates on into equivalence classes; all the members of an equivalence class are equal to each other. Members of an equivalence class are substitutable for each other, at least for some purposes.

      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:

    • 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 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 equals 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.
      Specified by:
      hashCode in interface Map<String,List<String>>
      Overrides:
      hashCode in class Object
      Returns:
      a hash code value for this object.
      See Also:

    • of

      public static Headers of(String... headers)
      Returns an immutable Headers with the given name value pairs as its set of headers.

      The supplied String instances must alternate as header names and header values. To add several values to the same name, the same name must be supplied with each new value. If the supplied headers is empty, then an empty Headers is returned.

      Parameters:
      headers - the list of name value pairs
      Returns:
      an immutable headers with the given name value pairs
      Throws:
      NullPointerException - if headers or any of its elements are null.
      IllegalArgumentException - if the number of supplied strings is odd.
      Since:
      18

    • of

      public static Headers of(Map<String,List<String>> headers)
      Returns an immutable Headers from the given headers with the same header names and values.
      Parameters:
      headers - a map of header names and values
      Returns:
      an immutable headers
      Throws:
      NullPointerException - if headers or any of its names or values are null, or if any value contains null.
      Since:
      18