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

Nested Class Summary

Nested classes/interfaces declared in interface Map

Map.Entry<K,V>

Modifier and Type	Interface	Description
`static interface`	`Map.Entry<K,V>`	A map entry (key-value pair).

Constructor Summary

Constructor	Description
`Headers()`	Creates an empty instance of `Headers`.
`Headers(Map<String, List<String>> headers)`	Creates a mutable `Headers` from the given `headers` with the same header names and values.

Method Summary

Modifier and Type	Method	Description
`void`	`add(String key, String value)`	Adds the given `value` to the list of headers for the given `key`.
`void`	`clear()`	Removes all of the mappings from this map (optional operation).
`boolean`	`containsKey(Object key)`	Returns `true` if this map contains a mapping for the specified key.
`boolean`	`containsValue(Object value)`	Returns `true` if this map maps one or more keys to the specified value.
`Set<Map.Entry<String, List<String>>>`	`entrySet()`	Returns a `Set` view of the mappings contained in this map.
`boolean`	`equals(Object o)`	Compares the specified object with this map for equality.
`List<String>`	`get(Object key)`	Returns the value to which the specified key is mapped, or `null` if this map contains no mapping for the key.
`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.
`int`	`hashCode()`	Returns the hash code value for this map.
`boolean`	`isEmpty()`	Returns `true` if this map contains no key-value mappings.
`Set<String>`	`keySet()`	Returns a `Set` view of the keys contained in this map.
`static Headers`	`of(String... headers)`	Returns an immutable `Headers` with the given name value pairs as its set of headers.
`static Headers`	`of(Map<String, List<String>> headers)`	Returns an immutable `Headers` from the given `headers` with the same header names and values.
`List<String>`	`put(String key, List<String> value)`	Associates the specified value with the specified key in this map (optional operation).
`void`	`putAll(Map<? extends String, ? extends List<String>> t)`	Copies all of the mappings from the specified map to this map (optional operation).
`List<String>`	`remove(Object key)`	Removes the mapping for a key from this map if it is present (optional operation).
`void`	`set(String key, String value)`	Sets the given `value` as the sole header value for the given `key`.
`int`	`size()`	Returns the number of key-value mappings in this map.
`Collection<List<String>>`	`values()`	Returns a `Collection` view of the values contained in this map.

Methods declared in class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Modifier and Type	Method	Description
`protected Object`	`clone()`	Creates and returns a copy of this object.
`boolean`	`equals(Object obj)`	Indicates whether some other object is "equal to" this one.
`protected void`	`finalize()`	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
`final Class<?>`	`getClass()`	Returns the runtime class of this `Object`.
`int`	`hashCode()`	Returns a hash code value for this object.
`final void`	`notify()`	Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()`	Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()`	Returns a string representation of the object.
`final void`	`wait()`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
`final void`	`wait(long timeoutMillis)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis, int nanos)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Methods declared in interface Map

compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

Modifier and Type	Method	Description
`default List<String>`	`compute(String key, BiFunction<? super String, ? super List<String>, ? extends List<String>> remappingFunction)`	Attempts to compute a mapping for the specified key and its current mapped value, or `null` if there is no current mapping (optional operation).
`default List<String>`	`computeIfAbsent(String key, Function<? super String, ? extends List<String>> mappingFunction)`	If the specified key is not already associated with a value (or is mapped to `null`), attempts to compute its value using the given mapping function and enters it into this map unless `null` (optional operation).
`default List<String>`	`computeIfPresent(String key, BiFunction<? super String, ? super List<String>, ? extends List<String>> remappingFunction)`	If the value for the specified key is present and non-null, attempts to compute a new mapping given the key and its current mapped value (optional operation).
`default void`	`forEach(BiConsumer<? super String, ? super List<String>> action)`	Performs the given action for each entry in this map until all entries have been processed or the action throws an exception.
`default List<String>`	`getOrDefault(Object key, List<String> defaultValue)`	Returns the value to which the specified key is mapped, or `defaultValue` if this map contains no mapping for the key.
`default List<String>`	`merge(String key, List<String> value, BiFunction<? super List<String>, ? super List<String>, ? extends List<String>> remappingFunction)`	If the specified key is not already associated with a value or is associated with null, associates it with the given non-null value (optional operation).
`default List<String>`	`putIfAbsent(String key, List<String> value)`	If the specified key is not already associated with a value (or is mapped to `null`) associates it with the given value and returns `null`, else returns the current value (optional operation).
`default boolean`	`remove(Object key, Object value)`	Removes the entry for the specified key only if it is currently mapped to the specified value (optional operation).
`default List<String>`	`replace(String key, List<String> value)`	Replaces the entry for the specified key only if it is currently mapped to some value (optional operation).
`default boolean`	`replace(String key, List<String> oldValue, List<String> newValue)`	Replaces the entry for the specified key only if currently mapped to the specified value (optional operation).
`default void`	`replaceAll(BiFunction<? super String, ? super List<String>, ? extends List<String>> function)`	Replaces each entry's value with the result of invoking the given function on that entry until all entries have been processed or the function throws an exception (optional operation).

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 interface: Map

Compares the specified object with this map for equality. Returns true if the given object is also a map and the two maps represent the same mappings. More formally, two maps m1 and m2 represent the same mappings if m1.entrySet().equals(m2.entrySet()). This ensures that the equals method works properly across different implementations of the Map interface.

Specified by:

equals in interface Map<String, List<String>>

Overrides:

equals in class Object

Parameters:

o - object to be compared for equality with this map

Returns:

true if the specified object is equal to this map

See Also:

hashCode

public int hashCode()

Description copied from interface: Map

Returns the hash code value for this map. The hash code of a map is defined to be the sum of the hash codes of each entry in the map's entrySet() view. This ensures that m1.equals(m2) implies that m1.hashCode()==m2.hashCode() for any two maps m1 and m2, as required by the general contract of Object.hashCode().

Specified by:

hashCode in interface Map<String, List<String>>

Overrides:

hashCode in class Object

Returns:

the hash code value for this map

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

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