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

Nested Class Summary

Nested classes/interfaces declared in interface java.util.Map

Map.Entry<K,V>

Constructor Summary

Constructors

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 java.lang.Object

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

Methods declared in interface java.util.Map

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

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:

• Object.hashCode()
• HashMap

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:

• Map.Entry.hashCode()
• Object.equals(Object)
• Map.equals(Object)

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