io.grpc

Class Metadata

java.lang.Object

io.grpc.Metadata

Direct Known Subclasses:

Metadata.Headers, Metadata.Trailers

@NotThreadSafe
public abstract class Metadata
extends Object

Provides access to read and write metadata values to be exchanged during a call.

This class is not thread safe, implementations should ensure that header reads and writes do not occur in multiple threads concurrently.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	Metadata.AsciiMarshaller<T> Marshaller for metadata values that are serialized into ASCII strings that contain only printable characters and space.
static interface	Metadata.BinaryMarshaller<T> Marshaller for metadata values that are serialized into raw binary.
static class	Metadata.Headers Concrete instance for metadata attached to the start of a call.
static class	Metadata.Key<T> Key for metadata entries.
static class	Metadata.Trailers Concrete instance for metadata attached to the end of the call.

Field Summary

Fields

Modifier and Type	Field and Description
static Metadata.AsciiMarshaller<String>	ASCII_STRING_MARSHALLER Simple metadata marshaller that encodes strings as is.
static String	BINARY_HEADER_SUFFIX All binary headers should have this suffix in their names.
static Metadata.AsciiMarshaller<Integer>	INTEGER_MARSHALLER Simple metadata marshaller that encodes an integer as a signed decimal string.

Method Summary

Modifier and Type	Method and Description
boolean	containsKey(Metadata.Key<?> key) Returns true if a value is defined for the given key.
<T> T	get(Metadata.Key<T> key) Returns the last metadata entry added with the name 'name' parsed as T.
<T> Iterable<T>	getAll(Metadata.Key<T> key) Returns all the metadata entries named 'name', in the order they were received, parsed as T or null if there are none.
boolean	isSerializable() Can this metadata be serialized.
void	merge(Metadata other) Perform a simple merge of two sets of metadata.
void	merge(Metadata other, Set<Metadata.Key<?>> keys) Merge values for the given set of keys into this set of metadata.
<T> void	put(Metadata.Key<T> key, T value)
<T> boolean	remove(Metadata.Key<T> key, T value) Remove a specific value.
<T> List<T>	removeAll(Metadata.Key<T> key) Remove all values for the given key.
byte[][]	serialize() Serialize all the metadata entries.

Methods inherited from class java.lang.Object

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

Field Detail

BINARY_HEADER_SUFFIX

public static final String BINARY_HEADER_SUFFIX

All binary headers should have this suffix in their names. Vice versa.

See Also:

Constant Field Values

ASCII_STRING_MARSHALLER

public static final Metadata.AsciiMarshaller<String> ASCII_STRING_MARSHALLER

Simple metadata marshaller that encodes strings as is.

This should be used with ASCII strings that only contain printable characters and space. Otherwise the output may be considered invalid and discarded by the transport.

INTEGER_MARSHALLER

public static final Metadata.AsciiMarshaller<Integer> INTEGER_MARSHALLER

Simple metadata marshaller that encodes an integer as a signed decimal string.

Method Detail

containsKey

public boolean containsKey(Metadata.Key<?> key)

Returns true if a value is defined for the given key.

get

public <T> T get(Metadata.Key<T> key)

Returns the last metadata entry added with the name 'name' parsed as T.

Returns:

the parsed metadata entry or null if there are none.

getAll

public <T> Iterable<T> getAll(Metadata.Key<T> key)

Returns all the metadata entries named 'name', in the order they were received, parsed as T or null if there are none.

put

public <T> void put(Metadata.Key<T> key,
                    T value)

remove

public <T> boolean remove(Metadata.Key<T> key,
                          T value)

Remove a specific value.

removeAll

public <T> List<T> removeAll(Metadata.Key<T> key)

Remove all values for the given key.

isSerializable

public boolean isSerializable()

Can this metadata be serialized. Metadata constructed from raw binary or ascii values cannot be serialized without merging it into a serializable instance using merge(Metadata, java.util.Set)

serialize

public byte[][] serialize()

Serialize all the metadata entries.

It produces serialized names and values interleaved. result[i*2] are names, while result[i*2+1] are values.

Names are ASCII string bytes. If the name ends with "-bin", the value can be raw binary. Otherwise, the value must be printable ASCII characters or space.

merge

public void merge(Metadata other)

Perform a simple merge of two sets of metadata.

Note that we can't merge non-serializable metadata into serializable.

merge

public void merge(Metadata other,
                  Set<Metadata.Key<?>> keys)

Merge values for the given set of keys into this set of metadata.