Httpcore Tutorial – Download as PDF File .pdf), Text File .txt) or read online. Google Git. Sign in · chromium / chromium / deps / httpcomponents-core / master / . / binary-distribution / tutorial / pdf / I recommend using OkHttp instead of HttpClient for new applications. OkHttp is extremely efficient and has a great API. This tutorial is still here.
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HttpCore has the following scope and goals: The message header of an HTTP request consists of a request line and a collection of header fields. The message header of an HTTP response consists of a status line and a collection of header fields. All HTTP messages must include hytpcore protocol version.
The http core tutorial
Some HTTP messages can optionally enclose a content body. The first line of that message includes the method to apply to the resource, the identifier of the resource, and the protocol version in use.
The first line of that message consists of the protocol version followed by a numeric status code and its associated textual phrase. HttpCore provides methods to retrieve, add, remove, and enumerate such headers.
Entities can be found in some requests and in some responses, as they are optional. Requests that use entities are referred tutorrial as entity-enclosing requests. The HTTP specification defines two entity-enclosing methods: Responses are usually expected to enclose a content entity. HttpCore distinguishes three kinds of entities, depending on where their content originates: The content is received from a stream, or generated on the fly. In particular, this category includes entities being received from a connection.
Streamed entities are generally not repeatable. The content is in memory or obtained by means that are independent from a connection or other entity. Self-contained entities are generally repeatable. The content is obtained from another entity Repeatable bttpcore An entity can be repeatable, meaning its content can be read more than once.
This is only possible with self-contained entities like ByteArrayEntity or StringEntity Using HTTP entities Since an entity can represent both binary and character content, it has support for character encodings to support the latter, i.
To read the content from the entity, one can either retrieve the input stream via the HttpEntity getContent method, which returns an java. Please note that some non-streaming self-contained entities may be tutoriall to represent their content as a java. The EntityUtils class exposes several static methods to simplify extracting the content tutkrial information from an entity.
Instead of reading the java. When the entity has been received with an incoming message, the methods HttpEntity getContentType and HttpEntity getContentLength methods can be used for reading the common metadata such as Content-Type and Content-Length headers if they are available. If the headers aren’t available, a length of -1 will be returned, and NULL for the content type.
If the Content-Type header is available, a Header object will be returned. When creating an entity for a outgoing message, this meta data has to be supplied by the creator of the entity. HttpCore provides the following implementations: In general, use this class for entities received from HTTP messages. This entity has an empty constructor. After construction, it represents no content, and has a negative content length.
One needs to set the content stream, and optionally the length. Supply the byte array to the constructor.
It has three constructors, one simply constructs with a given java. Construct it by supplying the input stream and the content length. Use the content length to limit the amount of data read from the java.
If the length matches the content length available on the input stream, then all data will be sent. Alternatively, a negative content length will read all data from the input stream, which is the same as supplying the exact content length, so use the length to limit the amount of data to read. The wrapping entity holds a reference to a wrapped entity and delegates all calls to it.
Implementations of wrapping entities can derive from this class and need to override only those methods that should not be delegated to the wrapped entity BufferedHttpEntity BufferedHttpEntity is a subclass of HttpEntityWrapper. Construct it by supplying another entity. It reads the content from the supplied entity, and buffers it in memory. This makes it possible to make a repeatable entity, from a non-repeatable entity.
If the supplied entity is already repeatable, it simply passes calls through to the underlying entity. Usually protocol interceptors are expected to act upon one specific header or a group of related headers of the incoming message or populate the outgoing message with one specific header or a group of related headers. Usually this is accomplished by using the ‘Decorator’ pattern where a wrapper entity class is used to decorate the original entity.
Several protocol interceptors can be combined to form one logical unit. HTTP protocol processor is a collection of protocol interceptors that implements the ‘Chain of Responsibility’ pattern, where each individual protocol interceptor is expected to work on the particular aspect of the HTTP protocol it is responsible for. Usually the order in which interceptors are executed should not matter as long as they do not depend on a particular state of the execution context.
If protocol interceptors have interdependencies and therefore must be executed in a particular order, they should be added to the protocol processor in the same sequence as their expected execution order. Protocol interceptors must be implemented as thread-safe. Similarly to servlets, protocol interceptors should not use instance variables unless access to those variables is synchronized Standard protocol interceptors HttpCore comes with a number of most essential protocol interceptors for client and server HTTP processing RequestContent RequestContent is the most important interceptor for outgoing requests.
It is responsible for delimiting content length by adding the Content-Length or Transfer-Content headers based on the properties of the enclosed entity and the protocol version.
This interceptor is required for correct functioning of client side protocol processors ResponseContent ResponseContent is the most important interceptor for outgoing responses. It is responsible for delimiting content length by adding Content-Length or Transfer-Content headers based on the properties of the enclosed entity and the protocol version.
This interceptor is recommended for server side protocol processors. This interceptor is optional for client side protocol processors ResponseDate ResponseDate is responsible for adding the Date header to the outgoing responses.
This interceptor is recommended for server side protocol processors RequestExpectContinue RequestExpectContinue is responsible for enabling the ‘expect-continue’ handshake by adding the Expect header.
This interceptor is recommended for client side protocol processors RequestTargetHost RequestTargetHost is responsible for adding the Host header.
Tutorual interceptor is recommended for client side protocol processors ResponseServer ResponseServer is responsible for adding the Server header. This interceptor is recommended for server side protocol processors Working with protocol processors Usually HTTP protocol processors are used to pre-process incoming messages prior to executing application specific processing logic and to post-process outgoing messages.
However, real world applications often need to be able to persist state information through several logically related request-response exchanges. Multiple logically related messages can participate in a logical session rutorial the same context is reused between consecutive requests. HTTP context functions similarly to a java.
It is simply a collection of logically related named values. Please nore HttpContext can contain arbitrary objects and therefore may be unsafe to share between multiple threads.
Care must be taken to ensure that HttpContext instances can be accessed by one thread at a time Context sharing Protocol interceptors can collaborate by sharing information – such as a processing state – through an HTTP execution context. HTTP context is a structure that can be used to map an attribute name to an attribute value. The tutorila purpose of the HTTP context is to facilitate information sharing among various logically related components.
HTTP context can be used to store a processing state for one message or several consecutive messages. Multiple logically related messages can participate in a logical session if the same context is reused between consecutive messages. One should rarely need to use HTTP connection objects directly.
java – Apache HttpCore, simple server to echo received post data – Stack Overflow
There are higher level protocol components intended for execution and processing of HTTP requests. However, in some cases direct interaction with HTTP connections may be necessary, for instance, to access properties such as the connection status, the socket timeout or the local and remote addresses. It is important to bear in mind that HTTP connections are not thread-safe. We strongly recommend limiting all interactions with HTTP connection objects to one thread.
Instead, blocking HTTP connections can be bound to any arbitrary network socket. The message head is transmitted first.
Depending on properties of the message head, a message body may follow it. Please note it is very important to always close the underlying content stream in order to signal that the processing of the message is complete. HTTP entities that stream out their content directly from the input stream of tutorixl underlying connection must ensure they fully consume the content of the message body for that connection to be potentially re-usable.
Over-simplified process of request execution on the client side may look like this: HTTP connections generate an entity object that encapsulates the content stream of the incoming message.
They merely inject an appropriate content codec based on the properties of the incoming message. The content can be retrieved by reading from the content input stream of the enclosed entity using HttpEntity getContent. The tutoroal data will be decoded automatically and completely transparently to the data consumer. The end of the content entity is determined by the value of the Content-Length header. The end of the content entity is demarcated by closing the underlying httpcoee end of stream condition.
For obvious reasons the identity encoding can only be used on the server side.
The content is sent in small chunks. The appropriate content stream class will be created automatically depending on properties tutrial the entity enclosed with the message Terminating HTTP connections HTTP connections can be terminated either gracefully by calling Httpcpre close or forcibly by calling HttpConnection shutdown.
The former tries to flush all buffered data prior to terminating the connection and may block indefinitely. The HttpConnection close method is not thread-safe.
The latter terminates the connection without flushing internal buffers tutoril returns control to the caller as soon as possible without blocking for long. HttpService is designed to take care of protocol specific aspects, whereas individual request handlers are expected to take care of application specific HTTP processing. The main purpose of a request handler is to generate a response object with a content entity to be sent back to the client in response to the given request.
HttpCore includes a very simple implementation of the request handler resolver based on a trivial pattern matching algorithm: HttpRequestHandlerRegistry supports only three formats: