CXF實戰之攔截器Interceptor(四)

攔截器（Interceptor）是CXF功能最主要的擴展點，可以在不對核心模塊進行修改的情況下，動態添加很多功能。攔截器和JAX-WS Handler、Filter的功能類似，當服務被調用時，就會創建一個攔截器鏈（Interceptor Chain），攔截器鏈在服務輸入（IN）或輸出（OUT）階段實現附加功能。
攔截器可以在客戶端，也可以在服務端添加。當客戶端發起一個WebService請求時，在客戶端會創建輸出攔截器鏈，服務端接收到客戶端的後，會創建輸入攔截器鏈。當服務端返回響應消息時，響應消息會經過服務端的輸出攔截鏈，客戶端接收到服務端的響應時，會創建輸入攔截器鏈，響應消息先經過輸入攔截器鏈處理。攔截器在服務端和客戶端的作用如圖所示。

攔截器鏈階段

攔截器鏈有多個階段，每個階段都有多個攔截器。攔截器在攔截器鏈的哪個階段起作用，可以在攔截器的構造函數中聲明。
輸入攔截器鏈有如下幾個階段，這些階段按照在攔截器鏈中的先後順序排列。

階段名稱	階段功能描述
RECEIVE	Transport level processing(接收階段，傳輸層處理)
(PRE/USER/POST)_STREAM	Stream level processing/transformations(流處理/轉換階段)
READ	This is where header reading typically occurs(SOAPHeader讀取)
(PRE/USER/POST)_PROTOCOL	Protocol processing, such as JAX-WS SOAP handlers(協議處理階段，例如JAX-WS的Handler處理)
UNMARSHAL	Unmarshalling of the request(SOAP請求解碼階段)
(PRE/USER/POST)_LOGICAL	Processing of the umarshalled request(SOAP請求解碼處理階段)
PRE_INVOKE	Pre invocation actions(調用業務處理之前進入該階段)
INVOKE	Invocation of the service(調用業務階段)
POST_INVOKE	Invocation of the outgoing chain if there is one(提交業務處理結果，並觸發輸入連接器)

輸出攔截器鏈有如下幾個階段，這些階段按照在攔截器鏈中的先後順序排列。

階段名稱	階段功能描述
SETUP	Any set up for the following phases(設置階段)
(PRE/USER/POST)_LOGICAL	Processing of objects about to marshalled
PREPARE_SEND	Opening of the connection(消息發送準備階段，在該階段創建Connection)
PRE_STREAM	流準備階段
PRE_PROTOCOL	Misc protocol actions(協議準備階段)
WRITE	Writing of the protocol message, such as the SOAP Envelope.(寫消息階段)
MARSHAL	Marshalling of the objects
(USER/POST)_PROTOCOL	Processing of the protocol message
(USER/POST)_STREAM	Processing of the byte level message(字節處理階段，在該階段把消息轉爲字節)
SEND	消息發送

在輸出攔截器鏈的SEND階段後，還會觸發以_ENDING結尾階段，這些ENDING階段與以上階段對應，主要用於清理或者關閉資源。ENDING階段觸發的順序如下：

1. SEND_ENDING
2. POST_STREAM_ENDING
3. USER_STREAM_ENDING
4. POST_PROTOCOL_ENDING
5. USER_PROTOCOL_ENDING
6. MARSHAL_ENDING
7. WRITE_ENDING
8. PRE_PROTOCOL_ENDING
9. PRE_STREAM_ENDING
10. PREPARE_SEND_ENDING
11. POST_LOGICAL_ENDING
12. USER_LOGICAL_ENDING
13. PRE_LOGICAL_ENDING
14. SETUP_ENDING
    
    

CXF默認攔截器鏈

在CXF中，所有對消息的處理都是通過各種攔截器實現。CXF已經實現了多種攔截器，如操縱消息頭、執行認證檢查、驗證消息數據、日誌記錄、消息壓縮等，有些攔截器在發佈服務、訪問服務時已經默認添加到攔截器鏈。
CXF默認輸入攔截器鏈，如果沒有添加額外的攔截器，CXF輸入會順序經過以下攔截器：

攔截器名稱	攔截器功能
AttachmentInInterceptor	Parse the mime headers for mime boundaries, finds the “root” part and resets the input stream to it, and stores the other parts in a collection of Attachments
StaxInInterceptor	Creates an XMLStreamReader from the transport InputStream on the Message
ReadHeadersInterceptor	Parses the SOAP headers and stores them on the Message
SoapActionInInterceptor	Parses “soapaction” header and looks up the operation if a unique operation can be found for that action.
MustUnderstandInterceptor	Checks the MustUnderstand headers, its applicability and process it, if required
SOAPHandlerInterceptor	SOAP Handler as per JAX-WS
LogicalHandlerInInterceptor	Logical Handler as per JAX-WS
CheckFaultInterceptor	Checks for fault, if present aborts interceptor chain and invokes fault handler chain
URIMappingInterceptor	Can handle HTTP GET, extracts operation info and sets the same in the Message
DocLiteralnInterceptor	Examines the first element in the SOAP body to determine the appropriate Operation (if soapAction did not find one) and calls the Databinding to read in the data.
SoapHeaderInterceptor	Perform databinding of the SOAP headers for headers that are mapped to parameters
WrapperClassInInterceptor	For wrapped doc/lit, the DocLiteralInInterceptor probably read in a single JAXB bean. This interceptor pulls the individual parts out of that bean to construct the Object[] needed to invoke the service.
SwAInInterceptor	For Soap w/ Attachments, finds the appropriate attachments and assigns them to the correct spot in the parameter list.
HolderInInterceptor	For OUT and IN/OUT parameters, JAX-WS needs to create Holder objects. This interceptor creates the Holders and puts them in the parameter list.
ServiceInvokerInInterceptor	Actually invokes the service.

CXF默認輸出攔截器鏈，如果沒有添加額外的攔截器，CXF輸入會順序經過以下攔截器：

攔截器名稱	攔截器功能
HolderOutInterceptor	For OUT and IN/OUT params, pulls the values out of the JAX-WS Holder objects (created in HolderInInterceptor) and adds them to the param list for the out message.
SwAOutInterceptor	For OUT parts that are Soap attachments, pulls them from the list and holds them for later.
WrapperClassOutInterceptor	For doc/lit wrapped, takes the remaining parts and creates a wrapper JAXB bean to represent the whole message.
SoapHeaderOutFilterInterceptor	Removes inbound marked headers
SoapActionOutInterceptor	Sets the SOAP Action
MessageSenderInterceptor	Calls back to the Destination object to have it setup the output streams, headers, etc… to prepare the outgoing transport.
SoapPreProtocolOutInterceptor	This interceptor is responsible for setting up the SOAP version and header, so that this is available to any pre-protocol interceptors that require these to be available.
AttachmentOutInterceptor	If this service uses attachments (either SwA or if MTOM is enabled), it sets up the Attachment marshallers and the mime stuff that is needed.
StaxOutInterceptor	Creates an XMLStreamWriter from the OutputStream on the Message.
SoapHandlerInterceptor	JAX-WS SOAPHandler
SoapOutInterceptor	Writes start element for soap:envelope and complete elements for other header blocks in the message. Adds start element for soap:body too.
LogicalHandlerOutInterceptor	JAX-WS Logical handler stuff
WrapperOutInterceptor	If wrapped doc/lit and not using a wrapper bean or if RPC lit, outputs the wrapper element to the stream.
BareOutInterceptor	Uses the databinding to write the params out.
SoapOutInterceptor$SoapOutEndingInterceptor	Closes the soap:body and soap:envelope
StaxOutInterceptor$StaxOutEndingInterceptor	Flushes the stax stream.
MessageSenderInt$MessageSenderEnding	Closes the exchange, lets the transport know everything is done and should be flushed to the client.