MQTT的學習研究（八）基於HTTP DELETE MQTT 訂閱消息服務端使用

時間  2019-11-18
標籤 mqtt 學習 研究 基於 http delete 訂閱 消息 服務 使用 欄目 HTTP/TCP 简体版
原文   原文鏈接

HTTP DELETE 訂閱主題請求協議和響應協議
http://publib.boulder.ibm.com/infocenter/wmqv7/v7r0/topic/com.ibm.mq.csqzau.doc/ts21240_.htmhtml

請求響應頭各個字段的含義的講解
http://publib.boulder.ibm.com/infocenter/wmqv7/v7r0/topic/com.ibm.mq.csqzau.doc/ts21250_.htmjava


響應錯誤處理
http://publib.boulder.ibm.com/infocenter/wmqv7/v7r0/topic/com.ibm.mq.csqzau.doc/ts21340_.htmapp

 

 

The HTTP DELETE operation gets a message from a WebSphere® MQ queue, or retrieves a publication from a topic. The message is removed from the queue. If the publication is retained, it is not removed. A response message is sent back to the client including information about the message.ui

Syntax

Read syntax diagram 
Skip visual syntax diagram
Request

>>-+-DELETE-+-- --| Path |-- --HTTP version--CRLF--------------->
   '-GET----'                                       

   .-CRLF---------------.  .-CRLF---------------.   
   V                    |  V                    |   
>----+----------------+-+----+----------------+-+--------------->
     '-general-header-'      '-request-header-'     

   .-CRLF----------------------------.   
   V                                 |   
>----+-----------------------------+-+-------------------------><
     '-| Entity-header (Request) |-'     

Path

|--/--contextRoot--/-------------------------------------------->

>--msg/--+-queue/--queueName--+-------------+-+--/--------------|
         |                    '-@--qMgrName-' |      
         '-topic/--topicName------------------'      

entity-header (Request)

|--+----------------------------------------------+-------------|
   +-standard entity-header-- --entity-value------+   
   +-x-msg-correlId - --correlation ID------------+   
   +-x-msg-msgId - --message ID-------------------+   
   +-x-msg-range-- --range------------------------+   
   +-x-msg-require-headers-- --entity header name-+   
   '-x-msg-wait - --wait time---------------------'   
Note:
  1. If a question mark (?) is used it must be substituted with %3f. For example, orange?topic should be specified as orange%3ftopic.
  2. @qMgrName is only valid on an HTTP POST
Read syntax diagram 
Skip visual syntax diagram
Response

>>-HTTP version-- --HTTP Status-Code-- --HTTP Reason-Phrase--CRLF-->

   .-CRLF---------------.  .-CRLF----------------.   
   V                    |  V                     |   
>----+----------------+-+----+-----------------+-+-------------->
     '-general-header-'      '-response-header-'     

   .-CRLF-----------------------------.                      
   V                                  |                      
>----+------------------------------+-+--+---------------+-----><
     '-| Entity-header (Response) |-'    '-CRLF--Message-'   

entity-header (Response)

|--+-----------------------------------------+------------------|
   +-standard entity-header-- --entity-value-+   
   +-x-msg-class-- --message type------------+   
   +-x-msg-correlId-- --correlation ID-------+   
   +-x-msg-encoding-- --encoding type--------+   
   +-x-msg-expiry-- --duration---------------+   
   +-x-msg-format-- --message format---------+   
   +-x-msg-msgId-- --message ID--------------+   
   +-x-msg-persistence-- --persistence-------+   
   +-x-msg-priority-- --priority class-------+   
   +-x-msg-replyTo-- --reply-to queue--------+   
   +-x-msg-timestamp-- --HTTP-date-----------+   
   '-x-msg-usr-- --user properties-----------'   

Request parameters

PathSee  URI Format. HTTP versionHTTP version; for example,  HTTP/1.1 general-headerSee  HTTP/1.1 - 4.5 General Header Fields. request-headerSee  HTTP/1.1 - 5.3 Request Header Fields. The  Host field is mandatory on an HTTP/1.1 request. It is often automatically inserted by the tool you use to create a client request. entity-header (Request)See  HTTP/1.1 - 7.1 Entity Header Fields. One of the entity headers listed in the Request syntax diagram.

Response parameters

PathSee  URI Format. HTTP versionHTTP version; for example,  HTTP/1.1 general-headerSee  HTTP/1.1 - 4.5 General Header Fields. response-headerSee  HTTP/1.1 - 6.2 Response Header Fields. entity-header (Response)See  HTTP/1.1 - 7.1 Entity Header Fields. One of the entity or response headers listed in the Response syntax diagram.The  Content–Length is always present in a response. It is set to zero if there is no message body. MessageMessage body.

Description

If the HTTP DELETE request is successful, the response message contains the data retrieved from the WebSphere MQ queue. The number of bytes in the body of the message is returned in the HTTP Content-Length header. The status code for the HTTP response is set to 200 OK. If x-msg-range is specified as 0, or0-0, then the status code of the HTTP response is 204 No Content.this

If the HTTP DELETE request is unsuccessful, the response includes a WebSphere MQ bridge for HTTP error message and an HTTP status code.url

HTTP DELETE example

HTTP DELETE gets a message from a queue and deletes the message, or retrieves and deletes a publication. The HTTPDELETE Java sample is an example an HTTP DELETE request reading a message from a queue. Instead of using Java, you could create an HTTP DELETE request using a browser form, or an AJAX toolkit instead.spa

Figure 1 is an HTTP request to delete the next message on queue called myQueue. In response, the message body is returned to the client. In WebSphere MQ terms, HTTP DELETE is a destructive get..net

The request contains the HTTP request header x-msg-wait, which instructs WebSphere MQ bridge for HTTP how long to wait for a message to arrive on the queue. The request also contains the x-msg-require-headersrequest header, which specifies that the client is to receive the message correlation ID in the response.code

Figure 1. Example of an HTTP DELETE request 
DELETE /msg/queue/myQueue/ HTTP/1.1
Host: www.example.org
x-msg-wait: 10
x-msg-require-headers: correlID

Figure 2, is the response returned to the client. The correlation ID is returned to the client, as requested in x-msg-require-headers of the request.orm

Figure 2. Example of an HTTP DELETE response 
HTTP/1.1 200 OK
Date: Wed, 2 Jan 2007 22:38:34 GMT
Server: Apache-Coyote/1.1 WMQ-HTTP/1.1 JEE-Bridge/1.1
Content-Length: 50
Content-Type: text/plain; charset=utf-8
x-msg-correlId: 1234567890

Here's my message body that will appear on the queue.

 

 

HTTP DELETE訂閱主題信息

Java代碼   收藏代碼
  1. package com.etrip.mqttv3.http;  
  2. /** 
  3.  * This sample shows how to delete a message. It has slightly enhanced function 
  4.  * of the amqsget command in that it will print out the timestamp, expiry and 
  5.  * persistence of the messages. The program continues until the queue is empty 
  6.  * or a request fails. This program can potentially take in three parameters: 
  7.  * <queueName> 
  8.  * <host:port> <context-root (the MQ Bridge for HTTP's context-root)> 
  9.  * defaults are: SYSTEM.DEFAULT.LOCAL.QUEUE localhost:8080 mq  
  10.  *  
  11.  * If there are any exceptions thrown from this program or errors returned from the server then they are  
  12.  * printed to standard output as-is. 
  13.  *    
  14.  * No more messages 
  15.  * HTTP DELETE Sample end 
  16.  */  
  17. import java.io.BufferedReader;  
  18. import java.io.IOException;  
  19. import java.io.InputStreamReader;  
  20. import java.net.HttpURLConnection;  
  21. import java.net.MalformedURLException;  
  22. import java.net.URL;  
  23. /** 
  24.  *  
  25.  * 採用HTTP DELETE方式的訂閱相關的MQTT的主題的信息 
  26.  *  
  27.  * @author longgangbai 
  28.  *  
  29.  *  
  30.  */  
  31. public class HTTPDELETE  
  32. {  
  33.    private static final String DEFAULT_HOST = "localhost";  
  34.    private static final String DEFAULT_PORT = "8080";  
  35.    private static final String DEFAULT_QUEUE = "SYSTEM.DEFAULT.LOCAL.QUEUE";  
  36.   
  37.    private static final String DEFAULT_CONTEXT_ROOT = "mq";  
  38.   
  39.    public static String newline = System.getProperty("line.separator");  
  40.   
  41.    private static final String MESSAGE_BOUNDARY = "_________________________________________________________________________________________";  
  42.   
  43.    // the maximum length of the message that we want to print to the screen  
  44.    private static final int MAX_OUTPUT_MESSAGE_SIZE = 256;  
  45.   
  46.   
  47.    private static int OK_RC = 200;  
  48.   
  49.      
  50.    /** 
  51.     * 構建訂閱主題隊列路徑 
  52.     *  
  53.     * @param host 
  54.     * @param port 
  55.     * @param context 
  56.     * @param queueName 
  57.     */  
  58.     private static String getPublishQueueURL(String host, String port,  
  59.             String context, String queueName) {  
  60.         StringBuffer urlString =new StringBuffer("http://");  
  61.            if(StringUtils.isEmtry(host)){  
  62.                host=DEFAULT_HOST;  
  63.            }  
  64.              
  65.            if(StringUtils.isEmtry(port)){  
  66.                port=DEFAULT_PORT;  
  67.            }  
  68.            urlString.append(host).append(":").append(port);  
  69.            if(StringUtils.isEmtry(context)){  
  70.                context=DEFAULT_CONTEXT_ROOT;  
  71.            }  
  72.            urlString.append("/");  
  73.            urlString.append(context);  
  74.            urlString.append("/msg/queue/");  
  75.            if(StringUtils.isEmtry(queueName)){  
  76.                queueName=DEFAULT_QUEUE;  
  77.            }  
  78.            urlString.append(queueName);  
  79.            System.out.println("urlString="+urlString);  
  80.            return urlString.toString();  
  81.     }  
  82.   
  83.       
  84.     /** 
  85.      *  經過HTTP POST 訂閱主題的具體實現 
  86.      * @param host 
  87.      * @param port 
  88.      * @param context 
  89.      * @param queueName 
  90.      * @return 
  91.      * @throws MalformedURLException 
  92.      */  
  93.        public static boolean subTopic(String host,String port,String context,String queueName ){  
  94.               String publishURL=getPublishQueueURL(host, port, context, queueName);  
  95.               URL url=null;  
  96.               HttpURLConnection connection=null;  
  97.                 try {  
  98.                       url = new URL(publishURL);  
  99.                       connection= (HttpURLConnection) url.openConnection();  
  100.                       /* Build the headers */  
  101.                       // the verb first.  
  102.                       connection.setRequestMethod("DELETE");  
  103.           
  104.                       // write out what headers we want back  
  105.                       // the header names are case-sensitive  
  106.                       connection.setRequestProperty("x-msg-require-headers",  
  107.                             "timestamp, expiry, persistence");  
  108.           
  109.                       // Now actually send the request message. There is no content as this is a  
  110.                       // DELETE  
  111.                       connection.connect();  
  112.                       String formattedMessage = null;  
  113.                       // check the response for errors  
  114.                       int responseCode = connection.getResponseCode();  
  115.                     if (responseCode == OK_RC)  
  116.                       {  
  117.                          // Get the headers first  
  118.                          String timestamp = connection.getHeaderField("x-msg-timestamp");  
  119.                          String expiry = connection.getHeaderField("x-msg-expiry");  
  120.                          String persistence = connection.getHeaderField("x-msg-persistence");  
  121.                          // now get the message data  
  122.                          BufferedReader reader = new BufferedReader(new InputStreamReader(  
  123.                                connection.getInputStream()));  
  124.                          String line = null;  
  125.                          StringBuffer messageBuffer = new StringBuffer();  
  126.                          while ((line = reader.readLine()) != null)  
  127.                          {  
  128.                             messageBuffer.append(line);  
  129.                          }  
  130.                          String messageBody = messageBuffer.toString();  
  131.                           
  132.                            
  133.                          formattedMessage = MESSAGE_BOUNDARY + newline;  
  134.                          // Which is greater the max output message size or the message length?  
  135.                          int messageSizeToPrint = messageBody.length() > MAX_OUTPUT_MESSAGE_SIZE ? MAX_OUTPUT_MESSAGE_SIZE  
  136.                                : messageBody.length();  
  137.                          formattedMessage += messageBody.substring(0, messageSizeToPrint)  
  138.                                + newline;  
  139.                          formattedMessage += "timestamp   = " + timestamp + newline;  
  140.                          formattedMessage += "expiry      = " + expiry + newline;  
  141.                          formattedMessage += "persistence = " + persistence + newline;  
  142.                            
  143.                          System.out.println("formattedMessage "+formattedMessage);  
  144.                       }else{  
  145.                           String responseMessage =connection.getResponseMessage();  
  146.                           System.out.println("responsere sponseCode "+responseCode+" response request ="+responseMessage);  
  147.                       }  
  148.                 } catch (MalformedURLException e) {  
  149.                     // TODO Auto-generated catch block  
  150.                     e.printStackTrace();  
  151.                 } catch (IOException e) {  
  152.                     // TODO Auto-generated catch block  
  153.                     e.printStackTrace();  
  154.                 }finally{  
  155.                     connection.disconnect();  
  156.                 }  
  157.            return false;  
  158.        }  
  159.   
  160.         public static void main(String[] args) {  
  161.            HTTPDELETE.subTopic("192.168.208.46", "8080", "mq", "java_lover");  
  162.         }  
  163.   
  164. }  
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