現在有個問題需要大家思考一下，有個已經上線了的項目，有好好幾千甚至上萬的客戶在使用了?，F在項目開發商想發布一個通知。在今天下午6點需要重新啟動服務器，想讓在線的人在在預定的時間內都收到消息，讓大家做好相應的準備，大家會怎么做？

1、逐個打電話

2、在前臺弄一個定時器，每隔一定的時間刷新一次

3、后臺消息主動往前臺推送

相信你已經做出選擇了。。。呵呵 ，下面講一個簡單的例子，

首先，新建一個web項目，添加開發flex需要的jar包，和blazeds相關文件，然后把web項目轉成flex項目(不明白怎么弄沒事，過幾天會寫一篇這樣的文章)，然后修改一下services-config.xml和messaging-config.xml文件，添加如下代碼

services-config.xml

1.??

2.?? id="my-streaming-amf"

3.?? class="mx.messaging.channels.StreamingAMFChannel">

4.??

5.?? url="http://{server.name}:{server.port}/{context.root}/messagebroker/streamingamf"

6.?? class="flex.messaging.endpoints.StreamingAMFEndpoint"

7.?? />

8.??

9.?? 0

10.? 10

11.? 5000

12.?

13.?

14.?

15.? match-on="MSIE"

16.? kickstart-bytes="2048"

17.? max-streaming-connections-per-session="1"

18.? />

19.?

20.? kickstart-bytes="2048"

21.? max-streaming-connections-per-session="1"

22.? />

23.?

24.?

25.?

復制代碼

messaging-config.xml

1.??

2.?? id="tick-data-feed">

3.??

4.??

5.?? true

6.?? .

7.??

8.??

9.??

10.?

11.? ref="my-polling-amf" />

12.?

13.? />

14.?

15.?

復制代碼

OK，完了之后，我們新建一個servlet作為服務端

1.?? package com.serverpush;

2.

3.?? import java.io.IOException;

4.?? import

5.?? javax.servlet.ServletException;

6.?? import

7.?? javax.servlet.http.HttpServlet;

8.?? import

9.?? javax.servlet.http.HttpServletRequest;

10.? import

11.? javax.servlet.http.HttpServletResponse;

12.

13.? import

14.? com.model.Tick;

15.

16.? import flex.messaging.MessageBroker;

17.? import

18.? flex.messaging.messages.AsyncMessage;

19.? import

20.? flex.messaging.util.UUIDUtils;

21.

22.? /**

23.? * Servlet implementation class

24.? TickCacheServlet

25.? */

26.? public class TickCacheServlet extendsHttpServlet

27.? {

28.? private static final long serialVersionUID= 1L;

29.? private static

30.? FeedThread thread;

31.

32.? /**

33.? * @see

34.? HttpServlet#HttpServlet()

35.? */

36.? public TickCacheServlet() {

37.? super();

38.? //

39.? TODO Auto-generated constructor stub

40.? }

41.

42.? /**

43.? * @see

44.? HttpServlet#doGet(HttpServletRequestrequest, HttpServletResponse

45.? *

46.? response)

47.? */

48.? protected void doGet(HttpServletRequest

49.? request,

50.? HttpServletResponse response) throwsServletException, IOException

51.? {

52.? //接收前臺參數

53.? String cmd =request.getParameter("cmd");

54.? if

55.? (cmd.equals("start")) {

56.? start();

57.? }

58.? if (cmd.equals("stop"))

59.? {

60.? stop();

61.? }

62.? }

63.

64.? public void start() {

65.? if (thread == null)

66.? {

67.? thread = new

68.? FeedThread();

69.? thread.start();

70.? }

71.? System.out.println("start!!");

72.? }

73.

74.? public

75.? void stop() {

76.? thread.running = false;

77.? thread = null;

78.? }

79.

80.? /**

81.? *

82.? @see HttpServlet#doPost(HttpServletRequestrequest, HttpServletResponse

83.? *

84.? response)

85.? */

86.? protected void doPost(HttpServletRequest

87.? request,

88.? HttpServletResponse response) throwsServletException, IOException

89.? {

90.? doGet(request, response);

91.? }

92.? //線程類，每隔多長時間發送一次

93.? public static class

94.? FeedThread extends Thread {

95.? public boolean running = true;

96.? public void

97.? run() {

98.? MessageBroker msgBroker =

99.? MessageBroker.getMessageBroker(null);

100. String clientID =

101. UUIDUtils.createUUID();

102. int i = 0;

103. while (running) {

104. Tick tick = new

105. Tick();

106. tick.setMessageCN("今天下午6點更新程序需重啟服務器");

107. tick.setSeqNo(String.valueOf(i));

108. System.out.println(i);

109.

110. AsyncMessage

111. msg = new

112. AsyncMessage();

113. msg.setDestination("tick-data-feed");

114. msg.setHeader("DSSubtopic",

115. "tick");

116. msg.setClientId(clientID);

117. msg.setMessageId(UUIDUtils.createUUID());

118. msg.setTimestamp(System.currentTimeMillis());

119. msg.setBody(tick);

120. msgBroker.routeMessageToService(msg,

121. null);

122. i++;

123. try {

124. Thread.sleep(2000);

125. } catch (InterruptedException

126. e) {

127. }

128. }

129. }

130. }

131. }

復制代碼

在新建一個model用來保存消息

1.?? package com.model;

2.

3.?? public class Tick {

4.?? private String

5.?? seqNo;

6.?? private String messageCN;

7.

8.?? public String getMessageCN()

9.?? {

10.? return messageCN;

11.? }

12.

13.? public void setMessageCN(String messageCN)

14.? {

15.? this.messageCN = messageCN;

16.? }

17.

18.? public String getSeqNo()

19.? {

20.? return seqNo;

21.? }

22.

23.? public void setSeqNo(String seqNo)

24.? {

25.? this.seqNo = seqNo;

26.? }

27.? }

復制代碼

后臺就搞定了。下面看前臺

新建一個mxml文件和一個VO文件

mxml:

1.?? <?xml version="1.0"

2.?? encoding="utf-8"?>

3.??

4.?? xmlns:fx="http://ns.adobe.com/mxml/2009"

5.?? xmlns:s="library://ns.adobe.com/flex/spark"

6.?? xmlns:mx="library://ns.adobe.com/flex/mx"

7.?? minWidth="955"

8.?? minHeight="600">

9.??

10.?

11.?

12.

13.?

14.?

15.? import

16.? mx.controls.Alert;

17.? import mx.messaging.ChannelSet;

18.? import

19.? mx.messaging.Consumer;

20.? import

21.? mx.messaging.events.MessageEvent;

22.

23.? protected function

24.? submsg():void

25.? {

26.? Alert.show("click start");

27.? var consumer:Consumer = new

28.? Consumer();

29.? consumer.destination ="tick-data-feed";

30.? consumer.subtopic =

31.? "tick";

32.? consumer.channelSet = new

33.? ChannelSet(["my-streaming-amf"]);

34.? //添加message的監聽，當后臺有消息發送時，調用messageHandler

35.

36.? consumer.addEventListener(MessageEvent.MESSAGE,messageHandler);

37.

38.? consumer.subscribe();

39.? }

40.? private function

41.? messageHandler(event:MessageEvent):void

42.? {

43.? var tick:TickVO =

44.? event.message.body as TickVO;

45.? txtTick.text = tick.messageCN+tick.seqNo;

46.

47.? }

48.

49.

50.? ]]>

51.?

52.

53.?

54.?

56.?

57.?

58.? x="32"

59.? y="43"

60.? width="362"

61.? height="302"

62.? layout="absolute"

63.? title="Watch

64.? Tick">

65.?

66.? x="72"

67.? y="43"

68.? text="Label"

69.? id="txtTick"/>

70.?

71.? x="132"

72.? y="71"

73.? label="Button"

74.? click="submsg()"/>

75.?

76.?

復制代碼

VO，就是對應后臺的model

1.?? package

2.?? {

3.?? //遠程到后臺的Tick，也就是說他們倆現在是對應的關系了，你在后臺給model賦值了，在前臺flex中就可以通過VO

4.?? //取得model中的值

5.?? [RemoteClass(alias="com.model.Tick")]

6.

7.?? [Bindable]

8.?? public class TickVO

9.?? {

10.? private var

11.? _seqNo:String;

12.? private var _messageCN:String;

13.

14.? public function

15.? TickVO()

16.? {

17.

18.? }

19.? public function get seqNo():String

20.? {

21.? return

22.? _seqNo;

23.? }

24.

25.? public function setseqNo(value:String):void

26.? {

27.? _seqNo

28.? = value;

29.? }

30.

31.? public function get messageCN():String

32.? {

33.? return

34.? _messageCN;

35.? }

36.

37.? public function set

38.? messageCN(value:String):void

39.? {

40.? _messageCN =

41.? value;

42.? }

43.

44.

45.? }

46.? }

復制代碼

ok，下面開始測試：運行mxml，界面如下

點擊button，啟動監聽。

然后在瀏覽器中輸入：http://localhost:8080/serverPush/TickCacheServlet?cmd=start，表示現在我要發消息了，當你運行了這個之后看看你剛才的那個mxml是不是有變化啦

稍后奉上flex+blazeds+spring+java后臺消息推送(這個稍微麻煩點)，有些配置不同了

flex+blazeds+java+spring后臺消息推送，有界面維護

總結

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