| 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
| 2 | <html> |
| 3 | <head> |
| 4 | <script type="text/javascript"> |
| 5 | <!-- |
| 6 | // Mozilla only implementation! |
| 7 | |
| 8 | // Constructor for generic HTTP client |
| 9 | function HTTPClient() {}; |
| 10 | |
| 11 | // Add methods and properties as array |
| 12 | HTTPClient.prototype = { |
| 13 | url: null, |
| 14 | |
| 15 | // Instance of XMLHttpRequest |
| 16 | xmlhttp: null, |
| 17 | |
| 18 | // Used to make sure multiple calls are not placed |
| 19 | // with the same client object while another in progress |
| 20 | callinprogress: false, |
| 21 | |
| 22 | // The user defined handler - see MyHandler below |
| 23 | userhandler: null, |
| 24 | |
| 25 | init: function(url) { |
| 26 | this.url = url; |
| 27 | this.xmlhttp = new XMLHttpRequest(); |
| 28 | }, |
| 29 | |
| 30 | // handler argument is a user defined object to be called |
| 31 | asyncGET: function (handler) { |
| 32 | |
| 33 | // Prevent multiple calls |
| 34 | if (this.callinprogress) { |
| 35 | throw "Call in progress"; |
| 36 | }; |
| 37 | |
| 38 | this.userhandler = handler; |
| 39 | |
| 40 | // Open an async request - third argument makes it async |
| 41 | this.xmlhttp.open(‘GET‘,this.url,true); |
| 42 | |
| 43 | // Have to assign "this" to a variable - not sure why can‘t use directly |
| 44 | var self = this; |
| 45 | |
| 46 | // Assign a closure to the onreadystatechange callback |
| 47 | this.xmlhttp.onreadystatechange = function() { |
| 48 | self.stateChangeCallback(self); |
| 49 | } |
| 50 | |
| 51 | // Send the request |
| 52 | this.xmlhttp.send(null); |
| 53 | }, |
| 54 | |
| 55 | stateChangeCallback: function(client) { |
| 56 | switch (client.xmlhttp.readyState) { |
| 57 | |
| 58 | // Request not yet made |
| 59 | case 1: |
| 60 | try { |
| 61 | client.userhandler.onInit(); |
| 62 | } catch (e) { /* Handler method not defined */ } |
| 63 | break; |
| 64 | |
| 65 | // Contact established with server but nothing downloaded yet |
| 66 | case 2: |
| 67 | try { |
| 68 | // Check for HTTP status 200 |
| 69 | if ( client.xmlhttp.status != 200 ) { |
| 70 | client.userhandler.onError( |
| 71 | client.xmlhttp.status, |
| 72 | client.xmlhttp.statusText |
| 73 | ); |
| 74 | |
| 75 | // Abort the request |
| 76 | client.xmlhttp.abort(); |
| 77 | |
| 78 | // Call no longer in progress |
| 79 | client.callinprogress = false; |
| 80 | } |
| 81 | } catch (e) { |
| 82 | /* Handler method not defined */ |
| 83 | } |
| 84 | break; |
| 85 | |
| 86 | // Called multiple while downloading in progress |
| 87 | case 3: |
| 88 | // Notify user handler of download progress |
| 89 | try { |
| 90 | // Get the total content length |
| 91 | // -useful to work out how much has been downloaded |
| 92 | try { |
| 93 | var contentLength = |
| 94 | client.xmlhttp.getResponseHeader("Content-Length"); |
| 95 | } catch (e) { |
| 96 | var contentLength = NaN; |
| 97 | } |
| 98 | |
| 99 | // Call the progress handler with what we‘ve got |
| 100 | client.userhandler.onProgress( |
| 101 | client.xmlhttp.responseText, |
| 102 | contentLength |
| 103 | ); |
| 104 | |
| 105 | } catch (e) { /* Handler method not defined */ } |
| 106 | break; |
| 107 | |
| 108 | // Download complete |
| 109 | case 4: |
| 110 | try { |
| 111 | client.userhandler.onLoad(client.xmlhttp.responseText); |
| 112 | } catch (e) { |
| 113 | /* Handler method not defined */ |
| 114 | } finally { |
| 115 | // Call no longer in progress |
| 116 | client.xmlhttp.callinprogress = false; |
| 117 | } |
| 118 | break; |
| 119 | } |
| 120 | } |
| 121 | } |
| 122 | |
| 123 | // A user defined handler to response to the XMLHTTPRequest |
| 124 | var MyHandler = { |
| 125 | onInit: function() { |
| 126 | echo("About to send request<br>"); |
| 127 | }, |
| 128 | onError: function(status,statusText) { |
| 129 | echo("Error: "+status+": "+statusText+"<br>"); |
| 130 | }, |
| 131 | onProgress: function(responseText,length) { |
| 132 | echo("Downloaded "+responseText.length+" of "+length+"<br>"); |
| 133 | }, |
| 134 | onLoad: function(result) { |
| 135 | echo("<pre>"+result+"</pre>"); |
| 136 | }, |
| 137 | } |
| 138 | |
| 139 | // Just a function to help display results |
| 140 | function echo(string) { |
| 141 | document.getElementById("results").innerHTML += string; |
| 142 | } |
| 143 | |
| 144 | // Invoke the client |
| 145 | function getPage() { |
| 146 | // Modify this to some page |
| 147 | var url = "http://localhost/test/test.txt"; |
| 148 | var client = new HTTPClient(); |
| 149 | client.init(url); |
| 150 | |
| 151 | try { |
| 152 | client.asyncGET(MyHandler); |
| 153 | } catch (e) { |
| 154 | alert(e); |
| 155 | } |
| 156 | echo("Async request so still able to do stuff here<br>"); |
| 157 | } |
| 158 | </script> |
| 159 | </head> |
| 160 | <body> |
| 161 | <a href="javascript:getPage();">getPage</a> |
| 162 | <div id="results"> |
| 163 | </div> |
| 164 | </body> |
| 165 | </html> |
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