101 lines
6.5 KiB
HTML
101 lines
6.5 KiB
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<title>Serializing Dates in JSON</title>
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<link href="styles.css" rel="stylesheet" type="text/css" />
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<link href="custom.css" rel="stylesheet" type="text/css" />
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</head>
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<body>
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<div id="control">
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<span class="productTitle">Json.NET - Quick Starts & API Documentation</span><br />
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<span class="topicTitle">Serializing Dates in JSON</span></div>
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<div id="content">
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<span style="color: DarkGray"> </span>
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<p>DateTimes in JSON are hard.</p>
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<p>
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The problem comes from the <a href="http://www.ietf.org/rfc/rfc4627.txt" target="_blank">JSON spec</a> itself, there is no literal syntax for dates in JSON. The spec has objects, arrays, strings, integers and floats, but it defines no standard for what a date looks like.</p>
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<p>The default format used by <a href="http://james.newtonking.com/projects/json-net.aspx" target="_blank">Json.NET</a>
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is the ISO 8601 standard: 2012-03-19T07:22Z. You can read more about it <a href="http://en.wikipedia.org/wiki/ISO_8601" target="_blank">here</a>.</p>
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<p>Prior to Json.NET 4.5 dates were written using the Microsoft format:
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"\/Date(1198908717056)\/". If you want to use this format, or you want to
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maintain compatibility with Microsoft JSON serializers or older versions of
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Json.NET then change the DateFormatHandling setting to MicrosoftDateFormat.</p>
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<h3>DateTime JsonConverters</h3>
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<p>With no standard for dates in JSON, the number of possible different formats when interoping with other systems is endless. Fortunately Json.NET has a solution to deal with reading and writing custom dates: JsonConverters. A JsonConverter is used to override how a type is serialized.</p>
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<div class="overflowpanel">
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<div class="code">
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<div style="font-size: 10pt; color: black; font-family: courier new;">
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<pre style="margin: 0px;"><span style="color: blue;">public</span> <span style="color: blue;">class</span> <span style="color: rgb(43, 145, 175);">LogEntry</span></pre>
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<pre style="margin: 0px;">{</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">public</span> <span style="color: blue;">string</span> Details { <span style="color: blue;">get</span>; <span style="color: blue;">set</span>; }</pre>
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<pre style="margin: 0px;"> <span style="color: blue;">public</span> <span style="color: rgb(43, 145, 175);">DateTime</span> LogDate { <span style="color: blue;">get</span>; <span style="color: blue;">set</span>; }</pre>
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<pre style="margin: 0px;">}</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;">[<span style="color: rgb(43, 145, 175);">Test</span>]</pre>
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<pre style="margin: 0px;"><span style="color: blue;">public</span> <span style="color: blue;">void</span> WriteJsonDates()</pre>
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<pre style="margin: 0px;">{</pre>
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<pre style="margin: 0px;"> <span style="color: rgb(43, 145, 175);">LogEntry</span> entry = <span style="color: blue;">new</span> <span style="color: rgb(43, 145, 175);">LogEntry</span></pre>
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<pre style="margin: 0px;"> {</pre>
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<pre style="margin: 0px;"> LogDate = <span style="color: blue;">new</span> <span style="color: rgb(43, 145, 175);">DateTime</span>(2009, 2, 15, 0, 0, 0, <span style="color: rgb(43, 145, 175);">DateTimeKind</span>.Utc),</pre>
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<pre style="margin: 0px;"> Details = <span style="color: rgb(163, 21, 21);">"Application started."</span></pre>
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<pre style="margin: 0px;"> };</pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"> <span style="color: blue;">string</span> defaultJson = <span style="color: rgb(43, 145, 175);">JsonConvert</span>.SerializeObject(entry);</pre>
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<pre style="margin: 0px;"> <span style="color: green;">// {"Details":"Application started.","LogDate":"\/Date(1234656000000)\/"}</span></pre>
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<pre style="margin: 0px;"></pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"> <span style="color: blue;">string</span> javascriptJson = <span style="color: rgb(43, 145, 175);">JsonConvert</span>.SerializeObject(entry, <span style="color: blue;">new</span> <span style="color: rgb(43, 145, 175);">JavaScriptDateTimeConverter</span>());</pre>
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<pre style="margin: 0px;"> <span style="color: green;">// {"Details":"Application started.","LogDate":new Date(1234656000000)}</span></pre>
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<pre style="margin: 0px;"> </pre>
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<pre style="margin: 0px;"> <span style="color: blue;">string</span> isoJson = <span style="color: rgb(43, 145, 175);">JsonConvert</span>.SerializeObject(entry, <span style="color: blue;">new</span> <span style="color: rgb(43, 145, 175);">IsoDateTimeConverter</span>());</pre>
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<pre style="margin: 0px;"> <span style="color: green;">// {"Details":"Application started.","LogDate":"2009-02-15T00:00:00Z"}</span></pre>
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<pre style="margin: 0px;">}</pre>
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</div>
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</div>
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</div>
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<p>Simply pass the JsonConverter you wish to use to the Json.NET serializer.</p>
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<h4>JavaScriptDateTimeConverter</h4>
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<p>The JavaScriptDateTimeConverter class is one of the two DateTime JsonConverters that come with Json.NET. This converter serializes a DateTime as a <a href="https://developer.mozilla.org/en/Core_JavaScript_1.5_Reference/Global_Objects/Date" target="_blank">JavaScript Date object</a>.</p>
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<div class="overflowpanel">
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<div class="code">
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<div style="font-size: 10pt; color: black; font-family: courier new;">
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<pre style="margin: 0px;">new Date(1234656000000)</pre>
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</div>
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</div>
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</div>
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<p>Technically this is invalid JSON according to the spec but all browsers, and some JSON frameworks including Json.NET, support it. </p>
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<h4>IsoDateTimeConverter</h4>
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<p>IsoDateTimeConverter seralizes a DateTime to an <a href="http://en.wikipedia.org/wiki/ISO_8601" target="_blank">ISO 8601</a> formatted string.
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Note that since Json.NET 4.5 dates are written using the ISO 8601 format by
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default and using this converter is unnecessary.</p>
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<div class="overflowpanel">
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<div class="code">
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<div style="font-size: 10pt; color: black; font-family: courier new;">
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<pre style="margin: 0px;"><span style="color: rgb(163, 21, 21);">"2009-02-15T00:00:00Z"</span></pre>
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</div>
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</div>
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</div>
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<p>The IsoDateTimeConverter class has a property, DateTimeFormat, to further customize the formatted string.</p>
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<p> </p>
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<p>One final thing to note is all date values returned by Json.NET are in <a href="http://en.wikipedia.org/wiki/Utc" target="_blank">UTC time</a>.</p>
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</div>
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</html>
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