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POSpring and JacksonJson, serialising different fields with views
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copied!<p>In a <a href="https://stackoverflow.com/questions/7578081/spring-and-jackson-json-serialising-two-different-sets-of-fields">previous similar question</a>, I asked about, how to serialise two different sets of fields using JacksonJson and Spring.</p> <p>My use case is the typical Controller mapping with <code>@ResponseBody</code> annotation returning directly a particular object or collections of objects, that are then rendered with JacksonJson whenever the client adds <code>application/json</code> in the <code>Accept</code> header.</p> <p>I had two answers, the first one suggests to return different interfaces with a different getter list, the second suggests to use Json Views.</p> <p>I don't have problems to understand the first way, however, for the second, after reading the documentation on <a href="http://wiki.fasterxml.com/JacksonJsonViews" rel="nofollow noreferrer"><code>JacksonJsonViews</code></a>, I don't know how to implement it with Spring.</p> <p>To stay with the example, I would declare three stub classes, inside the class Views:</p> <pre><code>// View definitions: public class Views { public static class Public { } public static class ExtendedPublic extends PublicView { } public static class Internal extends ExtendedPublicView { } } </code></pre> <p>Then I've to declare the classes mentioned:</p> <pre><code>public class PublicView { } public class ExtendedPublicView { } </code></pre> <p>Why on earth they declare empty static classes and external empty classes, I don't know. I understand that they need a "label", but then the static members of Views would be enough. And it's not that <code>ExtendedPublic</code> extends <code>Public</code>, as it would be logical, but they are in fact totally unrelated.</p> <p>And finally the bean will specify with annotation the view or list of views:</p> <pre><code>//changed other classes to String for simplicity and fixed typo //in classname, the values are hardcoded, just for testing public class Bean { // Name is public @JsonView(Views.Public.class) String name = "just testing"; // Address semi-public @JsonView(Views.ExtendedPublic.class) String address = "address"; // SSN only for internal usage @JsonView(Views.Internal.class) String ssn = "32342342"; } </code></pre> <p>Finally in the Spring Controller, I've to think how to change the original mapping of my test bean:</p> <pre><code>@RequestMapping(value = "/bean") @ResponseBody public final Bean getBean() { return new Bean(); } </code></pre> <p>It says to call:</p> <pre><code>//or, starting with 1.5, more convenient (ObjectWriter is reusable too) objectMapper.viewWriter(ViewsPublic.class).writeValue(out, beanInstance); </code></pre> <p>So I have an <code>ObjectMapper</code> instance coming out of nowhere and an <code>out</code> which is not the servlet typical <code>PrintWriter out = response.getWriter();</code>, but is an instance of <code>JsonGenerator</code> and that can't be obtained with the new operator. So I don't know how to modify the method, here is an incomplete try:</p> <pre><code>@RequestMapping(value = "/bean") @ResponseBody public final Bean getBean() throws JsonGenerationException, JsonMappingException, IOException { ObjectMapper objectMapper = new ObjectMapper(); JsonGenerator out; //how to create? objectMapper.viewWriter(Views.Public.class).writeValue(out, new Bean()); return ??; //what should I return? } </code></pre> <p>So I would like to know if anybody had success using <code>JsonView</code> with Spring and how he/she did. The whole concept seems interesting, but the documentation seems lacking, also the example code is missing.</p> <p>If it's not possible I will just use interfaces extending each others. Sorry for the long question.</p>

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