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POHow to return a partial JSON response using Java?
 

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  1. POHow to return a partial JSON response using Java?
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    <p>I'm building a RESTful API and want to provide developers with the option to choose which fields to return in the JSON response. <a href="http://blog.apigee.com/detail/restful_api_design_can_your_api_give_developers_just_the_information/" rel="noreferrer">This blog post</a> shows examples of how several API's (Google, Facebook, LinkedIn) allow developers to customize the response. This is referred to as partial response.</p> <p>An example might look like this:</p> <pre><code>/users/123?fields=userId,fullname,title </code></pre> <p>In the example above the API should return the userId, fullName and title fields for User "123".</p> <p>I'm looking for ideas of how to implement this in my RESTful web service. I'm currently using CXF (edit: and Jackson) but willing to try another JAX-RS implementation.</p> <p>Here's what I currently have. It returns a full User object. How can I return only the fields the API caller wants at runtime based on the "fields" paramaeter? I don't want to make the other fields Null. I simply don't want to return them.</p> <pre><code>@GET @Path("/{userId}") @Produces("application/json") public User getUser(@PathParam("userId") Long userId, @DefaultValue("userId,fullname,title") @QueryParam("fields") String fields) { User user = userService.findOne(userId); StringTokenizer st = new StringTokenizer(fields, ","); while (st.hasMoreTokens()) { // here's where i would like to select only the fields i want to return } return user; } </code></pre> <p><strong>UPDATE:</strong></p> <p>I followed unludo's link which then linked to this: <a href="http://wiki.fasterxml.com/JacksonFeatureJsonFilter" rel="noreferrer">http://wiki.fasterxml.com/JacksonFeatureJsonFilter</a></p> <p>With that info I added <code>@JsonFilter("myFilter")</code> to my domain class. Then I modified my RESTful service method to return String instead of User as follows:</p> <pre><code>@GET @Path("/{userId}") @Produces("application/json") public String getUser(@PathParam("userId") Long userId, @DefaultValue("userId,fullname,title") @QueryParam("fields") String fields) { User user = userService.findOne(userId); StringTokenizer st = new StringTokenizer(fields, ","); Set&lt;String&gt; filterProperties = new HashSet&lt;String&gt;(); while (st.hasMoreTokens()) { filterProperties.add(st.nextToken()); } ObjectMapper mapper = new ObjectMapper(); FilterProvider filters = new SimpleFilterProvider().addFilter("myFilter", SimpleBeanPropertyFilter.filterOutAllExcept(filterProperties)); try { String json = mapper.filteredWriter(filters).writeValueAsString(user); return json; } catch (IOException e) { e.printStackTrace(); return e.getMessage(); } } </code></pre> <p>I need to do more testing but so far so good.</p>
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