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POWhy is it that @MatrixParam values seem to only come from the final segment?
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copied!<p>I am exploring the use of <a href="http://www.w3.org/DesignIssues/MatrixURIs.html" rel="noreferrer">MatrixURIs</a> in a JAX-RS application. In the process I've noticed that the <a href="http://jsr311.java.net/nonav/releases/1.1/javax/ws/rs/MatrixParam.html" rel="noreferrer">@MatrixParam</a> annotated parameters seem to only get the matrix parameters from the final segment (which makes trying to use <a href="http://jersey.java.net/nonav/documentation/1.15/user-guide.html#d4e374" rel="noreferrer">sub-resource locators</a> a bit painful). I would like to know if this is a bug, or is part of the spec (and why?), or is simply an undefined crack. </p> <p>I know that I likely could devise a way to use the @Context injected <a href="http://jsr311.java.net/nonav/releases/1.1/javax/ws/rs/core/UriInfo.html" rel="noreferrer">UriInfo</a> object (which does change depending upon where in the locator chain one finds oneself), but this feels ugly.</p> <p>Thumbing quickly through the <a href="http://jcp.org/aboutJava/communityprocess/mrel/jsr311/index.html" rel="noreferrer">JAX-RS 1.1 spec</a>... the closest I could find to this not being supported was around: §3.2 </p> <blockquote> <p>Because injection occurs at object creation time, use of these annotations (with the exception of @Context) on resource class fields and bean properties is only supported for the default per-request resource class lifecycle.</p> </blockquote> <p>But that's talking about Constructor/Field injection, not method parameters like in §3.3.2: </p> <blockquote> <p>When a resource method is invoked, parameters annotated with @FormParam or one of the annotations listed in section 3.2 are mapped from the request according to the semantics of the annotation.</p> </blockquote> <p>But of course the semantics of the annotation are seemingly vague. </p> <h1>Runtime Environment Details:</h1> <ul> <li>Jersey 1.13, 1.15</li> <li>Tomcat 7.0.29</li> <li>Java 1.6.0_31 (Apple)</li> <li>MacOS X 10.7.5</li> </ul> <h1>Example resources:</h1> <pre><code>public class Zero { public static final String[] IDS = { "1", "2", "3" }; @GET @Produces(MediaType.APPLICATION_JSON) public Map<String, Object> getMe(@Context final UriInfo info) { final UriBuilder builder = info.getAbsolutePathBuilder().path("one"); final UriBuilder two = builder.clone().matrixParam("id", "{one}", "{two}"); final List<String> links = new ArrayList<String>(); for (int i = 0; i < IDS.length; i++) { final String first = IDS[i]; for (int j = i + 1; j < IDS.length; j++) { final String second = IDS[j]; links.add(two.build(first, second).toASCIIString()); } } final Map<String, Object> toReturn = new HashMap<String, Object>(); toReturn.put("class", getClass().getSimpleName()); toReturn.put("next", builder.build().toASCIIString()); toReturn.put("skip", links); return toReturn; } /*************************/ /**** <PROBLEM CHILD> ****/ /*************************/ @Path("one") public Object getNext(@MatrixParam("id") final Set<String> ids) { if (ids.isEmpty()) { return new One(); } return new Two(ids.toArray(new String[ids.size()])); } /*************************/ /**** </PROBLEM CHILD> ***/ /*************************/ public static class One { @GET @Produces(MediaType.APPLICATION_JSON) public Map<String, Object> getMe(@Context final UriInfo info) { final UriBuilder builder = info.getAbsolutePathBuilder().path("{id}"); final List<String> links = new ArrayList<String>(); for (final String id : IDS) { links.add(builder.build(id).toASCIIString()); } final Map<String, Object> toReturn = new HashMap<String, Object>(); toReturn.put("class", getClass().getSimpleName()); toReturn.put("next", links); toReturn.put("last", getLastURI(info)); return toReturn; } @Path("{id}") public Two getNext(@PathParam("id") final String id) { return new Two(id); } } public static class Two { private final String[] myids; private final Three three; public Two(final String... ids) { three = new Three(ids); myids = ids; } @GET @Produces(MediaType.APPLICATION_JSON) public Map<String, Object> getMe(@Context final UriInfo info) { final UriBuilder builder = info.getAbsolutePathBuilder().path("three"); final Map<String, Object> toReturn = new HashMap<String, Object>(); toReturn.put("class", getClass().getSimpleName()); toReturn.put("ids", myids); toReturn.put("next", builder.build().toASCIIString()); toReturn.put("last", getLastURI(info)); return toReturn; } @Path("three") public Three getNext() { return three; } } public static class Three { private final String[] myids; public Three(final String... ids) { myids = ids; } @GET @Produces(MediaType.APPLICATION_JSON) public Map<String, Object> getMe(@Context final UriInfo info) { final Map<String, Object> toReturn = new HashMap<String, Object>(); toReturn.put("class", getClass().getSimpleName()); toReturn.put("ids", myids); toReturn.put("last", getLastURI(info)); return toReturn; } } /** * Helper method since info.getMatchedURIs doesn't play nice with Matrix Params * @param info info object * @return parent URI */ public static final String getLastURI(final UriInfo info) { final List<PathSegment> segments = info.getPathSegments(false); final UriBuilder builder = info.getBaseUriBuilder(); for (int i = 0; i < segments.size() - 1; i++) { final PathSegment segment = segments.get(i); builder.path(segment.getPath()); final MultivaluedMap<String, String> matrixParams = segment.getMatrixParameters(); if (!matrixParams.isEmpty()) { for (final Map.Entry<String, List<String>> param : matrixParams.entrySet()) { final String name = param.getKey(); final String[] values = param.getValue().toArray(new String[param.getValue().size()]); builder.matrixParam(name, values); } } } return builder.build().toASCIIString(); } } </code></pre> <h1>Example Outputs from above:</h1> <h2><code>http://localhost:8080/context/zero/one/2</code></h2> <pre><code>{ "last":"http://localhost:8080/context/zero/one", "ids":["2"], "next":"http://localhost:8080/context/zero/one/2/three", "class":"Two" } </code></pre> <h2><code>http://localhost:8080/context/zero/one/2/three</code></h2> <pre><code>{ "last":"http://localhost:8080/context/zero/one/2", "ids":["2"], "class":"Three" } </code></pre> <h2><code>http://localhost:8080/context/zero/one;id=1;id=2</code></h2> <pre><code>{ "last":"http://localhost:8080/context/zero", "ids":["2","1"], "next":"http://localhost:8080/context/zero/one;id=1;id=2/three", "class":"Two" } </code></pre> <h2><code>http://localhost:8080/context/zero/one;id=1;id=2/three</code></h2> <pre><code>{ "last": "http://localhost:8080/context/zero/one;id=1;id=2", "ids": ["three"], "next": "http://localhost:8080/context/zero/one;id=1;id=2/three/three", "class": "Two" } </code></pre>

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