title=Sling Servlet Helpers and Internal Requests type=page status=published tags=servlets,requests,scripts,servletresolver
The [Sling Servlet Helpers](https://github.com/apache/sling-org-apache-sling-servlet-helpers) bundle provides mock implementations of the `SlingHttpServletRequest`, `SlingHttpServletResponse` and related classes, along with fluent `SlingInternalRequest` and `ServletInternalRequest` helpers for internal requests. The mock request/response implementations are meant to be used in tests and also with services like the `SlingRequestProcessor` when making requests to that service outside of an HTTP request processing context. They are used under the hood by the `SlingInternalRequest` and `ServletInternalRequest` helpers to provide a simple and foolproof way of executing internal Sling requests. The [GraphQL Core](https://github.com/apache/sling-org-apache-sling-graphql-core/) module, for example, uses them for internal requests that retrieve a GraphQL schema dynamically, taking into account the current Resource and request selectors. See the [automated tests](https://github.com/apache/sling-org-apache-sling-servlet-helpers) of the `servlet-helpers` module for more info, besides the general descriptions found below. ## InternalRequest helpers The internal request helpers use either a `SlingRequestProcessor` to execute internal requests using the full Sling request processing pipeline, or a `ServletResolver` to resolve and call a Servlet or Script directly. The necessary "mocking" of requests are responses happens under the hood which leads to much simpler code than using the mock request/response classes directly. The latter direct-to-servlet (or script) mode is more efficient but less faithful to the way HTTP requests are processed, as it bypasses all Servlet Filters, in particular. Here's an example using the `SlingInternalRequest` helper - see the test code for more. The `ServletInternalRequest` API is very similar but takes a `ServletResolver` and an actual `Resource` as its starting points. OutputStream os = new SlingInternalRequest(resourceResolver, slingRequestProcessor, path) .withResourceType("website/article/news") .withResourceSuperType("website/article") .withSelectors("print", "a4") .withExtension("pdf") .execute() .checkStatus(200) .checkResponseContentType("application/pdf") .getResponse() .getOutputStream() Not all servlets and scripts are suitable to be called by the `ServletInternalRequest`, depending on their "environmental" requirements like `Request` attributes for example. In case of doubt you can start with the `SlingInternalRequest` helper which uses the `SlingRequestProcessor` so that servlets or scripts should see no difference compared to HTTP requests. And once that works you can try the more efficient `ServletInternalRequest` helper to check if your scripts and servlets support that mode. In both cases, the standard [Sling Servlet/Script resolution mechanism](/documentation/the-sling-engine/servlets.html) is used, which can be useful to execute scripts that are resolved based on the current resource type, for non-HTTP operations. Inventing HTTP method names for this is fine and allows for reusing this powerful resolution mechanism in other contexts. ### Troubleshooting internal requests To help map log messages to internal requests, as several of those might be used to handle a single HTTP request, the `InternalRequest` parent class of the helpers discussed above sets a log4j _Mapped Diagnostic Context_ (MDC) value with the `sling.InternalRequest`key. The value of that key provides the essential attributes of the current request, so that using a log formatting pattern that displays it, like: %-5level [%-50logger{50}] %message ## %mdc{sling.InternalRequest} %n Causes the internal request information to be logged, like in this example (lines folded for readability): DEBUG [o.a.s.s.internalrequests.SlingInternalRequest ] Executing request using the SlingRequestProcessor ## GET P=/content/tags/monitor+array S=null EXT=json RT=samples/tag(null) WARN [org.apache.sling.engine.impl.request.RequestData ] SlingRequestProgressTracker not found in request attributes ## GET P=/content/tags/monitor+array S=null EXT=json RT=samples/tag(null) DEBUG [o.a.s.s.resolver.internal.SlingServletResolver ] Using cached servlet /apps/samples/tag/json.gql ## GET P=/content/tags/monitor+array S=null EXT=json RT=samples/tag(null) In these log messages, `GET P=/content/tags/monitor+array S=null EXT=json RT=samples/tag(null)` points to the current internal request, showing its method, path, selectors, extension, resource type and resource supertype. ## Mock Request/Response classes These are useful for testing or if you need to do something that the internal request helpers do not support. ### SlingHttpServletRequest Example for preparing a sling request with custom request data: #!java // prepare sling request MockSlingHttpServletRequest request = new MockSlingHttpServletRequest(resourceResolver); // simulate query string request.setQueryString("param1=aaa¶m2=bbb"); // alternative - set query parameters as map request.setParameterMap(ImmutableMap.<String,Object>builder() .put("param1", "aaa") .put("param2", "bbb") .build()); // set current resource request.setResource(resourceResolver.getResource("/content/sample")); // set sling request path info properties MockRequestPathInfo requestPathInfo = (MockRequestPathInfo)request.getRequestPathInfo(); requestPathInfo.setSelectorString("selector1.selector2"); requestPathInfo.setExtension("html"); // set method request.setMethod(HttpConstants.METHOD_POST); // set attributes request.setAttribute("attr1", "value1"); // set headers request.addHeader("header1", "value1"); // set cookies request.addCookie(new Cookie("cookie1", "value1")); ### SlingHttpServletResponse Example for preparing a sling response which can collect the data that was written to it: #!java // prepare sling response MockSlingHttpServletResponse response = new MockSlingHttpServletResponse(); // execute the code that writes to the response... // validate status code assertEquals(HttpServletResponse.SC_OK, response.getStatus()); // validate content type and content length assertEquals("text/plain;charset=UTF-8", response.getContentType()); assertEquals(CharEncoding.UTF_8, response.getCharacterEncoding()); assertEquals(55, response.getContentLength()); // validate headers assertTrue(response.containsHeader("header1")); assertEquals("5", response.getHeader("header2")); // validate response body as string assertEquals(TEST_CONTENT, response.getOutputAsString()); // validate response body as binary data assertArrayEquals(TEST_DATA, response.getOutput());