Allow preprocessing to be applied to every test

Following the reworking of the API, it was no longer possible to
apply preprocessing to every test and to still customize the snippets
used by that test.

This commit adds a new snippets() method to
RestDocumentationResultHandler that allows additional snippets to be
configured once the result handler has been created. The documentation
has been updated to describe how to apply preprocessing to every
test and Spring HATEOAS sample has been updated to illustrate the
approach.

Closes gh-88

docs/src/docs/asciidoc/customizing-requests-and-responses.adoc

@@ -11,11 +11,36 @@ static `preprocessRequest` and `preprocessResponse` methods on `Preprocessors`:
 
 [source,java,indent=0]
 ----
-include::{examples-dir}/com/example/Preprocessing.java[tags=general]
+include::{examples-dir}/com/example/PreprocessingPerTest.java[tags=preprocessing]
 ----
 <1> Apply a request preprocessor that will remove the header named `Foo`.
 <2> Apply a response preprocessor that will pretty print its content.
 
+Alternatively, you may want to apply the same preprocessors to every test. You can do
+so by configuring the preprocessors in your `@Before` method and using the
+<<documentating-your-api-parameterized-output-directories, support for parameterized
+output directories>>:
+
+[source,java,indent=0]
+----
+include::{examples-dir}/com/example/PreprocessingEveryTest.java[tags=setup]
+----
+<1> Create the `RestDocumentationResultHandler`, configured to preprocess the request
+	and response.
+<2> Create the `MockMvc` instance, configured to always call the documentation result
+	handler.
+
+Then, in each test, the `RestDocumentationResultHandler` can be configured with anything
+test-specific. For example:
+
+[source,java,indent=0]
+----
+include::{examples-dir}/com/example/PreprocessingEveryTest.java[tags=use]
+----
+<1> Document the links specific to the resource that is being tested
+<2> The `perform` call will automatically produce the documentation snippets due to the
+	use of `alwaysDo` above.
+
 Various built in preprocessors, including those illustrated above, are available via the
 static methods on `Preprocessors`. See below for further details.
 

docs/src/test/java/com/example/PreprocessingEveryTest.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 2014-2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example;
+
+import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
+import static org.springframework.restdocs.mockmvc.RestDocumentationRequestBuilders.get;
+import static org.springframework.restdocs.operation.preprocess.Preprocessors.preprocessRequest;
+import static org.springframework.restdocs.operation.preprocess.Preprocessors.preprocessResponse;
+import static org.springframework.restdocs.operation.preprocess.Preprocessors.prettyPrint;
+import static org.springframework.restdocs.operation.preprocess.Preprocessors.removeHeaders;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+import static org.springframework.restdocs.hypermedia.HypermediaDocumentation.links;
+import static org.springframework.restdocs.hypermedia.HypermediaDocumentation.linkWithRel;
+
+import org.junit.Before;
+import org.springframework.restdocs.mockmvc.RestDocumentationResultHandler;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.context.WebApplicationContext;
+
+public class PreprocessingEveryTest {
+	
+	private WebApplicationContext context;
+	
+	private MockMvc mockMvc;
+	
+	private RestDocumentationResultHandler document;
+	
+	// tag::setup[]
+	@Before
+	public void setup() {
+		 this.document = document("{method-name}", // <1>
+				 preprocessRequest(removeHeaders("Foo")),
+				 preprocessResponse(prettyPrint()));
+		 this.mockMvc = MockMvcBuilders
+				 .webAppContextSetup(this.context)
+				 .alwaysDo(this.document) // <2>
+				 .build();
+	}
+	// end::setup[]	
+
+	public void use() throws Exception {
+		// tag::use[]
+		this.document.snippets( // <1>
+				links(linkWithRel("self").description("Canonical self link")));
+		this.mockMvc.perform(get("/")) // <2>
+			.andExpect(status().isOk()); 
+		// end::use[]
+	}
+
+}

docs/src/test/java/com/example/PreprocessingPerTest.java

@@ -26,18 +26,18 @@ import static org.springframework.restdocs.operation.preprocess.Preprocessors.pr
 
 import org.springframework.test.web.servlet.MockMvc;
 
-public class Preprocessing {
+public class PreprocessingPerTest {
 
 	private MockMvc mockMvc;
 
 	public void general() throws Exception {
-		// tag::general[]
+		// tag::preprocessing[]
 		this.mockMvc.perform(get("/"))
 			.andExpect(status().isOk())
 			.andDo(document("index",
 					preprocessRequest(removeHeaders("Foo")), // <1>
 					preprocessResponse(prettyPrint()))); // <2>
-		// end::general[]
+		// end::preprocessing[]
 	}
 
 }