Add RestListService and RestDetailService; update README.

README.md

@@ -2,11 +2,95 @@
 
 A lightweight C++ REST and SOAP client and server library based on *Boost.Asio*.
 
-Please see the `doc` folder for tutorials and `example` folder for examples.
+## A Quick Look
+
+### REST Server
+
+Suppose you want to create a book server, and provide the following operations with RESTful API:
+
+- Query books based on some criterias.
+- Add a new book.
+- Get the detailed information of a book.
+- Update the information of a book.
+- Delete a book.
+
+The first two operations can be implemented by deriving from `webcc::RestListService`:
+
+```cpp
+class BookListService : public webcc::RestListService {
+ protected:
+  // Query books based on some criterias.
+  // GET /books?<query>
+  bool Get(const webcc::UrlQuery& query,
+           std::string* response_content) final;
+
+  // Add a new book.
+  // POST /books
+  // The new book's data is attached as request content in JSON format.
+  bool Post(const std::string& request_content,
+            std::string* response_content) final;
+};
+```
+
+The others, derive from `webcc::RestDetailService`:
+
+```cpp
+// The URL is like '/book/{BookID}', and the 'url_sub_matches' parameter
+// contains the matched book ID.
+class BookDetailService : public webcc::RestDetailService {
+ protected:
+  // Get the detailed information of a book.
+  bool Get(const std::vector<std::string>& url_sub_matches,
+           std::string* response_content) final;
+
+  // Update the information of a book.
+  bool Patch(const std::vector<std::string>& url_sub_matches,
+             const std::string& request_content,
+             std::string* response_content) final;
+
+  // Delete a book.
+  bool Delete(const std::vector<std::string>& url_sub_matches) final;
+};
+```
+
+As you can see, all you have to do is to override the proper virtual functions which are named after HTTP methods.
+
+The detailed implementation is out of the scope of this document, but here is an example:
+
+```cpp
+bool BookDetailService::Get(const std::vector<std::string>& url_sub_matches,
+                            std::string* response_content) {
+  if (url_sub_matches.size() != 1) {
+    return false;
+  }
+  const std::string& book_id = url_sub_matches[0];
+
+  // Get the book by ID from database.
+  // Convert the book details to JSON string.
+  // Assign JSON string to response_content.
+}
+```
+
+Last step, register the services and run the server:
+
+```cpp
+webcc::RestServer server(8080, 2);
+
+server.RegisterService(std::make_shared<BookListService>(),
+                       "/books");
+
+server.RegisterService(std::make_shared<BookDetailService>(),
+                       "/book/(\\d+)");
+
+server.Run();
+```
+
+**Please see the `example` folder for the complete examples (including the client).**
 
 ## Build Instructions
 
-A lot of C++11 features are used, e.g., `std::move`. But C++14 is not required. It means that you can still build `webcc` using VS2013.
+A lot of C++11 features are used, e.g., `std::move`. But C++14 is not required.
+(It means that you can still build `webcc` using VS2013 on Windows.)
 
 [CMake 3.1.0+](https://cmake.org/) is required as the build system. But if you don't use CMake, you can just copy the `src/webcc` folder to your own project then manage it by yourself.
 
@@ -25,3 +109,26 @@ option(WEBCC_BUILD_SOAP_EXAMPLE "Build SOAP example?" ON)
 ```
 
 If `WEBCC_ENABLE_SOAP` is `ON`, **pugixml** (already included) is used to parse and compose XML strings.
+
+### Build On Linux
+
+Create a build folder under the root (or any other) directory, and `cd` to it:
+```bash
+mkdir build
+cd build
+```
+Generate Makefiles with the following command:
+```bash
+cmake -G"Unix Makefiles" \
+    -DWEBCC_ENABLE_LOG=ON \
+    -DWEBCC_ENABLE_SOAP=ON \
+    -DWEBCC_BUILD_UNITTEST=OFF \
+    -DWEBCC_BUILD_REST_EXAMPLE=ON \
+    -DWEBCC_BUILD_SOAP_EXAMPLE=OFF \
+    ..
+```
+Feel free to change the build options (`ON` or `OFF`).
+Then make:
+```bash
+$ make -j4
+```