diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index b8065e2..09169fb 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -14,4 +14,6 @@ if(WEBCC_ENABLE_DEMO)
 		add_subdirectory(demo/soap/calc_client)
 		add_subdirectory(demo/soap/calc_server)
 	endif()
+	add_subdirectory(demo/rest/book_client)
+	add_subdirectory(demo/rest/book_server)
 endif()
\ No newline at end of file
diff --git a/src/demo/rest/book_client/CMakeLists.txt b/src/demo/rest/book_client/CMakeLists.txt
new file mode 100644
index 0000000..a435983
--- /dev/null
+++ b/src/demo/rest/book_client/CMakeLists.txt
@@ -0,0 +1,5 @@
+file(GLOB SRCS *.cc *.h)
+
+add_executable(rest_book_client ${SRCS})
+
+target_link_libraries(rest_book_client webcc)
diff --git a/src/demo/rest/book_client/book_client.cc b/src/demo/rest/book_client/book_client.cc
new file mode 100644
index 0000000..f46eb3c
--- /dev/null
+++ b/src/demo/rest/book_client/book_client.cc
@@ -0,0 +1,2 @@
+#include "book_client.h"
+
diff --git a/src/demo/rest/book_client/book_client.h b/src/demo/rest/book_client/book_client.h
new file mode 100644
index 0000000..bcba55b
--- /dev/null
+++ b/src/demo/rest/book_client/book_client.h
@@ -0,0 +1,6 @@
+#ifndef BOOK_CLIENT_H_
+#define BOOK_CLIENT_H_
+
+#include <string>
+
+#endif  // BOOK_CLIENT_H_
diff --git a/src/demo/rest/book_client/main.cc b/src/demo/rest/book_client/main.cc
new file mode 100644
index 0000000..c52b9f6
--- /dev/null
+++ b/src/demo/rest/book_client/main.cc
@@ -0,0 +1,88 @@
+#include <iostream>
+#include "boost/lexical_cast.hpp"
+
+#include "webcc/http_client.h"
+#include "webcc/http_request.h"
+#include "webcc/http_response.h"
+
+class BookListClient {
+public:
+  BookListClient() {
+    host_ = "localhost";
+    port_ = "8080";
+  }
+
+  bool ListBooks() {
+    webcc::HttpRequest http_request;
+
+    http_request.set_method(webcc::kHttpGet);
+    http_request.set_url("/books");
+    http_request.SetHost(host_, port_);
+
+    http_request.Build();
+
+    webcc::HttpResponse http_response;
+
+    webcc::HttpClient http_client;
+    webcc::Error error = http_client.SendRequest(http_request, &http_response);
+
+    if (error != webcc::kNoError) {
+      return false;
+    }
+
+    std::cout << "Book list: " << std::endl
+              << http_response.content() << std::endl;
+
+    return true;
+  }
+
+private:
+  std::string host_;
+  std::string port_;
+};
+
+class BookDetailClient {
+public:
+  BookDetailClient() {
+    host_ = "localhost";
+    port_ = "8080";
+  }
+
+  bool GetBook(const std::string& id) {
+    webcc::HttpRequest http_request;
+
+    http_request.set_method(webcc::kHttpGet);
+    http_request.set_url("/books/" + id);
+    http_request.SetHost(host_, port_);
+
+    http_request.Build();
+
+    webcc::HttpResponse http_response;
+
+    webcc::HttpClient http_client;
+    webcc::Error error = http_client.SendRequest(http_request, &http_response);
+
+    if (error != webcc::kNoError) {
+      return false;
+    }
+
+    std::cout << "Book: " << id << std::endl
+              << http_response.content() << std::endl;
+
+    return true;
+  }
+
+private:
+  std::string host_;
+  std::string port_;
+};
+
+int main() {
+  BookListClient book_list_client;
+  book_list_client.ListBooks();
+
+  BookDetailClient book_detail_client;
+  book_detail_client.GetBook("1");
+
+  return 0;
+}
diff --git a/src/demo/rest/book_server/CMakeLists.txt b/src/demo/rest/book_server/CMakeLists.txt
new file mode 100644
index 0000000..457a575
--- /dev/null
+++ b/src/demo/rest/book_server/CMakeLists.txt
@@ -0,0 +1,5 @@
+file(GLOB SRCS *.cc *.h)
+
+add_executable(rest_book_server ${SRCS})
+
+target_link_libraries(rest_book_server webcc)
diff --git a/src/demo/rest/book_server/book_services.cc b/src/demo/rest/book_server/book_services.cc
new file mode 100644
index 0000000..85c90e2
--- /dev/null
+++ b/src/demo/rest/book_server/book_services.cc
@@ -0,0 +1,138 @@
+#include "book_services.h"
+
+#include <list>
+#include "boost/lexical_cast.hpp"
+
+////////////////////////////////////////////////////////////////////////////////
+
+class Book {
+public:
+  std::string id;
+  std::string title;
+  double price;
+
+  bool IsNull() const {
+    return id.empty();
+  }
+};
+
+static const Book kNullBook{};
+
+class BookStore {
+public:
+  BookStore() {
+    books_.push_back({ "1", "Title1", 11.1 });
+    books_.push_back({ "2", "Title2", 22.2 });
+    books_.push_back({ "3", "Title3", 33.3 });
+  }
+
+  const std::list<Book>& books() const {
+    return books_;
+  }
+
+  const Book& GetBook(const std::string& id) const {
+    auto it = std::find_if(books_.begin(),
+                           books_.end(),
+                           [&id](const Book& book) { return book.id == id; });
+
+    if (it == books_.end()) {
+      return kNullBook;
+    }
+
+    return *it;
+  }
+
+  bool AddBook(const Book& new_book) {
+    auto it = std::find_if(
+        books_.begin(),
+        books_.end(),
+        [&new_book](const Book& book) { return book.id == new_book.id; });
+
+    if (it != books_.end()) {
+      return false;
+    }
+
+    books_.push_back(new_book);
+    return true;
+  }
+
+  bool DeleteBook(const std::string& id) {
+    auto it = std::find_if(books_.begin(),
+                           books_.end(),
+                           [&id](const Book& book) { return book.id == id; });
+
+    if (it == books_.end()) {
+      return false;
+    }
+
+    books_.erase(it);
+    return true;
+  }
+
+private:
+  std::list<Book> books_;
+};
+
+static BookStore g_book_store;
+
+////////////////////////////////////////////////////////////////////////////////
+
+// Naively create JSON object string for a book.
+// You should use real JSON library in your product code.
+static std::string CreateBookJson(const Book& book) {
+  std::string json = "{ ";
+  json += "\"id\": " + book.id + ", ";
+  json += "\"title\": " + book.title + ", ";
+  json += "\"price\": " + std::to_string(book.price);
+  json += " }";
+  return json;
+}
+
+bool BookListService::Handle(const std::string& http_method,
+                             const std::vector<std::string>& url_sub_matches,
+                             const std::string& request_content,
+                             std::string* response_content) {
+  if (http_method == webcc::kHttpGet) {
+    *response_content = "{ ";
+    for (const Book& book : g_book_store.books()) {
+      *response_content += CreateBookJson(book);
+      *response_content += ",";
+    }
+    *response_content += " }";
+    return true;
+  }
+
+  return false;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+bool BookDetailService::Handle(const std::string& http_method,
+                               const std::vector<std::string>& url_sub_matches,
+                               const std::string& request_content,
+                               std::string* response_content) {
+  if (url_sub_matches.size() != 1) {
+    return false;
+  }
+
+  const std::string& book_id = url_sub_matches[0];
+
+  if (http_method == webcc::kHttpGet) {
+    const Book& book = g_book_store.GetBook(book_id);
+
+    if (book.IsNull()) {
+      return false;
+    }
+
+    *response_content = CreateBookJson(book);
+
+    return true;
+
+  } else if (http_method == webcc::kHttpPost) {
+
+  } else if (http_method == webcc::kHttpDelete) {
+
+  }
+
+  return false;
+}
diff --git a/src/demo/rest/book_server/book_services.h b/src/demo/rest/book_server/book_services.h
new file mode 100644
index 0000000..d9bbb13
--- /dev/null
+++ b/src/demo/rest/book_server/book_services.h
@@ -0,0 +1,44 @@
+#ifndef BOOK_SERVICES_H_
+#define BOOK_SERVICES_H_
+
+#include "webcc/rest_service.h"
+
+// NOTE:
+// XxxListService and XxxDetailService are similar to the XxxListView
+// and XxxDetailView in Django (a Python web framework).
+
+// List Service handles the HTTP GET and returns the book list based on
+// query parameters specified in the URL.
+// The URL should be like:
+//   - /books
+//   - /books?name={BookName} 
+// The query parameters could be regular expressions.
+class BookListService : public webcc::RestService {
+public:
+  BookListService() = default;
+  ~BookListService() override = default;
+
+  bool Handle(const std::string& http_method,
+              const std::vector<std::string>& url_sub_matches,
+              const std::string& request_content,
+              std::string* response_content) override;
+};
+
+// Detail Service handles the following HTTP methods:
+//   - GET
+//   - PUT
+//   - PATCH
+//   - DELETE
+// The URL should be like: /books/{BookID}.
+class BookDetailService : public webcc::RestService {
+public:
+  BookDetailService() = default;
+  ~BookDetailService() override = default;
+
+  bool Handle(const std::string& http_method,
+              const std::vector<std::string>& url_sub_matches,
+              const std::string& request_content,
+              std::string* response_content) override;
+};
+
+#endif  // BOOK_SERVICE_H_
diff --git a/src/demo/rest/book_server/main.cc b/src/demo/rest/book_server/main.cc
new file mode 100644
index 0000000..937f1f7
--- /dev/null
+++ b/src/demo/rest/book_server/main.cc
@@ -0,0 +1,38 @@
+#include <iostream>
+#include "webcc/rest_server.h"
+#include "book_services.h"
+
+static void Help(const char* argv0) {
+  std::cout << "Usage: " << argv0 << " <port>" << std::endl;
+  std::cout << "  E.g.," << std::endl;
+  std::cout << "    " << argv0 << " 8080" << std::endl;
+}
+
+int main(int argc, char* argv[]) {
+  if (argc != 2) {
+    Help(argv[0]);
+    return 1;
+  }
+
+  unsigned short port = std::atoi(argv[1]);
+
+  std::size_t workers = 2;
+
+  try {
+    webcc::RestServer server(port, workers);
+
+    server.RegisterService(std::make_shared<BookListService>(),
+                           "/books");
+
+    server.RegisterService(std::make_shared<BookDetailService>(),
+                           "/books/(\\d+)");
+
+    server.Run();
+
+  } catch (std::exception& e) {
+    std::cerr << "Exception: " << e.what() << std::endl;
+    return 1;
+  }
+
+  return 0;
+}
diff --git a/src/webcc/http_message.h b/src/webcc/http_message.h
index 1b2ee7e..5056ee5 100644
--- a/src/webcc/http_message.h
+++ b/src/webcc/http_message.h
@@ -28,7 +28,7 @@ public:
     start_line_ = start_line;
   }
 
-  size_t content_length() const {
+  std::size_t content_length() const {
     return content_length_;
   }
 
@@ -43,7 +43,7 @@ public:
     SetHeader(kContentType, content_type);
   }
 
-  void SetContentLength(size_t content_length) {
+  void SetContentLength(std::size_t content_length) {
     content_length_ = content_length;
     SetHeader(kContentLength, std::to_string(content_length));
   }
@@ -53,7 +53,7 @@ public:
     content_ = std::move(content);
   }
 
-  void AppendContent(const char* data, size_t count) {
+  void AppendContent(const char* data, std::size_t count) {
     content_.append(data, count);
   }
 
@@ -62,8 +62,7 @@ public:
   }
 
   bool IsContentFull() const {
-    assert(IsContentLengthValid());
-    return content_.length() >= content_length_;
+    return IsContentLengthValid() && content_.length() >= content_length_;
   }
 
   bool IsContentLengthValid() const {
diff --git a/src/webcc/http_parser.cc b/src/webcc/http_parser.cc
index 53268e9..8e62c0a 100644
--- a/src/webcc/http_parser.cc
+++ b/src/webcc/http_parser.cc
@@ -10,11 +10,12 @@ namespace webcc {
 HttpParser::HttpParser(HttpMessage* message)
     : message_(message)
     , start_line_parsed_(false)
+    , content_length_parsed_(false)
     , header_parsed_(false)
     , finished_(false) {
 }
 
-Error HttpParser::Parse(const char* data, size_t len) {
+Error HttpParser::Parse(const char* data, std::size_t len) {
   if (header_parsed_) {
     // Add the data to the content.
     message_->AppendContent(data, len);
@@ -28,10 +29,10 @@ Error HttpParser::Parse(const char* data, size_t len) {
   }
 
   pending_data_.append(data, len);
-  size_t off = 0;
+  std::size_t off = 0;
 
   while (true) {
-    size_t pos = pending_data_.find("\r\n", off);
+    std::size_t pos = pending_data_.find("\r\n", off);
     if (pos == std::string::npos) {
       break;
     }
@@ -52,8 +53,8 @@ Error HttpParser::Parse(const char* data, size_t len) {
       }
     } else {
       // Currently, only Content-Length is important to us.
-      // Other fields are ignored.
-      if (!message_->IsContentLengthValid()) {
+      // Other header fields are ignored.
+      if (!content_length_parsed_) {
         ParseContentLength(line);
       }
     }
@@ -64,9 +65,16 @@ Error HttpParser::Parse(const char* data, size_t len) {
   if (header_parsed_) {
     // Headers just ended.
 
-    if (!message_->IsContentLengthValid()) {
-      // No Content-Length?
-      return kHttpContentLengthError;
+    if (!content_length_parsed_) {
+      // No Content-Length, no content.
+      message_->SetContentLength(0);
+      finished_ = true;
+      return kNoError;
+    } else {
+      // Invalid Content-Length in the request. 
+      if (!message_->IsContentLengthValid()) {
+        return kHttpContentLengthError;
+      }
     }
 
     message_->AppendContent(pending_data_.substr(off));
@@ -84,7 +92,7 @@ Error HttpParser::Parse(const char* data, size_t len) {
 }
 
 void HttpParser::ParseContentLength(const std::string& line) {
-  size_t pos = line.find(':');
+  std::size_t pos = line.find(':');
   if (pos == std::string::npos) {
     return;
   }
@@ -92,6 +100,8 @@ void HttpParser::ParseContentLength(const std::string& line) {
   std::string name = line.substr(0, pos);
 
   if (boost::iequals(name, kContentLength)) {
+    content_length_parsed_ = true;
+
     ++pos;  // Skip ':'.
     while (line[pos] == ' ') {  // Skip spaces.
       ++pos;
@@ -100,9 +110,9 @@ void HttpParser::ParseContentLength(const std::string& line) {
     std::string value = line.substr(pos);
 
     try {
-      message_->SetContentLength(boost::lexical_cast<size_t>(value));
+      std::size_t length = boost::lexical_cast<std::size_t>(value);
+      message_->SetContentLength(length);
     } catch (boost::bad_lexical_cast&) {
-      // TODO
     }
   }
 }
diff --git a/src/webcc/http_parser.h b/src/webcc/http_parser.h
index c50529d..9a846c2 100644
--- a/src/webcc/http_parser.h
+++ b/src/webcc/http_parser.h
@@ -17,7 +17,7 @@ public:
     return finished_;
   }
 
-  Error Parse(const char* data, size_t len);
+  Error Parse(const char* data, std::size_t len);
 
 protected:
   // Parse HTTP start line.
@@ -36,6 +36,7 @@ protected:
 
   // Parsing helper flags.
   bool start_line_parsed_;
+  bool content_length_parsed_;
   bool header_parsed_;
   bool finished_;
 };
diff --git a/src/webcc/http_request.cc b/src/webcc/http_request.cc
index 005c9af..75d5097 100644
--- a/src/webcc/http_request.cc
+++ b/src/webcc/http_request.cc
@@ -29,7 +29,7 @@ void HttpRequest::SetHost(const std::string& host, const std::string& port) {
   }
 }
 
-void HttpRequest::MakeStartLine() {
+void HttpRequest::Build() {
   if (start_line_.empty()) {
     start_line_ = method_;
     start_line_ += " ";
@@ -48,7 +48,6 @@ const char CRLF[] = { '\r', '\n' };
 // ATTENTION: The buffers don't hold the memory!
 std::vector<boost::asio::const_buffer> HttpRequest::ToBuffers() const {
   assert(!start_line_.empty());
-  assert(IsContentLengthValid());
 
   std::vector<boost::asio::const_buffer> buffers;
 
@@ -63,7 +62,9 @@ std::vector<boost::asio::const_buffer> HttpRequest::ToBuffers() const {
 
   buffers.push_back(boost::asio::buffer(misc_strings::CRLF));
 
-  buffers.push_back(boost::asio::buffer(content_));
+  if (content_length_ > 0) {
+    buffers.push_back(boost::asio::buffer(content_));
+  }
 
   return buffers;
 }
diff --git a/src/webcc/http_request.h b/src/webcc/http_request.h
index 22025e7..f7232a5 100644
--- a/src/webcc/http_request.h
+++ b/src/webcc/http_request.h
@@ -51,13 +51,13 @@ public:
   // \param port Numeric port number, "80" will be used if it's empty.
   void SetHost(const std::string& host, const std::string& port);
 
-  // Compose start line from method, url, etc.
-  void MakeStartLine();
+  // Compose start line, etc.
+  // Must be called before ToBuffers()!
+  void Build();
 
   // Convert the response into a vector of buffers. The buffers do not own the
   // underlying memory blocks, therefore the request object must remain valid
   // and not be changed until the write operation has completed.
-  // NOTE: Please call MakeStartLine() before.
   std::vector<boost::asio::const_buffer> ToBuffers() const;
 
 private:
diff --git a/src/webcc/rest_server.cc b/src/webcc/rest_server.cc
index c0b454c..b8e76e5 100644
--- a/src/webcc/rest_server.cc
+++ b/src/webcc/rest_server.cc
@@ -87,6 +87,7 @@ HttpStatus::Enum RestRequestHandler::HandleSession(HttpSessionPtr session) {
   // TODO: Error handling.
   std::string content;
   service->Handle(session->request().method(),
+                  sub_matches,
                   session->request().content(),
                   &content);
 
diff --git a/src/webcc/rest_service.h b/src/webcc/rest_service.h
index 0c32dad..0a69bfc 100644
--- a/src/webcc/rest_service.h
+++ b/src/webcc/rest_service.h
@@ -1,8 +1,9 @@
 #ifndef WEBCC_REST_SERVICE_H_
 #define WEBCC_REST_SERVICE_H_
 
-#include <string>
 #include <memory>
+#include <string>
+#include <vector>
 
 #include "webcc/common.h"
 
@@ -18,8 +19,9 @@ public:
   // Both the request and response parameters should be JSON.
   // TODO: Query parameters.
   virtual bool Handle(const std::string& http_method,
-                      const std::string& request,
-                      std::string* response) = 0;
+                      const std::vector<std::string>& url_sub_matches,
+                      const std::string& request_content,
+                      std::string* response_content) = 0;
 };
 
 typedef std::shared_ptr<RestService> RestServicePtr;