diff --git a/bak/encoding.cc b/bak/encoding.cc
deleted file mode 100644
index fd5ebae..0000000
--- a/bak/encoding.cc
+++ /dev/null
@@ -1 +0,0 @@
-#include "webcc/encoding.h"
diff --git a/bak/encoding.h b/bak/encoding.h
deleted file mode 100644
index 8b3cf96..0000000
--- a/bak/encoding.h
+++ /dev/null
@@ -1,21 +0,0 @@
-#ifndef WEBCC_ENCODING_H_
-#define WEBCC_ENCODING_H_
-
-#include <string>
-#include <codecvt>
-
-namespace webcc {
-
-std::string Utf16ToUtf8(const std::wstring& utf16_string) {
- std::wstring_convert<std::codecvt_utf8<wchar_t>> converter;
- return converter.to_bytes(utf16_string);
-}
-
-std::wstring Utf8ToUtf16(const std::string& utf8_string) {
- std::wstring_convert<std::codecvt_utf8<wchar_t>> converter;
- return converter.from_bytes(utf8_string);
-}
-
-}  // namespace webcc
-
-#endif  // WEBCC_ENCODING_H_
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index 63ffcb5..938cbc5 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -57,3 +57,8 @@ target_link_libraries(form_server ${EXAMPLE_LIBS})
 
 add_subdirectory(book_server)
 add_subdirectory(book_client)
+
+if(WIN32)
+    add_executable(url_unicode url_unicode.cc encoding.cc encoding.h)
+    target_link_libraries(url_unicode ${EXAMPLE_LIBS})
+endif()
diff --git a/examples/common/book.cc b/examples/common/book.cc
deleted file mode 100644
index 62ee25b..0000000
--- a/examples/common/book.cc
+++ /dev/null
@@ -1,61 +0,0 @@
-#include "examples/common/book.h"
-
-#include <algorithm>
-#include <iostream>
-
-const Book kNullBook{};
-
-std::ostream& operator<<(std::ostream& os, const Book& book) {
-  os << "{ " << book.id << ", " << book.title << ", " << book.price << " }";
-  return os;
-}
-
-const Book& BookStore::GetBook(const std::string& id) const {
-  auto it = FindBook(id);
-  return (it == books_.end() ? kNullBook : *it);
-}
-
-std::string BookStore::AddBook(const Book& book) {
-  std::string id = NewID();
-  books_.push_back({ id, book.title, book.price });
-  return id;
-}
-
-bool BookStore::UpdateBook(const Book& book) {
-  auto it = FindBook(book.id);
-  if (it != books_.end()) {
-    it->title = book.title;
-    it->price = book.price;
-    return true;
-  }
-  return false;
-}
-
-bool BookStore::DeleteBook(const std::string& id) {
-  auto it = FindBook(id);
-
-  if (it != books_.end()) {
-    books_.erase(it);
-    return true;
-  }
-
-  return false;
-}
-
-std::list<Book>::const_iterator BookStore::FindBook(const std::string& id)
-    const {
-  return std::find_if(books_.begin(), books_.end(),
-                      [&id](const Book& book) { return book.id == id; });
-}
-
-std::list<Book>::iterator BookStore::FindBook(const std::string& id) {
-  return std::find_if(books_.begin(), books_.end(),
-                      [&id](Book& book) { return book.id == id; });
-}
-
-std::string BookStore::NewID() const {
-  static int s_id_counter = 0;
-
-  ++s_id_counter;
-  return std::to_string(s_id_counter);
-}
diff --git a/examples/common/book.h b/examples/common/book.h
deleted file mode 100644
index 2dea1fa..0000000
--- a/examples/common/book.h
+++ /dev/null
@@ -1,52 +0,0 @@
-#ifndef EXAMPLE_COMMON_BOOK_H_
-#define EXAMPLE_COMMON_BOOK_H_
-
-#include <list>
-#include <string>
-
-#include "boost/filesystem/path.hpp"
-
-// In-memory test data.
-// There should be some database in a real product.
-
-struct Book {
-  std::string id;
-  std::string title;
-  double price;
-  boost::filesystem::path photo;
-
-  bool IsNull() const { return id.empty(); }
-};
-
-std::ostream& operator<<(std::ostream& os, const Book& book);
-
-extern const Book kNullBook;
-
-class BookStore {
-public:
-  const std::list<Book>& books() const {
-    return books_;
-  }
-
-  const Book& GetBook(const std::string& id) const;
-
-  // Add a book, return the ID.
-  // NOTE: The ID of the input book will be ignored so should be empty.
-  std::string AddBook(const Book& book);
-
-  bool UpdateBook(const Book& book);
-
-  bool DeleteBook(const std::string& id);
-
-private:
-  std::list<Book>::const_iterator FindBook(const std::string& id) const;
-
-  std::list<Book>::iterator FindBook(const std::string& id);
-
-  // Allocate a new book ID.
-  std::string NewID() const;
-
-  std::list<Book> books_;
-};
-
-#endif  // EXAMPLE_COMMON_BOOK_H_
diff --git a/examples/common/book_json.cc b/examples/common/book_json.cc
deleted file mode 100644
index c5fd817..0000000
--- a/examples/common/book_json.cc
+++ /dev/null
@@ -1,57 +0,0 @@
-#include "examples/common/book_json.h"
-
-#include <sstream>
-#include <iostream>
-
-#include "json/json.h"
-
-#include "examples/common/book.h"
-
-std::string JsonToString(const Json::Value& json) {
-  Json::StreamWriterBuilder builder;
-  return Json::writeString(builder, json);
-}
-
-Json::Value StringToJson(const std::string& str) {
-  Json::Value json;
-
-  Json::CharReaderBuilder builder;
-  std::stringstream stream(str);
-  std::string errs;
-  if (!Json::parseFromStream(builder, stream, &json, &errs)) {
-    std::cerr << errs << std::endl;
-  }
-
-  return json;
-}
-
-Json::Value BookToJson(const Book& book) {
-  Json::Value json;
-  json["id"] = book.id;
-  json["title"] = book.title;
-  json["price"] = book.price;
-  return json;
-}
-
-Book JsonToBook(const Json::Value& json) {
-  return {
-    json["id"].asString(),
-    json["title"].asString(),
-    json["price"].asDouble(),
-  };
-}
-
-std::string BookToJsonString(const Book& book) {
-  return JsonToString(BookToJson(book));
-}
-
-bool JsonStringToBook(const std::string& json_str, Book* book) {
-  Json::Value json = StringToJson(json_str);
-
-  if (!json) {
-    return false;
-  }
-
-  *book = JsonToBook(json);
-  return true;
-}
diff --git a/examples/common/book_json.h b/examples/common/book_json.h
deleted file mode 100644
index dbb7027..0000000
--- a/examples/common/book_json.h
+++ /dev/null
@@ -1,20 +0,0 @@
-#ifndef EXAMPLE_COMMON_BOOK_JSON_H_
-#define EXAMPLE_COMMON_BOOK_JSON_H_
-
-#include <string>
-
-#include "json/json-forwards.h"
-
-struct Book;
-
-std::string JsonToString(const Json::Value& json);
-
-Json::Value StringToJson(const std::string& str);
-
-Json::Value BookToJson(const Book& book);
-Book JsonToBook(const Json::Value& json);
-
-std::string BookToJsonString(const Book& book);
-bool JsonStringToBook(const std::string& json_str, Book* book);
-
-#endif  // EXAMPLE_COMMON_BOOK_JSON_H_
diff --git a/examples/encoding.cc b/examples/encoding.cc
new file mode 100644
index 0000000..4faadea
--- /dev/null
+++ b/examples/encoding.cc
@@ -0,0 +1,60 @@
+#include "encoding.h"
+
+#include <Windows.h>
+
+namespace {
+
+// Wrapper for Windows API MultiByteToWideChar.
+std::wstring MB2WC(const std::string& input, unsigned int code_page) {
+  if (input.empty()) {
+    return L"";
+  }
+
+  int length = ::MultiByteToWideChar(code_page, 0, &input[0],
+                                     static_cast<int>(input.size()),
+                                     NULL, 0);
+
+  std::wstring output(length, '\0');
+
+  ::MultiByteToWideChar(code_page, 0, &input[0], static_cast<int>(input.size()),
+                        &output[0], static_cast<int>(output.size()));
+
+  return output;
+}
+
+// Wrapper for Windows API WideCharToMultiByte.
+std::string WC2MB(const std::wstring& input, unsigned int code_page) {
+  if (input.empty()) {
+    return "";
+  }
+
+  // There do have other code pages which require the flags to be 0, e.g.,
+  // 50220, 50211, and so on. But they are not included in our charset
+  // dictionary. So, only consider 65001 (UTF-8) and 54936 (GB18030).
+  DWORD flags = 0;
+  if (code_page != 65001 && code_page != 54936) {
+    flags = WC_NO_BEST_FIT_CHARS | WC_COMPOSITECHECK | WC_DEFAULTCHAR;
+  }
+
+  int length = ::WideCharToMultiByte(code_page, flags, &input[0],
+                                     static_cast<int>(input.size()), NULL, 0,
+                                     NULL, NULL);
+
+  std::string output(length, '\0');
+
+  ::WideCharToMultiByte(code_page, flags, &input[0],
+                        static_cast<int>(input.size()), &output[0],
+                        static_cast<int>(output.size()), NULL, NULL);
+
+  return output;
+}
+
+}  // namespace
+
+std::string Utf16ToUtf8(const std::wstring& utf16_string) {
+  return WC2MB(utf16_string, CP_UTF8);
+}
+
+std::wstring Utf8ToUtf16(const std::string& utf8_string) {
+  return MB2WC(utf8_string, CP_UTF8);
+}
diff --git a/examples/encoding.h b/examples/encoding.h
new file mode 100644
index 0000000..cff9258
--- /dev/null
+++ b/examples/encoding.h
@@ -0,0 +1,12 @@
+#ifndef ENCODING_H_
+#define ENCODING_H_
+
+#include <string>
+
+// Convert UTF16 to UTF8.
+std::string Utf16ToUtf8(const std::wstring& utf16_string);
+
+// Convert UTF8 to UTF16.
+std::wstring Utf8ToUtf16(const std::string& utf8_string);
+
+#endif  // ENCODING_H_
diff --git a/examples/url_unicode.cc b/examples/url_unicode.cc
new file mode 100644
index 0000000..6d24a86
Binary files /dev/null and b/examples/url_unicode.cc differ
diff --git a/webcc/url.cc b/webcc/url.cc
index e758f0f..cf9a75d 100644
--- a/webcc/url.cc
+++ b/webcc/url.cc
@@ -83,7 +83,8 @@ std::string EncodeImpl(const std::string& raw,  // UTF8
 
   for (auto i = raw.begin(); i != raw.end(); ++i) {
     // For UTF8 encoded string, char ASCII can be greater than 127.
-    int c = static_cast<int>(*i);
+    // Cast to unsigned char firstly to make sure it's in [0,255].
+    int c = static_cast<unsigned char>(*i);
 
     if (should_encode(c)) {
       encoded.push_back('%');
@@ -101,7 +102,8 @@ std::string EncodeImpl(const std::string& raw,  // UTF8
 // are called unreserved. These include uppercase and lowercase letters, decimal
 // digits, hyphen, period, underscore, and tilde.
 inline bool IsUnreserved(int c) {
-  return std::isalnum(c) || c == '-' || c == '.' || c == '_' || c == '~';
+  return std::isalnum((unsigned char)c) || c == '-' || c == '.' || c == '_' ||
+         c == '~';
 }
 
 // General delimiters serve as the delimiters between different uri components.