diff --git a/webcc/async_rest_client.cc b/webcc/async_rest_client.cc
index 341e9c6..31b4525 100644
--- a/webcc/async_rest_client.cc
+++ b/webcc/async_rest_client.cc
@@ -10,7 +10,7 @@ AsyncRestClient::AsyncRestClient(boost::asio::io_context& io_context,
 
 void AsyncRestClient::Request(const std::string& method,
                               const std::string& url,
-                              const std::string& content,
+                              std::string&& content,
                               HttpResponseHandler response_handler) {
   response_handler_ = response_handler;
 
@@ -21,7 +21,8 @@ void AsyncRestClient::Request(const std::string& method,
   request->SetHost(host_, port_);
 
   if (!content.empty()) {
-    request->SetContent(content);
+    request->SetContent(std::move(content), true);
+    request->SetContentType(kAppJsonUtf8);
   }
 
   request->UpdateStartLine();
diff --git a/webcc/async_rest_client.h b/webcc/async_rest_client.h
index 0ef332b..64e09d3 100644
--- a/webcc/async_rest_client.h
+++ b/webcc/async_rest_client.h
@@ -2,6 +2,7 @@
 #define WEBCC_ASYNC_REST_CLIENT_H_
 
 #include <string>
+#include <utility>  // for move()
 
 #include "webcc/async_http_client.h"
 
@@ -10,8 +11,7 @@ namespace webcc {
 class AsyncRestClient {
  public:
   AsyncRestClient(boost::asio::io_context& io_context,  // NOLINT
-                  const std::string& host,
-                  const std::string& port);
+                  const std::string& host, const std::string& port);
 
   void set_timeout_seconds(int timeout_seconds) {
     timeout_seconds_ = timeout_seconds;
@@ -22,22 +22,19 @@ class AsyncRestClient {
     Request(kHttpGet, url, "", response_handler);
   }
 
-  void Post(const std::string& url,
-            const std::string& content,
+  void Post(const std::string& url, std::string&& content,
             HttpResponseHandler response_handler) {
-    Request(kHttpPost, url, content, response_handler);
+    Request(kHttpPost, url, std::move(content), response_handler);
   }
 
-  void Put(const std::string& url,
-           const std::string& content,
+  void Put(const std::string& url, std::string&& content,
            HttpResponseHandler response_handler) {
-    Request(kHttpPut, url, content, response_handler);
+    Request(kHttpPut, url, std::move(content), response_handler);
   }
 
-  void Patch(const std::string& url,
-             const std::string& content,
+  void Patch(const std::string& url, std::string&& content,
              HttpResponseHandler response_handler) {
-    Request(kHttpPatch, url, content, response_handler);
+    Request(kHttpPatch, url, std::move(content), response_handler);
   }
 
   void Delete(const std::string& url,
@@ -46,10 +43,8 @@ class AsyncRestClient {
   }
 
  private:
-  void Request(const std::string& method,
-               const std::string& url,
-               const std::string& content,
-               HttpResponseHandler response_handler);
+  void Request(const std::string& method, const std::string& url,
+               std::string&& content, HttpResponseHandler response_handler);
 
   boost::asio::io_context& io_context_;
 
diff --git a/webcc/globals.cc b/webcc/globals.cc
index 0bd937e..60d397f 100644
--- a/webcc/globals.cc
+++ b/webcc/globals.cc
@@ -16,7 +16,7 @@ const std::string kContentLength = "Content-Length";
 const std::string kSoapAction = "SOAPAction";
 #endif  // WEBCC_ENABLE_SOAP
 
-const std::string kTextJsonUtf8 = "text/json; charset=utf-8";
+const std::string kAppJsonUtf8 = "application/json; charset=utf-8";
 
 #ifdef WEBCC_ENABLE_SOAP
 // According to www.w3.org when placing SOAP messages in HTTP bodies, the HTTP
diff --git a/webcc/globals.h b/webcc/globals.h
index 970c3cb..6e36995 100644
--- a/webcc/globals.h
+++ b/webcc/globals.h
@@ -38,7 +38,7 @@ extern const std::string kContentLength;
 extern const std::string kSoapAction;
 #endif  // WEBCC_ENABLE_SOAP
 
-extern const std::string kTextJsonUtf8;
+extern const std::string kAppJsonUtf8;
 
 #ifdef WEBCC_ENABLE_SOAP
 extern const std::string kTextXmlUtf8;
diff --git a/webcc/http_connection.cc b/webcc/http_connection.cc
index f563b85..8dea87c 100644
--- a/webcc/http_connection.cc
+++ b/webcc/http_connection.cc
@@ -29,9 +29,9 @@ void HttpConnection::Close() {
 }
 
 void HttpConnection::SetResponseContent(std::string&& content,
-                                        const std::string& content_type) {
-  response_.SetContent(std::move(content));
-  response_.SetContentType(content_type);
+                                        const std::string& type) {
+  response_.SetContent(std::move(content), true);
+  response_.SetContentType(type);
 }
 
 void HttpConnection::SendResponse(HttpStatus::Enum status) {
diff --git a/webcc/http_connection.h b/webcc/http_connection.h
index 644cbcd..bc98810 100644
--- a/webcc/http_connection.h
+++ b/webcc/http_connection.h
@@ -35,8 +35,7 @@ class HttpConnection : public std::enable_shared_from_this<HttpConnection> {
   // Close the socket.
   void Close();
 
-  void SetResponseContent(std::string&& content,
-                          const std::string& content_type);
+  void SetResponseContent(std::string&& content, const std::string& type);
 
   // Send response to client with the given status.
   void SendResponse(HttpStatus::Enum status);
diff --git a/webcc/http_message.h b/webcc/http_message.h
index 3afcf73..08a74f3 100644
--- a/webcc/http_message.h
+++ b/webcc/http_message.h
@@ -38,19 +38,16 @@ class HttpMessage {
 
   void SetHeader(std::string&& name, std::string&& value);
 
-  // E.g., "text/xml; charset=utf-8"
+  // E.g., "application/json; charset=utf-8"
   void SetContentType(const std::string& content_type) {
     SetHeader(kContentType, content_type);
   }
 
-  void SetContent(std::string&& content) {
+  void SetContent(std::string&& content, bool set_length) {
     content_ = std::move(content);
-    SetContentLength(content_.size());
-  }
-
-  void SetContent(const std::string& content) {
-    content_ = content;
-    SetContentLength(content_.size());
+    if (set_length) {
+      SetContentLength(content_.size());
+    }
   }
 
   // Set start line according to other informations.
diff --git a/webcc/http_parser.cc b/webcc/http_parser.cc
index 1124740..1e26362 100644
--- a/webcc/http_parser.cc
+++ b/webcc/http_parser.cc
@@ -123,51 +123,19 @@ bool HttpParser::ParseHeader(const std::string& line) {
       LOG_ERRO("Failed to reserve content memory: %s.", e.what());
       return false;
     }
-  } else {
-    message_->SetHeader(std::move(name), std::move(value));
   }
 
+  message_->SetHeader(std::move(name), std::move(value));
+
   return true;
 }
-//
-//void HttpParser::ParseContentLength(const std::string& line) {
-//  std::size_t pos = line.find(':');
-//  if (pos == std::string::npos) {
-//    return;
-//  }
-//
-//  std::string name = line.substr(0, pos);
-//
-//  if (boost::iequals(name, kContentLength)) {
-//    content_length_parsed_ = true;
-//
-//    ++pos;  // Skip ':'.
-//    while (line[pos] == ' ') {  // Skip spaces.
-//      ++pos;
-//    }
-//
-//    std::string value = line.substr(pos);
-//
-//    try {
-//      content_length_ = static_cast<std::size_t>(std::stoul(value));
-//    } catch (const std::exception&) {
-//      LOG_ERRO("Invalid content length: %s.", value.c_str());
-//    }
-//
-//    LOG_INFO("Content length: %u.", content_length_);
-//
-//    try {
-//      // Reserve memory to avoid frequent reallocation when append.
-//      content_.reserve(content_length_);
-//    } catch (const std::exception& e) {
-//      LOG_ERRO("Failed to reserve content memory: %s.", e.what());
-//    }
-//  }
-//}
 
 void HttpParser::Finish() {
-  // Move content to message.
-  message_->SetContent(std::move(content_));
+  if (!content_.empty()) {
+    // Move content to message.
+    // "Content-Length" already set in ParseHeader().
+    message_->SetContent(std::move(content_), /*set_length*/false);
+  }
   finished_ = true;
 }
 
diff --git a/webcc/http_parser.h b/webcc/http_parser.h
index ad75875..4e38333 100644
--- a/webcc/http_parser.h
+++ b/webcc/http_parser.h
@@ -30,8 +30,6 @@ class HttpParser {
 
   bool ParseHeader(const std::string& line);
 
-  //void ParseContentLength(const std::string& line);
-
   void Finish();
 
   void AppendContent(const char* data, std::size_t count);
diff --git a/webcc/rest_client.cc b/webcc/rest_client.cc
index 545f0bc..511fe95 100644
--- a/webcc/rest_client.cc
+++ b/webcc/rest_client.cc
@@ -27,8 +27,8 @@ bool RestClient::Request(const std::string& method, const std::string& url,
   request.SetHost(host_, port_);
 
   if (!content.empty()) {
-    request.SetContent(std::move(content));
-    request.SetContentType(kTextJsonUtf8);
+    request.SetContent(std::move(content), true);
+    request.SetContentType(kAppJsonUtf8);
   }
 
   request.UpdateStartLine();
diff --git a/webcc/rest_request_handler.cc b/webcc/rest_request_handler.cc
index d464b09..f0cafee 100644
--- a/webcc/rest_request_handler.cc
+++ b/webcc/rest_request_handler.cc
@@ -8,8 +8,7 @@
 
 namespace webcc {
 
-bool RestRequestHandler::Bind(RestServicePtr service,
-                              const std::string& url,
+bool RestRequestHandler::Bind(RestServicePtr service, const std::string& url,
                               bool is_regex) {
   return service_manager_.AddService(service, url, is_regex);
 }
@@ -45,7 +44,9 @@ void RestRequestHandler::HandleConnection(HttpConnectionPtr connection) {
     return;
   }
 
-  connection->SetResponseContent(std::move(content), kTextJsonUtf8);
+  if (!content.empty()) {
+    connection->SetResponseContent(std::move(content), kAppJsonUtf8);
+  }
   connection->SendResponse(HttpStatus::kOK);
 }
 
diff --git a/webcc/soap_client.cc b/webcc/soap_client.cc
index 33b8e12..4879302 100644
--- a/webcc/soap_client.cc
+++ b/webcc/soap_client.cc
@@ -40,8 +40,8 @@ Error SoapClient::Call(const std::string& operation,
 
   http_request.set_method(kHttpPost);
   http_request.set_url(url_);
+  http_request.SetContent(std::move(http_content), true);
   http_request.SetContentType(kTextXmlUtf8);
-  http_request.SetContent(std::move(http_content));
   http_request.SetHost(host_, port_);
   http_request.SetHeader(kSoapAction, operation);
   http_request.UpdateStartLine();