Spring REST service: retrieving JSON from Request

Question

I am building a REST service on Spring 3.1. I am using @EnableWebMVC annotation for that. Since my service will only be accepting JSON requests, I would also like to dump the incoming request into a MongoDB collection for logging (and, later, for data transformation). I would like to access the raw JSON Request (which I could do on a non-spring implementation using "@Content HttpServletRequest request" as a method parameter).

I am a Spring newbie. So, kindly help me with directions to achieve this. Thanks!

UPDATE: The issue is not completely resolved. Only my tests with GET worked. It fails with POST. Therefore unchecked the accepted answer

The issue is, even if I create a HttpServletRequestWrapper, I cannot forward the request after I process and wrap the request. Here is what happens:

Interceptor:

public class DBLogInterceptor extends HandlerInterceptorAdapter {
    MyRequestWrapper requestWrapper;

    private final static Logger logger = Logger.getLogger(DBLogInterceptor.class);

    @Override
    public boolean preHandle(
            HttpServletRequest request,
            HttpServletResponse response,
            Object handler) throws Exception 
    {
        requestWrapper = new MyRequestWrapper(request);
        // Code removed, but it just dumps requestWrapper.getBody() into DB
        return super.preHandle(requestWrapper, response, handler);
    }
}

HTTP POST Servicing method

@RequestMapping(method = RequestMethod.POST, consumes="application/json", produces="application/json", value = "employee")
@ResponseBody
public String updateEntity(@RequestBody Employee emp) {
    // Do some DB Stuff. Anyway, the control flow does not reach this place.
    return "Employee " + emp.getName() + " updated successfully!";
}

Now I get an exception whenever I send a POST:

12:04:53,821 DEBUG DBLogInterceptor:22 - {"name":"Van Damme","dept":"Applied Martial Arts"}
12:04:53,843 DEBUG RequestResponseBodyMethodProcessor:117 - Reading [com.test.webapp.login.domain.Employee] as "application/json" using [org.springframework.http.converter.json.MappingJacksonHttpMessageConverter@154174f9]
12:04:53,850 DEBUG ExceptionHandlerExceptionResolver:132 - Resolving exception from handler [public java.lang.String com.test.webapp.controller.EmployeeService.updateEntity(com.test.webapp.login.domain.Employee)]: java.io.IOException: Stream closed
12:04:53,854 DEBUG ResponseStatusExceptionResolver:132 - Resolving exception from handler [public java.lang.String com.test.webapp.controller.EmployeeService.updateEntity(com.test.webapp.login.domain.Employee)]: java.io.IOException: Streamclosed
12:04:53,854 DEBUG DefaultHandlerExceptionResolver:132 - Resolving exception from handler [public java.lang.String com.test.webapp.controller.EmployeeService.updateEntity(com.test.webapp.login.domain.Employee)]: java.io.IOException: Streamclosed
12:04:53,859 DEBUG DispatcherServlet:910 - Could not complete request
java.io.IOException: Stream closed
        at org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:312)
        at org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:200)
        at org.codehaus.jackson.impl.ByteSourceBootstrapper.ensureLoaded(ByteSourceBootstrapper.java:507)
        at org.codehaus.jackson.impl.ByteSourceBootstrapper.detectEncoding(ByteSourceBootstrapper.java:129)
        at org.codehaus.jackson.impl.ByteSourceBootstrapper.constructParser(ByteSourceBootstrapper.java:224)
        at org.codehaus.jackson.JsonFactory._createJsonParser(JsonFactory.java:785)
        at org.codehaus.jackson.JsonFactory.createJsonParser(JsonFactory.java:561)
        at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1914)
        at org.springframework.http.converter.json.MappingJacksonHttpMessageConverter.readInternal(MappingJacksonHttpMessageConverter.java:124)
        at org.springframework.http.converter.AbstractHttpMessageConverter.read(AbstractHttpMessageConverter.java:153)
        at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:120)
        at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:91)
        at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:71)
        at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:75)
        at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:156)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:117)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
        at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:565)
        at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:307)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
        at java.lang.Thread.run(Unknown Source)

I expected the HttpServletRequestWrapper to be taking care of caching the request. But it doesn't happen somehow.

Answer 1

Using the HttpServletRequest object, you can get access to the URL the client used to make the request, the method used (GET, POST, PUT, etc), the query string, and headers.

Getting the RequestBody may be a bit trickier and may require using the HttpServletRequestWrapper object. Since the request body can only be read once, you'll need to extend the wrapper to access it so that your target controller can still access it later to deserialize your JSON into POJO objects.

public class MyRequestWrapper extends HttpServletRequestWrapper {
 private final String body;
 public MyRequestWrapper(HttpServletRequest request) throws IOException {
   super(request);
   StringBuilder stringBuilder = new StringBuilder();
   BufferedReader bufferedReader = null;
   try {
     InputStream inputStream = request.getInputStream();
     if (inputStream != null) {
       bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
       char[] charBuffer = new char[128];
       int bytesRead = -1;
       while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
         stringBuilder.append(charBuffer, 0, bytesRead);
       }
     } else {
       stringBuilder.append("");
     }
   } catch (IOException ex) {
       throw ex;
   } finally {
     if (bufferedReader != null) {
       try {
         bufferedReader.close();
       } catch (IOException ex) {
         throw ex;
       }
     }
   }
   body = stringBuilder.toString();
 }

 @Override
 public ServletInputStream getInputStream() throws IOException {
   final ByteArrayInputStream byteArrayInputStream = new     ByteArrayInputStream(body.getBytes());
   ServletInputStream servletInputStream = new ServletInputStream() {
     public int read() throws IOException {
       return byteArrayInputStream.read();
     }
   };
   return servletInputStream;
 }

 @Override
 public BufferedReader getReader() throws IOException {
   return new BufferedReader(new InputStreamReader(this.getInputStream()));
 }

 public String getBody() {
   return this.body;
 }
}

To access the requests in a central location, you can use either a Filter or a Spring Interceptor. Both of these are invoked prior to the request being delegated to the controller, and both have access to the servlet.

Here is an actual Logging example using a Spring Interceptor:

package com.vaannila.interceptor;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Logger;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler. HandlerInterceptorAdapter;

public class LoggerInterceptor extends HandlerInterceptorAdapter {
    static Logger logger = Logger.getLogger(LoggerInterceptor.class);

    static {
        BasicConfigurator.configure();
    }

    @Override

    public boolean preHandle(HttpServletRequest request,
        HttpServletResponse response, Object handler) throws Exception {

        logger.info("Before handling the request");
        return super.preHandle(request, response, handler);
    }

    @Override
    public void postHandle(HttpServletRequest request,
        HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {

        logger.info("After handling the request");
        super.postHandle(request, response, handler, modelAndView);
    }

    @Override
    public void afterCompletion(HttpServletRequest request,
        HttpServletResponse response, Object handler, Exception ex)
            throws Exception {

        logger.info("After rendering the view");
        super.afterCompletion(request, response, handler, ex);
    }
}


<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="viewResolver" class="org.springframework.web.servlet.view.    InternalResourceViewResolver" p:prefix="/WEB-INF/jsp/" p:suffix=".jsp" />

    <bean id="handlerMapping" class="org.springframework.web.servlet.handler. BeanNameUrlHandlerMapping" p:interceptors-ref="loggerInterceptor" />

    <bean id="loggerInterceptor" class="com.vaannila.interceptor.LoggerInterceptor" />

    <bean id="userService" class="com.vaannila.service.UserServiceImpl" />

    <bean name="/userRegistration.htm" class="com.vaannila.web.UserController" p:userService-ref="userService" p:formView="userForm" p:successView="userSuccess" />

</beans>

In the LoggerInterceptor, you could use the following code to access the request:

MyRequestWrapper myRequestWrapper = new MyRequestWrapper((HttpServletRequest) request);

String body = myRequestWrapper.getBody();
String clientIP = myRequestWrapper.getRemoteHost();
int clientPort = request.getRemotePort();
String uri = myRequestWrapper.getRequestURI();

System.out.println(body);
System.out.println(clientIP);
System.out.println(clientPort);
System.out.println(uri);