Custom HTTP Message Converter Not Being Used, 415 Unsupproted Media Type

Question

I am creating a test application to achieve conversion from XML String to Employee object before being passed to the controller. I don't want to use JAXB converter because the purpose is to test Custom HTTP Message Converter which I am going to use in my actual use case that involves XML parsing using SAX parser and some complex rules.

Here are the key steps performed:

• Creation of Employee.java Class : Domain Object
• Creation of EmployeeManagementController.java class : Spring MVC Controller for Managing Employee
• Creation of EmployeeConverter.java : Custom Converter for Converting XML String to Employee Object.
• Creation of employee-servlet.xml : Spring Configuration file
• Creation of web.xml : The Deployment Descriptor

Employee.java

@Component
@XmlRootElement(name="employee")
@XmlAccessorType(XmlAccessType.FIELD)
public class Employee{

@XmlElement(name="name")
String name;
@XmlElement(name="designation")
String designation;
@XmlElement(name="skill")
String skill;

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public String getSkill() {
return skill;
}
public void setSkill(String skill) {
this.skill = skill;
}

}

EmployeeManagementController.java

@Controller
@RequestMapping(value="/emp")
public class EmployeeManagementController {

    @RequestMapping(value="/add/employee", method=RequestMethod.POST, consumes="text/html")
    public void addEmployee(@RequestBody Employee employee){
        System.out.println("Employee Name : "+employee.getName());
        System.out.println("Employee Designation : "+employee.getDesignation());
        System.out.println("Employee Skill : "+employee.getSkill());

    }


}

EmployeeConverter.java

@Component
public class EmployeeConverter extends AbstractHttpMessageConverter<Employee>{

    @Override
    protected Employee readInternal(Class<? extends Employee> arg, HttpInputMessage inputMsg) throws IOException,
            HttpMessageNotReadableException {
        // TODO Auto-generated method stub
        Map<String,String> paramMap = getPostParameter(inputMsg);
        BufferedReader file =  new BufferedReader(new StringReader(paramMap.get("xml")));
        Employee employee = null;
        JAXBContext jaxbContext;
        try {
            jaxbContext = JAXBContext.newInstance(Employee.class);
            Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller();
            employee = (Employee) jaxbUnmarshaller.unmarshal(file);
        } catch (JAXBException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println(employee);
        return employee;
    }

    @Override
    protected boolean supports(Class<?> type) {
        if(type.getSimpleName().equalsIgnoreCase("Employee")){
            return true;
        }
        return false;
    }

    @Override
    protected void writeInternal(Employee arg0, HttpOutputMessage arg1)
            throws IOException, HttpMessageNotWritableException {
        // TODO Auto-generated method stub

    }

    private Map<String,String> getPostParameter(HttpInputMessage input) throws IOException{
        String payload = null;
        String[] params = null;
        BufferedReader buf = new BufferedReader(new InputStreamReader(input.getBody()));
        Map<String,String> paramMap = new HashMap<String,String>();

        String line="";
        while((line = buf.readLine())!=null){
            payload = payload+line;
        }

        if(payload.contains("&")){
            params = payload.split("&");
            for(String param : params){
                paramMap.put(param.split("=")[0],param.split("=")[1]);
            }
        }

        return paramMap;
    }


}

employee-servlet.xml

<?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:context="http://www.springframework.org/schema/context"
                xmlns:mvc="http://www.springframework.org/schema/mvc"
                xmlns:util="http://www.springframework.org/schema/util"
                xsi:schemaLocation="http://www.springframework.org/schema/beans 
                http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
                http://www.springframework.org/schema/context 
                http://www.springframework.org/schema/context/spring-context-3.1.xsd
                http://www.springframework.org/schema/mvc
                http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd
                http://www.springframework.org/schema/util
                http://www.springframework.org/schema/util/spring-util-3.1.xsd">

         <mvc:default-servlet-handler/> 

        <context:component-scan base-package="com"/>

         <mvc:annotation-driven>
            <mvc:message-converters>
                <bean class="com.converter.EmployeeConverter"/>             
            </mvc:message-converters>
        </mvc:annotation-driven>

        <bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
            <property name="mediaTypes">
                <map>
                    <entry key="json" value="application/json"/>
                    <entry key="xml" value="text/xml"/>
                    <entry key="htm" value="text/html"/>
                </map>
            </property>
            <property name="defaultContentType" value="text/html"/>
        </bean>

        <!-- <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
            <property name="messageConverters">    
                <util:list id="beanList">
                    <ref bean="employeeConverter"/>       
                </util:list>
            </property>
        </bean>  -->

        <!-- <bean id="employeeConverter" class="com.converter.EmployeeConverter"/> -->



</beans>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>TestConverter</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>    
  </welcome-file-list>

  <servlet>
    <servlet-name>employee</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
  <servlet-name>employee</servlet-name>
  <url-pattern>/*</url-pattern>
  </servlet-mapping>

<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/employee-servlet.xml</param-value>
</context-param>

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

</web-app>

When I Use FireFox RestClient I get Response as : 415 Unsupproted Media Type.

I set the Content-Type and Accept header as text/xml in RestClient and pass the following XML string in the body as parameter:

xml=<employee><name>Jack</name><designation>Account Director</designation><skill>Commuication</skill></employee>

Can somebody help and let me know what changes are required? I have also tried to use AnnotationMethodHandlerAdapter for registering the message converter.

Answer 1

1. Set Media Type

Comparing your implementation with some HttpMessageConverter implementations provided by Spring (for example ´MappingJackson2HttpMessageConverter´), shows that you missed to define the supportedMediaTypes.

The common way* of HttpMessageConverter that extends AbstractHttpMessageConverter<T> is to set the media type in the constructor, by using the super constructor AbstractHttpMessageConverter.(MediaType supportedMediaType).

 public class EmployeeConverter extends AbstractHttpMessageConverter<Employee> {
      public EmployeeConverter() {
            super(new MediaType("text", "xml", Charset.forName("UTF-8")));
      }
 }

BTW 1: you can also register more then one media type**

super(MediaType.APPLICATION_XML,
      MediaType.TEXT_XML,
      new MediaType("application", "*+xml")); 

BTW 2: for xml conterter one should think extending from AbstractXmlHttpMessageConverter<T>

2. Register you Converter

<mvc:annotation-driven>
    <mvc:message-converters>
       ...
       <bean class="com.example.YourConverter"/>
    </mvc:message-converters>
</mvc:annotation-driven>

The major drawback of <mvc:message-converters> is, that this replace the default configuration, so you must also register all default HttpMessageConverter explicit.

To keep the default message convertes you need to use: <mvc:message-converters register-defaults="true">...

• *used by the other implementations like MappingJackson2HttpMessageConverter´
• **example take from AbstractXmlHttpMessageConverter<T>