Question

I’m trying to add a simple REST service to a default Spring MVC Template project created using the SpringSource Tool Suite (STS) and Eclipse. The REST service I want to expose is basically a utility that’s not tied to any model. The input is a string and I want it to return the string reversed. The code part is easy, but the configuration is not. Below are my relevant files.

I don’t really understand why this doesn’t work, but when I type in the URL http://localhost:8080/projectName/restfultest/stringreverser/testString I get the error message
No mapping found for HTTP request with URI [/projectName/restfultest/stringreverser/] in DispatcherServlet with name ‘restfulServlet’

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee  http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

    <!-- The definition of the Root Spring Container shared by all Servlets and Filters -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/spring/root-context.xml</param-value>
    </context-param>

    <!-- Creates the Spring Container shared by all Servlets and Filters -->
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <servlet>
        <servlet-name>restfulServlet</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>/WEB-INF/spring/restfulServlet/servlet-context.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>restfulServlet</servlet-name>
        <url-pattern>/restfultest/*</url-pattern>
    </servlet-mapping>

</web-app>

servlet-context.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans:beans xmlns="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:beans="http://www.springframework.org/schema/beans"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

    <!-- DispatcherServlet Context: defines this servlet's request-processing infrastructure -->

    <!-- Enables the Spring MVC @Controller programming model -->
    <annotation-driven />

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



</beans:beans>

RestfulService.java

package com.sample.pkg;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
@RequestMapping(value = "/stringreverser")
public class RestfulService {

    @RequestMapping(value="/{id}", method=RequestMethod.GET)
    public String reverseId(@PathVariable("id") String id) {
        String reversed = "";
        for (int i = id.length() - 1; i <= 0; --i) {
            reversed += id.charAt(i);
        }

        return reversed;
    }
}

Thanks in advance for any help!

-Joe

Answer 1

First off, you reversal function is incorrect

for (int i = id.length() - 1; i <= 0; --i) {...}

It will never go in, as you expect i to be less than or equal to 0 on start.

Second of all, here’s some good news

Here is a working controller

@Controller
@RequestMapping( value="/stringreverser" )
public class HomeController {

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

    @RequestMapping( value="/{id}", method=RequestMethod.GET )
    public String reverseId( @PathVariable String id, Model model ) {

        StringBuilder reversed = new StringBuilder();
        for ( int i = id.length() - 1; i >= 0; i-- ) {
            reversed.append( id.charAt( i ) );
        }

        logger.debug( "\n\t [" + id + "] reversed ==> " + reversed.toString() );

        model.addAttribute( "originalId", id );
        model.addAttribute( "reversedId", reversed.toString() );

        return "home";
    }
}

Controller name is HomeController, since I used a templated Spring MVC app that you can create in two clicks with Spring Tool Suite:

• File => New => Spring Template Project
• Choose “Spring MVC Project”, enter project name, top level package ( e.g. org.guru.xyz ), click Next
• You have yourself a brand new “Spring MVC” project
• In order to deploy it, right click on your project ( on the left hand side ), go to “Run As” => “Run On Server”
• This will deploy it to Tomcat and open a “localhost:8080/somemvc/” where you would see “Hello world!”

But the way, it’ll already have a, missing from your code above, view resolver and a home.jsp, that you see rendered on the picture above.

Here is the home.jsp

<html>
  <head> <title>Mean ID Reverser</title> </head>
  <body>
    <h1> Mean ID Reverser </h1>
    <p>  I just reversed your ID "${originalId}" => "${reversedId}" </p>
  </body>
</html>

And

<url-pattern>/restfultest/*</url-pattern> in web.xml works just fine.

---

JSON Woodoo

In order to return it as JJ (Just JSON), there are just two things you need to do:

Add a Jackson Mapper dependency

<dependency>
    <groupId>org.codehaus.jackson</groupId>
    <artifactId>jackson-mapper-asl</artifactId>
    <version>1.9.2</version>
</dependency>

Change a return type to @ResponseBody Object

@RequestMapping( value="/{id}", method=RequestMethod.GET )
public @ResponseBody Object reverseIdJson(@PathVariable String id) {        
    return new ReverserResult( id );
}

I included an object ReversalResult instead of a simple String in order to demonstrate a transparent Jackson Mapper magic, and to see that it is truly a JSON response that comes back:

where a ReversalResult has two fields, a reverseString static method, and it reverses a String in a constructor:

    private String original;
    private String reversed;

    public ReverserResult( String reverseMe ) {
        this.original = reverseMe;
        this.reversed = reverseString( reverseMe );
    }

This of course would just be a stand alone function, but again, I wanted to show the Object with 1+ fields to come back as JSON.