Who implemente the spring BindingResult?

Question

I'm new to Spring MVC and I'm trying to understand the following code

package com.companyname.springapp.web;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.validation.Valid;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.companyname.springapp.service.PriceIncrease;
import com.companyname.springapp.service.ProductManager;

@Controller
@RequestMapping(value="/priceincrease.htm")
public class PriceIncreaseFormController {

    /** Logger for this class and subclasses */
    protected final Log logger = LogFactory.getLog(getClass());

    @Autowired
    private ProductManager productManager;

    @RequestMapping(method = RequestMethod.POST)
    public String onSubmit(@Valid PriceIncrease priceIncrease, BindingResult result)
    {
        if (result.hasErrors()) {
            return "priceincrease";
        }

        int increase = priceIncrease.getPercentage();
        logger.info("Increasing prices by " + increase + "%.");

        productManager.increasePrice(increase);

        return "redirect:/hello.htm";
    }

    @RequestMapping(method = RequestMethod.GET)
    protected PriceIncrease formBackingObject(HttpServletRequest request) throws ServletException {
        PriceIncrease priceIncrease = new PriceIncrease();
        priceIncrease.setPercentage(15);
        return priceIncrease;
    }

    public void setProductManager(ProductManager productManager) {
        this.productManager = productManager;
    }

    public ProductManager getProductManager() {
        return productManager;
    }

}

As far as I know the BindingResult is an interface and the onSubmit method receives a BindingResult object. What I don't understand is: Who implemented this interface to create the object and where is that implementation?

Here is the 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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/mvc
       http://www.springframework.org/schema/mvc/spring-mvc.xsd">

       <bean id="productManager" class="com.companyname.springapp.service.SimpleProductManager">
         <property name="products">
            <list>
                <ref bean="product1"/>
                <ref bean="product2"/>
                <ref bean="product3"/>
            </list>
         </property>
       </bean>

       <bean id="product1" class="com.companyname.springapp.domain.Product">
         <property name="description" value="Lamp"/>
         <property name="price" value="5.75"/>
       </bean>

       <bean id="product2" class="com.companyname.springapp.domain.Product">
         <property name="description" value="Table"/>
         <property name="price" value="75.25"/>
       </bean>

       <bean id="product3" class="com.companyname.springapp.domain.Product">
         <property name="description" value="Chair"/>
         <property name="price" value="22.79"/>
       </bean>

       <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
         <property name="basename" value="messages"/>
       </bean>

       <!-- Scans the classpath of this application for @Components to deploy as beans -->
       <context:component-scan base-package="com.companyname.springapp.web" />

       <!-- Configures the @Controller programming model -->
       <mvc:annotation-driven/>

       <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
         <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"></property>
         <property name="prefix" value="/WEB-INF/views/"></property>
         <property name="suffix" value=".jsp"></property>        
       </bean>
</beans>

I don't if this helps but I'm using Tomcat 7.0 and whole code is in here: http://docs.spring.io/docs/Spring-MVC-step-by-step/

Answer 1

Who implemented this interface to create the object and where is that implementation?

Implemented in the Spring framework and instantiated by your context. In the above example BeanPropertyBindingResult.class is exact implementation of BindingResult instantiated http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/validation/BeanPropertyBindingResult.html