Correct way for declaring beans in spring MVC? - spring

Question

I created a project named "Testing" using maven in eclipse j2ee. I created a web.xml file in WEB-INF folder as follows :
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"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/dispatcher-servlet.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
And this is my dispatcher servlet that i placed withing WEB-INF folder.
dispatcher-servlet.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="
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">
<context:component-scan base-package="com.spring.trial" />
<context:property-placeholder location="classpath:jdbc.properties" />
<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix">
<value>/WEB-INF/views/</value>
</property>
<property name="suffix">
<value>.jsp</value>
</property>
</bean>
<!-- Employee DB data source. -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"
destroy-method="close">
<property name="driverClass" value="${jdbc.driverClassName}" />
<property name="jdbcUrl" value="${jdbc.employee_db_url}" />
<property name="user" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
<property name="maxPoolSize" value="${jdbc.maxPoolSize}" />
<property name="minPoolSize" value="${jdbc.minPoolSize}" />
<property name="maxStatements" value="${jdbc.maxStatements}" />
<property name="testConnectionOnCheckout" value="${jdbc.testConnection}" />
<property name="idleConnectionTestPeriod" value="200" />
<property name="loginTimeout" value="300" />
<property name="maxIdleTime" value="2700"></property>
<property name="testConnectionOnCheckin" value="true" />
<property name="maxIdleTimeExcessConnections" value="60"></property>
</bean>
<bean name="transactionManager"
class="org.springframework.jdbc.datasource.DataSourceTransactionManager"
scope="singleton">
<property name="dataSource" ref="dataSource"></property>
</bean>
<bean id="categories" class="com.spring.trial.access.Categories"></bean>
I have a controller called helloworldcontroller as follows
package com.spring.trial;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;
import com.spring.trial.access.Categories;
#Controller
public class HelloWorldController {
String message = "Welcome to Spring MVC!";
#Autowired
Categories categories;
#RequestMapping("/hello")
public ModelAndView showMessage(
#RequestParam(value = "name", required = false, defaultValue = "World") String name) {
System.out.println("in controller");
ModelAndView mv = new ModelAndView("helloworld");
mv.addObject("message", message);
mv.addObject("name", name);
return mv;
}
}
Okay now for the triky part....
1)i went through various tutorials online and in some sites the web.xml file has context params that pass the dispatcher-servlet to the context loader class. Does this mean that all the beans in the dispatcher servlet be initialised and autowired . And does it mean that the dispatcher servlet context is now the root application context??
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/dispatcher-servlet.xml</param-value>
</context-param>
<!-- this class is responsible for auto-wiring all the beans together in
spring -->
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
In some sites the web.xml file is intialised as follows:
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/application-context.xml
</param-value>
</context-param>
<!-- Configurations for the DispatcherServlet application context (child context) -->
<servlet>
<servlet-name>spring-mvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>
/WEB-INF/spring-mvc-servlet.xml
</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>spring-mvc</servlet-name>
<url-pattern>/admin/*</url-pattern>
</servlet-mapping>
2) so again what is happening in this web.xml file?? is it loading 2 different contexts one for root and the other for dispatcher servlet??
and in case 2 they hace application-context.xml so on a jsp page i can easily retrieve a bean using
applicationContext context = new classpathxmlapplicationcontext("application-context.xml);
myclass mclass = (myclass)context.getbean("mclassname");
but in case I(first web.xml file that i posted on top) i dont have any application context so how am i supposed to retrive bean on my jsp page?? I just have the dispatcher and all the beans are declared in the dispatcher. please help me i am so confused ryt now.....