This
is continuation to my previous post. IN my previous post, we mapped the request
parameters to a model object and pass the model object to the view using
@ModelAttribute annotation like below.
@RequestMapping(value
= "getEmpDetails", method = RequestMethod.POST)
public
ModelAndView getWelcomeMessage(@ModelAttribute Employee emp) {
modelAndView.addObject("employeeDetails",
emp);
return modelAndView;
}
You
can even apply @ModelAttribute annotation on top of a method to remove the
boilerplate code.
Example
@Controller
public
class HelloWorldController {
@RequestMapping("/hello")
public ModelAndView getHelloMessage() {
ModelAndView modelAndView =
new ModelAndView("hello");
modelAndView.addObject("greeting",
"Good morning");
modelAndView.addObject("quote",
"Live not one’s life as though one had a thousand years, but live each day
as the last.");
return modelAndView;
}
@RequestMapping("/welcome")
public ModelAndView getWelcomeMessage()
{
ModelAndView modelAndView =
new ModelAndView("hello");
modelAndView.addObject("greeting",
"Good morning");
modelAndView.addObject("quote",
"There are two great days in a person's life - the day we are born and the
day we discover why.");
return modelAndView;
}
}
As
you see above controller class, below statement is duplicated in
getHelloMessage(), getWelcomeMessage() methods.
modelAndView.addObject("greeting",
"Good morning");
How can I remove this
boilerplate code?
Move
the common code to some other function and annotate it with @ModelAttribute
annotation.
@ModelAttribute
public
void commonData(Model model) {
model.addAttribute("greeting",
"Good morning");
}
Find
the below working example.
package com.sample.myApp.controllers; import org.springframework.stereotype.Controller; import org.springframework.ui.Model; import org.springframework.web.bind.annotation.ModelAttribute; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.servlet.ModelAndView; @Controller public class HelloWorldController { @ModelAttribute public void commonData(Model model) { model.addAttribute("greeting", "Good morning"); } @RequestMapping("/hello") public ModelAndView getHelloMessage() { ModelAndView modelAndView = new ModelAndView("hello"); modelAndView.addObject("quote", "Live not one’s life as though one had a thousand years, but live each day as the last."); return modelAndView; } @RequestMapping("/welcome") public ModelAndView getWelcomeMessage() { ModelAndView modelAndView = new ModelAndView("hello"); modelAndView.addObject("quote", "There are two great days in a person's life - the day we are born and the day we discover why."); return modelAndView; } }
Create
hello.jsp file under WEB-INF/jsp folder.
hello.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>Hello World Spring Web MVC</title> </head> <body> <h1>${message}</h1> <h2>${quote}</h2> </body> </html>
Create
web.xml, HelloWorld-servlet.xml file under WEB-INF folder.
web.xml
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <display-name>Spring MVC Hello WorldApplication</display-name> <servlet> <servlet-name>HelloWorld</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <load-on-startup>1</load-on-startup> </servlet> <servlet-mapping> <servlet-name>HelloWorld</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> </web-app>
HelloWorld-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.sample.myApp" /> <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="prefix" value="/WEB-INF/jsp/" /> <property name="suffix" value=".jsp" /> </bean> </beans>
Create
index.jsp file under webapp folder.
index.jsp
<html> <head> <title>User Information Page</title> </head> <body> <h1>Hello World</h1> </body> </html>
Project
structure looks like below.
Run
the application server and hit below URL.
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