Understanding the MVC framework with server-side Java 3/4 Controller

キャプチャ.PNG

** ↑ Image of this framework **

Introduction

This time is the mountain. I don't think it comes to my mind very much, but at first it is. Let's do our best.

things to do

Let's create a website using the framework of the subject Breakdown of all 4 times

1. Create a front page with View jsp *
1. Model Create a model with JavaBeans * ** 3. Create a Servlet that connects Controller V and M **
1. Create a method to access DB2 with Model *

Premise

--Eclipse installed --DB2 installed (required for 4th time)

procedure

jsp fix

`Top.jsp`



<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%><!--Character code specification-->
<!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>Top</title>
<h1>top</h1>
</head>
<body>

<form action="/MVC/Controller" method="post">   <!--Declaration to send ↓ information in post [Addition] Set the action value to Controller-->
    <input type="text" name="keyword">   <!--Search keyword input field-->
    <input type="hidden" name="beanid" value="practice.Product"><!--[Add] Declare the bean to be used-->
    <input type="hidden" name="pageto" value="Result.jsp"><!--[Addition] Specifying the transition destination-->
    <input type="submit" value="Search"> <!--Keyword send button-->
</form>

</body>
</html>

Model creation (partially reprinted)

`Product.java`


package practice;


public class Product extends SuperBean{
        //Keep member variables private
    private int price;
    private int weight;
    private String name;
    private String material1;
    private String category;

    public void runBean(){//[Change] The method name has been changed from setAll.
    	String keyword = (String) super.request.getParameter("keyword");//[Change] Output the received value and check
    	System.out.println("The search keyword is"+keyword+"was. I will search the DB using this next time");

    	//Since we will not make a DB connection this time, we will set the value directly to each attribute of the bean.
        this.price=1404;
        this.weight=300;
        this.name=""My disappearance" Fuminori Nakamura";
        this.material1="paper";
        this.category="book";

    }


    public int getPrice() {
        return price;
    }
    public int getWeight() {
        return weight;
    }
    public String getName() {
        return name;
    }
    public String getMaterial1() {
        return material1;
    }
    public String getCategory() {
        return category;
    }
}

Creating a SuperBean

Created to organize common bean processing into parent class

`SuperBean.java`


package practice;

import javax.servlet.http.HttpServletRequest;

public abstract class SuperBean {
	protected HttpServletRequest request;//Hold request
	void setJspInfo(HttpServletRequest request){
		this.request = request;
	}
	protected void runBean(){//Run bean

	}

}

Creating a Controller

Since then, Controller is designed so that editing is not required even when adding functions (jsp, beans). I think it's hard to write now, but it's useful when adding features. To create a Servlet, right-click the practice package → New → Servlet.

`Controller.java`


package practice;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
 * Servlet implementation class Controller
 */
@WebServlet("/Controller")
public class Controller extends HttpServlet {
	private static final long serialVersionUID = 1L;

    /**
     * Default constructor.
     */
    public Controller() {
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		doPost(request,response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub



		//session(A container for returning an instance to the jsp side)Generate a.
		HttpSession session= request.getSession();

			//It takes the bean name as a variable and instantiates that bean. This allows you to use methods such as getters. The Product class is instantiated here.
			//Character code specification
			request.setCharacterEncoding("UTF-8");
			String beanid = (String)request.getParameter("beanid");
			String pageto = (String)request.getParameter("pageto");
			try {
				SuperBean bean = (SuperBean) Class.forName(beanid).newInstance();


			//Pass the information received from jsp to the bean
			bean.setJspInfo(request);

			//Run bean
			bean.runBean();

			//Store beans in session
			session.setAttribute("bean", bean);

			//transition
			RequestDispatcher rd =request.getRequestDispatcher(pageto);
			rd.forward(request, response);
			} catch (InstantiationException e) {
				//TODO auto-generated catch block
				e.printStackTrace();
			} catch (IllegalAccessException e) {
				//TODO auto-generated catch block
				e.printStackTrace();
			} catch (ClassNotFoundException e) {
				//TODO auto-generated catch block
				e.printStackTrace();
			}



	}

}

Creating a result output page

`Result.jsp`


<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import="practice.Product"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%request.setCharacterEncoding("UTF-8"); %>
<%Product bean = (Product)session.getAttribute("bean"); %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>

</head>
<body>
Product name:<%=bean.getName() %><br>
price:\&nbsp;<%=bean.getPrice() %><br>
weight:<%=bean.getWeight() %><br>
Product Category:<%=bean.getCategory() %><br>
</body>
</html>

This completes MVC excluding DB connection. The content of this time was much more difficult than before. Thank you for your hard work. I think I'll run into errors, so I'm waiting for your question.