Custom MVC principle

Catalog

One ： Customize mvc Working principle diagram of the frame ：

Two . What is? MVC：

3、 ... and . Concrete realization ：

1. Writing CPU servlet

2.Action Interface definition

3. Realization Action Interface definition of :

4. Implement sub controllers ：

 5. Request distribution function

6. Running results ：

7. Code perfect ：

7.1 Use profile configuration action

7.2. At night, CPU ：

---

One ： Customize mvc Working principle diagram of the frame ：

---

 ActionSevlet: The central controller （ It is mainly used to control one or more sub controllers Action To deal with requests ）

Core component description ：

• The central controller （ActionServlet）： Responsible for receiving all requests , And give specific treatment to the controller .
• Sub controller （Action）： Responsible for processing requests allocated by the central processing unit
• View （view）： jsp page , Responsible for the display
• Model （Model）： Responsible for business processing logic

Two . What is? MVC：

---

MVC The full name is Model View Controller, It's a model (model)－ View (view)－ controller (controller) Abbreviation . It's a software design paradigm .

Using a business logic 、 data 、 The interface displays the separated method organization code , Gather business logic into a component , While improving and personalizing the interface and user interaction , No need to rewrite business logic .

Improved program maintainability 、 Portability 、 Scalability and reusability , It reduces the difficulty of program development . It is mainly divided into models 、 View 、 Controller layer 3 .

• Model （model）： It is the main part of the application , It mainly includes business logic module （web In the project dao class ） And data module （pojo class ）.pojo Generally, it can be called entity domain model ,dao and service It is called process domain model .
• View （view）： The interface with which the user interacts 、 stay web The middle view is generally composed of jsp,html form , Others include android,ios wait .
• controller （controller）： Receive requests from the interface And give it to the model for processing In this process, the controller does not do any processing, but plays a connecting role .

What's not enough ：

• Increase the complexity of system structure and implementation . For a simple interface , Strictly observe MVC, Need to make the model 、 View separate from controller , Increase system complexity
• The relationship between view and controller is too close

3、 ... and . Concrete realization ：

1. Writing CPU servlet

/**
 *  Each sub controller must implement this interface , Responsible for processing requests allocated by the central processing unit 
 * @author Administrator
 */
public interface Action {
	
	/**
	 *  Processing requests 
	 * @param request   request 
	 * @param response  Respond to 
	 * @return String  Return forwarded or redirected jsp Page name 
	 */
	String exeute(HttpServletRequest request, HttpServletResponse response);

}

2.Action Interface definition

/**
 *  Each sub controller must implement this interface , Responsible for processing requests allocated by the central processing unit 
 * @author Administrator
 */
public interface Action {
	
	/**
	 *  Processing requests 
	 * @param request   request 
	 * @param response  Respond to 
	 * @return String  Return forwarded or redirected jsp Page name 
	 */
	String exeute(HttpServletRequest request, HttpServletResponse response);

}/**
 *  Each sub controller must implement this interface , Responsible for processing requests allocated by the central processing unit 
 * @author Administrator
 */
public interface Action {
	
	/**
	 *  Processing requests 
	 * @param request   request 
	 * @param response  Respond to 
	 * @return String  Return forwarded or redirected jsp Page name 
	 */
	String exeute(HttpServletRequest request, HttpServletResponse response);

}

3. Realization Action Interface definition of :

/**
 *  Each sub controller must implement this interface , Responsible for processing requests allocated by the central processing unit 
 * @author Administrator
 */
public interface Action {
	
	/**
	 *  Processing requests 
	 * @param request   request 
	 * @param response  Respond to 
	 * @return String  Return forwarded or redirected jsp Page name 
	 */
	String exeute(HttpServletRequest request, HttpServletResponse response);

}

4. Implement sub controllers ：

public class BookAction implements Action {

	@Override
	public String exeute(HttpServletRequest request, HttpServletResponse response) {
		
		return "bookList";
	}

}

public class StudentAction implements Action {

	@Override
	public String exeute(HttpServletRequest request, HttpServletResponse response) {
		// TODO Auto-generated method stub
		return "students";
	}

}

 5. Request distribution function

**
 *  The central controller , Be responsible for receiving all requests and giving them to the controller for specific processing 
 * @author Administrator
 */
@WebServlet("*.action")
public class ActionDispatchServlet extends HttpServlet {
	
	// Used to hold path And action Mapping of sub controllers 
	public static Map<String, Action> actionMap = new HashMap<>();
	
	static {
		actionMap.put("/studentAction", new StudentAction());
		actionMap.put("/bookAction", new BookAction());
	}
	
	@Override
	public void doGet(HttpServletRequest request, HttpServletResponse response) {
		doPost(request, response);
	}
	
	@Override
	public void doPost(HttpServletRequest request, HttpServletResponse response) {
		String servletPath = request.getServletPath();
		String path = servletPath.split("\\.")[0];
		
		Action action = actionMap.get(path);
		
		String rpath = action.exeute(request, response);
		
		System.out.println(rpath);
	}

}

6. Running results ：

7. Code perfect ：

---

7.1 Use profile configuration action

studentAction Is defined above , As shown in the figure ：

type It's a brand new name , As shown in the figure ：、

 

name yes jsp Name ：

hinder path Namely jsp Permission naming for

 

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE config[
	<!ELEMENT config (action*)>
	<!ELEMENT action (forward*)>
	<!ELEMENT forward EMPTY>
	<!ATTLIST action
	  path CDATA #REQUIRED
	  type CDATA #REQUIRED
	>
	<!ATTLIST forward
	  name CDATA #REQUIRED
	  path CDATA #REQUIRED
	  redirect (true|false) "false"
	>
]>
<config>
	<action path="/studentAction" type="org.lisen.mvc.action.StudentAction">
		<forward name="students" path="/students/studentList.jsp" redirect="false"/>
	</action>
</config>

7.2. At night, CPU ：

@WebServlet("*.action")
public class ActionDispatchServlet extends HttpServlet {
	
	// Used to hold path And action Mapping of sub controllers 
	//public static Map<String, Action> actionMap = new HashMap<>();
	
	private static ConfigModel configModel;
	
	static {
		//actionMap.put("/students", new StudentAction());
		//actionMap.put("/books", new BookAction());
		configModel  = ConfigModelFactory.getConfigModel();
	}
	
	@Override
	public void doGet(HttpServletRequest request, HttpServletResponse response) 
			throws IOException, ServletException {
		doPost(request, response);
	}
	
	@Override
	public void doPost(HttpServletRequest request, HttpServletResponse response) 
			throws IOException, ServletException {
		
		String servletPath = request.getServletPath();
		String path = servletPath.split("\\.")[0];
		
		Action action = getActionByPath(path);
		String name = action.exeute(request, response);
		
		ForwardModel forwardModel = getForwardModel(path, name);
		if (forwardModel.isRedirect()) {
			response.sendRedirect(request.getContextPath() + "/" + forwardModel.getPath());
		} else {
			request.getRequestDispatcher(forwardModel.getPath()).forward(request, response);
		}
	}
	
	// Get the corresponding... Through the request path action example 
	private Action getActionByPath(final String path) {
		ActionModel action = configModel.find(path);
		try {
			Class<?> clazz = Class.forName(action.getType());
			return (Action)clazz.newInstance();
		} catch (Exception e) {
			throw new RuntimeException(" establish Action Instance exception "+e.getMessage(), e);
		}
	}
	
	public ForwardModel getForwardModel(String path, String name) {
		return configModel.find(path).find(name);
	}

}