自定义MVC框架

一、实现自定义MVC的体系结构图

1.png

1、Model I模式开发Web应用时，分两种情况：

纯JSP技术方式开发

JSP+JavaBean方式开发

2、Model I模式开发的不足：

JSP页面中嵌入大量的Java代码，可读性差。

大量代码在JSP中难以复用。

后期维护及扩展的难度大。

3、为了克服Model I模式的缺陷，引入了Model II的模式开发

Model II模式体现了基于MVC(Model-View-Controller,模型-视图-控制器)的设计模式，简单的说，Model II模式就是将数据显示、流程控制和业务逻辑处理分离，使之相互独立。

4、MVC设计模式由3个部分组成各部分的作用。

Model：模型，主要用于数据和业务的处理。

View：视图，用于数据显示。

Controller：控制器，用于流程控制。

5、MVC设计模式的特点

*一个模型可以对应多个视图。

*显示与逻辑控制分离。

*分层控制，减低了代码间的耦合。

二、 我们如何创建一个自己的MVC框架？？

（一）我们要在lib里面准备一个夹包

dom4j-1.6.1.jar 主要作用：解析xml文件

(二)准备配置文档（在src下）

<!DOCTYPE myframework[

<!ELEMENT myframework (actions) >

<!ELEMENT actions (action*)>

<!ELEMENT action (result*)>

<!ATTLIST action name CDATA #REQUIRED

class CDATA #REQUIRED

<!ATTLIST result name CDATA #IMPLIED

redirect (true|false) "false"

]>

解释：

2.png

解释：根据上述约束完成的****“”****代表该节点可以出现多次*

<myframework>

<actions>

<action name="LoginAction" class="cn.action.LoginAction">

<result name="success">success.jsp</result>

<result name="login">login.jsp</result>

</action>

</actions>

</myframework>

（三）自己准备一个Action接口，用于放入结果集和执行方法

package cn.framework;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public interface Action {

public final String SUCCESS = "success";

public final String ERROR = "error";

public final String LOGIN = "login";

public final String INPUT = "input";

public String execute(HttpServletRequest request,

HttpServletResponse response);

}

（四）定义一个ResultMapping用来存放result节点

package cn.framework;

public class ResultMapping {

//result节点名字

private String name;

//是否重定向

private boolean redirect;

//跳转的页面

private String url;

public ResultMapping() {

}

public ResultMapping(String name, boolean redirect, String url) {

this.name = name;

this.redirect = redirect;

this.url = url;

}

public String getName() {

return name;

}

public void setName(<u>String</u> name) {

this.name = name;

}

public boolean isRedirect() {

return redirect;

}

public void setRedirect(boolean redirect) {

this.redirect = redirect;

}

public String getUrl() {

return url;

}

public void setUrl(String url) {

this.url = url;

}

}

（五）定义一个ActionMapping用来存放Action节点

package cn.framework;

import java.util.HashMap;

import java.util.Map;

public class ActionMapping {

// Action名称

private String name;

// Action名称对应的Action的类的全称

private String className;

// result集合

private Map<String, ResultMapping> results = new HashMap<String, ResultMapping>();

public ActionMapping() {

}

public ActionMapping(String name, String className, Map<String, ResultMapping> results) {

super();

this.name = name;

this.className = className;

this.results = results;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getClassName() {

return className;

}

public void setClassName(String className) {

this.className = className;

}

public Map<String, ResultMapping> getResults() {

return results;

}

public void setResults(Map<String, ResultMapping> results) {

this.results = results;

}

}

（六）准备一个ActionMappingManager是用来管理ActionMapping的

package cn.framework;

import java.io.InputStream;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import org.dom4j.Attribute;

import org.dom4j.Document;

import org.dom4j.Element;

import org.dom4j.io.SAXReader;

public class ActionMappingManager {

Map<String, ActionMapping> actionMapping = new HashMap<String, ActionMapping>();

public ActionMappingManager() {

init();

}

public ActionMapping getActionMapping(String actionName) {

return actionMapping.get(actionName);

}

public ActionMappingManager(<u>String</u> fileName) {

}

public Map<String, ActionMapping> getActionMapping() {

return actionMapping;

}

public void setActionMapping(Map<String, ActionMapping> actionMapping) {

this.actionMapping = actionMapping;

}

public static void main(String[] args) {

new ActionMappingManager().init();

}

public void init() {

InputStream is = this.getClass().getResourceAsStream("/myframework.xml");

SAXReader sr = new SAXReader();

try {

Document doc = sr.read(is);

Element elRoot = doc.getRootElement();

List<Element> listActions = <u>elRoot</u><u>.elements()</u>;

for (Element elActions : listActions) {

List<Element> listAction = <u>elActions</u><u>.elements()</u>;

for (Element elAction : listAction) {

ActionMapping aMapping = new ActionMapping();

Attribute attName = elAction.attribute("name");

Attribute attClass = elAction.attribute("class");

aMapping.setName(attName.getValue());

aMapping.setClassName(attClass.getValue());

List<Element> listResult = <u>elAction</u><u>.elements()</u>;

for (Element elResult : listResult) {

ResultMapping rMapping = new ResultMapping();

Attribute attResultName = elResult.attribute("name");

Attribute attResultRedirect = elResult.attribute("redirect");

rMapping.setName(attResultName.getValue());

rMapping.setRedirect(Boolean.parseBoolean(attResultRedirect.getValue()));

rMapping.setUrl(elResult.getTextTrim());

aMapping.getResults().put(rMapping.getName(), rMapping);

}

actionMapping.put(aMapping.getName(), aMapping);

}

}

} catch (Exception e) {

e.printStackTrace();

}

}

}

（七）利用反射机制找到自己的实列

package cn.framework;

public class ActionManager {

public static Action createAction(String className) {

Class<?> clz = null;

try {

clz = Thread.currentThread().getContextClassLoader().loadClass(className);

} catch (Exception ex) {

ex.printStackTrace();

}

try {

if (clz == null) {

clz = Class.forName(className);

}

} catch (Exception ex) {

ex.printStackTrace();

}

Action action = null;

try {

action = (Action) clz.newInstance();

} catch (Exception ex) {

ex.printStackTrace();

}

return action;

}

}

（八）写一个业务逻辑

package cn.action;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import cn.framework.Action;

public class LoginAction implements Action {

@Override

public String execute(HttpServletRequest request, HttpServletResponse response) {

return "success";

}

}

（九）核心控制器Servlet

package cn.framework;

import java.io.IOException;

import javax.servlet.ServletConfig;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class MVCServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

protected void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

}

ActionMappingManager amanager = null;

@Override

public void init(ServletConfig config) throws ServletException {

amanager = new ActionMappingManager();

}

protected void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

ActionMapping am = amanager.getActionMapping(getActionName(request));

Action action = ActionManager.createAction(am.getClassName());

String r = action.execute(request, response);

ResultMapping rm = am.getResults().get(r);

if (rm.isRedirect()) {

response.sendRedirect(rm.getUrl());

} else {

request.getRequestDispatcher(rm.getUrl()).forward(request, response);

}

}

public String getActionName(HttpServletRequest request) {

String actionName = null;

String uri = request.getRequestURI();

String contentPath = request.getContextPath();

String actionPath = uri.substring(contentPath.length());

actionName = actionPath.substring(1, actionPath.indexOf(".")).trim();

return actionName;

}

}

（十）修改web.xml

<servlet>

<servlet-name>MVCServlet</servlet-name>

<servlet-class>cn.framework.MVCServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>MVCServlet</servlet-name>

<url-pattern>*.action</url-pattern>

</servlet-mapping>

（十一）准备一个login.jsp页面

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（十二）发布到Tomcat运行

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