MVC在软件架构中是一种比较重要的架构思想，已经被广泛的应用在实际的java web项目开发中，我们所要了解和掌握的是mvc的架构思想和使用mvc模式来分析和解决问题的方法。当然相同或不同的项目都有各种分析解决的思路，这里采用一个应用struts2+hibernate+jsp的实例系统来进一步分析mvc模式。
以班级管理系统为例的架构图:
首先由用户通过VIEW层对系统进行业务请求:
classAdd.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%>新增班级 班级管理 > 新增班级
请输入新增班级信息
然后由Controller层通过struts的拦截器对view层的拦截过滤，实现调用不同的业务处理逻辑。
web.xml
login.html struts2 org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter struts2 /* contextConfigLocation /WEB-INF/classes/applicationContext.xml org.springframework.web.context.ContextLoaderListener openSessionInView org.springframework.orm.hibernate3.support.OpenSessionInViewFilter openSessionInView /*
struts.xml
home.jsp login.html classInformation.jsp classAdd.jsp classInformation.jsp classInformation.jsp studentInformation.jsp studentAdd.jsp studentInformation.jsp studentInformation.jsp
找到相应的action去处理相应的业务:
ClassAddAction.java
package com.zdr.action;import com.opensymphony.xwork2.ActionSupport;import com.zdr.entity.Classunit;import com.zdr.service.ClassunitService;public class ClassAddAction extends ActionSupport{ //变量 private String classunitname = ""; private String classunitnumber = ""; private String result = ""; private ClassunitService classunitService; private Classunit classnumber; //函数 public String getClassunitname() { return classunitname; } public void setClassunitname(String classunitname) { this.classunitname = classunitname; } public String getClassunitnumber() { return classunitnumber; } public void setClassunitnumber(String classunitnumber) { this.classunitnumber = classunitnumber; } public String getResult() { return result; } public void setResult(String result) { this.result = result; } public ClassunitService getClassunitService() { return classunitService; } public void setClassunitService(ClassunitService classunitService) { this.classunitService = classunitService; } @Override public String execute() throws Exception { if(classunitService.checkClassnumber(getClassunitnumber())) { //result = "班级编号重复!"; return ERROR; } else { classnumber = new Classunit(); classnumber.setClassNumber(classunitnumber); classnumber.setClassName(classunitname); classunitService.addClassunit(classnumber); } return SUCCESS; } } 通过调用关系，调用model层dao层方法完成业务处理:
package com.zdr.dao;import java.util.List;import java.util.Set;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.hibernate.Criteria;import org.hibernate.LockMode;import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.criterion.Restrictions;import org.springframework.context.ApplicationContext;import org.springframework.orm.hibernate3.support.HibernateDaoSupport;import com.zdr.entity.Classunit;import com.zdr.entity.Student;/** * A data access object (DAO) providing persistence and search support for * Classunit entities. Transaction control of the save(), update() and delete() * operations can directly support Spring container-managed transactions or they * can be augmented to handle user-managed Spring transactions. Each of these * methods provides additional information for how to configure it for the * desired type of transaction control. * * @see com.zdr.entity.Classunit * @author MyEclipse Persistence Tools */public class ClassunitDAO extends HibernateDaoSupport { private static final Log log = LogFactory.getLog(ClassunitDAO.class); private SessionFactory sessionFactory; private Session session; // property constants public static final String CLASS_NAME = "className"; protected void initDao() { // do nothing } public boolean checkClassnumber(String classunitnumber) { if(classunitnumber!= null) { Classunit cun = findById(classunitnumber); if(cun == null) { return false; } } return true; } public Classunit findclassunitnumber(String classunitnumber) { if(classunitnumber!=null) { return findById(classunitnumber); } return null; } public void save(Classunit transientInstance) { log.debug("saving Classunit instance"); try { getHibernateTemplate().save(transientInstance); log.debug("save successful"); } catch (RuntimeException re) { log.error("save failed", re); throw re; } } public void delete(Classunit persistentInstance) { log.debug("deleting Classunit instance"); try { getHibernateTemplate().delete(persistentInstance); log.debug("delete successful"); } catch (RuntimeException re) { log.error("delete failed", re); throw re; } } public Classunit findById(java.lang.String id) { log.debug("getting Classunit instance with id: " + id); try { Classunit instance = (Classunit) getHibernateTemplate().get( "com.zdr.entity.Classunit", id); return instance; } catch (RuntimeException re) { log.error("get failed", re); throw re; } } public List findByExample(Classunit instance) { log.debug("finding Classunit instance by example"); try { List results = (List ) getHibernateTemplate() .findByExample(instance); log.debug("find by example successful, result size: " + results.size()); return results; } catch (RuntimeException re) { log.error("find by example failed", re); throw re; } } public List findByProperty(String propertyName, Object value) { log.debug("finding Classunit instance with property: " + propertyName + ", value: " + value); try { String queryString = "from Classunit as model where model." + propertyName + "= ?"; return getHibernateTemplate().find(queryString, value); } catch (RuntimeException re) { log.error("find by property name failed", re); throw re; } } public List findByClassName(Object className) { return findByProperty(CLASS_NAME, className); } public List findAll() { log.debug("finding all Classunit instances"); try { String queryString = "from Classunit"; return getHibernateTemplate().find(queryString); } catch (RuntimeException re) { log.error("find all failed", re); throw re; } } public Classunit merge(Classunit detachedInstance) { log.debug("merging Classunit instance"); try { Classunit result = (Classunit) getHibernateTemplate().merge( detachedInstance); log.debug("merge successful"); return result; } catch (RuntimeException re) { log.error("merge failed", re); throw re; } } public void attachDirty(Classunit instance) { log.debug("attaching dirty Classunit instance"); try { getHibernateTemplate().saveOrUpdate(instance); log.debug("attach successful"); } catch (RuntimeException re) { log.error("attach failed", re); throw re; } } public void attachClean(Classunit instance) { log.debug("attaching clean Classunit instance"); try { getHibernateTemplate().lock(instance, LockMode.NONE); log.debug("attach successful"); } catch (RuntimeException re) { log.error("attach failed", re); throw re; } } public static ClassunitDAO getFromApplicationContext(ApplicationContext ctx) { return (ClassunitDAO) ctx.getBean("ClassunitDAO"); }} 处理结果再由struts.xml去返回相应的结果所对应的业务方向。
调用关系图:
总结:
当用户通过view层向系统发送业务请求时，struts.xml根据已经定义好的处理逻辑进行相应的处理，将其业务分给指定的action来处理。而model层通过不同的业务逻辑调用实现试图和逻辑的分层，由action去调用相应的dao层业务进行业务逻辑处理，处理结果再由struts.xml去返回相应的结果所对应的业务方向。
通过mvc体现的质量属性:
可修改性:将视图与业务逻辑分离，易于业务的变动和修改。