SpringMVC实例分析

Spring的MVC模块

Spring提供了自己的MVC框架实现，相比Struts、WebWork等MVC模块，Spring的MVC模块显得小巧而灵活。Spring的MVC使用Controller处理用户请求，此处的Controller类似于Struts1.x中的Action。SpringMVC作为Spring框架的一部分，在进行框架整合时不需要像Struts1&2那样特意的去融合到Spring里面，其本身就在Spring里面。

先定义如下各层：

域模型层实体类Cat：

 package com.spring.mvc;

 import java.util.Date;

 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 import javax.persistence.Table;
 import javax.persistence.Temporal;
 import javax.persistence.TemporalType;

 @Entity
 @Table(name = "tb_cat")
 public class Cat {

     @Id
     @GeneratedValue(strategy = GenerationType.AUTO)
     private Integer id;
     private String name;
     @Temporal(value = TemporalType.TIMESTAMP)
     private Date createdDate;
     public Date getCreatedDate() {
         return createdDate;
     }

     public void setCreatedDate(Date createdDate) {
         this.createdDate = createdDate;
     }

     public Integer getId() {
         return id;
     }

     public void setId(Integer id) {
         this.id = id;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }
 }

业务逻辑层接口ICatService：

 package com.spring.mvc;

 import java.util.List;

 public interface ICatService {
     public void createCat(Cat cat);
     public List<Cat> listCats();
     public int getCatsCount();
 }

业务逻辑层接口的实现类CatServiceImpl：

 package com.spring.mvc;

 import java.util.List;

 public class CatServiceImpl implements ICatService {
     private ICatDao catDao;
     public ICatDao getCatDao() {
         return catDao;
     }

     public void setCatDao(ICatDao catDao) {
         this.catDao = catDao;
     }

     public void createCat(Cat cat) {
         if (catDao.findCatByName(cat.getName()) != null){
             throw new RuntimeException("猫" + cat.getName() + "已经存在。" );
         }
         catDao.createCat(cat);
     }

     public int getCatsCount() {
         return catDao.getCatsCount();
     }

     public List<Cat> listCats() {
         return catDao.listCats();
     }
 }

数据库持久层接口ICatDao：

 package com.spring.mvc;

 import java.util.List;

 public interface ICatDao {
     public void createCat(Cat cat);
     public Cat findCatByName(String name);
     public List<Cat> listCats();
     public int getCatsCount();
 }

数据库持久层实现类CatDaoImpl：

 package com.spring.mvc;

 import java.util.List;

 import org.springframework.orm.hibernate3.support.HibernateDaoSupport;

 public class CatDaoImpl extends HibernateDaoSupport implements ICatDao {

     public void createCat(Cat cat) {
         this.getHibernateTemplate().persist(cat);
     }

     public Cat findCatByName(String name) {
         List<Cat> catList = this.getHibernateTemplate().find(" select c from Cat c where c.name = ? ", name);
         if (catList.size() > 0)
             return catList.get(0);
         return null;
     }

     public int getCatsCount() {
         return (Integer) this.getSession(true).createQuery(" select count(c) from Cat c ").uniqueResult();
     }

     public List<Cat> listCats() {
         return this.getHibernateTemplate().find(" select c from Cat c ");
     }
 }

SpringMVC的控制层和视图层

SpringMVC的控制层是Controller。Controller是个接口，一般直接继承AbstractController抽象类，并实现handleRequestInternal方法，此方法类似于Struts1.x中的execute()方法。

SpringMVC的视图层使用的是ModelAndView对象。handleRequestInternal方法返回的即时此对象，ModelAndView相当于Struts1.x中的ActionForward。
ModelAndView可以方便的传递参数，例如
return new ModelAndView("cal/listCat","cat",cat);
等价于
request.setAttribute("cat",cat);
return new ModelAndView("cal/listCat");

当传递多个参数时，可以使用Map，例如：
Map map = new HashMap();
map.put("cat",cat);
map.put("catList",catList);
return new ModelAndView("cat/listCat",map);

 package com.spring.mvc;

 import java.util.Date;
 import java.util.List;

 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.mvc.AbstractController;

 public class CatController extends AbstractController {

     private ICatService catService;

     @Override
     protected ModelAndView handleRequestInternal(HttpServletRequest request,HttpServletResponse response) throws Exception {
         String action = request.getParameter("action");
         if ("add".equals(action)) {
             return this.add(request, response);
         }
         return this.list(request, response);
     }

     protected ModelAndView list(HttpServletRequest request,HttpServletResponse response) throws Exception {
         List<Cat> catList = catService.listCats();
         request.setAttribute("catList", catList);
         return new ModelAndView("cat/listCat");
     }

     protected ModelAndView add(HttpServletRequest request,HttpServletResponse response) throws Exception {
         Cat cat = new Cat();
         cat.setName(request.getParameter("name"));
         cat.setCreatedDate(new Date());
         catService.createCat(cat);
         return new ModelAndView("cat/listCat", "cat", cat);
     }

     public ICatService getCatService() {
         return catService;
     }

     public void setCatService(ICatService catService) {
         this.catService = catService;
     }
 }

多业务分发器

如果一个Controller需要处理多种业务逻辑，可以使用MultiActionController。MultiActionController就是一个分发器，相当于Struts1.x中的DispatchAction分发器，能根据某参数值将不同的请求分发到不同的方法上，比如可以设置分发器参数为method，则URL地址访问catMulti.mvc?method=add时将会执行add方法。CatMultiController不需要继承父类的任何方法，只需要定义形如public ModelAndView xxx(HttpServletRequest request,HttpServletResponse response)的方法，当地址栏参数method为xxx时，Spring会通过反射调用xxx()方法。

 package com.spring.mvc;

 import java.util.Date;
 import java.util.List;

 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.springframework.web.servlet.ModelAndView;
 import org.springframework.web.servlet.mvc.multiaction.MultiActionController;

 public class CatMultiController extends MultiActionController {

     private ICatService catService;

     public ICatService getCatService() {
         return catService;
     }

     public void setCatService(ICatService catService) {
         this.catService = catService;
     }

     @SuppressWarnings("unchecked")
     public ModelAndView add(HttpServletRequest request,HttpServletResponse response) {
         Cat cat = new Cat();
         cat.setName(request.getParameter("name"));
         cat.setCreatedDate(new Date());
         catService.createCat(cat);
         return this.list(request, response);
     }

     @SuppressWarnings("unchecked")
     public ModelAndView list(HttpServletRequest request,HttpServletResponse response) {
         List<Cat> catList = catService.listCats();
         request.setAttribute("catList", catList);
         return new ModelAndView("cat/listCat");
     }

 }