heshencao

最近对一个别人的WEB项目进行维护，看到这样的实现方法：
1.只有一个Controller的servlet 类
2.一个Service接口
3.一些实现Service接口的类

Controller类负责进行控制，动态产生业务逻辑的类的实例（所有的类需要实现Service接口)，然后通过
httpservletrequest.setAttribute("USERLIST", userList);向WEB端赋值，

具体的可以参考部分代码:
Controller 类(extends HttpServlet )
我现在想知道的 1.这种实现方案怎么样？为什么这么做，有什么好处 2.产生的service 类对象有没有必要用hashmap保存，以避免产生更多的对象

	protected void doPost(HttpServletRequest request,HttpServletResponse response)throws ServletException, IOException {       
		//service name,example for packagename.ServiceName        
		String serviceName = request.getParameter(Constant.SERVICE);		
		if (serviceName == null)
			throw new ServletException("There isn't service parameter![?service=]");
		String targetName = request.getParameter(Constant.TARGET);     
		//the targeted file name,example for /fileName.jsp		
		if (targetName == null)			
			throw new ServletException("There isn't target parameter![?target=]");		
		ServletContext servletcontext = getServletContext();		
		try {           
			//TODO:hashmap to reduce the generated instance? 			
			Class serviceClass = Class.forName(serviceName);			
			Service service = (Service) serviceClass.newInstance();			
			service.execute(request, response, servletcontext);		
			} 
		catch (ClassNotFoundException classnotfoundexception) {			
			throw new ServletException(classnotfoundexception.getMessage());		
			} 
		catch (IllegalAccessException illegalaccessexception) {			
			throw new ServletException(illegalaccessexception.getMessage());		
			} 
		catch (Exception exception) {			
				throw new ServletException(exception.getMessage());		
				}		
		forward(request, response, targetName);	
		}
	}

 

一个实现service的类（相当于业务类)

public interface Service {	
	public abstract void execute(		
		HttpServletRequest httpservletrequest,		
		HttpServletResponse httpservletresponse,		
		ServletContext servletcontext)throws Exception;
	}

public class StartService implements Service {	
	public void execute(		
			HttpServletRequest httpservletrequest,		
			HttpServletResponse httpservletresponse,		
			ServletContext servletcontext)throws Exception {    
		//test data		
		List userList = new ArrayList();
		httpservletrequest.setAttribute("USERNAME", "TestUser");        
		httpservletrequest.setAttribute("USERLIST", userList);	
	}
}

JSP 页面文件

<%String userName=(String)request.getAttribute("USERNAME");List userList=(List)request.getAttribute("USERLIST");%>

访问的时候：
/service.Controller?service=StartService&target=/StartPage.jsp

//TODO:hashmap to reduce the generated instance? 
Class serviceClass = Class.forName(serviceName);
Service service = (Service) serviceClass.newInstance();
service.execute(request, response, servletcontext);

 
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