BaseServlet优化Servlet，实现类似struts2的一些简单效果
package cn.itcast.web.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class AServlet extends BaseServlet { private static final long serialVersionUID = 1L; /*@Override public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { * 1、获取参数，用来说明要调用的方法 * 2、然后判断是哪个方法执行 String methodName=req.getParameter("method"); if(methodName == null || methodName.trim().isEmpty()){ throw new RuntimeException("您没有传递method参数，无法确定要调用的方法"); } // if(methodName.equals("addUser")){ // addUser(req,res); // }else if(methodName.equals("eidtUser")){ // editUser(req,res); // }else if(methodName.equals("deleteUser")){ // deleteUser(req,res); // } * 我们发现这样的代码不好复用 * 1、我们可以通过方法名称，使用反射调用呢？ * 需要得到class，然后调用它的方法进行查询 * 我们查询的是当前类的方法 Class c=this.getClass(); Method method=null; try{ method=c.getMethod(methodName,HttpServletRequest.class,HttpServletResponse.class); }catch(Exception e){ throw new RuntimeException("您要调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse) 不存在"); } * 调用method try { method.invoke(this, req,res); } catch (Exception e) { System.out.println("您调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse) 内部抛出了异常"); throw new RuntimeException(e); } }*/ public void addUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("addUser()..."); throw new IOException("测试一下"); } public void editUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("editUser()..."); } public void findAll(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("findAllUser()..."); } public void deleteUser(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("deleteUser()..."); } } /** * 我们发现这样复用性还是不够理想，我们可以抽象出一个弗雷给别人继承 */
package cn.itcast.web.servlet; import java.io.IOException; import java.lang.reflect.Method; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; @SuppressWarnings({"rawtypes","unchecked"}) public class BaseServlet extends HttpServlet { private static final long serialVersionUID = 1L; @Override public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { String methodName=req.getParameter("method"); if(methodName == null || methodName.trim().isEmpty()){ throw new RuntimeException("您没有传递method参数，无法确定要调用的方法"); } Class c=this.getClass(); Method method=null; try{ method=c.getMethod(methodName,HttpServletRequest.class,HttpServletResponse.class); }catch(Exception e){ throw new RuntimeException("您要调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse) 不存在"); } String text=null;//获取返回值 try { text=(String) method.invoke(this, req,res); /* *获取请求处理方法后返回的字符串，它表示转发或者重定向的路径 *如果返回值中不包含“:”，表示使用默认方式：转发 *如果返回值中包含“：”，将字符串通过“：”截取为两部分，前一部分表示标识，f代表转发，r代表重定向 *如果返回的字符串是null或者""，我们什么也不干 */ } catch (Exception e) { System.out.println("您调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse) 内部抛出了异常"); throw new RuntimeException(e); } if(text==null || text.trim().isEmpty()) return; if(!text.contains(":")){ req.getRequestDispatcher(text).forward(req, res); }else{ int index=text.indexOf(":"); String bz=text.substring(0, index); String path=text.substring(index+1); if(bz.equalsIgnoreCase("r")){ res.sendRedirect(path); }else if(bz.equalsIgnoreCase("f")){ req.getRequestDispatcher(path).forward(req, res); }else{ throw new RuntimeException("您的指定："+bz+"暂时没有开通此业务"); } } } /** * 我们在Servlet中实现重定向和转发感觉有点麻烦，我们希望抽象出来再BaseServlet中处理 * request.getRequestDispatcher("xxx").forward(request,response) * response.sendRedirect("xxx") */ }
package cn.itcast.web.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class BServlet extends BaseServlet { private static final long serialVersionUID = 1L; public String fun1(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{ //return "forward:/index.jsp"; System.out.println("fun1()..."); return "f:/index.jsp"; } public String fun2(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{ //return "redirect:/index.jsp"; System.out.println("fun2()..."); return "r:"+req.getContextPath()+"/index.jsp"; } public String fun3(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{ System.out.println("fun3()..."); return "/index.jsp"; } public String fun4(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{ System.out.println("fun4()..."); return null; } public String fun5(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException{ System.out.println("fun3()..."); return "d:/index.jsp"; } }
BaseServlet
1.我们希望在一个Servlet中可以有多个请求处理方法
2、客户端发送请求时，必须多给出一个参数，用来说明要调用的方法
3、参数名遵守约定
4、希望帮助简化重定向和转发，利用返回值
domain：User
dao：UserDao
service：UserService
servlet：UserServlet
void init(ServletConfig config)
void destory()
void service(ServletRequest,ServletResponse)throws IOException,ServletException{
在这里让它去调用其他方法！
要求：用户发出请求时，必须给出一个参数
