通过反射机制减少Servlet类的创建

素颜马尾好姑娘i 2023-07-04 11:27 8阅读 0赞

例如我们要开发2个模块一个是登录模块，一个是注册模块，我们首先要做的是创建2个对应的Servlet来完成请求  
LoginUserServlet,RegUserServlet  
如果我们的关于用户的功能特别多的时候，就要创建巨多的Servlet我们如何更少的创建Servlet呢  
就要使用Class中的反射机制。  
我们可以同一个dao接口的方法，只创建一个Servlet  
在Servlet中通过方法名字完成匹配和调用  
1 servelt创建

package com.servlet;
    
    import javax.servlet.ServletException;
    import javax.servlet.ServletRequest;
    import javax.servlet.ServletResponse;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    
    
    public class AServlet extends HttpServlet { 
    /* 为什么要使用反射呢，因为你后期无论在增加对应的dao调用方法，也不用在多写重复性的代码，直接反射匹配就可以了。 */
        @Override
        protected void service(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException { 
            System.out.println("******");
            String mehtodName=req.getParameter("method");
            if(mehtodName==null||mehtodName.trim().isEmpty()){ 
                throw new RuntimeException("没有获得到method参数");
            }
            Class c=this.getClass();
            Method method=null;
            try { 
                method= c.getMethod(mehtodName, HttpServletRequest.class, HttpServletResponse.class);
    
            } catch (NoSuchMethodException e) { 
                throw new RuntimeException("调用的方法不存在-->"+mehtodName);
            }
    
            try { 
                method.invoke(this,req,resp);
            } catch (Exception e) { 
                throw new RuntimeException("调用的方法-->"+mehtodName+"，在内部发生了异常。。。"+e.getMessage());
            }
        }
      public void addUser(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { 
            System.out.println("addUser()....");
        }
        public void editUser(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { 
            System.out.println("editUser()....");
        }
        public void deleteUser(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { 
            System.out.println("deleteUser()....");
        }
    }

# ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5nNjEzMjMyNg_size_16_color_FFFFFF_t_70]   ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3poYW5nNjEzMjMyNg_size_16_color_FFFFFF_t_70 1] #

我们还可以提取一下Servlet  
1 创建一个基础的抽象的Servlet类

package com.servlet;
    
    import javax.servlet.ServletException;
    
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.lang.reflect.Method;
    
    
    public abstract class BaseServlet extends HttpServlet { 
        @Override
        public void service(HttpServletRequest req, HttpServletResponse resp)
                throws ServletException, IOException { 
            System.out.println("******");
            String mehtodName=req.getParameter("method");
            if(mehtodName==null||mehtodName.trim().isEmpty()){ 
                throw new RuntimeException("没有获得到method参数");
            }
            Class c=this.getClass();
            Method method=null;
            try { 
                method= c.getMethod(mehtodName, HttpServletRequest.class, HttpServletResponse.class);
    
            } catch (NoSuchMethodException e) { 
                throw new RuntimeException("调用的方法不存在-->"+mehtodName);
            }
    
            try { 
                method.invoke(this,req,resp);
            } catch (Exception e) { 
                throw new RuntimeException("调用的方法-->"+mehtodName+"，在内部发生了异常。。。"+e.getMessage());
            }
        }
    }

2 创建一个BaseServlet 的子类

package com.servlet;
    
    import javax.servlet.ServletException;
    
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    
    
    public class AServlet extends BaseServlet { 
    
    
        public void addUser(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { 
            System.out.println("addUser()....");
        }
        public void editUser(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { 
            System.out.println("editUser()....");
        }
        public void deleteUser(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException { 
            System.out.println("deleteUser()....");
        }
    }

最后我们就可以调用AServlet 子类完成各种请求了，这样一来你才创建其他的子类就更加方便了  
BServlet CServlet DServlet …

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