仿写Servlet，实现servlet原理（涉及反射）

电玩女神 2023-03-04 10:25 7阅读 0赞

个人码云：https://gitee.com/zzz444/imitateServlet/  
可以克隆下载学习；  
**目录结构**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZyaXN0amNqZG5jZw_size_16_color_FFFFFF_t_70]

package com.james.test;
    
    import com.james.interfaces.HttpServlet;
    import com.james.interfaces.WebServlet;
    
    @WebServlet("/test")
    public class TestMyServlet implements HttpServlet { 
        @Override
        public void doGet() { 
            System.out.println("调用了TsetMyServlet/doGet方法");
        }
    
        @Override
        public void doPost() { 
            System.out.println("调用了TsetMyServlet/doPost方法");
        }
    }

在这里插入代码片

package com.james.interfaces;
    
    
    import java.lang.annotation.*;
    
    @Documented
    @Retention(RetentionPolicy.RUNTIME) //runtime：注解不仅被保存到class文件中，jvm加载class文件之后，仍然存在
    @Target({ ElementType.TYPE,ElementType.METHOD}) //接口、类、枚举、注解 //方法
    public @interface WebServlet { 
            String value() default "";//默认返回空字符串
    }

package com.james.ServletMain;
    
    
    import com.james.Main;
    import com.james.interfaces.HttpMethodEnum;
    import com.james.interfaces.HttpServlet;
    import com.james.interfaces.WebServlet;
    
    import java.io.File;
    import java.lang.reflect.Method;
    import java.util.*;
    import java.util.regex.Matcher;
    
    public class ServletMain { 
    
    
        public static void exec(String path , HttpMethodEnum Method){ 
            String mainPath = Main.class.getResource("").getPath();
            System.out.println(mainPath);
            String mainPackageName = Main.class.getPackage().getName();
            List<String> paths = traverseFolder2(mainPath);
            for (String p : paths) { 
                p=p.substring(mainPath.length()-1);
                String className=mainPackageName+"."+p.replaceAll( Matcher.quoteReplacement(File.separator),".");
                String tempClassPath = className.replace(".class", "");
                execMain(path,Method,tempClassPath);
            }
        }
    
        public static void execMain( String path, HttpMethodEnum Method, String tempClassPath){ 
            try { 
                Class<?> aClass = ClassLoader.getSystemClassLoader().loadClass(tempClassPath);
                WebServlet annotation = aClass.getAnnotation(WebServlet.class);
                if(annotation!=null){ 
                    if(annotation.value().equals(path)){ 
                        System.out.println("路径"+ tempClassPath + path +"验证完成");
                        success(aClass,Method);
                    }else{ 
                        System.out.println("路径"+ tempClassPath +path +"验证失败");
                    }
                }else{ 
                    System.out.println(tempClassPath + "没有注解");
                }
    
            } catch (ClassNotFoundException e) { 
                e.printStackTrace();
            }
        }
    
        public static void success(Class<?> aClass,HttpMethodEnum Method){ 
            try { 
                Object o = aClass.newInstance();
                HttpServlet hs = null;
                if(o instanceof HttpServlet){ 
                    hs = (HttpServlet) o;
                    if(Method.equals(HttpMethodEnum.GET)){ 
                        hs.doGet();
                    }
                    if(Method.equals(HttpMethodEnum.POST)){ 
                        hs.doPost();
                    }
                }else{ 
                    return;
                }
            } catch (InstantiationException e) { 
                e.printStackTrace();
            } catch (IllegalAccessException e) { 
                e.printStackTrace();
            }
        }
    
        public static List<String> traverseFolder2(String path) { 
            File file = new File(path);
            List<String> classFiles=new ArrayList<>();
            if (file.exists()) { 
                LinkedList<File> list = new LinkedList<File>();
                File[] files = file.listFiles();
                for (File file2 : files) { 
                    if (file2.isDirectory()) { 
                        list.add(file2);
                    } else { 
                        classFiles.add(file2.getAbsolutePath());
                    }
                }
                File temp_file;
                while (!list.isEmpty()) { 
                    temp_file = list.removeFirst();
                    files = temp_file.listFiles();
                    for (File file2 : files) { 
                        if (file2.isDirectory()) { 
                            list.add(file2);
                        } else { 
                            classFiles.add(file2.getAbsolutePath());
                        }
                    }
                }
            } else { 
    
            }
            return classFiles;
        }
    }

package com.james;
    
    import com.james.ServletMain.ServletMain;
    import com.james.interfaces.HttpMethodEnum;
    
    public class Main { 
    
    
    
        public static void main(String[] args) { 
            ServletMain.exec("/test",HttpMethodEnum.GET);
    // ServletMain.exec("/tttt", HttpMethodEnum.GET);
    // ServletMain.exec("", HttpMethodEnum.GET);
        }
    }

具体代码 可以下载之后详细阅读。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2ZyaXN0amNqZG5jZw_size_16_color_FFFFFF_t_70]: /images/20230208/7d2d1abc3c174d1f9c57bcf42a905ea0.png