一步一步编写自己的Web MVC框架——Action中方法的装载

﹏ヽ暗。殇╰゛Y 2022-06-16 14:28 176阅读 0赞

我准备用一个@MyActionde 的注解，来配上需要装载进入方法容器的类，自定义在类上写上@MyAction(value="/root")，则代码访问该类需要"/root"根路径，然后在方法上加上@MyAction(value = "/test")，表示执行该方法的路径为，“/root/test”。

package action;
    
    import myframe.annotation.MyAction;
    import myframe.annotation.MyMethod;
    
    /**
     * Created by yuyufeng on 2017/5/5.
     */
    @MyAction(value="/root")
    public class TestAction {
        @MyAction(value = "/test")
        public String testMyMethod() {
            System.out.println("TestAction.testMyMethod");
            return "index";
        }
    
        @MyAction(value = "/test2")
        public String testMyMethod2() {
            System.out.println("TestAction.testMyMethod2");
            return "test";
        }
    }

在容器map中，设计路径为键，要执行的类方法为值。

注解MyAction

package myframe.annotation;
    
    import java.lang.annotation.*;
    
    /**
     * Created by yuyufeng on 2017/5/5.
     */
    @Target({ElementType.TYPE, ElementType.METHOD})
    @Retention(value = RetentionPolicy.RUNTIME)
    @Documented
    @Inherited
    public @interface MyAction {
        String value() default  "";
    }

Map容器中值为类方法，所以先设计类结构ActionBean如下：

package myframe.bean;
    
    import java.lang.reflect.Method;
    
    /**
     * Created by yuyufeng on 2017/5/5.
     */
    public class ActionBean {
        private Class<?> clazz;
        private Method method;
    
        public ActionBean(Class<?> clazz, Method method) {
            this.clazz = clazz;
            this.method = method;
        }
    
        public Class<?> getClazz() {
            return clazz;
        }
    
        public void setClazz(Class<?> clazz) {
            this.clazz = clazz;
        }
    
        public Method getMethod() {
            return method;
        }
    
        public void setMethod(Method method) {
            this.method = method;
        }
    }

整理一下思路就是，通过uri去执行一个对象实例中的某个方法。  
所以，我们需要两个容器。一个容器装载Action类实例，一个容器装载uri和ActionBean。

因为我们是通过方法调用的，所以只需要一个实例就好，一个Action放如一个实例到容器即可。（这个容器也类似Spring的IOC管理bean）

在反射过程中，我们需要从项目的package中获取带有@MyAction注解的类和方法，我们需要一个类扫描器，

类扫描工具类如下：

[ClassUtil.java][]

我们执行一个junit测试类，去执行扫描执行。

Action实例：

package action;
    
    import myframe.annotation.MyAction;
    
    /**
     * Created by yuyufeng on 2017/5/5.
     */
    @MyAction(value="/root")
    public class TestAction {
        @MyAction(value = "/test")
        public String testMyMethod() {
            System.out.println("TestAction.testMyMethod");
            return "index";
        }
    
        @MyAction(value = "/test2")
        public String testMyMethod2() {
            System.out.println("TestAction.testMyMethod2");
            return "test";
        }
    }

test:

import myframe.annotation.MyAction;
    import myframe.bean.ActionBean;
    import myframe.commons.ClassUtil;
    import org.junit.Test;
    
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.util.HashMap;
    import java.util.Map;
    import java.util.Set;
    
    /**
     * Created by yuyufeng on 2017/5/5.
     */
    public class TestAnno {
    
        private static Map<String, ActionBean> map = new HashMap<String, ActionBean>();
        private static Map<Class<?>, Object> objectMap = new HashMap<Class<?>, Object>();
    
        @Test
        public void test() throws IllegalAccessException, InstantiationException {
    
            Set<Class<?>> classes = ClassUtil.getClasses("action");
            for (Class<?> aClass : classes) {
                System.out.println(aClass);
                if (aClass.isAnnotationPresent(MyAction.class)) {
                    MyAction mac = aClass.getAnnotation(MyAction.class);
                    String classAnnoValue = mac.value().trim();
                    objectMap.put(aClass,aClass.newInstance());
    
                    for (Method method : aClass.getMethods()) {
                        if (method.isAnnotationPresent(MyAction.class)) {
                            MyAction mam = method.getAnnotation(MyAction.class);
                            String methodAnnoValue = mam.value().trim();
                            String actionName = classAnnoValue + methodAnnoValue;
    
                            map.put(actionName,new ActionBean(aClass,method));
                        }
                    }
                }
            }
    
    
            ActionBean ab = map.get("/root/test2");
            System.out.println(ab);
            try {
    
                String result= (String) ab.getMethod().invoke(objectMap.get(ab.getClazz()));
                System.out.println(result);
    
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }
    
        }
    
    
    }

执行结果：

Connected to the target VM, address: '127.0.0.1:59438', transport: 'socket'
    class action.TestAction
    myframe.bean.ActionBean@475530b9
    TestAction.testMyMethod2
    test
    Disconnected from the target VM, address: '127.0.0.1:59438', transport: 'socket'
    
    Process finished with exit code 0

到这一步，根据uri反射执行类方法已经初步实现。

这些方法在框架初始化阶段执行装载即可。

建立一个初始化执行类：

package myframe.init;
    
    import myframe.annotation.MyAction;
    import myframe.bean.ActionBean;
    import myframe.commons.ClassUtil;
    
    import java.lang.reflect.Method;
    import java.util.HashMap;
    import java.util.Map;
    import java.util.Set;
    
    /**
     * Created by yuyufeng on 2017/5/5.
     */
    public class MyFrameInit {
        private static Map<String, ActionBean> actionMap;
        private static Map<Class<?>, Object> objectMap;
        public static Object getObject(Class<?> clazz) {
            return objectMap.get(clazz);
        }
        public static ActionBean getActionBean(String key) {
            return actionMap.get(key);
        }
    
        public static void init() throws IllegalAccessException, InstantiationException {
            actionMap = new HashMap<String, ActionBean>();
            objectMap = new HashMap<Class<?>, Object>();
            Set<Class<?>> classes = ClassUtil.getClasses("action");
            for (Class<?> aClass : classes) {
                System.out.println(aClass);
                if (aClass.isAnnotationPresent(MyAction.class)) {
                    MyAction mac = aClass.getAnnotation(MyAction.class);
                    String classAnnoValue = mac.value().trim();
                    objectMap.put(aClass, aClass.newInstance());
    
                    for (Method method : aClass.getMethods()) {
                        if (method.isAnnotationPresent(MyAction.class)) {
                            MyAction mam = method.getAnnotation(MyAction.class);
                            String methodAnnoValue = mam.value().trim();
                            String actionName = classAnnoValue + methodAnnoValue;
                            actionMap.put(actionName, new ActionBean(aClass, method));
                        }
                    }
                }
            }
    
            System.out.println("MyFrameInit.init==================初始化完毕");
        }
    
    
    }

然后，我们在入口Servlet第一次执行的时候去调用初始化方法：

public class MyFrameServlet extends HttpServlet {
        @Override
        public void init(ServletConfig config) throws ServletException {
            try {
                MyFrameInit.init();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InstantiationException e) {
                e.printStackTrace();
            }
        }

入口Servlet的doGet完善

@Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            //获取要执行的动作
            String uri = req.getRequestURI();
            String actionName = uri.substring(0, uri.indexOf(".do"));
            System.out.println("访问Action:" + actionName);
    
            //do
            ActionBean actionBean = MyFrameInit.getActionBean(actionName);
            String result = "";
            try {
                result = (String) actionBean.getMethod().invoke(MyFrameInit.getObject(actionBean.getClazz()));
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }
    
            //return
            String fileName = result;
            System.out.println("执行完毕，跳转路径"+"/WEB-INF/jsp/" + fileName + ".jsp");
            req.getRequestDispatcher("/WEB-INF/jsp/" + fileName + ".jsp").forward(req, resp);
    
        }

配置tomcat，启动

访问http://127.0.0.1:8080/root/test.do

访问http://127.0.0.1:8080/root/test2.do

日志打印：

class action.TestAction
    MyFrameInit.init==================初始化完毕
    访问Action:/root/test
    TestAction.testMyMethod
    执行完毕，跳转路径/WEB-INF/jsp/index.jsp
    访问Action:/root/test2
    TestAction.testMyMethod2
    执行完毕，跳转路径/WEB-INF/jsp/test.jsp

现在，页面的控制以及服务器方法的执行已经成功了。

[ClassUtil.java]: https://github.com/yyfyyf1994/MyWebFrame/blob/master/myweb/src/main/java/myframe/commons/ClassUtil.java