一步一步编写自己的Web MVC框架——属性自动获取和传递

爱被打了一巴掌 2022-06-15 00:10 151阅读 0赞

这篇文章将进行属性的获取与返回的开发。

在Servlet中，属性是通过request中的parameterMap获取的。通过  request.getParameter("name名称") 取得，还不知道获取的类型。

在Struts2中，是用过类的字段获取，或者模型驱动获取自定义的实体类。

在Spring MVC中，我们是通过方法参数的名称去实现的。

在我这次的开发中，我打算使用类似Spring MVC的方式。（由于java 中 的方法的参数的名称是无法获取到的，要从文件中的名称获取或者其它方式，在 编译之前就拿到，这样让新手很难理解)所以，我使用了注解的方式去获取。

[https://github.com/yyfyyf1994/MyWebFrame][https_github.com_yyfyyf1994_MyWebFrame]

首先，在html中写一个表单

然后，我们需要一个处理此post请求的Action

@MyAction("/user")
    public class UserAction {
        private static List<User> users = new ArrayList<User>();
    
        static {
            for (long i = 0; i < 8; i++) {
                users.add(new User(i, "用户" + i));
            }
        }
    
        @MyAction("/list")
        public Model userList() {
            Model model = new Model();
            model.addAttribute("users", users);
            model.setReturnPath("user/list");
            return model;
        }
    
        @MyAction("/add")
        public Model userAdd(@MyParam("user") User user, @MyParam("note") String note) {
            Model model = new Model();
            model.addAttribute("message", "增加用户成功！");
            users.add(user);
            System.out.println("note:"+note);
            model.addAttribute("users", users);
            model.setReturnPath("user/list");
            return model;
        }
    }

，如果直接在网页中调试开发，比较蛮烦。我们直接模拟一个request的parameterMap，并往里面填好参数。下面是测试实现过程

public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException, InstantiationException {
            Class clazz = UserAction.class;
            Object object = clazz.newInstance();
    
            Method method = clazz.getMethod("userAdd", User.class, String.class);
    
            Annotation[][] annotations = method.getParameterAnnotations();
            Class<?>[] classes = method.getParameterTypes();
    
            Map<String, String[]> reqMap = new HashMap<String, String[]>();
            reqMap.put("userId", new String[]{"123"});
            reqMap.put("userName", new String[]{"用户1"});
            reqMap.put("note", new String[]{"这是备注信息"});
    
    
            Object[] prarms = new Object[classes.length];
    
            for (int i = 0; i < classes.length; i++) {
                //获取方法上参数的注解
                MyParam myParam = (MyParam) annotations[i][0];
                Class<?> clz = classes[i];
    //            System.out.println(clz + " " + myParam.value());
                Object cob = null;
                //如果是基本类型
                if (ConvertFactory.isJavaClass(clz)) {
                    for (String s : reqMap.keySet()) {
                        //找到对应的参数
                        if (myParam.value().equals(s)) {
                            try {
                                cob = ConvertFactory.convert(clz, reqMap.get(s)[0]);
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                        //填充数据
                        prarms[i] = cob;
                    }
                } else if (clz == List.class) {
                    //如果是集合类
                } else {
                    //如果是自定义实体
                    Object paramObject = clz.newInstance();
                    LoadUtil.getMyObject(reqMap, clz, paramObject);
                    prarms[i] = paramObject;
                }
    
    
            }
    
    
            method.invoke(object, prarms);
        }

LoadUtil.java

package myframe.commons;
    
    import myframe.annotation.MyParam;
    import myframe.convert.ConvertFactory;
    
    import java.lang.annotation.Annotation;
    import java.lang.reflect.Method;
    import java.util.List;
    import java.util.Map;
    
    /**
     * Created by yuyufeng on 2017/5/18.
     */
    public class LoadUtil {
        /**
         * 参数装载
         * @param reqMap
         * @param method
         * @param prarms
         * @throws InstantiationException
         * @throws IllegalAccessException
         */
        public static void loadParams(Map<String, String[]> reqMap, Method method, Object[] prarms) throws InstantiationException, IllegalAccessException {
            Class<?>[] classes = method.getParameterTypes();
            Annotation[][] annotations = method.getParameterAnnotations();
            for (int i = 0; i < classes.length; i++) {
                //获取方法上参数的注解
                MyParam myParam = (MyParam) annotations[i][0];
                Class<?> clz = classes[i];
    //            System.out.println(clz + " " + myParam.value());
                Object cob = null;
                //如果是基本类型
                if (ConvertFactory.isJavaClass(clz)) {
                    for (String s : reqMap.keySet()) {
                        //找到对应的参数
                        if (myParam.value().equals(s)) {
                            try {
                                cob = ConvertFactory.convert(clz, reqMap.get(s)[0]);
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                        //填充数据
                        prarms[i] = cob;
                    }
                } else if (clz == List.class) {
                    //如果是集合类
                } else {
                    //如果是自定义实体
                    Object paramObject = clz.newInstance();
                    getMyObject(reqMap, clz, paramObject);
                    prarms[i] = paramObject;
                }
    
    
            }
        }
        //自定义对象装载
        public static void getMyObject(Map<String, String[]> reqMap, Class<?> clz, Object paramObject) {
            List<Method> methods = GetterSetterUtil.setter(clz);
            for (Method method1 : methods) {
                Class<?> method1PrarmType = method1.getParameterTypes()[0];
                String pName = GetterSetterUtil.getPropertyName(method1);
                for (String s : reqMap.keySet()) {
                    //判断对象里面有getParam方法
                    if (pName.equals(s)) {
                        //对象里面的参数也是基本类型。如果自定义对象里面还有自定义对象，则此处需要做递归处理
                        if (ConvertFactory.isJavaClass(method1PrarmType)) {
                            try {
                                method1.invoke(paramObject, ConvertFactory.convert(method1PrarmType, reqMap.get(s)[0]));
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    }
                }
            }
        }
    }

我们在方法里面添加上打印信息，以确定执行过该方法，并且成功传递了参数

@MyAction("/add")
        public Model userAdd(@MyParam("user") User user, @MyParam("note") String note) {
            Model model = new Model();
            model.addAttribute("message", "增加用户成功！");
            users.add(user);
            System.out.println("note:"+note);
            System.out.println("user:"+user);
            model.addAttribute("users", users);
            model.setReturnPath("user/list");
            return model;
        }

执行之后，控制台信息：

Connected to the target VM, address: '127.0.0.1:64455', transport: 'socket'
    note:这是备注信息
    user:User{userId=123, userName='用户1'}
    Disconnected from the target VM, address: '127.0.0.1:64455', transport: 'socket'
    
    Process finished with exit code 0

可以看到，我们的方法已经执行了。并且。参数也成功传递了。

然后，我们需要将参数传递给页面，我也构造了一个Model类，去传递（类似Spring MVC），这样就方便很多

package myframe.bean;
    
    import myframe.enums.ReturnTypeEnum;
    
    import java.util.HashMap;
    import java.util.Map;
    
    /**
     * Created by yuyufeng on 2017/5/17.
     */
    public class Model {
        private ReturnTypeEnum returnType = ReturnTypeEnum.forward; //响应类型
        private String returnPath; //返回路径
    
        private Map<String, Object> map = new HashMap<String, Object>();
    
        public void addAttribute(String var1, Object var2) {
            map.put(var1, var2);
        }
    
        public Map<String, Object> getModelMap() {
            return map;
        }
    
        public ReturnTypeEnum getReturnType() {
            return returnType;
        }
    
        public void setReturnType(ReturnTypeEnum returnType) {
            this.returnType = returnType;
        }
    
        public String getReturnPath() {
            return returnPath;
        }
    
        public void setReturnPath(String returnPath) {
            this.returnPath = returnPath;
        }
    }

在Servlet入口类中，这么返回：

//判断返回的类型，然后执行不同的动作
                if (returnType == Model.class) {
                    Model modelResult = (Model) result;
                    path = modelResult.getReturnPath();
                    //重定向
                    if (modelResult.getReturnType() == ReturnTypeEnum.redirect) {
                        System.out.println("执行重定向完毕，跳转路径" + path);
                        resp.sendRedirect(path);
                    }
                    //设置属性
                    for (String s : modelResult.getModelMap().keySet()) {
                        req.setAttribute(s, modelResult.getModelMap().get(s));
                    }
                } else if (returnType == String.class) {
                    path = (String) result;
                }
    
    
            System.out.println("执行完毕，跳转路径" + "/WEB-INF/jsp/" + path + ".jsp");  ///WEB-INF/jsp/这些暂时写死，到时候可以到配置中获取
            req.getRequestDispatcher("/WEB-INF/jsp/" + path + ".jsp").forward(req, resp);

这样我们的参数就可以成功传递到request的attribute里面了

现在在整理一下入口Servlet中的doGet()

@Override
        protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
            req.setCharacterEncoding("UTF-8");
            //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ActionMethod:" + actionName);
            //do
            String path = "";
            ActionBean actionBean = MyFrameInit.getActionBean(actionName);
            Object result;
            try {
                Class<?> returnType = actionBean.getMethod().getReturnType();
    
                //执行方法的参数填充
                Map<String, String[]> reqMap = req.getParameterMap();
    
                Object[] prarms = new Object[actionBean.getMethod().getParameterTypes().length];
                //参数装载
                LoadUtil.loadParams(reqMap, actionBean.getMethod(), prarms);
    
                result = actionBean.getMethod().invoke(MyFrameInit.getObject(actionBean.getClazz()), prarms);
    
    
                //判断返回的类型，然后执行不同的动作
                if (returnType == Model.class) {
                    Model modelResult = (Model) result;
                    path = modelResult.getReturnPath();
                    //重定向
                    if (modelResult.getReturnType() == ReturnTypeEnum.redirect) {
                        System.out.println("执行重定向完毕，跳转路径" + path);
                        resp.sendRedirect(path);
                    }
                    //设置属性
                    for (String s : modelResult.getModelMap().keySet()) {
                        req.setAttribute(s, modelResult.getModelMap().get(s));
                    }
                } else if (returnType == String.class) {
                    path = (String) result;
                }
    
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            } catch (InstantiationException e) {
                e.printStackTrace();
            }
    
    
            System.out.println("执行完毕，跳转路径" + "/WEB-INF/jsp/" + path + ".jsp");  ///WEB-INF/jsp/这些暂时写死，到时候可以到配置中获取
            req.getRequestDispatcher("/WEB-INF/jsp/" + path + ".jsp").forward(req, resp);
        }

建立的测试Action

package action;
    
    import entity.User;
    import myframe.annotation.MyAction;
    import myframe.annotation.MyParam;
    import myframe.bean.Model;
    import myframe.commons.GetterSetterUtil;
    import myframe.commons.LoadUtil;
    import myframe.convert.ConvertFactory;
    
    import java.lang.annotation.Annotation;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;
    import java.util.ArrayList;
    import java.util.HashMap;
    import java.util.List;
    import java.util.Map;
    
    /**
     * Created by yuyufeng on 2017/5/17.
     */
    @MyAction("/user")
    public class UserAction {
        private static List<User> users = new ArrayList<User>();
    
        static {
            for (long i = 0; i < 8; i++) {
                users.add(new User(i, "用户" + i));
            }
        }
    
        @MyAction("/list")
        public Model userList() {
            Model model = new Model();
            model.addAttribute("users", users);
            model.setReturnPath("user/list");
            return model;
        }
    
        @MyAction("/add")
        public Model userAdd(@MyParam("user") User user, @MyParam("note") String note) {
            Model model = new Model();
            model.addAttribute("message", "增加用户成功！");
            users.add(user);
            System.out.println("note:"+note);
            System.out.println("user:"+user);
            model.addAttribute("users", users);
            model.setReturnPath("user/list");
            return model;
        }
    
    
        
    
    
    }

部署启动tomcat

输入http://127.0.0.1:8080/user/list.do

MyFrameInit.init==================初始化完毕
    访问ActionMethod:/user/list
    执行完毕，跳转路径/WEB-INF/jsp/user/list.jsp

![Center][]

输入信息增加一个用户，点击提交

访问ActionMethod:/user/add
    note:备注~
    user:User{userId=123, userName='测试用户'}
    执行完毕，跳转路径/WEB-INF/jsp/user/list.jsp

![Center 1][]

这样，MyFrame框架的属性自动获取和传递功能基本已经编写完毕

[https_github.com_yyfyyf1994_MyWebFrame]: https://github.com/yyfyyf1994/MyWebFrame
[Center]: /images/20220615/c0d3874d2ea84c7b81814b70f7027fd5.png
[Center 1]: /images/20220615/ab73b42239d042359027614d7b7ce107.png