自定义Java web框架(六)

不念不忘少年蓝@ 2022-05-14 15:56 165阅读 0赞

接续上一篇文章[自定义Java web框架(五)][Java web]  
本章主要讲解请求转发到后端之后如何处理的请求转发，也叫路由。  
实现思路如下：  
我们需要编写一个Servlet，让它来处理所有的请求，从HttpServletRequest对象中获取请求方法与请求路径，通过ControllerHelper\#getHandler方法来获取Handler对象。当拿到这个Handler对象之后，可以获取Controller的类，进而通过BeanHelper来获取Controller实例对象，然后获取Action方法，返回View对象或者是Json数据。  
首先，封装请求参数对象如下：

public class Param {
    
        private Map<String, Object> paramMap;
    
        public Param(Map<String, Object> paramMap) {
            this.paramMap = paramMap;
        }
    
        /**
         * 根据参数名获取 long 型参数值
         * @param name
         * @return
         */
        public long getLong(String name) {
            return CastUtil.castLong(paramMap.get(name));
        }
    
        /**
         * 获取所有字段信息
         * @return
         */
        public Map<String, Object> getMap() {
            return paramMap;
        }
    }

然后，封装返回视图数据如下：

public class View {
    
        /**
         * 视图路径
         */
        private String path;
    
        /**
         * 模型数据
         */
        private Map<String, Object> model;
    
        public View(String path) {
            this.path = path;
            model = new HashMap<>();
        }
    
        public View adModel(String key, Object value) {
            model.put(key, value);
            return this;
        }
    
        public String getPath() {
            return path;
        }
    
        public Map<String, Object> getModel() {
            return model;
        }
    }

封装返回JSON数据如下：

public class Data {
    
        private Object model;
    
        public Data(Object model) {
            this.model = model;
        }
    
        public Object getModel() {
            return model;
        }
    }

核心请求转发器类如下：

public class DispatcherServlet extends HttpServlet {
    
        @Override
        public void init(ServletConfig servletConfig) throws ServletException {
            //初始化相关 Helper类
            HelperLoader.init();
            //获取ServletContext对象(用于注册Servlet)
            ServletContext servletContext = servletConfig.getServletContext();
            //注册处理JSP的Servlet
            ServletRegistration jspServlet = servletContext.getServletRegistration("jsp");
            jspServlet.addMapping(ConfigHelper.getAppJspPath() + "*");
            //注册处理静态资源的默认servlet
            ServletRegistration defaultServlet = servletContext.getServletRegistration("default");
            defaultServlet.addMapping(ConfigHelper.getAppAssetPath() + "*");
        }
    
        @Override
        public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //获取请求方法与请求路径
            String requestMethod = request.getMethod().toLowerCase();
            String requestPath = request.getPathInfo();
            //获取Action处理器
            Handler handler = ControllerHelper.getHandler(requestMethod, requestPath);
            if (handler != null) {
                //获取 Controller 类及其 Bean实例
                Class<?> controllerClass = handler.getControllerClass();
                Object controllerBean = BeanHelper.getBean(controllerClass);
                // 创建请求参数对象
                Map<String, Object> paramMap = new HashMap<>();
                Enumeration<String> paramNames = request.getParameterNames();
                while (paramNames.hasMoreElements()) {
                    String paramName = paramNames.nextElement();
                    String paramValue = request.getParameter(paramName);
                    paramMap.put(paramName, paramValue);
                }
                String body = CodecUtil.decodeURL(StreamUtil.getString(request.getInputStream()));
                if (StringUtils.isNotEmpty(body)) {
                    String[] params = StringUtils.split(body, "&");
                    if (ArrayUtil.isNotEmpty(params)) {
                        for (String param : params) {
                            String[] array =StringUtils.split(param, "=");
                            if (ArrayUtil.isNotEmpty(array) && array.length == 2) {
                                String paramName = array[0];
                                String paramValue = array[1];
                                paramMap.put(paramName, paramValue);
                            }
                        }
                    }
                }
    
                Param param = new Param(paramMap);
                //调用Action 方法
                Method actionMethod = handler.getActionMethod();
                Object result = ReflectionUtil.invokeMethod(controllerBean, actionMethod, param);
                if (result instanceof View) {
                    //返回 JSP 页面
                    View view = (View) result;
                    String path = view.getPath();
                    if (StringUtils.isNotEmpty(path)) {
                        if (path.startsWith("/")) {
                            response.sendRedirect(request.getContextPath() + path);
                        } else {
                            Map<String, Object> model = view.getModel();
                            for (Map.Entry<String,Object> entry : model.entrySet()) {
                                request.setAttribute(entry.getKey(), entry.getValue());
                            }
                            request.getRequestDispatcher(ConfigHelper.getAppJspPath() + path).forward(request, response);
                        }
                    } else if (result instanceof Data) {
                        //返回 JSON 数据
                        Data data = (Data) result;
                        Object model = data.getModel();
                        if (model != null) {
                            response.setContentType("application/json");
                            response.setCharacterEncoding("UTF-8");
                            PrintWriter writer = response.getWriter();
                            String json = JsonUtil.toJson(model);
                            writer.write(json);
                            writer.flush();
                            writer.close();
                        }
                    }
                }
            }
        }
    
    }

相关的工具类如下：

public class CastUtil {
    
    
        /**
         * 转为long类型
         * @param obj
         * @return
         */
        public static long castLong(Object obj){
            return CastUtil.castLong(obj,0);
        }
    
        /**
         * 转为long
         * @param obj
         * @param defaultValue
         * @return
         */
        public static long castLong(Object obj,long defaultValue){
            long value = defaultValue;
            if (obj!=null){
                String strValue = castString(obj);
                if (StringUtils.isNotEmpty(strValue)){
                    try{
                        value = Long.parseLong(strValue);
                    }catch (NumberFormatException e){
                        value = defaultValue;
                    }
                }
            }
            return value;
        }
    
        /**
         * 转为String
         * @param obj
         * @return
         */
        public static String castString(Object obj){
            return CastUtil.castString(obj,"");
        }
    
        /**
         * 转为String
         * @param obj
         * @param defaultValue
         * @return
         */
        public static String castString(Object obj,String defaultValue){
            return obj!=null?String.valueOf(obj):defaultValue;
        }
    
    
    }
    
    public final class CodecUtil {
    
        private static final Logger LOGGER = LoggerFactory.getLogger(CodecUtil.class);
    
        /**
         * 将URL编码
         * @param source
         * @return
         */
        public static String encodeURL(String source) {
            String target;
            try {
                target = URLEncoder.encode(source, "UTF-8");
            } catch (Exception e) {
                LOGGER.error("encode url failure", e);
                throw new RuntimeException(e);
            }
            return target;
        }
    
        /**
         * 将URL解码
         * @param source
         * @return
         */
        public static String decodeURL(String source) {
            String target;
            try {
                target = URLDecoder.decode(source, "UTF-8");
            } catch (Exception e) {
                LOGGER.error("dencode url failure", e);
                throw new RuntimeException(e);
            }
            return target;
        }
    }
    
    public class StreamUtil {
    
        private static final Logger LOGGER = LoggerFactory.getLogger(StreamUtil.class);
    
        /**
         * 从输入流中获取字符串
         * @param inputStream
         * @return
         */
        public static String getString(InputStream inputStream) {
            StringBuilder sb = new StringBuilder();
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
                String line;
                while ((line = reader.readLine()) != null) {
                    sb.append(line);
                }
            } catch (Exception e) {
                LOGGER.error("get String failure", e);
                throw new RuntimeException(e);
            }
            return sb.toString();
        }
    }

到这里简单的MVC框架已经完成，接下来需要写些简单的业务功能代码，进一步熟悉下整个处理流程。  
[代码地址][Link 1]如果本文对您有帮助， 动动小手给个star。

[Java web]: https://blog.csdn.net/u011915230/article/details/83472627
[Link 1]: https://github.com/lyin226/custom-framework