手把手写Spring框架
目录
- 初始化阶段
- 运行阶段
- HandlerAdapter
- 形参列表:编译后就能拿到值
- 实参列表:要运行时才能拿到值
- 最后反射
- 总结:
这部分目标是MVC!
主要完成3个重要组件:
HandlerMapping:保存URL映射关系
HandlerAdapter:动态参数适配器
ViewResolvers:视图转换器,模板引擎
SpringMVC核心组件执行流程:
相对应的,用以下几个类来实现上述的功能:
初始化阶段
在DispatcherServlet这个类的init方法中,将mvc部分替换为initStrategies(context):
并且调用初始化三个组件的方法。
分别完善这几个方法:
private void initViewResolvers(PigApplicationContext context) { //模板引擎的根路径 String tempateRoot = context.getConfig().getProperty("templateRoot"); String templateRootPath = this.getClass().getClassLoader().getResource(tempateRoot).getFile(); File templateRootDir = new File(templateRootPath); for (File file : templateRootDir.listFiles()) { this.viewResolvers.add(new PIGViewResolver(tempateRoot)); } } private void initHandlerAdapters(PigApplicationContext context) { for (PIGHandlerMapping handlerMapping : handlerMappings) { this.handlerAdapters.put(handlerMapping,new PIGHandlerAdapter()); } } private void initHandlerMappings(PigApplicationContext context) { if(context.getBeanDefinitionCount() == 0){ return; } String [] beanNames = context.getBeanDefinitionNames(); for (String beanName : beanNames) { Object instance = context.getBean(beanName); Class<?> clazz = instance.getClass(); if(!clazz.isAnnotationPresent(PIGController.class)){ continue; } String baseUrl = ""; if(clazz.isAnnotationPresent(PIGRequestMapping.class)){ PIGRequestMapping requestMapping = clazz.getAnnotation(PIGRequestMapping.class); baseUrl = requestMapping.value(); } //默认只获取public方法 for (Method method : clazz.getMethods()) { if(!method.isAnnotationPresent(PIGRequestMapping.class)){continue;} PIGRequestMapping requestMapping = method.getAnnotation(PIGRequestMapping.class); // //demo//query String regex = ("/" + baseUrl + "/" + requestMapping.value().replaceAll("\\*",".*")).replaceAll("/+","/"); Pattern pattern = Pattern.compile(regex); handlerMappings.add(new PIGHandlerMapping(pattern,instance,method)); System.out.println("Mapped " + regex + "," + method); } } }
全局变量:
private List<PIGHandlerMapping> handlerMappings = new ArrayList<PIGHandlerMapping>();
private Map<PIGHandlerMapping,PIGHandlerAdapter> handlerAdapters = new HashMap<PIGHandlerMapping, PIGHandlerAdapter>();
private List<PIGViewResolver> viewResolvers = new ArrayList<PIGViewResolver>();
HandlerMapping与HandlerAdapter是一一对应的关系。
运行阶段
整体思路:
getHandler就是通过请求拿到URI,并与handlerMappings中存好的模板进行匹配:
private PIGHandlerMapping getHandler(HttpServletRequest req) { String url = req.getRequestURI(); String contextPath = req.getContextPath(); url = url.replaceAll(contextPath,"").replaceAll("/+","/"); for (PIGHandlerMapping handlerMapping : this.handlerMappings) { Matcher matcher = handlerMapping.getPattern().matcher(url); if(!matcher.matches()){continue;} return handlerMapping; } return null; }
HandlerAdapter
HandlerAdapter的handle方法负责反射调用具体方法。需要匹配参数,那么需要先保存好实参和形参列表。
形参列表:编译后就能拿到值
Map<String,Integer> paramIndexMapping = new HashMap<String, Integer>(); //提取加了PIGRequestParam注解的参数的位置 Annotation[][] pa = handler.getMethod().getParameterAnnotations(); for (int i = 0; i < pa.length; i ++){ for (Annotation a : pa[i]) { if(a instanceof PIGRequestParam){ String paramName = ((PIGRequestParam) a).value(); if(!"".equals(paramName.trim())){ paramIndexMapping.put(paramName,i); } } } } //提取request和response的位置 Class<?> [] paramTypes = handler.getMethod().getParameterTypes(); for (int i = 0; i < paramTypes.length; i++) { Class<?> type = paramTypes[i]; if(type == HttpServletRequest.class || type == HttpServletResponse.class){ paramIndexMapping.put(type.getName(),i); } }
实参列表:要运行时才能拿到值
Map<String,String[]> paramsMap = req.getParameterMap(); //声明实参列表 Object [] parameValues = new Object[paramTypes.length]; for (Map.Entry<String,String[]> param : paramsMap.entrySet()) { String value = Arrays.toString(paramsMap.get(param.getKey())) .replaceAll("\\[|\\]","") .replaceAll("\\s",""); if(!paramIndexMapping.containsKey(param.getKey())){continue;} int index = paramIndexMapping.get(param.getKey()); parameValues[index] = caseStringVlaue(value,paramTypes[index]); } if(paramIndexMapping.containsKey(HttpServletRequest.class.getName())){ int index = paramIndexMapping.get(HttpServletRequest.class.getName()); parameValues[index] = req; } if(paramIndexMapping.containsKey(HttpServletResponse.class.getName())){ int index = paramIndexMapping.get(HttpServletResponse.class.getName()); parameValues[index] = resp; }
最后反射
总结:
本篇文章就到这里了,希望能给你带来帮助,也希望您能够多多关注我们的更多内容!
赞 (0)