struts过滤器的原理

  1 package cn.itcast.framework.core;
  2 
  3 import java.io.IOException;
  4 import java.lang.reflect.Method;
  5 import java.util.HashMap;
  6 import java.util.List;
  7 import java.util.Map;
  8 
  9 import javax.servlet.Filter;
 10 import javax.servlet.FilterChain;
 11 import javax.servlet.FilterConfig;
 12 import javax.servlet.ServletException;
 13 import javax.servlet.ServletRequest;
 14 import javax.servlet.ServletResponse;
 15 import javax.servlet.http.HttpServletRequest;
 16 import javax.servlet.http.HttpServletResponse;
 17 
 18 import org.apache.commons.beanutils.BeanUtils;
 19 import org.dom4j.Document;
 20 import org.dom4j.Element;
 21 
 22 import cn.itcast.framework.util.Dom4JUtil;
 23 
 24 public class CenterFilter implements Filter {
 25     //存取配置文件信息。key：对应action中的name value：Action对象
 26     private Map<String, Action> actions = new HashMap<String, Action>();
 27     private FilterConfig filterConfig;
 28     
 29     public void init(FilterConfig filterConfig) throws ServletException {
 30         initCfg();//初始化配置文件
 31         this.filterConfig = filterConfig;
 32         
 33     }
 34     //初始化配置文件
 35     private void initCfg() {
 36         //读取XML配置文件：把配置文件中的信息封装到对象中.再放到actions中
 37         
 38         Document document = Dom4JUtil.getDocument();
 39         Element root = document.getRootElement();
 40         //得到所有的action元素，创建Action对象，封装信息
 41         List<Element> actionElements = root.elements("action");
 42         if(actionElements!=null&&actionElements.size()>0){
 43             for(Element actionElement:actionElements){
 44                 //封装action信息开始
 45                 Action action = new Action();
 46                 action.setName(actionElement.attributeValue("name"));
 47                 action.setClassName(actionElement.attributeValue("class"));
 48                 String methodXmlAttrValue = actionElement.attributeValue("method");
 49                 if(methodXmlAttrValue!=null)
 50                     action.setMethod(methodXmlAttrValue);
 51                 //封装action信息结束
 52                 
 53                 
 54                 //得到每个action元素中的result元素，创建Result对象，封装信息
 55                 //封装属于当前action的结果
 56                 List<Element> resultElements = actionElement.elements("result");
 57                 if(resultElements!=null&&resultElements.size()>0){
 58                     for(Element resultElement:resultElements){
 59                         Result result = new Result();
 60                         result.setName(resultElement.attributeValue("name"));
 61                         result.setTargetUri(resultElement.getText().trim());
 62                         String typeXmlValue = resultElement.attributeValue("type");
 63                         if(typeXmlValue!=null){
 64                             result.setType(ResultType.valueOf(typeXmlValue));
 65                         }
 66                         action.getResults().add(result);
 67                     }
 68                 }
 69                 //封装属于当前action的结果
 70                 
 71                 
 72                 
 73                 //把Action对象都放到Map中
 74                 actions.put(action.getName(), action);
 75             }
 76         }
 77     }
 78     public void doFilter(ServletRequest req, ServletResponse resp,
 79             FilterChain chain) throws IOException, ServletException {
 80         try {
 81             HttpServletRequest request = (HttpServletRequest)req;
 82             HttpServletResponse response = (HttpServletResponse)resp;
 83             //真正的控制器部分
 84             
 85             //取一个配置参数
 86             String aciontPostFixs [] = {"action","","do"};//你请求的地址以action\do\空结尾的话，才真正过滤。默认值
 87             String aciontPostFix = filterConfig.getInitParameter("aciontPostFix");
 88             if(aciontPostFix!=null){
 89                 aciontPostFixs = aciontPostFix.split("\\,");
 90             }
 91             
 92             //解析用户请求的URI
 93             String uri = request.getRequestURI();//   /strutsDay01MyFramework/addCustomer.action
 94             
 95             //截取后缀名，看看是否需要我们的框架进行处理
 96             //切后缀名
 97             String extendFileName = uri.substring(uri.lastIndexOf(".")+1);// /strutsDay01MyFramework/addCustomer.action   action
 98                                                                             // 
 99 
100 /strutsDay01MyFramework/addCustomer.do   do
101                                                                             // 
102 
103 /strutsDay01MyFramework/addCustomer   ""
104             boolean needProcess = false;
105             for(String s:aciontPostFixs){
106                 if(extendFileName.equals(s)){
107                     needProcess = true;
108                     break;
109                 }
110             }
111             
112             if(needProcess){
113                 //需要框架处理
114                 //解析uri中的动作名称
115                 String requestActionName = uri.substring(uri.lastIndexOf("/")+1, uri.lastIndexOf("."));
116                 System.out.println("您的请求动作名是："+requestActionName);
117                 //查找actions中对应的Action对象
118                 if(actions.containsKey(requestActionName)){
119                     Action action = actions.get(requestActionName);
120                     //得到类名称的字节码
121                     Class clazz = Class.forName(action.getClassName());
122                     //封装数据到JavaBean中,利用BeanUtils框架
123                     Object bean = clazz.newInstance();
124                     BeanUtils.populate(bean, request.getParameterMap());
125                     //实例化，调用其中指定的方法名称
126                     Method m = clazz.getMethod(action.getMethod(), null);
127                     //根据方法的返回值，遍历结果
128                     String resultValue = (String)m.invoke(bean, null);
129                     
130                     List<Result> results = action.getResults();
131                     if(results!=null&&results.size()>0){
132                         for(Result result:results){
133                             
134                             if(resultValue.equals(result.getName())){
135                                 //根据结果中的type决定是转发还是重定向
136                                 //重定向的目标就是结果中的targetUri
137                                 if("dispatcher".equals(result.getType().toString())){
138                                     //转发
139                                     request.getRequestDispatcher(result.getTargetUri()).forward(request, response);
140                                 }
141                                 if("redirect".equals(result.getType().toString())){
142                                     //重定向
143                                     response.sendRedirect(request.getContextPath()+result.getTargetUri());
144                                 }
145                             }
146                         }
147                     }
148                 }else{
149                     throw new RuntimeException("The action "+requestActionName+" is not founded in your config files!");
150                 }
151                 
152             }else{
153                 chain.doFilter(request, response);
154             }
155         } catch (Exception e) {
156             throw new RuntimeException(e);
157         }
158         
159     }
160 
161     public void destroy() {
162 
163     }
164 
165 }