1.WebApp

解析web.xml文件，并通过路径获取servlet

  1. public class WebApp {
  2.     private static WebContext webContext;
  3.     //解析xml文件
  4.     static {
  5.         try {
  6.             SAXParserFactory factory = SAXParserFactory.newInstance();
  7.             SAXParser parse = factory.newSAXParser();
  9.             WebHandler handler = new WebHandler();
  10.             parse.parse(Thread.currentThread().getContextClassLoader().getResourceAsStream("web.xml"), handler);
  12.             List<Entity> entitys = handler.getEntitys();
  13.             List<Mapping> mappings = handler.getMappings();
  14.             webContext = new WebContext(entitys, mappings);
  15.         }catch(Exception e) {
  16.             System.out.println("解析配置文件错误");
  17.         }
  18.     }
  20.     public static Servlet getServletFromUrl(String url){
  21.         String name = webContext.getClz("/" + url);
  23.         Class clz;
  24.         try {
  25.             clz = Class.forName(name);
  26.             Servlet servlet = (Servlet)clz.getConstructor().newInstance();
  27.             return servlet;
  28.         } catch (Exception e) {
  29.             // TODO Auto-generated catch block
  30.             e.printStackTrace();
  31.         }
  32.         return null;
  34.     }
  35. }

2.handler处理器

  1. public class WebHandler extends DefaultHandler{
  3.     private List<Entity> entitys;
  4.     private List<Mapping> mappings;
  5.     private Entity entity;
  6.     private Mapping mapping;
  7.     //存储当前标签名
  8.     private String tag;
  9.     //判断当前标签是否为servlet-mapping
  10.     private boolean isMapping;
  12.     @Override
  13.     public void startDocument() throws SAXException {
  14.         entitys = new ArrayList<Entity>();
  15.         mappings = new ArrayList<Mapping>();
  16.     }
  18.     @Override
  19.     public void endDocument() throws SAXException {    }
  21.     @Override
  22.     public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
  23.         if(null != qName) {
  24.             tag = qName;
  25.             if(qName.equals("servlet")) {
  26.                 entity = new Entity();
  27.                 isMapping = false;
  28.             }
  29.             else if(qName.equals("servlet-mapping")) {
  30.                 mapping = new Mapping();
  31.                 isMapping = true;
  32.             }
  33.         }    
  34.     }
  36.     @Override
  37.     public void endElement(String uri, String localName, String qName) throws SAXException {
  38.         if(qName != null) {
  39.             if(qName.equals("servlet")) {
  40.                 entitys.add(entity);
  41.             }
  42.             else if(qName.equals("servlet-mapping")) {
  43.                 mappings.add(mapping);
  44.             }
  45.         }
  46.         //避免结束标签与另外的开始标签之间的空内容覆盖标签内容
  47.         tag = null;
  48.     }
  50.     @Override
  51.     //读取标签之间的内容，不管标签是否一一对应
  52.     public void characters(char[] ch, int start, int length) throws SAXException {
  53.         String msg = new String(ch, start, length).trim();
  54.         if(tag != null) {
  55.             if(isMapping) {//操作servlet-mapping
  56.                 if(tag.equals("servlet-name")) {
  57.                     mapping.setName(msg);
  58.                 }
  59.                 if(tag.equals("url-pattern")) {
  60.                     mapping.add(msg);
  61.                 }
  62.             }else {//操作servlet
  63.                 if(tag.equals("servlet-name")) {
  64.                     entity.setName(msg);
  65.                 }
  66.                 if(tag.equals("servlet-class")) {
  67.                     entity.setClz(msg);
  68.                 }
  69.             }    
  70.         }
  71.     }
  73.     public List<Entity> getEntitys() {
  74.         return entitys;
  75.     }
  78.     public List<Mapping> getMappings() {
  79.         return mappings;
  80.     }    
  81. }

3.修改receive代码
image.png