import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
代码很短,我真的很不理解为什么不能写红色的那句,重写从HttpServlet 继承的service方法不添加SUPER怎么会完成其功能呢?
而且一定要加上SUPER也是个错的?如果要加SUPER怎么加啊?
public class HelloWS extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
super.service(req, resp);
PrintWriter out = resp.getWriter();
out.println("<html><head><title></title></head><body></body></html>");
out.close();
}
/*@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
PrintWriter out = resp.getWriter();
out.println("<html><head><title>adfadfad</title></head><body>a星星得过</body></html>");
out.close();
}*/
private static final long serialVersionUID = 1L;
}
------解决方案--------------------
答:我贴上HttpServlet的源代码,这下楼主就更清楚了:(由于只能8000字,我只好贴出核心)
- Java code
package javax.servlet.http;public abstract class HttpServlet extends GenericServlet implements Serializable{ private static final String METHOD_DELETE = "DELETE"; private static final String METHOD_HEAD = "HEAD"; private static final String METHOD_GET = "GET"; private static final String METHOD_OPTIONS = "OPTIONS"; private static final String METHOD_POST = "POST"; private static final String METHOD_PUT = "PUT"; private static final String METHOD_TRACE = "TRACE"; private static final String HEADER_IFMODSINCE = "If-Modified-Since"; private static final String HEADER_LASTMOD = "Last-Modified"; private static final String LSTRING_FILE = "javax.servlet.http.LocalStrings"; private static ResourceBundle lStrings = ResourceBundle.getBundle("javax.servlet.http.LocalStrings"); /*synthetic*/ static Class class$javax$servlet$http$HttpServlet; protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String protocol = req.getProtocol(); String msg = lStrings.getString("http.method_get_not_supported"); if (protocol.endsWith("1.1")) resp.sendError(405, msg); else resp.sendError(400, msg); } protected long getLastModified(HttpServletRequest req) { return -1L; } protected void doHead(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { NoBodyResponse response = new NoBodyResponse(resp); doGet(req, response); response.setContentLength(); } protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String protocol = req.getProtocol(); String msg = lStrings.getString("http.method_post_not_supported"); if (protocol.endsWith("1.1")) resp.sendError(405, msg); else resp.sendError(400, msg); } protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String protocol = req.getProtocol(); String msg = lStrings.getString("http.method_put_not_supported"); if (protocol.endsWith("1.1")) resp.sendError(405, msg); else resp.sendError(400, msg); } protected void doDelete (HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String protocol = req.getProtocol(); String msg = lStrings.getString("http.method_delete_not_supported"); if (protocol.endsWith("1.1")) resp.sendError(405, msg); else resp.sendError(400, msg); } private static Method[] getAllDeclaredMethods(Class c) { if (c.equals(class$javax$servlet$http$HttpServlet == null ? (class$javax$servlet$http$HttpServlet = class$("javax.servlet.http.HttpServlet")) : class$javax$servlet$http$HttpServlet)) return null; Method[] parentMethods = getAllDeclaredMethods(c.getSuperclass()); Method[] thisMethods = c.getDeclaredMethods(); if (parentMethods != null && parentMethods.length > 0) { Method[] allMethods = new Method[parentMethods.length + thisMethods.length]; System.arraycopy(parentMethods, 0, allMethods, 0, parentMethods.length); System.arraycopy(thisMethods, 0, allMethods, parentMethods.length, thisMethods.length); thisMethods = allMethods; } return thisMethods; } protected void doOptions (HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { Method[] methods = getAllDeclaredMethods(this.getClass()); boolean ALLOW_GET = false; boolean ALLOW_HEAD = false; boolean ALLOW_POST = false; boolean ALLOW_PUT = false; boolean ALLOW_DELETE = false; boolean ALLOW_TRACE = true; boolean ALLOW_OPTIONS = true; for (int i = 0; i < methods.length; i++) { Method m = methods[i]; if (m.getName().equals("doGet")) { ALLOW_GET = true; ALLOW_HEAD = true; } if (m.getName().equals("doPost")) ALLOW_POST = true; if (m.getName().equals("doPut")) ALLOW_PUT = true; if (m.getName().equals("doDelete")) ALLOW_DELETE = true; } String allow = null; if (ALLOW_GET && allow == null) allow = "GET"; if (ALLOW_HEAD) { if (allow == null) allow = "HEAD"; else allow += ", HEAD"; } if (ALLOW_POST) { if (allow == null) allow = "POST"; else allow += ", POST"; } if (ALLOW_PUT) { if (allow == null) allow = "PUT"; else allow += ", PUT"; } if (ALLOW_DELETE) { if (allow == null) allow = "DELETE"; else allow += ", DELETE"; } if (ALLOW_TRACE) { if (allow == null) allow = "TRACE"; else allow += ", TRACE"; } if (ALLOW_OPTIONS) { if (allow == null) allow = "OPTIONS"; else allow += ", OPTIONS"; } resp.setHeader("Allow", allow); } protected void doTrace (HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String CRLF = "\r\n"; String responseString = "TRACE " + req.getRequestURI() + " " + req.getProtocol(); Enumeration reqHeaderEnum = req.getHeaderNames(); while (reqHeaderEnum.hasMoreElements()) { String headerName = (String) reqHeaderEnum.nextElement(); responseString += ((String) CRLF + headerName + ": " + req.getHeader(headerName)); } responseString += (String) CRLF; int responseLength = responseString.length(); resp.setContentType("message/http"); resp.setContentLength(responseLength); ServletOutputStream out = resp.getOutputStream(); out.print(responseString); out.close(); } //这是核心:根据请求的方法不同,自动地分别调用doXXX(...)方法 protected void service (HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String method = req.getMethod(); if (method.equals("GET")) { long lastModified = getLastModified(req); if (lastModified == -1L) doGet(req, resp); else { long ifModifiedSince = req.getDateHeader("If-Modified-Since"); if (ifModifiedSince < lastModified / 1000L * 1000L) { maybeSetLastModified(resp, lastModified); doGet(req, resp); } else resp.setStatus(304); } } else if (method.equals("HEAD")) { long lastModified = getLastModified(req); maybeSetLastModified(resp, lastModified); doHead(req, resp); } else if (method.equals("POST")) doPost(req, resp); else if (method.equals("PUT")) doPut(req, resp); else if (method.equals("DELETE")) doDelete(req, resp); else if (method.equals("OPTIONS")) doOptions(req, resp); else if (method.equals("TRACE")) doTrace(req, resp); else { String errMsg = lStrings.getString("http.method_not_implemented"); Object[] errArgs = new Object[1]; errArgs[0] = method; errMsg = MessageFormat.format(errMsg, errArgs); resp.sendError(501, errMsg); } } private void maybeSetLastModified(HttpServletResponse resp, long lastModified) { if (!resp.containsHeader("Last-Modified")) { if (lastModified >= 0L) resp.setDateHeader("Last-Modified", lastModified); } } //这个是容器真正自动调用的service(...)方法 public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException { HttpServletRequest request; HttpServletResponse response; try { request = (HttpServletRequest) req; response = (HttpServletResponse) res; } catch (ClassCastException e) { throw new ServletException("non-HTTP request or response"); } service(request, response); //自动调用HttpServlet版本的service(...)方法 } }