Second, Java Web--use servlet to display server time

Last Update:2017-04-05 Source: Internet

Author: User

Tags java web

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First, create the following package under the project, and the servlet

The resulting servlet is as follows:

@WebServlet (name= "Timmerservlet", Urlpatterns = "/showtime.do" ) Public classTimmerservletextendsHttpServlet {Private Static Final LongSerialversionuid = 1L;  PublicTimmerservlet () {Super(); }    protected voiddoget (httpservletrequest request, httpservletresponse response)throwsservletexception, IOException {//set Refresh Auto-load event interval to 1 secondsResponse.setintheader ("Refresh", 1); //Setting the response content typeResponse.setcontenttype ("text/html"); //gets the current timeCalendar now = calendar.getinstance (Timezone.gettimezone ("Gmt+8")); PrintWriter out=Response.getwriter (); Out.println ("<! DOCTYPE HTML public \ "-//W3C//DTD HTML 4.01 transitional//en\" > "); Out.println ("<HTML>"); Out.println ("); Out.println ("<BODY>");          Out.print (Now.gettime ()); Out.println ("</BODY>"); Out.println ("</HTML>");          Out.flush ();    Out.close (); }    protected voidDoPost (httpservletrequest request, httpservletresponse response)throwsservletexception, IOException {doget (request, response); }}

Second, @WebServlet annotations

Under servlet3.0, Webservlet annotations are provided to replace the steps to configure <servlet>, <servlet-mapping> under Web. Xml.

The annotated source code is as follows:

 Packagejavax.servlet.annotation;Importjava.lang.annotation.Annotation;Importjava.lang.annotation.Documented;Importjava.lang.annotation.Retention;ImportJava.lang.annotation.RetentionPolicy;ImportJava.lang.annotation.Target; @Target ({Java.lang.annotation.ElementType.TYPE}) @Retention ( Retentionpolicy.runtime) @Documented Public@InterfaceWebservlet {//Specifies the Name property of the Servlet, equivalent to <servlet-name>. If not explicitly specified, the value of the Servlet is the fully qualified name of the class.      Public AbstractString name (); //This property is equivalent to the Urlpatterns property. Two attributes cannot be used at the same time.      Public Abstractstring[] Value (); //Specifies the URL-matching pattern for a set of Servlets. Equivalent to <url-pattern> tag.      Public Abstractstring[] Urlpatterns (); //specifies the order in which the Servlet is loaded, equivalent to the <load-on-startup> tag.      Public Abstract intLoadonstartup (); //specifies a set of Servlet initialization parameters, equivalent to the <init-param> tag.      Public Abstractwebinitparam[] InitParams (); //declares whether the Servlet supports asynchronous operation patterns, equivalent to <async-supported> tags.      Public Abstract Booleanasyncsupported ();  Public AbstractString SmallIcon ();  Public AbstractString LargeIcon (); //The Servlet's descriptive information is equivalent to the <description> tag.      Public AbstractString description (); //the display name of the Servlet, usually used in conjunction with the tool, is equivalent to the <display-name> tag.      Public AbstractString displayName ();}

Second, Urlpatterns wildcard characters

There are only three matching methods, either path matching ( beginning with the "/" character and ending with "/*" ) or extension matching ( "*."). Start ), either exact match, three matching methods cannot be combined, do not assume that wildcards or regular rules are used.

such as <url-pattern>/user/*.action</url-pattern> is illegal

Also note that:<url-pattern>/aa/*/bb</url-pattern> is precisely matched, legal, and here the * is not the meaning of the wildcard

<servlet-mapping>    <Servlet-name>Servlet</Servlet-name>    <Url-pattern>*.do</Url-pattern></servlet-mapping><servlet-mapping>    <Servlet-name>Servlet</Servlet-name>    <Url-pattern>/action/*</Url-pattern></servlet-mapping>

Three, start Tomcat, type http://localhost:8080/jeb/showtime.do, you can see the server time is displayed every second

Second, Java Web--use servlet to display server time

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