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Servlet learning, servlet
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Servlet Basics
1. What is Servelet?
Servelet is a small program running on the server. A Servlet is a Java class.
And can be accessed through the "request-response" programming model. This resident in the server memory
Servlet program. Servlet is the predecessor of jsp.
2. Tomcat container level
Tomcat containers are divided into four levels: Servlet container management Context container, one
Context corresponds to a Web project. Engine is an Engine container; Host is a Host container.
3. Compile a Servlet
There are three steps.
1. Compile a class to inherit HttpServlet
2. Rewrite the doGet () or doPost () method. It depends on the submission method.
3. Register Servlet.
The procedure is as follows:
Code in index. jsp:
<Body>Code in HelloServlet. java:
Package Servlet; 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; // inherit from HttpServletpublic class HelloServlet extends HttpServlet {// rewrite method @ Overrideprotected void doGet (HttpServletRequest request, HttpServletResponse response) throws S ErvletException, IOException {// TODO Auto-generated method stubSystem. out. println ("processing Get () requests... "); // get an out object output to the browser, type: PrintWriterPrintWriter out = response. getWriter (); // specify the type of the output file response. setContentType ("text/html; charset = UTF-8"); // use the out object to output a message to the browser. You can use the html code out. println ("<strong> Hello Servelet! </Strong> <br> "); // 3. register; web in WEB-INF. register in xml} @ Overrideprotected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// TODO Auto-generated method stubSystem. out. println ("processing post () requests... "); // get an out object output to the browser, type: PrintWriterPrintWriter out = response. getWriter (); // specify the type of the output file response. setContentType ("text/html; charset = UTF-8"); // use the out object to output a message to the browser. You can use the html code out. println ("<strong> Hello Servelet! Post </strong> <br> "); // 3. Register; register in web. xml in the WEB-INF; do not repeat after registration }}Registration Code in web. xml:
The registration process is to add two tags in web. xml.
<Servlet> </serclet> and <servlet-mapping> </servlet-mapping>
Each tag must contain two sub-tags.
In <servlet> </servlet>, you must include <servlet-name> to give the Servlet a name.
</Servlet> and <servlet-calss> the Class Name of the Servlet to be accessed (package name + class name)
</Servlet-class>
In <servlet-mapping> </servlet-mapping>
Get a Servlet name (Note: The name must be the same as above) </servlet> and <urlpattern>
Servlet access path </url-pattern><servlet> <servlet-name>HelloServlet</servlet-name> <servlet-class>Servlet.HelloServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>HelloServlet</servlet-name> <url-pattern>/servlet/HelloServlet</url-pattern> </servlet-mapping>
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