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This article mainly introduces the JavaEE Servlet core API how to use the relevant knowledge, the content is detailed and easy to understand, the operation is simple and fast, has a certain reference value, I believe that everyone after reading this JavaEE Servlet core API how to use the article will have a harvest, let's take a look.

1. Introduction to core API 1. Servlet execution process

Servlet is one of the three major components of JavaWeb (Servlet, Filter, Listener). It belongs to dynamic resources. The function of Servlet is to process the request, and the server will send the received request to Servlet for processing. In Servlet, it usually needs to receive the request data, process the request, and complete the response.

2. Introduction to core API API function description ServletConfig acquires servlet initialization parameters and servletContext objects. ServletContext shares data among dynamic resources throughout the Web application. ServletRequest encapsulates the Http request information and creates it at the time of the request. ServletResponse encapsulates the Http response information and is created on request. II. ServletConfig interface 1. Brief introduction to the interface

When the container initializes the servlet, it creates a servletConfig object for the servlet, passes it through the init () method, and saves it in the Servlet object. Core role: 1. Get initialization information; 2. Gets the ServletContext object.

2. Code case

Configuration file

My-name cicada servletOneImpl com.node02.servlet.impl.ServletOneImpl servletOneImpl / servletOneImpl

API usage

Public class ServletOneImpl implements Servlet {@ Override public void init (ServletConfig servletConfig) throws ServletException {String servletName= servletConfig.getServletName (); System.out.println ("servletName=" + servletName); String myName= servletConfig.getInitParameter ("my-name"); System.out.println ("myName=" + myName); Enumeration paramNames = servletConfig.getInitParameterNames () While (paramNames.hasMoreElements ()) {String paramKey= String.valueOf (paramNames.nextElement ()); String paramValue= servletConfig.getInitParameter (paramKey); System.out.println ("paramKey=" + paramKey+ "; paramValue=" + paramValue);} ServletContext servletContext = servletConfig.getServletContext (); servletContext.setAttribute ("cicada", "smile");}} III. ServletContext Interface 1, Interface introduction

A project has only one ServletContext object, which can be obtained in multiple Servlet, and can be used to pass data to multiple Servlet. The object is created when the Tomcat is started and destroyed when the Tomcat is closed! The function is to share data among dynamic resources of the entire Web application.

Acquisition mode

1, ServletConfig#getServletContext (); 2, GenericServlet#getServletContext (); 3, HttpSession#getServletContext () 4, ServletContextEvent#getServletContext () 2, four domain objects

ServletContext is one of the four domain objects of JavaWeb:

1 、 PageContext;2 、 ServletRequest;3 、 HttpSession;4 、 ServletContext

All domain objects have the ability to access data because there is a Map inside the domain object to store data.

3. Code case

Configuration file

My-blog 2019-11-19 servletTwoImpl com.node02.servlet.impl.ServletTwoImpl servletTwoImpl / servletTwoImpl

API usage

Public class ServletTwoImpl extends HttpServlet {@ Override protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType ("text/html;charset=utf-8"); / / 1, parameter passing ServletContext servletContext = this.getServletContext (); String value= String.valueOf (servletContext.getAttribute ("cicada")); System.out.println ("value=" + value) / / 2. Get initialization parameters String myBlog= servletContext.getInitParameter ("my-blog"); System.out.println ("myBlog=" + myBlog); / / 3. Get application information String servletContextName= servletContext.getServletContextName (); System.out.println ("servletContextName=" + servletContextName); / / 4. Get path String pathOne = servletContext.getRealPath ("/") String pathTwo= servletContext.getRealPath ("/ WEB-INF/"); System.out.println ("pathOne=" + pathOne+ "; pathTwo=" + pathTwo); response.getWriter () .print ("execution: doGet; value:" + value);}} IV, ServletRequest interface 1, interface introduction

The HttpServletRequest interface inherits the ServletRequest interface and is used to encapsulate the request information. This object is created and passed into the service () method of the servlet each time the user requests servlet, in which the incoming servletRequest will be forced to be converted into a HttpservletRequest object to process the HTTP request information. Core role: 1. Get the request message information; 2. Get the network connection information; 3. Gets the requested domain attribute information.

2. Code case

Configuration file

ServletThreeImpl com.node02.servlet.impl.ServletThreeImpl servletThreeImpl / servletThreeImpl

API usage

Public class ServletThreeImpl extends HttpServlet {@ Override protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/ / http://localhost:6003/servletThreeImpl?myName=cicada String method= request.getMethod (); System.out.println ("method=" + method); / / GET String requestURL= request.getRequestURL () .toString (); / / http://localhost:6003/servletThreeImpl System.out.println ("requestURL=" + requestURL) String requestURI= request.getRequestURI (); System.out.println ("requestURI=" + requestURI); / / servletThreeImpl String queryString= request.getQueryString (); System.out.println ("queryString=" + queryString); / / myName=cicada String myName= request.getParameter ("myName"); System.out.println ("myName=" + myName); / / cicada}} V, ServletResponse Interface 1, Interface introduction

HttpServletResponse inherits from ServletResponse and encapsulates Http response information. For each request from the client, the server creates a response object and passes it to the Servlet.service () method. Core role: 1. Set the response header information; 2. Send status code; 3. Set the response text; 4. Redirect

2. Code case

Configuration file

ServletFourImpl com.node02.servlet.impl.ServletFourImpl servletFourImpl / servletFourImpl

API usage

Public class ServletFourImpl extends HttpServlet {@ Override protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType ("text/html;charset=utf-8"); response.setCharacterEncoding ("UTF-8"); response.setStatus; response.getWriter (). Print ("Hello, cicada");} 3, forwarding and redirection

Forwarding

Control of page jump on the server side

Request.getRequestDispatcher ("/ forwarding address") .forward (request, response)

Redirect

The server responds to the jump information, and the browser performs the page jump.

Response.sendRedirect ("redirect address")

Comparison of forwarding and redirection

Differentiate forward redirect address bar unchanged jump server jump number of browser jump requests once and twice data will not be lost in the domain

This is the end of the article on "how to use JavaEE's Servlet core API". Thank you for reading! I believe you all have a certain understanding of the knowledge of "how to use JavaEE's Servlet core API". If you want to learn more, you are welcome to follow the industry information channel.

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