Servlet [first introduction]

servlet

1.1 serlvt brief introduction

• servlet Namely sun Company development trends web A technology of
• Sun In these Apl Provides an interface called ：Servlet, If you want to develop a Serlvet Program , Just two small steps ：
  • Write a class , Realization Serlvet Interface
  • Put the developed Java Class deployment to web Server .
• To achieve Serlvet Interface java The program is called ：Serlvet

1.2 HelloSerlvet

• Serlvet Interface sun The company has two default implementation classes ：HttpServlet

1. Build a common Maven project 【 Don't use templates 】, Delete the inside src Catalog , It will be established in this project in the future model; This is an empty project Maven Main works
   
   

2. About Maven Understanding of father son project ：
   There will be ：

	<modules>
        <module>servlet-01</module>
    </modules>

There will be ：

<parent>
        <artifactId>javaweb-02-maven</artifactId>
        <groupId>com.yang</groupId>
        <version>1.0-SNAPSHOT</version>
</parent>

In the parent project Java Subprojects can directly use

son extends father

3. Maven Environmental optimization
   1. modify web.xml For the latest
   2. take maven The structure of the building is complete
4. Write a Servlet Program
   1. Write a common class
   2. Realization Serlvet Interface , Direct inheritance HttpServlet
      

public class HelloServlet extends HttpServlet {
    // because get perhaps post It's just that the request is implemented in a different way , Can call each other , The business logic is the same 
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        PrintWriter writer = resp.getWriter();
        writer.println("hello,servlet");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        super.doPost(req, resp);
    }
}

5. To write Servlet Mapping
   Why do I need to map ： The browser needs to connect web The server , What we're writing is IAVA Program , But access it through a browser , So we need to web Registration in the service we wrote Servlet, You also need to give him a path that the browser can access

<!-- register Servlet-->
    <servlet>
        <servlet-name>hello</servlet-name>
        <servlet-class>com.yang.servlet.HelloServlet</servlet-class>
    </servlet>
    <!--Servlet The request path for -->
    <servlet>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet>

6. To configure Tomcat
   Be careful ： Just configure the project publishing path
7. Start the test

1.3 Servlet Execution principle

1.4 Mapping problem

1. One Servlet You can specify a mapping path
   
2. One servlet Multiple mapping paths can be specified
   
3. One Servlet You can specify a generic mapping path
   
4. Request default path
   
5. Specify some suffixes or prefixes and so on ……
   
6. Priority questions
   Fixed mapping path is specified with the highest priority , If you can't find it, you will go to the default processing request ;