Servlet学习笔记（一）

使用Servlet所需要导入的包： java.io.*;

                                                javax.servlet.*;

                                                javax.servlet.http.*;

配置Tomcat 的web.xml文件

<web-app>
    <servlet>
        <servlet-name>HelloWorld</servlet-name>
        <servlet-class>HelloWorld</servlet-class>
    </servlet>
     <servlet-mapping>
        <servlet-name>HelloWorld</servlet-name>
        <url-pattern>/HelloWorld</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>HelloWorldTwo</servlet-name>
        <servlet-class>HelloWorldTwo</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>HelloWorldTwo</servlet-name>
        <url-pattern>/HelloWorldTwo</url-pattern>
    </servlet-mapping>
</web-app>

                       

Servlet创建的三种方式：

1.实现Servlet接口

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class HelloWorldTwo implements Servlet{
    private String message;
    public void  init( ServletConfig arg0) throws ServletException{
        
        System.out.println("初始化init");
        message="我是实现接口Servlet的HelloWorld";
    }
    
    public  void service(ServletRequest request, ServletResponse response) throws ServletException ,IOException{
        
      System.out.println("service");
      request.setCharacterEncoding("UTF-8");
      String name= request.getParameter("name");
      // 设置响应内容类型
      response.setContentType("text/html");
      response.setCharacterEncoding("UTF-8");
      // 实际的逻辑是在这里
      PrintWriter out = response.getWriter();
      out.println("<h1>" + name + "</h1>");
    
    }
    
    public void destroy(){
        
        System.out.println("*******destory******");
    }
    public ServletConfig getServletConfig() {

        return null;
    }

    public String getServletInfo() {

        return null;
    }
}

2.继承GenericService类

3.继承HttpServlet类

// 导入必需的 java 库
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

// 扩展 HttpServlet 类
public class HelloWorld extends HttpServlet {
 
  private String message;

  public void init() throws ServletException
  {   System.out.println("初始化init");
      // 执行必需的初始化
      message = "我是继承HttpServlet的HelloWorld";
  }
  @Override
  public void doGet(HttpServletRequest request,
                    HttpServletResponse response)
            throws ServletException, IOException
  {
       System.out.println("doGet");
      // 设置响应内容类型
      response.setContentType("text/html");
      response.setCharacterEncoding("UTF-8");
      // 实际的逻辑是在这里
      PrintWriter out = response.getWriter();
      out.println("<h1>" + message + "</h1>");
  }
  
  public void destroy()
  {
      // 什么也不做
      System.out.println("destroy");
  }
}

其中1和2两种方式实现的是service方法，第三种实现的是doGet 和 doPost