创建servlet的三种方式(Servlet,GenericServlet,HttpServlet)

1 实现Servlet接口的方式

新建ServletDemo实现类

/*
* 实现Servlet的三种方法
* 1实现Servlet接口
* 缺点：必须实现所有方法
* */
public class ServletDemo implements Servlet {

    @Override
    public void init(ServletConfig servletConfig) throws ServletException {

    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        servletResponse.setContentType("text/html;charset=utf-8");
        servletResponse.getWriter().write("<h1>hello<h1>");
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }
}

配置web.xml

 <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>servletDemo</servlet-name>
        <servlet-class>com.by.servlet.ServletDemo</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>servletDemo</servlet-name>
        <url-pattern>/servletDemo</url-pattern>
    </servlet-mapping>

输出结果

?

2 继承GenericServlet抽象类的方式

新建GenericServlet类

/*
* 实现Servlet的三种方法
* 2继承GenericServlet抽象类
* 优点：只用重写service方法
* */
public class GenericServlet extends javax.servlet.GenericServlet {

    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        servletResponse.setContentType("text/html;charset=utf-8");
        servletResponse.getWriter().append("我是第二种创建Servlet的方法");
    }
}

?配置web.xml

 <servlet>
        <servlet-name>genericServlet</servlet-name>
        <servlet-class>com.by.servlet.GenericServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>genericServlet</servlet-name>
        <url-pattern>/genericServlet</url-pattern>
    </servlet-mapping>

?输出结果

3 继承HttpServlet的方式

新建HttpServletDemo类

/*
* 实现Servlet的三种方法
* 3 继承HttpServlet抽象类
1.可以减少对其他方法的要求 init destroy

2.可以根据前端的要求进行分门别类 doGet doPost
* */
public class HttpServletDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setContentType("text/html;charset=utf-8");
        resp.getWriter().println("我是HttpServlet创建的Servlet");
    }
}

配置web.xml

 <servlet>
        <servlet-name>httpServlet</servlet-name>
        <servlet-class>com.by.servlet.HttpServletDemo</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>httpServlet</servlet-name>
        <url-pattern>/httpServlet</url-pattern>
    </servlet-mapping>

?输出结果