SpringBoot注册Servlet的三种方法详解

本文栈长教你如何在 Spring Boot 注册 Servlet、Filter、Listener。

一、Spring Boot 注册

Spring Boot 提供了 ServletRegistrationBean, FilterRegistrationBean, ServletListenerRegistrationBean 三个类分别用来注册 Servlet, Filter, Listener，下面是 Servlet 的示例代码。

import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


public class RegisterServlet extends HttpServlet {

  @Override
  protected void service(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String name = getServletConfig().getInitParameter("name");
    String sex = getServletConfig().getInitParameter("sex");

    resp.getOutputStream().println("name is " + name);
    resp.getOutputStream().println("sex is " + sex);
  }

}

@Bean
public ServletRegistrationBean registerServlet() {
  ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean(
      new RegisterServlet(), "/registerServlet");
  servletRegistrationBean.addInitParameter("name", "javastack");
  servletRegistrationBean.addInitParameter("sex", "man");
  return servletRegistrationBean;
}

二、组件扫描注册

Servlet 3.0 之前，Servlet、Filter、Listener 这些组件都需要在 web.xml 中进行配置，3.0 之后开始不再需要 web.xml 这个配置文件了，所有的组件都可以通过代码配置或者注解来达到目的。

如下图所示，截图自 Servlet 3.1。

Servlet 3.0 开始提供了这 3 个注解来代替。

@WebServlet => 代替 servlet 配置

@WebFilter => 代替 filter 配置

@WebListener => 代替 listener 配置

配置 Servlet 示例

import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


@WebServlet(name = "javaServlet", urlPatterns = "/javastack.cn", asyncSupported = true,
    initParams = {
    @WebInitParam(name = "name", value = "javastack"),
    @WebInitParam(name = "sex", value = "man") })
public class JavaServlet extends HttpServlet {

  @Override
  protected void service(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String name = getServletConfig().getInitParameter("name");
    String sex = getServletConfig().getInitParameter("sex");

    resp.getOutputStream().println("name is " + name);
    resp.getOutputStream().println("sex is " + sex);
  }

}

配置 Filter 示例

@WebFilter(filterName = "javaFilter", urlPatterns = "
@WebServlet(name = "javaServlet", urlPatterns = "/javastack.cn", asyncSupported = true,
    initParams = {
    @WebInitParam(name = "name", value = "javastack"),
    @WebInitParam(name = "sex", value = "man") })
public class JavaServlet extends HttpServlet {

  @Override
  protected void service(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    String name = getServletConfig().getInitParameter("name");
    String sex = getServletConfig().getInitParameter("sex");

    resp.getOutputStream().println("name is " + name);
    resp.getOutputStream().println("sex is " + sex);
  }

}

import cn.javastack.springbootbestpractice.servlet.InitServlet;
import org.springframework.boot.web.servlet.ServletContextInitializer;
import org.springframework.stereotype.Component;

import javax.servlet.ServletContext;
import javax.servlet.ServletRegistration;


@Component
public class ServletConfig implements ServletContextInitializer {

  @Override
  public void onStartup(ServletContext servletContext) {
    ServletRegistration initServlet = servletContext
 .addServlet("initServlet", InitServlet.class);
    initServlet.addMapping("/initServlet");
    initServlet.setInitParameter("name", "javastack");
    initServlet.setInitParameter("sex", "man");
  }

}

总结

本文介绍了在 Spring Boot 下的 3 种注册 Servlet、Filter、Listener 的方式，大家灵活运用。

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持考高分网。