内嵌tomcat最简单用法

时间：2022-03-15 15:26:32

maven项目引入内嵌tomcat依赖

<dependency>

    <groupId>org.apache.tomcat.embed</groupId>

    <artifactId>tomcat-embed-core</artifactId>

    <version>8.5.37</version>

</dependency>

编写如下main方法

 package com;

 import org.apache.catalina.Context;

 import org.apache.catalina.LifecycleException;

 import org.apache.catalina.startup.Tomcat;

 import org.apache.tomcat.util.descriptor.web.FilterDef;

 import org.apache.tomcat.util.descriptor.web.FilterMap;

 import org.springframework.web.filter.OncePerRequestFilter;

 import javax.servlet.Filter;

 import javax.servlet.FilterChain;

 import javax.servlet.ServletException;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 import java.io.IOException;

 import java.nio.charset.Charset;

 /**

  * @author allen

  * @date 2019-01-22 13:20

  */

 public class TomcatWebServer {

     public static void main(String[] args) {

         Tomcat tomcat = new Tomcat();

         HttpServlet httpServlet = new HttpServlet() {

             @Override

             protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {

                 resp.getWriter().write("hello, i'm embed tomcat");

             }

             @Override

             protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {

                 doGet(req, resp);

             }

         };

         tomcat.setHostname("localhost");

         tomcat.setPort(8080);

         final Context context = tomcat.addContext("/embed-tomcat", null);

         Tomcat.addServlet(context, "dispatch", httpServlet);

         context.addServletMappingDecoded("/dispatch", "dispatch");

         Filter filter = new OncePerRequestFilter() {

             @Override

             protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain) throws ServletException, IOException {

                 System.out.println("filter do something");

                 filterChain.doFilter(httpServletRequest, httpServletResponse);

             }

         };

         FilterDef filterDef = new FilterDef();

         filterDef.setFilter(filter);

         filterDef.setFilterName("myFilter");

         filterDef.addInitParameter("userName", "Allen");

         FilterMap filterMap = new FilterMap();

         filterMap.addURLPatternDecoded("/*");

         filterMap.addServletName("*");

         filterMap.setFilterName("myFilter");

         filterMap.setCharset(Charset.forName("UTF-8"));

         context.addFilterDef(filterDef);

         context.addFilterMap(filterMap);

         try {

             tomcat.init();

             tomcat.start();

             tomcat.getServer().await();

         } catch (LifecycleException e) {

             e.printStackTrace();

         }

     }

 }

注意其中OncePerRequestFilter是spring提供的对filter接口的实现类，没有引入spring依赖的可自行改用其他实现类。

运行main方法，一个最简单的tomcat实例已经运行起来。浏览器打开http://localhost:8080/embed-tomcat/dispatch，页面可以看到输出内容，控制台也打印了过滤器执行的内容。

springboot默认就是使用tomcat作为内嵌容器的，基本原理通上述代码，只不过spring做了更深层次的封装，结合其ioc容器，可以实现只要往ioc容器中注入servlet、filter接口的实现类，spring的适配器可自动完成配置。

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