內嵌tomcat最簡單用法

maven項目引入內嵌tomcat依賴

<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-core</artifactId>
    <version>8.5.37</version>
</dependency>

編寫以下main方法

 1 package com;  2 
 3 import org.apache.catalina.Context;  4 import org.apache.catalina.LifecycleException;  5 import org.apache.catalina.startup.Tomcat;  6 import org.apache.tomcat.util.descriptor.web.FilterDef;  7 import org.apache.tomcat.util.descriptor.web.FilterMap;  8 import org.springframework.web.filter.OncePerRequestFilter;  9 
10 import javax.servlet.Filter; 11 import javax.servlet.FilterChain; 12 import javax.servlet.ServletException; 13 import javax.servlet.http.HttpServlet; 14 import javax.servlet.http.HttpServletRequest; 15 import javax.servlet.http.HttpServletResponse; 16 import java.io.IOException; 17 import java.nio.charset.Charset; 18 
19 /**
20  * @author allen 21  * @date 2019-01-22 13:20 22  */
23 public class TomcatWebServer { 24     public static void main(String[] args) { 25         Tomcat tomcat = new Tomcat(); 26         HttpServlet httpServlet = new HttpServlet() { 27  @Override 28             protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException { 29                 resp.getWriter().write("hello, i'm embed tomcat"); 30  } 31 
32  @Override 33             protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException { 34  doGet(req, resp); 35  } 36  }; 37         tomcat.setHostname("localhost"); 38         tomcat.setPort(8080); 39         final Context context = tomcat.addContext("/embed-tomcat", null); 40         Tomcat.addServlet(context, "dispatch", httpServlet); 41         context.addServletMappingDecoded("/dispatch", "dispatch"); 42         Filter filter = new OncePerRequestFilter() { 43  @Override 44             protected void doFilterInternal(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, FilterChain filterChain) throws ServletException, IOException { 45                 System.out.println("filter do something"); 46  filterChain.doFilter(httpServletRequest, httpServletResponse); 47  } 48  }; 49         FilterDef filterDef = new FilterDef(); 50  filterDef.setFilter(filter); 51         filterDef.setFilterName("myFilter"); 52         filterDef.addInitParameter("userName", "Allen"); 53 
54         FilterMap filterMap = new FilterMap(); 55         filterMap.addURLPatternDecoded("/*"); 56         filterMap.addServletName("*"); 57         filterMap.setFilterName("myFilter"); 58         filterMap.setCharset(Charset.forName("UTF-8")); 59 
60  context.addFilterDef(filterDef); 61  context.addFilterMap(filterMap); 62         try { 63  tomcat.init(); 64  tomcat.start(); 65  tomcat.getServer().await(); 66         } catch (LifecycleException e) { 67  e.printStackTrace(); 68  } 69  } 70 }

注意其中OncePerRequestFilter是spring提供的對filter接口的實現類，沒有引入spring依賴的可自行改用其餘實現類。

運行main方法，一個最簡單的tomcat實例已經運行起來。瀏覽器打開http://localhost:8080/embed-tomcat/dispatch，頁面能夠看到輸出內容，控制檯也打印了過濾器執行的內容。

springboot默認就是使用tomcat做爲內嵌容器的，基本原理通上述代碼，只不過spring作了更深層次的封裝，結合其ioc容器，能夠實現只要往ioc容器中注入servlet、filter接口的實現類，spring的適配器可自動完成配置。