一、为什么需要嵌入式Tomcat

1.部署复杂度  :要去频繁改server.xml
2.架构约束    :额外加载监听器、引擎、JSP等用不到的一些东西
3.微服务架构  :

二、使用嵌入式Tomcat

案例1：嵌入式tomcat启动一个servlet

1.加嵌入式tomcat依赖包
<dependencies>
        <!-- 嵌入式tomcat -->
        <dependency>
            <groupId>org.apache.tomcat.embed</groupId>
            <artifactId>tomcat-embed-core</artifactId>
            <version>8.5.34</version>
        </dependency>

        <!-- 嵌入式tomcat的jsp支持 -->
        <dependency>
            <groupId>org.apache.tomcat</groupId>
            <artifactId>tomcat-jasper</artifactId>
            <version>8.5.34</version>
        </dependency>
</dependencies>

2.嵌入式tomcat运行servlet
public class ServletDemo {
    public static void main(String[] args) throws LifecycleException {
    	//1.引入tomcat
        Tomcat tomcat = new Tomcat();

        //2.自定义servlet，专门处理http请求
        HttpServlet httpServlet = new HttpServlet() {
            @Override
            public void service(ServletRequest request, ServletResponse response) throws IOException {
                response.getWriter().write("hello world");
            }
        };        

        //3.部署应用
        Context context = tomcat.addContext("/demo", null);
        //4.往应用添加servlet
        tomcat.addServlet(context, "hello", httpServlet);
        //servlet映射
        context.addServletMappingDecoded("/hello", "hello");

        //5.启动tomcat
        tomcat.init();
        tomcat.start();
        tomcat.getServer().await();  //阻塞tomcat，等待请求过来(相当于双击startup.bat)
    }
}

3.测试： 浏览器输入 http://localhost:8080/demo/hello    输出hello world

案例2：嵌入式tomcat启动一个项目

public class WebAppDemo {
    public static void main(String[] args) throws Exception {
        //1.引入嵌入式tomcat
        Tomcat tomcat = new Tomcat();

        //2.部署项目
        tomcat.addWebapp("/test", "E:\\code\\newenergy-app-backend-ccw\\out\\production\\classes");

        //3.启动tomcat
        tomcat.init();
        tomcat.start();
        tomcat.getServer().await();
    }
}

测试: 浏览器输入http://localhost:8080/test/控制层访问路径