20. Spring Boot Servlet【从零开始学Spring Boot】

Web开发使用 Controller基本上可以完成大部分需求，但是我们还可能会用到 Servlet、Filter、Listener、Interceptor 等等。

当使用Spring-Boot时，嵌入式Servlet容器通过扫描注解的方式注册Servlet、Filter和Servlet规范的所有监听器（如HttpSessionListener监听器）。 
Spring boot 的主 Servlet 为DispatcherServlet，其默认的url-pattern为“/”。也许我们在应用中还需要定义更多的Servlet，该如何使用SpringBoot来完成呢？

在spring boot中添加自己的Servlet有两种方法，代码注册Servlet和注解自动注册（Filter和Listener也是如此）。

一、代码注册通过ServletRegistrationBean、 FilterRegistrationBean和ServletListenerRegistrationBean 获得控制。 
也可以通过实现 ServletContextInitializer 接口直接注册。

二、在SpringBootApplication 上使用@ServletComponentScan注解后，Servlet、Filter、Listener 可以直接通过 @WebServlet、@WebFilter、@WebListener 注解自动注册，无需其他代码。

这里我们新建一个spring-boot-hello2java工程进行测试；这里不过多进行说明，如果这个还不会的话，请回到上上上一章进行查看。

通过代码注册Servlet示例代码：

  1. com.kfit.servlet.MyServlet1：
  2.  
  3. package com.kfit.servlet;
  4.  
  5.  
  6.  
  7. import java.io.IOException;
  8.  
  9. import java.io.PrintWriter;
  10.  
  11.  
  12.  
  13. import javax.servlet.ServletException;
  14.  
  15. import javax.servlet.annotation.WebServlet;
  16.  
  17. import javax.servlet.http.HttpServlet;
  18.  
  19. import javax.servlet.http.HttpServletRequest;
  20.  
  21. import javax.servlet.http.HttpServletResponse;
  22.  
  23.  
  24.  
  25. /**
  27.  *
  29.  *@author Angel(公众号：SpringBoot)
  31.  *@version v.0.1
  33.  */
  34.  
  35. //这个不需要添加.
  36.  
  37. //@WebServlet(urlPatterns="/myServlet1/*", description="Servlet的说明")
  38.  
  39. public class MyServlet1 extends HttpServlet{
  40.  
  41.       
  42.  
  43.        private static final long serialVersionUID = 1L;
  44.  
  45.  
  46.  
  47.        @Override
  48.  
  49.    protected void doGet(HttpServletRequestreq, HttpServletResponse resp) throwsServletException, IOException {
  50.  
  51.         System.out.println(">>>>>>>>>>doGet()<<<<<<<<<<<");
  52.  
  53.         doPost(req,resp);
  54.  
  55.    }
  56.  
  57.  
  58.  
  59.    @Override
  60.  
  61.    protected void doPost(HttpServletRequestreq, HttpServletResponse resp) throwsServletException, IOException {
  62.  
  63.         System.out.println(">>>>>>>>>>doPost()<<<<<<<<<<<");
  64.  
  65.         resp.setContentType("text/html"); 
  66.  
  67.         PrintWriter out = resp.getWriter(); 
  68.  
  69.         out.println("<html>"); 
  70.  
  71.         out.println("<head>"); 
  72.  
  73.         out.println("<title>HelloWorld</title>"); 
  74.  
  75.         out.println("</head>"); 
  76.  
  77.         out.println("<body>"); 
  78.  
  79.         out.println("<h1>这是：MyServlet1</h1>"); 
  80.  
  81.         out.println("</body>"); 
  82.  
  83.         out.println("</html>");
  84.  
  85.    }
  86.  
  87. }

在com.kfit.App中注册：

package com.kfit;

  1. import org.springframework.boot.SpringApplication;
  2.  
  3. import org.springframework.boot.autoconfigure.SpringBootApplication;
  4.  
  5. import org.springframework.boot.context.embedded.ServletRegistrationBean;
  6.  
  7. import org.springframework.boot.web.servlet.ServletComponentScan;
  8.  
  9. import org.springframework.context.annotation.Bean;
  10.  
  11.  
  12.  
  13. import com.kfit.servlet.MyServlet1;
  14.  
  15.  
  16.  
  17. /**
  19.  *
  21.  *
  23.  *大家也许会看到有些demo使用了3个注解：@Configuration；
  25.  *
  27.  *@EnableAutoConfiguration
  29.  * @ComponentScan
  31.  *
  33.  *                        其实：@SpringBootApplication申明让spring boot自动给程序进行必要的配置，
  35.  *
  37.  *               等价于以默认属性使用@Configuration，
  39.  *                @EnableAutoConfiguration和@ComponentScan
  41.  *
  43.  *所以大家不要被一些文档误导了，让自己很迷茫了，希望本文章对您有所启发；
  45.  *
  47.  * @authorAngel(QQ:412887952)
  49.  * @version v.0.1
  51.  */
  52.  
  53. @SpringBootApplication
  54.  
  55. public class App {
  56.  
  57.       
  58.  
  59.        /**
  61.         *注册Servlet.不需要添加注解：@ServletComponentScan
  63.         * @return
  65.         */
  66.  
  67.        @Bean
  68.  
  69.        publicServletRegistrationBean MyServlet1(){
  70.  
  71.               return new ServletRegistrationBean(new MyServlet1(),"/myServlet/*");
  72.  
  73.        }
  74.  
  75.       
  76.  
  77.        public static void main(String[] args) {
  78.  
  79.               SpringApplication.run(App.class,args);
  80.  
  81.        }
  82.  
  83. }





右键Run As JavaApplication进行访问http://127.0.0.1:8080/myServlet1

使用注解注册Servlet示例代码

com.kfit.servlet.MyServlet2.java

  1. package com.kfit.servlet;
  2.  
  3.  
  4.  
  5. import java.io.IOException;
  6.  
  7. import java.io.PrintWriter;
  8.  
  9.  
  10.  
  11. import javax.servlet.ServletException;
  12.  
  13. import javax.servlet.annotation.WebServlet;
  14.  
  15. import javax.servlet.http.HttpServlet;
  16.  
  17. import javax.servlet.http.HttpServletRequest;
  18.  
  19. import javax.servlet.http.HttpServletResponse;
  20.  
  21.  
  22.  
  23. /**
  25.  *
  27.  * @authorAngel(QQ:412887952)
  29.  * @version v.0.1
  31.  */
  32.  
  33. @WebServlet(urlPatterns="/myServlet2/*",description="Servlet的说明")
  34.  
  35. public class MyServlet2 extends HttpServlet{
  36.  
  37.       
  38.  
  39.        private static final long serialVersionUID = 1L;
  40.  
  41.  
  42.  
  43.        @Override
  44.  
  45.     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throwsServletException, IOException {
  46.  
  47.        System.out.println(">>>>>>>>>>doGet()<<<<<<<<<<<");
  48.  
  49.         doPost(req, resp);
  50.  
  51.     }
  52.  
  53.  
  54.  
  55.     @Override
  56.  
  57.     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throwsServletException, IOException {
  58.  
  59.        System.out.println(">>>>>>>>>>doPost()<<<<<<<<<<<");
  60.  
  61.         resp.setContentType("text/html"); 
  62.  
  63.         PrintWriter out =resp.getWriter(); 
  64.  
  65.        out.println("<html>"); 
  66.  
  67.        out.println("<head>"); 
  68.  
  69.        out.println("<title>Hello World</title>"); 
  70.  
  71.        out.println("</head>"); 
  72.  
  73.         out.println("<body>"); 
  74.  
  75.        out.println("<h1>这是：myServlet2</h1>"); 
  76.  
  77.        out.println("</body>"); 
  78.  
  79.        out.println("</html>");
  80.  
  81.     }
  82.  
  83. }

SpringBootSampleApplication.java

  1. package com.kfit;
  2.  
  3.  
  4.  
  5. import org.springboot.sample.servlet.MyServlet;
  6.  
  7. import org.springframework.boot.SpringApplication;
  8.  
  9. import org.springframework.boot.autoconfigure.SpringBootApplication;
  10.  
  11. import org.springframework.boot.context.embedded.ServletRegistrationBean;
  12.  
  13. import org.springframework.boot.web.servlet.ServletComponentScan;
  14.  
  15. import org.springframework.context.annotation.Bean;
  16.  
  17. import org.springframework.web.servlet.DispatcherServlet;
  18.  
  19.  
  20.  
  21. @SpringBootApplication
  22.  
  23. @ServletComponentScan//这个就是扫描相应的Servlet包;
  24.  
  25. public class SpringBootSampleApplication {
  26.  
  27.  
  28.  
  29.     public static void main(String[]args) {
  30.  
  31.         SpringApplication.run(SpringBootSampleApplication.class, args);
  32.  
  33.     }
  34.  
  35. }

访问http://127.0.0.1:8080/myServlet2

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