24.注册Web组件

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1.Web组件

  1. Servlet
  2. Filter
  3. Listener

项目目录结构:

自定义的servlet、filter、listener的注册器:

2.1 自定义的servlet

UserServlet

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package com.example.demo.servlet;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class UserServlet extends HttpServlet {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	@Override
	public void init(ServletConfig config) throws ServletException {
		super.init(config);
		String env = config.getInitParameter("env");
		String dataSource = config.getInitParameter("dataSource");
		System.out.println("servlet env = " + env);
		System.out.println("servlet dataSource = " + dataSource);
	}
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		doPost(req, resp);
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		System.out.println("doPost()");
	}
	
}

2.2 自定义的Filter

MyFilter

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package com.example.demo.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class MyFilter implements Filter {

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		String env = filterConfig.getInitParameter("env");
		String dataSource = filterConfig.getInitParameter("dataSource");
		System.out.println("filter env = " + env);
		System.out.println("filter dataSource = " + dataSource);
	}
	
	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
		System.out.println("doFilter()");
		// 放行
		chain.doFilter(request, response);
	}

}

2.3 自定义的Listener

MyListener

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package com.example.demo.listener;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class MyListener implements ServletContextListener {

	@Override
	public void contextInitialized(ServletContextEvent sce) {
		ServletContext servletContext = sce.getServletContext();
		servletContext.setAttribute("contextPath", servletContext.getContextPath());
		
		/*
		 * 自定义的listener可以从servletContext中获取参数，
		 * 但是在配置类中无法向servletContext中设置参数
		 */
		// String env = servletContext.getInitParameter("env");
		// String dataSource = servletContext.getInitParameter("dataSource");
		// System.out.println("listener env = " + env);
		// System.out.println("listener dataSource = " + dataSource);
		
		System.out.println("MyListener contextInitialized");
	}
	
	@Override
	public void contextDestroyed(ServletContextEvent sce) {
		// TODO Auto-generated method stub
		ServletContextListener.super.contextDestroyed(sce);
	}
	
}

3. Config

WebObjectConfig

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package com.example.demo.config;

import java.util.ArrayList;
import java.util.Collection;

import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.example.demo.filter.MyFilter;
import com.example.demo.listener.MyListener;
import com.example.demo.servlet.UserServlet;

@Configuration
@ConfigurationProperties(prefix = "myweb")
public class WebObjectConfig {
	
	/******************** servlet 开始 ****************************/
	
	private static final String USER_SERVLET_NAME = "userServlet";
	
	private String[] servletUrl;

	public String[] getServletUrl() {
		return servletUrl;
	}

	public void setServletUrl(String[] servletUrl) {
		this.servletUrl = servletUrl;
	}

	/*
	 * 创建Servlet对象
	 */
	@Bean(USER_SERVLET_NAME)
	public UserServlet getUserServlet() {
		return new UserServlet();
	}
	
	/*
	 * 进行注册
	 */
	@Bean
	@ConditionalOnBean(value = UserServlet.class, name = USER_SERVLET_NAME)
	public ServletRegistrationBean<UserServlet> servletRegistrationBeanUserServlet(UserServlet userServlet) {
		// 创建一个注册器
		ServletRegistrationBean<UserServlet> servletRegistrationBean = new ServletRegistrationBean<>();
		// 注入servlet
		servletRegistrationBean.setServlet(userServlet);
		// 注入url-pattern
        /*
		 * 参数可以直接写字符串，也可以通过application.yml文件注入
		 */
		// servletRegistrationBean.addUrlMappings("/user.do", "/user.test");
		servletRegistrationBean.addUrlMappings(servletUrl);
		// 注入初始化参数
		servletRegistrationBean.addInitParameter("env", "test");
		servletRegistrationBean.addInitParameter("dataSource", "mysql");
		
		// 设置启动时加载
		servletRegistrationBean.setLoadOnStartup(1);
		
		return servletRegistrationBean;
	}
	
	/******************** servlet 结束 ****************************/
	

	/******************** filter 开始 ****************************/
	
	private static final String MYFILE_NAME = "myFilter";
	/*
	 * 创建filter对象
	 */
	@Bean(name = MYFILE_NAME)
	public MyFilter myFilter() {
		return new MyFilter();
	}
	
    /*
	 * 进行注册
	 */
	@Bean
	@ConditionalOnBean(name = MYFILE_NAME, value = MyFilter.class)
	public FilterRegistrationBean<MyFilter> filterRegistrationBeanMyFilter(MyFilter myFilter) {
		// 创建一个注册器
		FilterRegistrationBean<MyFilter> filterRegistrationBean = new FilterRegistrationBean<>();
		// 注入servlet
		filterRegistrationBean.setFilter(myFilter);
		
		// 注入url-pattern
		Collection<String> urlPatterns = new ArrayList<>();
		urlPatterns.add("/*");
		filterRegistrationBean.setUrlPatterns(urlPatterns);

		// 注入初始化参数
		filterRegistrationBean.addInitParameter("env", "prd");
		filterRegistrationBean.addInitParameter("dataSource", "oracle");
		
		/*
		 * filter和listener在启动时就会自动加载，只有servlet需要设置启动时加载
		 */
		
		return filterRegistrationBean;
	}
	
	/******************** filter 结束 ****************************/
	

	/******************** listener 开始 ****************************/
	
	/*
	 * 创建listener对象
	 */
	@Bean
	public MyListener myListener() {
		return new MyListener();
	}
	
    /*
	 * 进行注册
	 */
	@Bean
	public ServletListenerRegistrationBean<MyListener> servletListenerRegistrationBeanMyListener(MyListener myListener) {
		ServletListenerRegistrationBean<MyListener> servletListenerRegistrationBean = new ServletListenerRegistrationBean<>();
		servletListenerRegistrationBean.setListener(myListener);
		/*
		 * 自定义的listener可以从servletContext中获取参数，
		 * 但是在配置类中无法向servletContext中设置参数
		 */
		return servletListenerRegistrationBean;
	}
	
	/******************** listener 结束 ****************************/
		
}

4. application.yml

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myweb:
  servlet-url:
  - /user.do
  - /user.test

5. 启动类

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package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}

}

运行结果: 

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  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.4.5)

2022-06-02 21:41:18.370  INFO 15132 --- [  restartedMain] com.example.demo.Application             : Starting Application using Java 1.8.0_271 on DESKTOP-IOB28AF with PID 15132 (E:\SpringToolSuite\project\demo-4.8.1\10_springboot_web_3components\target\classes started by Tom in E:\SpringToolSuite\project\demo-4.8.1\10_springboot_web_3components)
2022-06-02 21:41:18.373  INFO 15132 --- [  restartedMain] com.example.demo.Application             : No active profile set, falling back to default profiles: default
2022-06-02 21:41:18.411  INFO 15132 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : Devtools property defaults active! Set 'spring.devtools.add-properties' to 'false' to disable
2022-06-02 21:41:18.411  INFO 15132 --- [  restartedMain] .e.DevToolsPropertyDefaultsPostProcessor : For additional web related logging consider setting the 'logging.level.web' property to 'DEBUG'
2022-06-02 21:41:19.292  INFO 15132 --- [  restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2022-06-02 21:41:19.301  INFO 15132 --- [  restartedMain] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2022-06-02 21:41:19.302  INFO 15132 --- [  restartedMain] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.45]
2022-06-02 21:41:19.343  INFO 15132 --- [  restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2022-06-02 21:41:19.343  INFO 15132 --- [  restartedMain] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 932 ms
MyListener contextInitialized
filter env = prd
filter dataSource = oracle
2022-06-02 21:41:19.502  INFO 15132 --- [  restartedMain] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2022-06-02 21:41:19.645  INFO 15132 --- [  restartedMain] o.s.b.d.a.OptionalLiveReloadServer       : LiveReload server is running on port 35729
servlet env = test
servlet dataSource = mysql
2022-06-02 21:41:19.671  INFO 15132 --- [  restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2022-06-02 21:41:19.681  INFO 15132 --- [  restartedMain] com.example.demo.Application             : Started Application in 1.642 seconds (JVM running for 2.035)

浏览器访问: http://localhost:8080/user.do或http://localhost:8080/user.test

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doFilter()
doPost()

扩展

1.Servlet的注册

(1) Java2EE方法

web.xml

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<servlet>
    <servlet-name>userServlet</servlet-name>
    <servlet-class>com.sxt.servlet.UserServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>userServlet</servlet-name>
    <url-patten>/user.do</url-patten>
</servlet-mapping>

(2) 注解的方式

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@WebServlet("/user.do")

2.Filter的注册

(1) Java2EE方法

web.xml

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<filter>
    <filter-name></filter-name>
    <filter-class></filter-class>
</filter>

<filter-mapping>
    <filter-name></filter-nane>
    <!-- 
        <servlet-name></servlet-name>
        或
        <url-patten></url-patten>
     -->
</filter-mapping>

(2) 注解的方式

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@WebFilter("/*")

3.Listener的注册

(1) Java2EE方法

web.xml

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<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

(2) 注解的方式

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@WebListener

监听的内容: 

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ServletContext
	|--ServletContextListener     ServletContextAttributeListener
HttpSession
	|--HttpSessionListener        HttpSessionAttributeListener
ServletRequet
	|-- ServletRequestListener    ServletRequestAttributeListener