Listener、Filter、Servlet 初始化

• listener、Filter、Servlet都有一个初始化的过程
• 那么它们的初始化顺序是: listener > Filter > Servlet;
• servlet初始化

  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 TestFilter implements Filter{
   
   
    public void init(FilterConfig filterConfig) throws ServletException { 
           System.out.println("Filter 初始化。。。"); 
       } 
       public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { 
           System.out.println("doFilter 。。。"); 
           chain.doFilter(request, response); 
       } 
       public void destroy() { 
           System.out.println("Filter 销毁。。。"); 
       } 
  }

  
  
  
• filter初始化

  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 TestFilter implements Filter{
   
   
    public void init(FilterConfig filterConfig) throws ServletException { 
           System.out.println("Filter 初始化。。。"); 
       } 
       public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { 
           System.out.println("doFilter 。。。"); 
           chain.doFilter(request, response); 
       } 
       public void destroy() { 
           System.out.println("Filter 销毁。。。"); 
       } 
  }

• Listener 初始化

  import javax.servlet.ServletContextEvent;
  import javax.servlet.ServletContextListener;
  
  public class TestListener implements ServletContextListener{
    public void contextInitialized(ServletContextEvent arg0) { 
           System.out.println("Listener 初始化。。。"); 
       } 
       public void contextDestroyed(ServletContextEvent arg0) { 
           System.out.println("Listener 销毁。。。"); 
       } 
  }

  
  
  web.xml

  <servlet> 
          <servlet-name>s</servlet-name> 
          <servlet-class>com.zm.test.TestServlet</servlet-class> 
      </servlet> 
      <servlet-mapping> 
          <servlet-name>s</servlet-name> 
          <url-pattern>/login</url-pattern> 
      </servlet-mapping> 
      <filter> 
          <filter-name>f</filter-name> 
          <filter-class>com.zm.test.TestFilter</filter-class> 
      </filter> 
      <filter-mapping> 
          <filter-name>f</filter-name> 
          <url-pattern>/*</url-pattern> 
      </filter-mapping> 
      <listener> 
          <listener-class>com.zm.test.TestListener</listener-class> 
      </listener>