Spring Boot之 Servlet、Fiter、Listener的使用
Servlet的使用
新建MyServlet类
package com.adagio.chat.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet(
name = "myservlet",
urlPatterns = {"/myservlet1", "/myservlet2"}
)
public class MyServlet extends HttpServlet {
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{
Writer writer = response.getWriter();
writer.write("<html><body>Hello World</body></html>");
}
}启动类添加注解 @ServletComponentScan(basePackages = {"com.adagio.chat.servlet"})
启动运行访问：http://localhost:8080/myservlet1和http://localhost:8080/myservlet2
-
servlet的使用很简单：
添加注解 @WebServlet
配置name，可以不用配置
配置路径，urlPatterns 可以配置多值
Filter的使用
使用方式和Servlet十分类似
package com.adagio.chat.servlet;
import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.filter.OncePerRequestFilter;
//@WebFilter(servletNames = "myservlet")
@WebFilter(urlPatterns = "/myservlet1")
public class MyFilter extends OncePerRequestFilter {
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
ServletContext servletContext = getServletContext();
servletContext.log("url myservlet was filter");
filterChain.doFilter(request, response);
}
}
可以直接使用servletNames过滤，如@WebFilter(servletNames = "myservlet")，访问http://localhost:8080/myservlet1和http://localhost:8080/myservlet2都会在控制台打印日志
也可以使用@WebFilter(urlPatterns = "/myservlet1")，访问上面两个链接，只有访问http://localhost:8080/myservlet1这个地址才会打印日志
Listener的使用
使用方式也是类似的
package com.adagio.chat.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.annotation.WebListener;
import javax.servlet.http.HttpServletRequest;
@WebListener
public class MyListener implements ServletRequestListener {
@Override
public void requestDestroyed(ServletRequestEvent sre) {
HttpServletRequest request = (HttpServletRequest)sre.getServletRequest();
ServletContext servletContext = request.getServletContext();
servletContext.log("request was destroyed");
}
@Override
public void requestInitialized(ServletRequestEvent sre) {
HttpServletRequest request = (HttpServletRequest)sre.getServletRequest();
ServletContext servletContext = request.getServletContext();
servletContext.log("request was initialized");
}
}
访问http://localhost:8080/myservlet2 观察控制台
执行顺序
2017-09-10 16:11:18.247 INFO 7692 --- [io-8080-exec-10] o.a.c.c.C.[Tomcat].[localhost].[/] : request was initialized
2017-09-10 16:11:18.271 INFO 7692 --- [io-8080-exec-10] o.a.c.c.C.[Tomcat].[localhost].[/] : url myservlet was filter
2017-09-10 16:11:18.271 INFO 7692 --- [io-8080-exec-10] o.a.c.c.C.[Tomcat].[localhost].[/] : servlet was doGet
2017-09-10 16:11:18.275 INFO 7692 --- [io-8080-exec-10] o.a.c.c.C.[Tomcat].[localhost].[/] : request was destroyed先监听器的初始化，再经过滤器，然后执行doGet方法，最后执行监听器的消亡
使用注入的方式注册
效果和上面的方式一样的，具体实现见代码
package com.adagio.chat.spring.boot;
import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.context.request.RequestAttributes;
import org.springframework.web.context.request.RequestContextHolder;
import org.springframework.web.context.request.ServletRequestAttributes;
import org.springframework.web.filter.OncePerRequestFilter;
public class MyFilter2 extends OncePerRequestFilter {
@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
// ServletContext servletContext = getServletContext();
//
// //动态获取URI
// String requestURI = request.getRequestURI();
//
// servletContext.log("url "+requestURI+" was filter from MyFilter2");
doSomething();
filterChain.doFilter(request, response);
}
/**
* 当没有request的时候，可以使用这种方式获取request
*/
public void doSomething(){
RequestAttributes requestAttributes = RequestContextHolder.getRequestAttributes();
ServletRequestAttributes servletRequestAttributes = (ServletRequestAttributes)requestAttributes;
HttpServletRequest request = servletRequestAttributes.getRequest();
ServletContext servletContext = getServletContext();
//动态获取URI
String requestURI = request.getRequestURI();
servletContext.log("url "+requestURI+" was filter from MyFilter2");
}
}
package com.adagio.chat.spring.boot;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class MyServlet2 extends HttpServlet {
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException{
ServletContext servletContext = request.getServletContext();
servletContext.log("servlet2 was doGet");
Writer writer = response.getWriter();
writer.write("<html><body>Hello World From MyServlet2</body></html>");
}
}
package com.adagio.chat;
import javax.servlet.DispatcherType;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletComponentScan;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import com.adagio.chat.servlet.MyListener;
import com.adagio.chat.spring.boot.MyFilter2;
import com.adagio.chat.spring.boot.MyServlet2;
@SpringBootApplication
@ServletComponentScan(basePackages = {"com.adagio.chat.servlet"})
public class ChatApplication {
public static void main(String[] args) {
SpringApplication.run(ChatApplication.class, args);
}
@Bean
public static ServletRegistrationBean servletRegistrationBean(){
ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean();
servletRegistrationBean.setServlet(new MyServlet2());
servletRegistrationBean.addUrlMappings("/spring/boot/myservelt2");
servletRegistrationBean.setName("myservlet2");
return servletRegistrationBean;
}
@Bean
public static FilterRegistrationBean filterRegistrationBean(){
FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
filterRegistrationBean.setFilter(new MyFilter2());
// filterRegistrationBean.addUrlPatterns("/spring/boot/myservelt2");
filterRegistrationBean.addServletNames("myservlet2");
filterRegistrationBean.setDispatcherTypes(DispatcherType.REQUEST, DispatcherType.FORWARD, DispatcherType.INCLUDE);
return filterRegistrationBean;
}
/**
* 监听器会监听所有请求
* 可以重复注册监听器
* @return
*/
@Bean
public static ServletListenerRegistrationBean<MyListener> servletListenerRegistrationBean(){
ServletListenerRegistrationBean<MyListener> servletListenerRegistrationBean = new ServletListenerRegistrationBean<>(new MyListener());
return servletListenerRegistrationBean;
}
}
急事慢做：成长是长时间努力、积累和进步的结果，是水到渠成的事情，绝不是心急就能做到的。
生长速度越快的树木，其致密度就越低，生命往往也越短暂；而松树、柏树、胡杨等树种，要上百年才能成材，用起来却可千年不朽。 - 俞敏洪
java
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