servlet-filter-listener
程序员文章站
2022-06-03 09:46:33
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javaWeb的三大组件
servlet
1、web.xml
<servlet>
<servlet-name>HelloWorld</servlet-name>
<servlet-class>com.htp.servlet.ServletDemo</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloWorld</servlet-name>
<url-pattern>/HelloWorld</url-pattern>
</servlet-mapping>
2、实现类 此处继承httpServlet接口,实现doGet()
package com.htp.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class ServletDemo
*/
@WebServlet("/ServletDemo")
public class ServletDemo extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public ServletDemo() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
// 设置响应内容类型
response.setContentType("text/html");
// 实际的逻辑是在这里
PrintWriter out = response.getWriter();
out.println("<h1>" + "HELLO WORLD" + "</h1>");
System.out.println("servletDemo end...");
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
}
filter
1、web.xml
<filter>
<filter-name>FilterDemo</filter-name>
<filter-class>com.htp.filter.FilterDemo</filter-class>
</filter>
<filter-mapping>
<filter-name>FilterDemo</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
2、实现类 (实现filter接口)
package com.htp.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;
import javax.servlet.annotation.WebFilter;
/**
* Servlet Filter implementation class FliterDemo
*/
@WebFilter(description = "测试过滤器", urlPatterns = { "/FilterDemo" })
public class FilterDemo implements Filter {
/**
* Default constructor.
*/
public FilterDemo() {
// TODO Auto-generated constructor stub
}
/**
* @see Filter#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
System.out.println("test fliter end....");
}
/**
* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
// place your code here
// 对request和response进行一些预处理
request.setCharacterEncoding("UTF-8");
response.setCharacterEncoding("UTF-8");
response.setContentType("text/html;charset=UTF-8");
System.out.println("before FilterDemo!!!");
// pass the request along the filter chain 让资源放行
chain.doFilter(request, response);
System.out.println("after FilterDemo!!!");
}
/**
* @see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
// TODO Auto-generated method stub
System.out.println("test fliter init....");
}
}
listener
1、web.xml
<listener>
<listener-class>com.htp.listener.ListenerDemo2</listener-class>
</listener>
2、实现类
package com.htp.listener;
import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;
import javax.servlet.annotation.WebListener;
/**
* Application Lifecycle Listener implementation class ListenerDemo2
*
*/
@WebListener
public class ListenerDemo2 implements ServletRequestListener {
/**
* Default constructor.
*/
public ListenerDemo2() {
// TODO Auto-generated constructor stub
}
/**
* @see ServletRequestListener#requestDestroyed(ServletRequestEvent)
*/
public void requestDestroyed(ServletRequestEvent arg0) {
// TODO Auto-generated method stub
ServletRequest servletRequest = arg0.getServletRequest();
System.out.println("ServletRequest destroyed. Remote IP="+servletRequest.getRemoteAddr());
}
/**
* @see ServletRequestListener#requestInitialized(ServletRequestEvent)
*/
public void requestInitialized(ServletRequestEvent arg0) {
// TODO Auto-generated method stub
ServletRequest servletRequest = arg0.getServletRequest();
System.out.println("ServletRequest initialized. Remote IP="+servletRequest.getRemoteAddr());
}
}
总结:
执行顺序为listener–filter—servlet