标签：修改 tco 声明 als eve http prot listener equals
web中执行顺序，加载context-param参数 -> 按声明顺序执行listener -> 执行filter链 -> 执行servlet
一. context-param
context-param用来设置属性值，在listener，filter，servlet中都可以读取到该值
<!--自定义属性-->
<context-param>
<param-name>customName</param-name>
<param-value>customValue</param-value>
</context-param>
<!--ContextLoaderListener会读取contextConfigLocation属性-->
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
二. listener
在servlet-api中提供了ServletContextListener和ServletRequestListener两种监听器
下面我们自定义一个Listener，实现ServletContextListener接口，在该方法中获取context-param配置的属性值
public class SomeListener implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent sce) { System.out.println("SomeListener.contextInitialized"); ServletContext sc = sce.getServletContext(); String value = sc.getInitParameter("customName"); System.out.println("get customName value: " + value); } @Override public void contextDestroyed(ServletContextEvent sce) { System.out.println("SomeListener.contextDestroyed"); } }
在web.xml中配置listener
<listener>
<listener-class>com.xxx.listener.SomeListener</listener-class>
</listener>
使用spring web中的ContextLoaderListener，该类同样实现了ServletContextListener接口
执行该Listener时，默认会读取/WEB-INF/applicationContext.xml文件
可以通过context-param中的contextConfigLocation属性修改读取文件的位置
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
三. filter
实现Filter接口，在初始化时可以获取到context-param中的参数信息，也可以获取到filter中的init-param信息
在doFilter时可以做一些过滤操作，比如Shiro中的认证授权操作。
public class SessionFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { System.out.println("SessionFilter.init"); String filterValue = filterConfig.getInitParameter("filterKey"); System.out.println("SessionFilter get filterKey: " + filterValue); String customValue = filterConfig.getServletContext().getInitParameter("customName"); System.out.println("SessionFilter get customValue: " + customValue); } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //do somthing if(request instanceof HttpServletRequest){ HttpServletRequest httpRequest = (HttpServletRequest) request; Cookie[] cookies = httpRequest.getCookies(); for (Cookie cookie : cookies) { if ("JSESSIONID".equals(cookie.getName())) { String sessionId = cookie.getValue(); System.out.println("sessionId is: " + sessionId); } } } chain.doFilter(request,response); } @Override public void destroy() { System.out.println("SessionFilter.destroy"); } }
配置web.xml
url-pattern4中匹配规则
所以Filter中的url-pattern要使用 /* 而不能使用 /
<filter>
<filter-name>sessionFilter</filter-name>
<filter-class>com.xxx.filter.SessionFilter</filter-class>
<init-param>
<param-name>filterKey</param-name>
<param-value>filterValue</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>sessionFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
四. servlet
当请求经过filter过滤后，就会交给servlet处理，servlet是一个接口，其中service()是最终要调用的方法
如下我们继承HttpServlet，并重写他的service方法，在service方法中会传进来HttpServletRequest和HttpServletResponse
public class HelloServlet extends HttpServlet {
@Override
public ServletConfig getServletConfig() {
System.out.println("HelloServlet.getServletConfig");
return super.getServletConfig();
}
@Override
public void init() throws ServletException {
System.out.println("HelloServlet.init");
}
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
HttpSession session = req.getSession();
session.setAttribute("username","sicwen");
session.setAttribute("password","123");
req.getRequestDispatcher("hello.jsp").forward(req,resp);
System.out.println("HelloServlet.service");
}
@Override
public void destroy() {
System.out.println("HelloServlet.destroy");
}
}
在web.xml中配置
<servlet>
<servlet-name>hello</servlet-name>
<servlet-class>com.xxx.servlet.HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>hello</servlet-name>
<url-pattern>/hello</url-pattern>
</servlet-mapping>
标签：修改 tco 声明 als eve http prot listener equals
原文地址：https://www.cnblogs.com/Sicwen/p/10595506.html
