ServletContext全局對象:
import javax.servlet.ServletConfig;
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;
import javax.servlet.http.HttpSession;
import java.io.IOException;
public class HelloServlet extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
ServletConfig config = this.getServletConfig();//建立ServletConfig對象
System.out.println(config.getInitParameter("className"));
System.out.println(config.getInitParameter("url"));
ServletContext servletContext = this.getServletContext();
// servletContext.getAttribute()//得到對象中的值 通過name的
// servletContext.setAttribute();//加入參數 鍵值對
// servletContext.removeAttribute(); 删除參數
// servletContext.getAttributeNames(); 得到對象中的參數名稱
System.out.println("servletContext.getRealPath(\"/WEB-INF\") = " + servletContext.getRealPath("/WEB-INF"));
//獲得檔案的絕對路徑
System.out.println("servletContext.getContextPath() = "
+ servletContext.getContextPath());
//得到工程路徑如果工程在root路徑下那就是空的
// this.getServletConfig().getServletContext() 獲得SerivetContext對象方式
// this.getServletContext() 獲得SerivetContext對象方式
// req.getServletContext() 獲得SerivetContext對象方式
// req.getSession().getServletContext() 獲得SerivetContext對象方式
}
}
過濾器:
所有資源通路之前被調用對象
1.資料庫加載
2.權限驗證
3.資料檢查
4.資料加工
5.資料緩存
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
//@WebFilter("*")
public class AFilter implements Filter {
//過濾器實作的是一個接口
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest servletRequest,
ServletResponse servletResponse,
FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) servletRequest;
HttpServletResponse response = (HttpServletResponse) servletResponse;
if (request.getRequestURL().toString().endsWith(".jpg")) {//判斷條件
//通行
//FilterChain 中的方法
filterChain.doFilter(servletRequest, servletResponse);
}
}
@Override
public void destroy() {
}
}
監聽器裡面有監聽Session建立啊銷毀啊添加啊等方法
@WebListener
public class SessionListener implements HttpSessionIdListener,
HttpSessionListener, HttpSessionAttributeListener{
public void sessionIdChanged(HttpSessionEvent var1, String var2){
System.out.println("sessionIdChanged..");
}
@Override
public void sessionCreated(HttpSessionEvent httpSessionEvent) {
System.out.println("sessionCreated..");
}
@Override
public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
System.out.println("sessionDestroyed..");
}
@Override
public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
System.out.println("attributeAdded..");
}
@Override
public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
System.out.println("attributeRemoved..");
}
@Override
public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {
System.out.println("attributeReplaced..");
}
}