java中的過濾器
阿新 • • 發佈：2018-12-19
過濾器相當於一個特殊的java類
如何在xml中配置過濾器
<filter>
<filter-name>filter</filter-name>
<filter-class>five.MyFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>filter</filter-name>
<url-pattern>/show.jsp</url-pattern>
</filter-mapping>
如判斷使用者登入
package five;
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.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
public class MyFilter implements Filter
@Override
public void destroy() {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req=(HttpServletRequest)request;
HttpSession session=req.getSession();
String name=(String)session.getAttribute("name"); //得到servlet儲存的session使用者名稱
if(name==null||"".equals(name)){
request.getRequestDispatcher("index.jsp").forward(request, response);
}
chain.doFilter(request, response);//如果存在則執行jsp頁面或servlet
}
@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
}
}