Filter:过滤器,用来过滤网站的数据:
Filter开发步骤
1.导包
2.编写过滤器
import javax.servlet.*;
public class CharacterEncodingFilter implements Filter{
//初始化
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("init");
}
//chain: 链
/*
* 1.过滤中的所有代码,在过滤特定请求的时候都会执行
* 2.必须要让过滤器继续同行
* */
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=UTF-8");
System.out.println("执行前");
chain.doFilter(request,response);//让我们的请求继续走,如果不写,程序到这里就被拦截
System.out.println("执行后");
}
//销毁
public void destroy() {
System.out.println("destory");
}
}
在web.xml中配置Filter
<filter>
<filter-name>CharacterEncodingFilter</filter-name>
<filter-class>top.ltyzqhh.Filter.CharacterEncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CharacterEncodingFilter</filter-name>
<!--只要是/servlet-->
<url-pattern>/servlet/*</url-pattern>
</filter-mapping>
</web-app>