前置条件需要配置webxml
<filter> <filter-name>FilterDemo3</filter-name> <filter-class>cn.web.servlet.filter.FilterDemo3</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>FilterDemo3</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
java代码
import java.io.IOException;import java.util.Enumeration;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class FilterDemo3 implements Filter { private FilterConfig filterConfig; public FilterDemo3() { } @Override public void init(FilterConfig filterConfig) throws ServletException { this.filterConfig = filterConfig; } //WEB容器 @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //从web.xml中全部获取参数 Enumeration<String> enums = filterConfig.getInitParameterNames(); while(enums.hasMoreElements()) { String key = enums.nextElement(); String value = filterConfig.getInitParameter(key); System.out.println(key+":"+value); } String encoding = filterConfig.getInitParameter("encoding"); response.setContentType("text/html;charset="+encoding); chain.doFilter(request,response); } @Override public void destroy() { System.out.println("摧毁 方法: destroy()"); }}结果：
摧毁 方法: destroy()
四月 18, 2018 9:38:57 下午 org.apache.catalina.core.StandardContext reload
信息: Reloading Context with name [/day04] has started
四月 18, 2018 9:38:57 下午 org.apache.catalina.core.StandardContext reload
信息: Reloading Context with name [/day04] is completed
encoding:UTF-8
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