使用FilterConfig读取配置文件的信息 ---学习笔记

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