过滤器

照着书上的例子写了个过滤器

package org.lxh.filterdemo;
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;
public class EncodingFilter implements Filter {
	private String charSet;
	public void init(FilterConfig config) throws ServletException {
		this.charSet = config.getInitParameter("charset");
	}
	public void doFilter(ServletRequest request, ServletResponse response,
		FilterChain chain) throws IOException, ServletException {
		request.setCharacterEncoding(this.charSet);
	}
	public void destroy() {
	}
}

写完后配置web.xml

<filter>	
	<filter-name>encoding</filter-name>
	<filter-class>org.lxh.filterdemo.EncodingFilter</filter-class>
	<init-param>
		<param-name>charset</param-name>
		<param-value>GBK</param-value>
	</init-param>
  </filter>
   <filter-mapping>	<filter-name>encoding</filter-name>
	<url-pattern>/*</url-pattern>
  </filter-mapping>

话说这个程序没有什么肉眼看的出的效果,但是我发现此时运行原先的一些jsp程序,发现浏览器都是一片空白。搞了半天,最后发现把过滤器加一行就可以了:



package org.lxh.filterdemo;
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;
public class EncodingFilter implements Filter {
	private String charSet;
	public void init(FilterConfig config) throws ServletException {
		this.charSet = config.getInitParameter("charset");
	}
	public void doFilter(ServletRequest request, ServletResponse response,
		FilterChain chain) throws IOException, ServletException {
		request.setCharacterEncoding(this.charSet);
		chain.doFilter(request, response);
	}
	public void destroy() {
	}
}



  • 原因,过滤器要将过滤的结果传给链上的后一个过滤器,或者传给最终的jsp程序,所以必须加chain.doFilter(request, response);否则就请求就在这里终止了。
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